METHOD OF MAKING NON-GALLING PARTS USING AMORPHOUS METAL SURFACES
Provided is a method for increasing anti-galling of parts using a coating material comprising an amorphous alloy. The parts may be a vehicle or machine component, for example, that are subject to frictional and sliding forces. The disclosed coating reduces galling and friction between surfaces, and increases the lift of such parts.
The present invention is generally related to a method of making non-galling parts using amorphous metal surfaces.
Description of Related ArtThe deterioration of surfaces is a huge problem in many industries. Metal parts are subject to rubbing against other metal parts in everyday use. Many times, these parts when wearing each other will lock up rather than just wearing away. This phenomenon is called “galling” where the metal parts under the high pressure bonds to the material from the other side.
SUMMARYIt is an aspect of this disclosure to provide a method of increasing galling resistance of a substrate that includes coating a material over at least a portion of a surface of a substrate, wherein the coating material includes an amorphous alloy.
In embodiments, the substrate may be a portion of a vehicle component such as an automotive transmission component, an automotive engine component, or an automotive drivetrain component.
Another aspect provides an article including a substrate and a coating material disposed over at least a portion of a surface of the substrate. The coating material includes an amorphous alloy.
Other aspects, features, and advantages of the present invention will become apparent from the following detailed description, the accompanying drawings, and the appended claims.
The term “hot chamber” is used throughout. This is because in all concepts the supply of molten metal can come directly from either:
A crucible or furnace which is continuously fed a new supply of feedstock material (e.g., ingots, scrap, or raw materials), or
A holding tank, transfer tank, dosing tank, or dosing furnace which is fed from a crucible or furnace, then transported to the die cast machine
The term “melt” is generally used as a noun, referring to the molten alloy of which the casting itself will be made.
In the molten state, amorphous alloys are generally reactive with air. The reaction products prevent the end casting products from achieving cosmetic finishes, and may degrade their mechanical properties as well. Thus, the systems embodied by these concepts ensure that from the time that the feedstock is melted, to the time that it has been injected and solidified in the mold cavity, it is never exposed to air, but rather exposed only to an inert environment. Exemplary inert environments include, but are not limited to, vacuum and argon gas.
Amorphous alloys in the molten state are also generally reactive with many other metals, including iron. The duration of exposure is a factor in the extent of reaction. Thus, in any area of the system in which the melt is in contact with an element of the system for more than a few seconds, that element should be made of a material that does not react with the melt. In general, certain ceramics are the best material choice for this purpose.
Ceramic components such as the feed tube(s) going from the crucible/hot tank to the shot chamber or valve, and the valve and valve bodies themselves, need to be heated as a minimum, above the solidus temperature of the alloy being cast. Induction heating will not work with ceramics, so the best method is believed to be resistive heating. Resistive heating may be used in conjunction with thermocouples in a feedback loop to achieve precise temperature control.
In the molten state, amorphous alloys exhibit fluid rheological properties that vary as a function of temperature. It is thus important to control the temperature of the melt being injected, at various locations throughout the system, by controlling the temperature of the surfaces with which the melt comes into contact. Controlling melt temperature thus is a method to prevent defects in the final casting product by preventing premature solidification, as well as ensuring that the mold cavity is able to completely fill before the melt solidifies. These concepts mention specific heating requirements that are unique to each concept. However, die heating and cooling are barely, if at all, mentioned in these concepts because, to some extent, they considered to be part of each concept. This statement applies to all concepts: The extent of die heating and cooling may vary depending on the efficiency of the various systems in delivering melt at the proper temperature and speed to the mold cavity. Dies, the mold cavity, and various components such as sprue bushings may be heated with fluids such as oil or heat transfer fluids, or with inductive or resistive electrical heating elements. Cooling may be accomplished with oils, water, or water-based heat transfer fluids. Depending on the needs at specific locations within the system, components may be continuously heated, continuously cooled, neither actively heated or cooled, or alternately heated and cooled with each cycle.
Each system is presumed to be capable of using recycled cast material with minimal reprocessing by feeding it into the crucible.
In some of these concepts, where a concept requires a pump in the hot chamber, EM pumps are cited as the preferred embodiment. However, in each case, the function of the pump is only to transfer the molten alloy to the PMV, shot sleeve, or mold cavity; the pump is not required to generate high pressure. (The fact that the final high pressure squeeze comes from another source is one reason that we think we can get away with old school, pump-in-hot-chamber technology with these high-melting temperature alloys.) We believe that EM pumps will work, or can be made to work with our alloys because they work with aluminum, and our liquidus temperatures aren't too higher than that of aluminum. However, if EM pumps won't work, ceramic centrifugal pumps or piston/sleeve submerged pumps, either made of ceramic materials, should work.
Definitions“Biscuit”—the portion of a casting that is where the melt first entered the mold cavity. The biscuit is waste material that is trimmed off the casting after its ejection from the mold cavity. The function of the biscuit is to serve as a sink for shrinkage in the critical areas of the casting, and to serve as a collector for gas bubbles and oxidized particulates that tend to be entrained in the last bit of melt to be injected into the die.
Feed tube—a tube connecting, and feeding melt between, a hot chamber an another element (e.g., a cold shot chamber).
Dies—two large plates that clamp together and provide the force required to constrain the pressurized melt during injection. Dies generally contain mold cavity inserts. Die casting machines generally have a moving, or ejector, die, and a stationary, or cover, die. The melt is generally first injected through the cover die. Dies must come together (close) to allow the melt to be injected into the mold cavity, and separate (open) to eject the solidified casting.
Mold cavity—the internal, formed surfaces within the dies that create the exterior surface of the finished casting itself. The mold cavity is generally constructed of mold inserts that are affixed to the dies, as well as various components such as cores and sliders that are used to create certain features.
Inert gas—a gas, or mixture of gases, that has little or no tendency to react chemically with the melt.
Cold chamber, or cold shot chamber—a piston-and-cylinder arrangement that injects melt into the mold cavity at high pressure. The cold chamber is generally maintained at a nominal temperature well below that of the melt itself.
Shot sleeve—the cylinder that houses the plunger. A shot sleeve generally has a fill port into which melt is poured. As the melt is rammed into the mold cavity by the plunger, the shot sleeve must withstand significant pressure.
Plunger—the piston in the shot sleeve.
Shot—a specific volume of melt that is injected into the mold cavity to form the casting.
Waterfalling—a condition in which melt flows down a surface, often leaving artifacts such as gas bubbles and solidification-induced particulates and layers in the casting.
“Advance”—movement of a plunger, pump, or melt itself that causes melt to progress toward the mold cavity
“Retract”—movement of a plunger, pump, or melt itself that causes melt to progress away from the mold cavity
“Metering”—pumping, or allow the transfer, of a predetermined volume of melt (a “shot”) that will completely fill the mold cavity with a calculated, small amount of excess
System Objectives:
Low melt fluid velocities (no turbulence)
No gas bubble entrapment in casting
No reaction of melt with air or container (hot chamber, pump, etc.) materials
“Cosmetic” finish on certain surfaces
Where the atmosphere in the mold cavity is inert gas, that gas may be used at roughly atmospheric pressure, or its pressure may be increased to provide “counter pressure”—that is, pressure greater than atmospheric pressure. One benefit of counter pressure is that it may be used to control the properties of the advancing front of melt. The tendency of the melt to “wet” the mold cavity surface is affected by counter pressure. Another benefit of counter pressure is that to the extent that there are any gas bubbles in the melt, counter pressure will compress those bubbles to a smaller size. Further, flow-induces effect such as cavitation, which can cause damage to the mold cavity surfaces and leave defects in the casting, are suppressed by counter pressure. Each concept disclosure has a table that identifies whether use of counter pressure is a viable option with the given configurations.
Galling is a severe form of wear, defined by the ASTM G40 standard—ASTM G40-99 and ASTM G40-15, both of which are incorporated herein in their entireties—as “a form of surface damage arising between sliding solids, distinguished by microscopic, usually localized, roughening and creation of protrusions (i.e., lumps) above the original surface.” As such, galling is a form of severe adhesive wear. Adhesive wear occurs between two metal surfaces that are in relative motion and under sufficient load to permit the transfer of material. This is a solid-phase welding process. The load must be sufficient, during relative motion, to disrupt the protective oxide layer covering surface asperities of the metal and permit metal to metal contact. Under high stress and poor lubrication conditions, stronger bonds may form over a larger surface area. Large fragments or surface protrusions may be formed and the result is galling of the surfaces. Severe galling can result in the seizure of metal components.
For mechanical equipment such as pumps, valves, bearings, seals, conveyors, and fasteners, in which mating metal surfaces rub together, consideration may also be given to wear and galling. Galling can occur when metal parts, such as the thread of nuts and bolts, are forced together and rubbing generates friction among the asperities on the surface. The friction causes heat, which is mainly isolated to these asperities. The asperities weld together but further displacement causes these tiny welds to break, which makes the surface even rougher, creating more opportunity for friction.
Galling is also a type of metal-to-metal contact wear that rips and tears out portions of metal surfaces. It is often caused by metal parts seizing together because of lack of lubrication. It usually occurs when the metals moving together are of the same hardness. Friction heat promotes this type of wear.
To prevent galling on sliding metal contact with itself or with other alloy materials, extra lubrication materials are conventionally used. These extra lubrication materials reduce the galling tendency and preventing seizure of metal due to galling. Finding the most effective material to withstand wear and galling, while meeting other property requirements, constitutes a worrisome problem for equipment engineers and manufacturers, especially when there is a risk of corrosion or there is need for sanitation as in food or pharmaceutical process, which precludes the use of lubricants. Not only does wear directly affect equipment life, but galling in a critical, part can shut down, or endanger an entire plant.
Numerous factors have been found to affect wear and galling of parts, including, but not limited to the following: material properties, hardness (wear volume is inversely proportional to the hardness of the surface being worn away, and that this hardness is not the bulk hardness measured before the wear process, but rather that attained at the wear interface during sliding), surface finish (generally the rougher the surface, the greater the wear; however, very smooth surfaces increase molecular interaction forces that promote cold welding and increase the strength of welds), microstructure (in contrast to the austenitic (fee) stainless steels, the hardenable martensitic (bct/bcc) stainless steels have better resistance to galling as a result of their hardnesses that can be in excess of 53 HRc, applied load, design, contact area, sliding distance, lubrication, and type of motion.
Coatings have been used in a variety of applications to improve service life and reduce needs for frequent inspections of wear in parts in vehicular and industrial applications. Among pre-existing low-friction coatings are nickel containing coatings, molybdenum containing coatings, and Inconel® type coatings. However, these preexisting coatings do not offer the wear resistance and friction characteristics desired for many applications.
Amorphous materials do not seize up like other materials and thus parts having such a coating will either not seize up or have reduced wear. Amorphous materials, because they do not have crystalline structure, do not work harden under high pressure. Rather it creates a smoother surface as atoms rearrange under pressure. As a result, amorphous materials in a solid or a coating form will not gall when parts are put into use.
Amorphous AlloysAn “alloy” may refer to a mixture, including a solid solution, of two or more metal elements—e.g., at least 2, 3, 4, 5, or more elements. The term “element” herein may refer to a chemical symbol that may be found in a Periodic Table. A “metal” may refer to any of alkali metals, alkaline earth metals, transition metals, post-transition metals, lanthanides, and actinides.
An amorphous alloy may refer to an alloy having an amorphous, non-crystalline atomic structure or microstructure. The amorphous structure may refer to a glassy structure with no observable long range order; in some instances, an amorphous structure may exhibit some short range order. Thus, an amorphous alloy may sometimes be referred to as a “metallic glass.” An amorphous alloy may refer to an alloy of which at least about 50% is an amorphous phase—e.g., at least about 60%, about 70%, about 80%, about 90%, about 95%, about 99% or more. The percentage herein may refer to volume percent or weight percent, depending on the context. The term “phase” herein may refer to a physically distinctive form of a substance, such as microstructure. For example, a solid and a liquid are different phases. Similarly, an amorphous phase is different from a crystalline phase.
Amorphous alloys may contain a variety of metal elements. In some embodiments, the amorphous alloys may comprise iron, chromium, silicon, boron, manganese, nickel, molybdenum, niobium, copper, cobalt, carbon, zirconium, titanium, beryllium, aluminum, gold, platinum, palladium, phosphorous, tungsten, yttrium, tantalum, or combinations thereof. In some embodiments, the amorphous alloys may be zirconium-based, titanium-based, iron-based, copper-based, nickel-based, gold-based, platinum-based, palladium-based, or aluminum-based. The term “M-based” when referring to an alloy may refer to an alloy comprising at least about 30% of the “M” element—e.g., about 40%, about 50%, about 60%, about 70%, about 80%, about 90%, about 95%, or more. The percentage herein may refer to volume percent or weight percent, depending on the context.
An amorphous alloy may be a bulk solidifying amorphous alloy. A bulk solidifying amorphous alloy, bulk metallic glass (“BMG”), or bulk amorphous alloy may refer to an amorphous alloy that may be adapted to have at least one dimension in the millimeter range. In one embodiment, this dimension may refer to the smallest dimension. Depending on the geometry, the dimension may refer to thickness, height, length, width, radius, and the like. In some embodiments, this smallest dimension may be at least about 0.5 mm—e.g., about 1 mm, about 2 mm, about 3 mm, about 4 mm, about 5 mm, about 6 mm, about 8 mm, about 10 mm, about 12 mm, or more. The magnitude of the largest dimension is not limited and may be in the millimeter range, centimeter range, or even meter range. Bulk-solidifying amorphous alloys, or bulk metallic glasses (“BMG”) may be solidified and cooled at relatively slow rates, and they retain the amorphous, non-crystalline (i.e., glassy) state at room temperature. Amorphous alloys have many superior properties than their crystalline counterparts. However, if the cooling rate is not sufficiently high, crystals may form inside the alloy during cooling, so that the benefits of the amorphous state can be lost. For example, one challenge with the fabrication of bulk amorphous alloy parts is partial crystallization of the parts due to either slow cooling or impurities in the raw alloy material. As a high degree of amorphicity (and, conversely, a low degree of crystallinity) is desirable in BMG parts, there is a need to develop methods for casting BMG parts having controlled amount of amorphicity.
An amorphous alloy, including a bulk amorphous alloy, described herein may have a critical cooling rate of about 500 K/sec or less. The term “critical cooling rate” herein may refer to the cooling rate below which an amorphous structure is not energetically favorable and thus is not likely to form during a fabrication process. In some embodiments, the critical cooling rate of the amorphous alloy may be, for example, about 400 K/sec or less—e.g., about 300 K/sec or less, about 250 K/sec or less, about 200 K/sec or less.
Even though there is no liquid/crystallization transformation for a bulk solidifying amorphous metal, a “melting temperature” Tm may be defined as the thermodynamic liquidus temperature of the corresponding crystalline phase. Under this regime, the viscosity of bulk-solidifying amorphous alloys at the melting temperature could lie in the range of about 0.1 poise to about 10,000 poise, and even sometimes under 0.01 poise. A lower viscosity at the “melting temperature” would provide faster and complete filling of intricate portions of the shell/mold with a bulk solidifying amorphous metal for forming the BMG parts. Furthermore, the cooling rate of the molten metal to form a BMG part has to such that the time-temperature profile during cooling does not traverse through the nose-shaped region bounding the crystallized region in the TTT diagram of
The supercooled liquid region, the temperature region between Tg and Tx is a manifestation of the extraordinary stability against crystallization of bulk solidification alloys. In this temperature region the bulk solidifying alloy can exist as a high viscous liquid. The viscosity of the bulk solidifying alloy in the supercooled liquid region can vary between 1012 Pa s at the glass transition temperature down to 105 Pa s at the crystallization temperature, the high temperature limit of the supercooled liquid region. Liquids with such viscosities can undergo substantial plastic strain under an applied pressure. The embodiments herein make use of the large plastic formability in the supercooled liquid region as a forming and separating method.
One needs to clarify something about Tx. Technically, the nose-shaped curve shown in the TTT diagram describes Tx as a function of temperature and time. Thus, regardless of the trajectory that one takes while heating or cooling a metal alloy, when one hits the TTT curve, one has reached Tx. In
The schematic TTT diagram of
Typical differential scanning calorimeter (DSC) heating curves of bulk-solidifying amorphous alloys taken at a heating rate of 20 C/min describe, for the most part, a particular trajectory across the TTT data where one would likely see a Tg at a certain temperature, a Tx when the DSC heating ramp crosses the TTT crystallization onset, and eventually melting peaks when the same trajectory crosses the temperature range for melting. If one heats a bulk-solidifying amorphous alloy at a rapid heating rate as shown by the ramp up portion of trajectories (2), (3) and (4) in
Phase
The term “phase” herein can refer to one that can be found in a thermodynamic phase diagram. A phase is a region of space (e.g., a thermodynamic system) throughout which all physical properties of a material are essentially uniform. Examples of physical properties include density, index of refraction, chemical composition and lattice periodicity. A simple description of a phase is a region of material that is chemically uniform, physically distinct, and/or mechanically separable. For example, in a system consisting of ice and water in a glass jar, the ice cubes are one phase, the water is a second phase, and the humid air over the water is a third phase. The glass of the jar is another separate phase. A phase can refer to a solid solution, which can be a binary, tertiary, quaternary, or more, solution, or a compound, such as an intermetallic compound. As another example, an amorphous phase is distinct from a crystalline phase.
Metal, Transition Metal, and Non-Metal
The term “metal” refers to an electropositive chemical element. The term “element” in this Specification refers generally to an element that can be found in a Periodic Table. Physically, a metal atom in the ground state contains a partially filled band with an empty state close to an occupied state. The term “transition metal” is any of the metallic elements within Groups 3 to 12 in the Periodic Table that have an incomplete inner electron shell and that serve as transitional links between the most and the least electropositive in a series of elements. Transition metals are characterized by multiple valences, colored compounds, and the ability to form stable complex ions. The term “nonmetal” refers to a chemical element that does not have the capacity to lose electrons and form a positive ion.
Depending on the application, any suitable nonmetal elements, or their combinations, can be used. The alloy (or “alloy composition”) can comprise multiple nonmetal elements, such as at least two, at least three, at least four, or more, nonmetal elements. A nonmetal element can be any element that is found in Groups 13-17 in the Periodic Table. For example, a nonmetal element can be any one of F, Cl, Br, I, At, O, S, Se, Te, Po, N, P, As, Sb, Bi, C, Si, Ge, Sn, Pb, and B. Occasionally, a nonmetal element can also refer to certain metalloids (e.g., B, Si, Ge, As, Sb, Te, and Po) in Groups 13-17. In one embodiment, the nonmetal elements can include B, Si, C, P, or combinations thereof. Accordingly, for example, the alloy can comprise a boride, a carbide, or both.
A transition metal element can be any of scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, mercury, rutherfordium, dubnium, seaborgium, bohrium, hassium, meitnerium, ununnilium, unununium, and ununbium. In one embodiment, a BMG containing a transition metal element can have at least one of Sc, Y, La, Ac, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Tc, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, and Hg. Depending on the application, any suitable transitional metal elements, or their combinations, can be used. The alloy composition can comprise multiple transitional metal elements, such as at least two, at least three, at least four, or more, transitional metal elements.
The presently described alloy or alloy “sample” or “specimen” alloy can have any shape or size. For example, the alloy can have a shape of a particulate, which can have a shape such as spherical, ellipsoid, wire-like, rod-like, sheet-like, flake-like, or an irregular shape. The particulate can have any size. For example, it can have an average diameter of between about 1 micron and about 100 microns, such as between about 5 microns and about 80 microns, such as between about 10 microns and about 60 microns, such as between about 15 microns and about 50 microns, such as between about 15 microns and about 45 microns, such as between about 20 microns and about 40 microns, such as between about 25 microns and about 35 microns. For example, in one embodiment, the average diameter of the particulate is between about 25 microns and about 44 microns. In some embodiments, smaller particulates, such as those in the nanometer range, or larger particulates, such as those bigger than 100 microns, can be used.
The alloy sample or specimen can also be of a much larger dimension. For example, it can be a bulk structural component, such as an ingot or even a portion of a structural component that has dimensions in the millimeter, centimeter, or meter range.
Solid Solution
The term “solid solution” refers to a solid form of a solution. The term “solution” refers to a mixture of two or more substances, which may be solids, liquids, gases, or a combination of these. The mixture can be homogeneous or heterogeneous. The term “mixture” is a composition of two or more substances that are combined with each other and are generally capable of being separated. Generally, the two or more substances are not chemically combined with each other.
Alloy
In some embodiments, the alloy composition described herein can be fully alloyed. In one embodiment, an “alloy” refers to a homogeneous mixture or solid solution of two or more metals, the atoms of one replacing or occupying interstitial positions between the atoms of the other; for example, brass is an alloy of zinc and copper. An alloy, in contrast to a composite, can refer to a partial or complete solid solution of one or more elements in a metal matrix, such as one or more compounds in a metallic matrix. The term alloy herein can refer to both a complete solid solution alloy that can give single solid phase microstructure and a partial solution that can give two or more phases. An alloy composition described herein can refer to one comprising an alloy or one comprising an alloy-containing composite.
Thus, a fully alloyed alloy can have a homogenous distribution of the constituents, be it a solid solution phase, a compound phase, or both. The term “fully alloyed” used herein can account for minor variations within the error tolerance. For example, it can refer to at least 90% alloyed, such as at least 95% alloyed, such as at least 99% alloyed, such as at least 99.5% alloyed, such as at least 99.9% alloyed. The percentage herein can refer to either volume percent or weight percentage, depending on the context. These percentages can be balanced by impurities, which can be in terms of composition or phases that are not a part of the alloy.
Amorphous or Non-Crystalline Solid
An “amorphous” or “non-crystalline solid” is a solid that lacks lattice periodicity, which is characteristic of a crystal. As used herein, an “amorphous solid” includes “glass” which is an amorphous solid that softens and transforms into a liquid-like state upon heating through the glass transition. Generally, amorphous materials lack the long-range order characteristic of a crystal, though they can possess some short-range order at the atomic length scale due to the nature of chemical bonding. The distinction between amorphous solids and crystalline solids can be made based on lattice periodicity as determined by structural characterization techniques such as x-ray diffraction and transmission electron microscopy.
The terms “order” and “disorder” designate the presence or absence of some symmetry or correlation in a many-particle system. The terms “long-range order” and “short-range order” distinguish order in materials based on length scales.
The strictest form of order in a solid is lattice periodicity: a certain pattern (the arrangement of atoms in a unit cell) is repeated again and again to form a translationally invariant tiling of space. This is the defining property of a crystal. Possible symmetries have been classified in 14 Bravais lattices and 230 space groups.
Lattice periodicity implies long-range order. If only one unit cell is known, then by virtue of the translational symmetry it is possible to accurately predict all atomic positions at arbitrary distances. The converse is generally true, except, for example, in quasi-crystals that have perfectly deterministic tilings but do not possess lattice periodicity.
Long-range order characterizes physical systems in which remote portions of the same sample exhibit correlated behavior. This can be expressed as a correlation function, namely the spin-spin correlation function: G(x,x′)=s(x),s(x′).
In the above function, s is the spin quantum number and x is the distance function within the particular system. This function is equal to unity when x=x′ and decreases as the distance |x−x′| increases. Typically, it decays exponentially to zero at large distances, and the system is considered to be disordered. If, however, the correlation function decays to a constant value at large |x−x′|, then the system can be said to possess long-range order. If it decays to zero as a power of the distance, then it can be called quasi-long-range order. Note that what constitutes a large value of |x−x′| is relative.
A system can be said to present quenched disorder when some parameters defining its behavior are random variables that do not evolve with time (i.e., they are quenched or frozen)—e.g., spin glasses. It is opposite to annealed disorder, where the random variables are allowed to evolve themselves. Embodiments herein include systems comprising quenched disorder.
The alloy described herein can be crystalline, partially crystalline, amorphous, or substantially amorphous. For example, the alloy sample/specimen can include at least some crystallinity, with grains/crystals having sizes in the nanometer and/or micrometer ranges. Alternatively, the alloy can be substantially amorphous, such as fully amorphous. In one embodiment, the alloy composition is at least substantially not amorphous, such as being substantially crystalline, such as being entirely crystalline.
In one embodiment, the presence of a crystal or a plurality of crystals in an otherwise amorphous alloy can be construed as a “crystalline phase” therein. The degree of crystallinity (or “crystallinity” for short in some embodiments) of an alloy can refer to the amount of the crystalline phase present in the alloy. The degree can refer to, for example, a fraction of crystals present in the alloy. The fraction can refer to volume fraction or weight fraction, depending on the context. A measure of how “amorphous” an amorphous alloy is can be amorphicity. Amorphicity can be measured in terms of a degree of crystallinity. For example, in one embodiment, an alloy having a low degree of crystallinity can be said to have a high degree of amorphicity. In one embodiment, for example, an alloy having 60 vol % crystalline phase can have a 40 vol % amorphous phase.
Amorphous Alloy or Amorphous Metal
An “amorphous alloy” is an alloy having an amorphous content of more than 50% by volume, preferably more than 90% by volume of amorphous content, more preferably more than 95% by volume of amorphous content, and most preferably more than 99% to almost 100% by volume of amorphous content. Note that, as described above, an alloy high in amorphicity is equivalently low in degree of crystallinity. An “amorphous metal” is an amorphous metal material with a disordered atomic-scale structure. In contrast to most metals, which are crystalline and therefore have a highly ordered arrangement of atoms, amorphous alloys are non-crystalline. Materials in which such a disordered structure is produced directly from the liquid state during cooling are sometimes referred to as “glasses.” Accordingly, amorphous metals are commonly referred to as “metallic glasses” or “glassy metals.” In one embodiment, a bulk metallic glass (“BMG”) can refer to an alloy, of which the microstructure is at least partially amorphous. However, there are several ways besides extremely rapid cooling to produce amorphous metals, including physical vapor deposition, solid-state reaction, ion irradiation, melt spinning, and mechanical alloying. Amorphous alloys can be a single class of materials, regardless of how they are prepared.
Amorphous metals can be produced through a variety of quick-cooling methods. For instance, amorphous metals can be produced by sputtering molten metal onto a spinning metal disk. The rapid cooling, on the order of millions of degrees a second, can be too fast for crystals to form, and the material is thus “locked in” a glassy state. Also, amorphous metals/alloys can be produced with critical cooling rates low enough to allow formation of amorphous structures in thick layers—e.g., bulk metallic glasses.
The terms “bulk metallic glass” (“BMG”), bulk amorphous alloy (“BAA”), and bulk solidifying amorphous alloy are used interchangeably herein. They refer to amorphous alloys having the smallest dimension at least in the millimeter range. For example, the dimension can be at least about 0.5 mm, such as at least about 1 mm, such as at least about 2 mm, such as at least about 4 mm, such as at least about 5 mm, such as at least about 6 mm, such as at least about 8 mm, such as at least about 10 mm, such as at least about 12 mm. Depending on the geometry, the dimension can refer to the diameter, radius, thickness, width, length, etc. A BMG can also be a metallic glass having at least one dimension in the centimeter range, such as at least about 1.0 cm, such as at least about 2.0 cm, such as at least about 5.0 cm, such as at least about 10.0 cm. In some embodiments, a BMG can have at least one dimension at least in the meter range. A BMG can take any of the shapes or forms described above, as related to a metallic glass. Accordingly, a BMG described herein in some embodiments can be different from a thin film made by a conventional deposition technique in one important aspect—the former can be of a much larger dimension than the latter.
Amorphous metals can be an alloy rather than a pure metal. The alloys may contain atoms of significantly different sizes, leading to low free volume (and therefore having viscosity up to orders of magnitude higher than other metals and alloys) in a molten state. The viscosity prevents the atoms from moving enough to form an ordered lattice. The material structure may result in low shrinkage during cooling and resistance to plastic deformation. The absence of grain boundaries, the weak spots of crystalline materials in some cases, may, for example, lead to better resistance to wear and corrosion. In one embodiment, amorphous metals, while technically glasses, may also be much tougher and less brittle than oxide glasses and ceramics.
Thermal conductivity of amorphous materials may be lower than that of their crystalline counterparts. To achieve formation of an amorphous structure even during slower cooling, the alloy may be made of three or more components, leading to complex crystal units with higher potential energy and lower probability of formation. The formation of amorphous alloy can depend on several factors: the composition of the components of the alloy; the atomic radius of the components (preferably with a significant difference of over 12% to achieve high packing density and low free volume); and the negative heat of mixing the combination of components, inhibiting crystal nucleation and prolonging the time the molten metal stays in a supercooled state. However, as the formation of an amorphous alloy is based on many different variables, it can be difficult to make a prior determination of whether an alloy composition would form an amorphous alloy.
Amorphous alloys, for example, of boron, silicon, phosphorus, and other glass formers with magnetic metals (iron, cobalt, nickel) may be magnetic, with low coercivity and high electrical resistance. The high resistance leads to low losses by eddy currents when subjected to alternating magnetic fields, a property useful, for example, as transformer magnetic cores.
Amorphous alloys may have a variety of potentially useful properties. In particular, they tend to be stronger than crystalline alloys of similar chemical composition, and they can sustain larger reversible (“elastic”) deformations than crystalline alloys. Amorphous metals derive their strength directly from their non-crystalline structure, which can have none of the defects (such as dislocations) that limit the strength of crystalline alloys. For example, one modern amorphous metal, known as Vitreloy™, has a tensile strength that is almost twice that of high-grade titanium. In some embodiments, metallic glasses at room temperature are not ductile and tend to fail suddenly when loaded in tension, which limits the material applicability in reliability-critical applications, as the impending failure is not evident. Therefore, to overcome this challenge, metal matrix composite materials having a metallic glass matrix containing dendritic particles or fibers of a ductile crystalline metal can be used. Alternatively, a BMG low in element(s) that tend to cause embitterment (e.g., Ni) can be used. For example, a Ni-free BMG can be used to improve the ductility of the BMG.
Another useful property of bulk amorphous alloys is that they can be true glasses; in other words, they can soften and flow upon heating. This can allow for easy processing, such as by injection molding, in much the same way as polymers. As a result, amorphous alloys can be used for making sports equipment, medical devices, electronic components and equipment, cutting tools, and thin films. Thin films of amorphous metals can be deposited as protective coatings via a high velocity oxygen fuel technique.
A material can have an amorphous phase, a crystalline phase, or both. The amorphous and crystalline phases can have the same chemical composition and differ only in the microstructure—i.e., one amorphous and the other crystalline. Microstructure in one embodiment refers to the structure of a material as revealed by a microscope at 25× magnification or higher. Alternatively, the two phases can have different chemical compositions and microstructures. For example, a composition can be partially amorphous, substantially amorphous, or completely amorphous.
As described above, the degree of amorphicity (and conversely the degree of crystallinity) can be measured by fraction of crystals present in the alloy. The degree can refer to volume fraction of weight fraction of the crystalline phase present in the alloy. A partially amorphous composition can refer to a composition of at least about 5 vol % of which is of an amorphous phase, such as at least about 10 vol %, such as at least about 20 vol %, such as at least about 40 vol %, such as at least about 60 vol %, such as at least about 80 vol %, such as at least about 90 vol %. The terms “substantially” and “about” have been defined elsewhere in this application. Accordingly, a composition that is at least substantially amorphous can refer to one of which at least about 90 vol % is amorphous, such as at least about 95 vol %, such as at least about 98 vol %, such as at least about 99 vol %, such as at least about 99.5 vol %, such as at least about 99.8 vol %, such as at least about 99.9 vol %. In one embodiment, a substantially amorphous composition can have some incidental, insignificant amount of crystalline phase present therein.
In one embodiment, an amorphous alloy composition can be homogeneous with respect to the amorphous phase. A substance that is uniform in composition is homogeneous. This is in contrast to a substance that is heterogeneous. The term “composition” refers to the chemical composition and/or microstructure in the substance. A substance is homogeneous when a volume of the substance is divided in half and both halves have substantially the same composition. For example, a particulate suspension is homogeneous when a volume of the particulate suspension is divided in half and both halves have substantially the same volume of particles. However, it might be possible to see the individual particles under a microscope. Another example of a homogeneous substance is air where different ingredients therein are equally suspended, though the particles, gases and liquids in air can be analyzed separately or separated from air.
A composition that is homogeneous with respect to an amorphous alloy can refer to one having an amorphous phase substantially uniformly distributed throughout its microstructure. In other words, the composition macroscopically comprises a substantially uniformly distributed amorphous alloy throughout the composition. In an alternative embodiment, the composition can be of a composite, having an amorphous phase having therein a non-amorphous phase. The non-amorphous phase can be a crystal or a plurality of crystals. The crystals can be in the form of particulates of any shape, such as spherical, ellipsoid, wire-like, rod-like, sheet-like, flake-like, or an irregular shape. In one embodiment, it can have a dendritic form. For example, an at least partially amorphous composite composition can have a crystalline phase in the shape of dendrites dispersed in an amorphous phase matrix; the dispersion can be uniform or non-uniform, and the amorphous phase and the crystalline phase can have the same or a different chemical composition. In one embodiment, they have substantially the same chemical composition. In another embodiment, the crystalline phase can be more ductile than the BMG phase.
The methods described herein can be applicable to any type of amorphous alloy. Similarly, the amorphous alloy described herein as a constituent of a composition or article can be of any type. The amorphous alloy can comprise the element Zr, Hf, Ti, Cu, Ni, Pt, Pd, Fe, Mg, Au, La, Ag, Al, Mo, Nb, Be, or combinations thereof. Namely, the alloy can include any combination of these elements in its chemical formula or chemical composition. The elements can be present at different weight or volume percentages. For example, an iron “based” alloy can refer to an alloy having a non-insignificant weight percentage of iron present therein, the weight percent can be, for example, at least about 20 wt %, such as at least about 40 wt %, such as at least about 50 wt %, such as at least about 60 wt %, such as at least about 80 wt %. Alternatively, in one embodiment, the above-described percentages can be volume percentages, instead of weight percentages. Accordingly, an amorphous alloy can be zirconium-based, titanium-based, platinum-based, palladium-based, gold-based, silver-based, copper-based, iron-based, nickel-based, aluminum-based, molybdenum-based, and the like. The alloy can also be free of any of the aforementioned elements to suit a particular purpose. For example, in some embodiments, the alloy, or the composition including the alloy, can be substantially free of nickel, aluminum, titanium, beryllium, or combinations thereof. In one embodiment, the alloy or the composite is completely free of nickel, aluminum, titanium, beryllium, or combinations thereof.
The amorphous alloy may have a variety of chemical compositions. In one embodiment, the amorphous alloy is a Zr-based alloy, such as a Zr—Ti based alloy, such as (Zr, Ti)a(Ni, Cu, Fe)b(Be, Al, Si, B)c, where each of a, b, and c is independently a number representing atomic % and a is in the range of from 30 to 75, b is in the range of from 5 to 60, and c in the range of from 0 to 50. Other incidental, inevitable minute amounts of impurities may also be present. In some embodiments, these alloys may accommodate substantial amounts of other transition metals, such as Nb, Cr, V, Co. A “substantial amount” in one embodiment may refer to about 5 atm % or more—e.g., 10 atm %, 20 atm %, 30 atm %, or more.
For example, the amorphous alloy can have the formula (Zr, Ti)a(Ni, Cu, Fe)b(Be, Al, Si, B)c, wherein a, b, and c each represents a weight or atomic percentage. In one embodiment, a is in the range of from 30 to 75, b is in the range of from 5 to 60, and c is in the range of from 0 to 50 in atomic percentages. Alternatively, the amorphous alloy can have the formula (Zr, Ti)a(Ni, Cu)b(Be)c, wherein a, b, and c each represents a weight or atomic percentage. In one embodiment, a is in the range of from 40 to 75, b is in the range of from 5 to 50, and c is in the range of from 5 to 50 in atomic percentages. The alloy can also have the formula (Zr, Ti)a(Ni, Cu)b(Be)C, wherein a, b, and c each represents a weight or atomic percentage. In one embodiment, a is in the range of from 45 to 65, b is in the range of from 7.5 to 35, and c is in the range of from 10 to 37.5 in atomic percentages. Alternatively, the alloy can have the formula (Zr)a(Nb, Ti)b(Ni, Cu)c(Al)d, wherein a, b, c, and d each represents a weight or atomic percentage. In one embodiment, a is in the range of from 45 to 65, b is in the range of from 0 to 10, c is in the range of from 20 to 40 and d is in the range of from 7.5 to 15 in atomic percentages. One exemplary embodiment of the aforedescribed alloy system is a Zr—Ti—Ni—Cu—Be based amorphous alloy under the trade name Vitreloy™, such as Vitreloy-1 and Vitreloy-101, as fabricated by Liquidmetal Technologies, CA, USA. Some examples of amorphous alloys of the different systems are provided in Table 1 and Table 2.
Other exemplary ferrous metal-based alloys include compositions such as those disclosed in U.S. Patent Application Publication Nos. 2007/0079907 and 2008/0118387. These compositions include the Fe(Mn, Co, Ni, Cu) (C, Si, B, P, Al) system, wherein the Fe content is from 60 to 75 atomic percentage, the total of (Mn, Co, Ni, Cu) is in the range of from 5 to 25 atomic percentage, and the total of (C, Si, B, P, Al) is in the range of from 8 to 20 atomic percentage, as well as the exemplary composition Fe48Cr15Mo14Y2C15B6. They also include the alloy systems described by Fe—Cr—Mo—(Y,Ln)-C—B, Co—Cr—Mo-Ln-C—B, Fe—Mn—Cr—Mo—(Y,Ln)-C—B, (Fe, Cr, Co)—(Mo,Mn)—(C,B)—Y, Fe—(Co,Ni)—(Zr,Nb,Ta)—(Mo,W)—B, Fe—(Al,Ga)—(P,C,B,Si,Ge), Fe—(Co, Cr,Mo,Ga,Sb)—P—B—C, (Fe, Co)—B—Si—Nb alloys, and Fe—(Cr—Mo)—(C,B)—Tm, where Ln denotes a lanthanide element and Tm denotes a transition metal element. Furthermore, the amorphous alloy can also be one of the exemplary compositions Fe80P12.5C5B2.5, Fe80P11C5B2.5Si1.5, Fe74.5Mo5.5P12.5C5B2.5, Fe74.5Mo5.5P11C5B2.5Si1.5, Fe70Mo5Ni5P12.5C5B2.5, Fe70Mo5Ni5P11C5B2.5Si1.5, Fe68Mo5Ni5Cr2P12.5C5B2.5, and Fe68Mo5Ni5Cr2P11C5B2.5Si1.5, described in U.S. Patent Application Publication No. 2010/0300148.
The amorphous alloys can also be ferrous alloys, such as (Fe, Ni, Co) based alloys. Examples of such compositions are disclosed in U.S. Pat. Nos. 6,325,868; 5,288,344; 5,368,659; 5,618,359; and U.S. Pat. No. 5,735,975, Inoue et al., Appl. Phys. Lett., Volume 71, p 464 (1997), Shen et al., Mater. Trans., JIM, Volume 42, p 2136 (2001), and Japanese Patent Application No. 200126277 (Pub. No. 2001303218 A). One exemplary composition is Fe72Al5Ga2P11C6B4. Another example is Fe72Al7Zr10Mo5W2B15. Another iron-based alloy system that can be used in the coating herein is disclosed in U.S. Patent Application Publication No. 2010/0084052, wherein the amorphous metal contains, for example, manganese (1 to 3 atomic %), yttrium (0.1 to 10 atomic %), and silicon (0.3 to 3.1 atomic %) in the range of composition given in parentheses; and that contains the following elements in the specified range of composition given in parentheses: chromium (15 to 20 atomic %), molybdenum (2 to 15 atomic %), tungsten (1 to 3 atomic %), boron (5 to 16 atomic %), carbon (3 to 16 atomic %), and the balance iron.
In another embodiment, the amorphous alloy may have the chemical formula (Zr)a(Nb, Ti)b(Ni, Cu)c(Al)d, where each of a, b, c, and d is independently a number representing atomic % and a is in the range of from 45 to 65, b is in the range of from 0 to 10, c is in the range of from 20 to 40, and d is in the range of from 7.5 to 15. Other incidental, inevitable minute amounts of impurities may also be present.
In some embodiments, the amorphous alloy may be a ferrous-metal based alloy, such as (Fe, Ni, Co) based compositions. Examples of such compositions are disclosed in U.S. Pat. No. 6,325,868 and in publications (A. Inoue et. al., Appl. Phys. Lett., Volume 71, p 464 (1997)), (Shen et, al., Mater. Trans., JIM, Volume 42, p 2136 (2001)), and Japanese patent application 2000126277 (Publ. #2001303218 A). For example, the alloy may be Fe72A15Ga2P11C6B4, or Fe72A17Zr10Mo5W2B15.
In some embodiments, the amorphous alloy may be at least one of Fe—Cr—B—Mo—C alloy, Ni—Cr—Si—B—Mo—Cu—Co alloy, Fe—Cr—B—Mn—Si alloy, Fe—Cr—B—Si alloy, Fe—Cr—B—Mn—Si—Cu—Ni—Mo alloy, Fe—Cr—B—Mn—Si—Ni alloy, Fe—Cr—Si—B—Mn—Ni—WC—TiC alloy, Fe—Cr—Si—Mn—C—Nd—Ti alloy, Fe—Cr—P—C alloy, Fe—Cr—Mo—P—C alloy, Fe—Cr—Mo—P—C—Ni alloy, Fe—P—C—B—Al alloy, Fe—Cr—Mo—B—C—Si—Ni—P alloy, Fe—Cr—Mo—B—C—Si—W—Ni alloy, Ni—Cr—Mo—B alloy, Fe—B—Si—Cr—Nb—W alloy, Fe—Cr—Mo—B—C—Y alloy, Fe—Cr—Mo—B—C—Y—Co alloy, Fe—Cr—Mo—W—Nb alloy, Fe—Cr—Mo—B—C—Si—W—Mn alloy, and Fe—Cr—Si—W—Nb alloy. In at least one embodiment, the amorphous alloy may be an Fe-based alloy or a Ni/Cr-based alloy. The term “M-based” when referring to an alloy may refer to an alloy comprising at least about 30% of the “M” element—e.g., about 40%, about 50%, about 60%, about 70%, about 80%, about 90%, about 95%, or more. The percentage herein may refer to volume percent or weight percent, depending on the context.
The aforedescribed amorphous alloy systems can further include additional elements, such as additional transition metal elements, including Nb, Cr, V, and Co. The additional elements can be present at less than or equal to about 30 wt %, such as less than or equal to about 20 wt %, such as less than or equal to about 10 wt %, such as less than or equal to about 5 wt %. In one embodiment, the additional, optional element is at least one of cobalt, manganese, zirconium, tantalum, niobium, tungsten, yttrium, titanium, vanadium and hafnium to form carbides and further improve wear and corrosion resistance. Further optional elements may include phosphorous, germanium and arsenic, totaling up to about 2%, and preferably less than 1%, to reduce melting point. Otherwise incidental impurities should be less than about 2% and preferably 0.5%.
In some embodiments, a composition having an amorphous alloy can include a small amount of impurities. The impurity elements can be intentionally added to modify the properties of the composition, such as improving the mechanical properties (e.g., hardness, strength, fracture mechanism, etc.) and/or improving the corrosion resistance. Alternatively, the impurities can be present as inevitable, incidental impurities, such as those obtained as a byproduct of processing and manufacturing. The impurities can be less than or equal to about 10 wt %, such as about 5 wt %, such as about 2 wt %, such as about 1 wt %, such as about 0.5 wt %, such as about 0.1 wt %. In some embodiments, these percentages can be volume percentages instead of weight percentages. In one embodiment, the alloy sample/composition consists essentially of the amorphous alloy (with only a small incidental amount of impurities). In another embodiment, the composition includes the amorphous alloy (with no observable trace of impurities).
In one embodiment, the final parts exceeded the critical casting thickness of the bulk solidifying amorphous alloys.
In embodiments herein, the existence of a supercooled liquid region in which the bulk-solidifying amorphous alloy can exist as a high viscous liquid allows for superplastic forming. Large plastic deformations can be obtained. The ability to undergo large plastic deformation in the supercooled liquid region is used for the forming and/or cutting process. As oppose to solids, the liquid bulk solidifying alloy deforms locally which drastically lowers the required energy for cutting and forming. The ease of cutting and forming depends on the temperature of the alloy, the mold, and the cutting tool. As higher is the temperature, the lower is the viscosity, and consequently easier is the cutting and forming.
Embodiments herein can utilize a thermoplastic-forming process with amorphous alloys carried out between Tg and Tx, for example. Herein, Tx and Tg are determined from standard DSC measurements at typical heating rates (e.g. 20° C./min) as the onset of crystallization temperature and the onset of glass transition temperature.
The amorphous alloy components can have the critical casting thickness and the final part can have thickness that is thicker than the critical casting thickness. Moreover, the time and temperature of the heating and shaping operation is selected such that the elastic strain limit of the amorphous alloy could be substantially preserved to be not less than 1.0%, and preferably not being less than 1.5%. In the context of the embodiments herein, temperatures around glass transition means the forming temperatures can be below glass transition, at or around glass transition, and above glass transition temperature, but preferably at temperatures below the crystallization temperature Tx. The cooling step is carried out at rates similar to the heating rates at the heating step, and preferably at rates greater than the heating rates at the heating step. The cooling step is also achieved preferably while the forming and shaping loads are still maintained.
Amorphous alloys, including bulk solidifying amorphous alloys, may have high strength and high hardness. The strength may refer to tensile or compressive strength, depending on the context. For example, Zr and Ti-based amorphous alloys may have tensile yield strengths of about 250 ksi or higher, hardness values of about 450 HV or higher, or both. In some embodiments, the tensile yield strength may be about 300 ksi or higher—e.g., at least about 400 ksi, about 500 ksi, about 600 ksi, about 800 ksi, or higher. In some embodiments, the hardness value may be at least about 500 HV—e.g., at least about 550 HV, about 600 HV, about 700 HV, about 800 HV, about 900 HV, about 1000 HV, or higher.
In one embodiment, Fe-based amorphous alloys, including the Fe-based bulk solidifying amorphous alloys, can have tensile yield strengths of about 500 ksi or higher and hardness values of about 1000 HV or higher. In some embodiments, the tensile yield strength may be about 550 ksi or higher—e.g., at least about 600 ksi, about 700 ksi, about 800 ksi, about 900 ksi, or higher. In some embodiments, the hardness value may be at least about 1000 HV—e.g., at least about 1100 HV, about 1200 HV, about 1400 HV, about 1500 HV, about 1600 HV, or higher.
As such, any of the aforedescribed amorphous alloys may have a desirable strength-to-weight ratio. Furthermore, amorphous alloys may exhibit good corrosion resistance and environmental durability. The corrosion herein may refer to chemical corrosion, stress corrosion, or a combination thereof.
The amorphous alloys, including bulk amorphous alloys, described herein may have a high elastic strain limit of at least about 0.5%, including at least about 1%, about 1.2%, about 1.5%, about 1.6%, about 1.8%, about 2%, or more—this value is much higher than any other metal alloy known to date.
In some embodiments, the amorphous alloys, including bulk amorphous alloys, may additionally comprise some crystalline materials, such as crystalline alloys. The crystalline material may have the same or different chemistry from the amorphous alloy. For example, in the case wherein the crystalline alloy and the amorphous alloy have the same chemical composition, they may differ from each other only with respect to the microstructure.
In some embodiments, crystalline precipitates in amorphous alloys may have an undesirable effect on the properties of amorphous alloys, especially on the toughness and strength of these alloys, and as such it is generally preferred to minimize the volume fraction of these precipitates. However, there may be cases in which ductile crystalline phases precipitate in-situ during the processing of amorphous alloys, which may be beneficial to the properties of amorphous alloys, especially to the toughness and ductility of the alloys. One exemplary case is disclosed in C. C. Hays et. al, Physical Review Letters, Vol. 84, p 2901, 2000. In at least one embodiment herein, the crystalline precipitates may comprise a metal or an alloy, wherein the alloy may have a composition that is the same as the composition of the amorphous alloy or a composition that is different from the composition of the amorphous alloy. Such amorphous alloys comprising these beneficial crystalline precipitates may be employed in at least one embodiment described herein.
Again, since amorphous materials do not seize up like other materials, parts or coatings containing amorphous materials will not gall when put into use.
Accordingly, it has been determined that contacted metal-to-metal layer of amorphous materials give vehicle and machine components that are exposed to high mechanical loads exceptionally good sliding properties coupled with excellent wear resistance. Piston rings, synchronizer rings, synchronizing assemblies, shift forks and other vehicle components are protected by amorphous containing coating to extend their life time with the combination of higher hardness, good scuffing resistance, and low friction coefficient of amorphous material.
Long wear life is desired if not required on hardened steel automotive parts assembly. Traditional nickel and molybdenum type thermal spray did not provide adequate performance or life in this service application. Applying wear resistant, low friction, anti-galling coating of amorphous containing alloy to those parts for long life and durability to withstand the demanding heavy load environment is thus disclosed herein in accordance with the described embodiments.
Successful enhancement of critical wear surface with lower friction coefficient from amorphous containing thermal spray coating has excellence bonding and a longer life than traditional nickel and molybdenum coatings. Longer life product to ensure reliable operation of automobile parts in demanding service environment that traditional, coating could not provide.
Thermal spray is one of the most versatile deposition processes for coating materials and its use for industrial applications has been greatly increased. There are several different processes for thermal spray coating deposition and mostly used are flame spray, electric arc wire spray, plasma spray and high velocity oxy-fuel spray process (HVOF). Thermal spraying is, in fact, a generic group of processes in which the coating material feedstock (wire/powder) is fed to a heating zone, where it becomes molten, and is then propelled to the surface to be coated. The goal of thermal sprayed amorphous containing coating is to extend the life of parts and thus save time, energy, and money.
Following are more detailed descriptions of various concepts related to, and embodiments of, an inventive metal-containing coating and methods of making and using the coating. It should be appreciated that various concepts introduced above and discussed in greater detail below may be implemented in any of numerous ways, as the disclosed concepts are not limited to any particular manner of implementation. Examples of specific implementations and applications are provided primarily for illustrative purposes.
One embodiment is related to a method of increasing galling resistance of a substrate that includes coating a material over at least a portion of a surface of a substrate, wherein the coating material includes an amorphous alloy. Another embodiment is related to an article including a substrate and a coating material disposed over at least a portion of a surface of the substrate. The coating material includes an amorphous alloy. It is an aspect of this disclosure to provide a method of increasing galling resistance of a substrate that includes coating a material over at least a portion of a surface of a substrate, wherein the coating material includes an amorphous alloy.
Coating MaterialThe coating materials described herein may be disposed over a substrate. One embodiment provides a coating material that comprises at least one amorphous alloy.
The amorphous alloy may be any of the amorphous alloys described herein. In at least one embodiment, the amorphous alloy may be a bulk amorphous alloy. In another embodiment, the amorphous alloy may not be a bulk amorphous alloy.
The coating material may further comprise a crystalline material. The crystalline material may be a crystalline alloy having the same or different chemical composition from the amorphous alloy. The crystalline material may have a melting temperature below the degradation temperature of the substrate material. The degradation temperature of a material herein may refer to a temperature when the material starts to exhibit changes in at least one property. For example, the degradation may be a melting temperature, glass transition temperature, crystallization temperature, or other temperatures, depending on the context and the material. In another embodiment, degradation may refer to a temperature at which the material begins to interact chemically with another material (e.g., chemical reaction).
In at least one embodiment, the crystalline material comprises crystal (or “grain”) sizes in the nanometer range, micron range, millimeter range, centimeter range, or any combinations thereof. For example, the crystalline material may comprise a nano-crystalline material. The crystalline material may comprise an alloy of the same composition as the amorphous alloy in the coating material, an alloy different from the amorphous alloy in the coating material, a metal, a non-metal, or any combinations thereof.
The substrate may comprise a metal and/or a metal alloy. In one embodiment, the substrate may comprise iron, aluminum, titanium, copper, cobalt, nickel, tungsten, or alloys thereof. In another embodiment, the substrate may comprise a steel material, an aluminum alloy, a titanium alloy, or any other suitable metal or alloy material. In one embodiment, the substrate may comprise an alloy selected from ASTM 5120, ASTM 8620, or ASTM A48. In another embodiment the substrate may comprise cast iron, carbon steel, or stainless steel. In another embodiment the substrate may be a portion of a component of a vehicle or machine where increased wear resistance or reduced friction is desired. In one embodiment, the substrate may be a portion of a vehicle or machine component. In at least some embodiments, a “vehicle” is a device for transporting people or things. In at least some embodiments, a “machine” is a device that transmits a force or directs its application. In one embodiment, a vehicle is a specific type of machine. For example, a vehicle may be an automotive, an aeronautical, a marine, or an aerospace machinery. Thus, in one embodiment, the substrate may be a portion of an automotive, aeronautical, marine, or aerospace vehicle component. In another embodiment, a machine has nothing to do with a vehicle. For example, the machine may refer to an industrial machine or a commercial machine. Thus, in one embodiment, the substrate may be a portion of an industrial machine component or a commercial machine component.
In one embodiment, the substrate may be a portion of a piston ring, a synchronizer ring, a synchronizing assembly, a shift fork, a differential shaft, a differential pin, a transaxle assembly, a fuel injector, a cam follower, a gear, a valve, a pump component, or a lathe bedway. In another embodiment, the substrate may be a portion of a vehicle component such as an automotive transmission component, an automotive engine component, or an automotive drivetrain component. In one embodiment the substrate may be a portion of a machine component subjected to fretting or sliding wear.
The coating material described herein may have a tensile stiffness of greater than about 50 GPa—e.g., greater than about 100 GPa, about 150 GPa, about 200 GPa, about 250 GPa, about 300 GPa, about 350 GPa, about 400 GPa, about 450 GPa, or more. In at least one embodiment, the tensile stiffness is in the range of about 100 to about 500 GPa—e.g., about 150 to about 450 GPa, about 200 to about 400 GPa or about 250 to about 350 GPa.
The coating material described herein may have a Vickers hardness of about 400 HV to about 1500 HV—e.g., about 450 HV to about 1450 HV, about 500 HV to about 1400 HV, about 550 HV to about 1350 HV, about 600 HV to about 1300 HV, about 650 HV to about 1250 HV, about 700 HV to about 1200 HV, about 750 HV to about 1150 HV, about 800 HV to about 1100 HV, about 850 HV to about 1050 HV, or about 900 HV to about 1000 HV. In one embodiment, the coating material exhibits a Vickers hardness of at least about 400 HV—e.g., at least about 425 HV, about 450 HV, about 475 HV, about 500 HV, about 525 HV, about 550 HV, about 575 HV, about 600 HV, about 625 HV, about 650 HV, about 675 HV, about 700 HV, about 725 HV, about 750 HV, about 775 HV, about 800 HV, about 825 HV, about 850 HV, about 875 HV, about 900 HV, about 925 HV, about 950 HV, about 975 HV, about 1000 HV, about 1025 HV, about 1050 HV, about 1075 HV, about 1100 HV, about 1125 HV, about 1150 HV, about 1175 HV, about 1200 HV, about 1225 HV, about 1250 HV, about 1275 HV, about 1300 HV, about 1325 HV, about 1350 HV, about 1375 HV, or more. In another embodiment, the coating material may have a Vickers hardness of about 400 HV to about 1400 HV.
The coating materials described herein may be resistant to corrosion. In one embodiment, the corrosion may refer to chemical corrosion, stress corrosion, or both. In another embodiment, the coating material may exhibit substantially no, or completely no, weight loss when exposed to various corrosive environments, including hydrochloric acid, sulfuric acid, hydrofluoric acid, and chlorine. According to one embodiment, the coating materials may exhibit substantially no corrosion when subjected to a salt spray test performed according to the ASTM B117 standard. In another embodiment, the coating materials are exhibited no corrosion when exposed to solutions of nitric acid and hydrogen chloride or by solutions of ferric chloride and hydrogen chloride.
The coating materials described herein may be resistant to wear. The wear resistance may be related to the hardness of the material, with wear resistance increasing as hardness increases. In at least one embodiment, the wear resistance is at least about twice as high—e.g., at least about three times as high, about four times as high, or about five times as high, or more, as the wear resistance of a coating material that does not comprise an amorphous alloy. In one embodiment, the coating material may have a wear resistance measured as volume loss according to the ASTM G65 standard of less than or equal to about 50 mm3—e.g., less than about 45 mm3, about 40 mm3, about 35 mm3, about 30 mm3, about 25 mm3, about 20 mm3, about 15 mm3, about 10 mm3, about 7.5 mm3, about 5 mm3, or less. In another embodiment, the coating material may have a wear resistance measured as volume loss according to the ASTM G65 standard of about 5 mm3 to about 50 mm3—e.g., about 7.5 mm3 to about 45 mm3, about 10 mm3 to about 40 mm3, about 15 mm3 to about 35 mm3, or about 20 mm3 to about 30 mm3.
The coating materials described herein may be resistant to galling. In one embodiment, galling refers to a form of adhesive wear that occurs between metal surfaces that are in relative motion and under sufficient load to permit the transfer of material. Again, the ASTM G40 standard (the previously incorporated ASTM G40-99, ASTM G40-15 standards) defines galling as “a form of surface damage arising between sliding solids distinguished by microscopic, usually localized, roughening and creation of protrusions (i.e., lumps) above the original surface.” Galling may be the result of a heat increase resulting from friction between asperities of metal surfaces. The friction-created heat may be isolated to the asperities, causing the asperities to weld together. Continued relative motion may break the welds between the asperities, producing additional surface roughness and opportunity for friction-created heat. In some cases, large surface protrusions, surface fragmentation or even seizure of the metal surfaces may result. Galling may result when the load applied to the metal surfaces is sufficient to disrupt an oxide layer present on the metal surfaces, allowing direct metal-to-metal contact. Metal contact surfaces with substantially the same, or the same, hardness are especially susceptible to galling.
ASTM G 98-02 standard, which is hereby incorporated by reference in its entirety herein, describes the standard test method for galling resistance of materials. The coating materials used herein are capable of withstanding testing according to the ASTM G 98-02 standard (e.g. see
The galling resistance of the coating materials described herein may be related to the hardness of the coating material. In one embodiment, the hardness of the coating material is significantly higher than an opposing metal surface and provides a galling resistance that is significantly higher than materials that do not comprise an amorphous alloy. In another embodiment, the coating material undergoes substantially no galling, or completely no galling, throughout the lifetime of the component. As utilized herein the “lifetime” of a component is the duration of time in which the component is useful for its intended purpose. According to one embodiment, the coating material is resistant to galling even in the absence of additional lubricants. The amorphous structure of the coating materials may allow the surface of the coating to rearrange under load and produce a smoother surface. In contrast to the behavior of crystalline materials, the amorphous alloy containing coating material according to one embodiment does not work harden under high pressure use. For example, one example of component subject to high pressure use or high pressure loading is an automobile transmission shift fork. A shift fork is typically a “U” shaped piece of steel that engages slider gears and pushes them into positions desired by the driver to create the intended gear. The normal position for each slider is free wheeling, or neutral. When a gear is desired, first the driver moves the lever to a range position (such as 1&2, or 3&4) and then by moving the shift lever forward or rearward the driver causes the chosen fork to push the slider so that it locks the intended gear to the shaft. Over time, the fork wears both from use, and occasionally from a driver's habit of continually leaning their hand on the shift lever. This is one reason why it is common to see a particular transmission lose certain gears. Many transmissions lose the second or third gear before they lose any other.
The galling resistance of the coating material may also be a product of the low coefficient of friction of the amorphous alloy in the coating material. The low coefficient of friction helps prevent the surface of the coating material from reaching a specific temperature, such as the melting temperature of the surface, at which galling will occur during use even in the absence of lubricants.
Additionally, the low heat conductivity of the amorphous alloy in the coating material may minimize transfer of the heat produced (e.g., during operation of a device).
The high crystallization temperature of the amorphous alloy in the coating material may prevent crystallization of the coating material that typically occurs as a result of frictional heat produced during operation, thus preserving the anti-galling effect of the coating material.
The articles containing the coating materials described herein may exhibit increased useful lifetimes. In one embodiment, the article containing the coating material may exhibit a useful lifetime increase that is about 10% greater. In another embodiment, the lifetime of the part is increased about 25%. In another embodiment, the lifetime is increased at least about 50%—e.g., at least about 55%, about 60%, about 65%, about 70%, about 75%, about 80%, about 85%, about 90%, about 95%, about 100%, about 125%, about 150%, about 175%, about 200%, about 225%, about 250%, about 275%, about 300%, or more. The increase in useful lifetime of the article may be in comparison to the substrate in the absence of the coating material. In another embodiment, the increase in useful lifetime of the article may be in comparison to the substrate with a pre-existing coating that does not comprise an amorphous alloy.
The coating materials described herein may have a friction coefficient of less than or equal to about 0.1—e.g., less than about 0.095, about 0.09, about 0.085, about 0.08, about 0.075, about 0.07, about 0.065, about 0.06, about 0.055, about 0.05, or less. In at least one embodiment the coating material has a friction coefficient of about 0.05. In one embodiment the coating material may exhibit improved sliding properties in comparison to materials that do not comprise an amorphous alloy. In another embodiment, the coating material may exhibit improved fretting wear resistance in comparison to materials that do not comprise an amorphous alloy. According to one embodiment, the low friction coefficient of the coating material may reduce the energy required to operate the machine or vehicle containing the substrate upon which it is disposed.
The coating materials described herein may be resistant to temperature induced degradation at temperatures up to about 350° C.—e.g., up to about 375° C., about 400° C., about 425° C., about 450° C., about 475° C., about 500° C., about 525° C., about 550° C., about 575° C., about 600° C., about 625° C., about 650° C., about 675° C., about 700° C., about 725° C., about 750° C., about 775° C., about 800° C., about 825° C., about 850° C., about 875° C., about 900° C., about 925° C., about 950° C., about 975° C., about 1000° C., or higher. In one embodiment the coating material experiences substantially no, or completely no temperature induced degradation at temperatures of up to about 350° C.—e.g., up to about 375° C., about 400° C., about 425° C., about 450° C., about 475° C., about 500° C., about 525° C., about 550° C., about 575° C., about 600° C., about 625° C., about 650° C., about 675° C., about 700° C., about 725° C., about 750° C., about 775° C., about 800° C., about 825° C., about 850° C., about 875° C., about 900° C., about 925° C., about 950° C., about 975° C., about 1000° C., or higher. The temperature induced degradation of the coating material may refer to a temperature induced change in at least one property of the coating material. In another embodiment, temperature induced degradation may refer to a chemical interaction between the coating material and another material (e.g., chemical reaction).
The coating materials described herein may have a crystallization temperature (Tx) of at least about 600° C.—e.g., at least about 625° C., about 650° C., about 675° C., about 700° C., about 725° C., about 750° C., about 775° C., about 800° C., about 825° C., about 850° C., about 875° C., about 900° C., about 925° C., about 950° C., about 975° C., about 1000° C., or more. The crystallization temperature may be dependent on the composition of the coating layer.
The coating material may be in the form of a layer disposed over a substrate. In one embodiment, the coating material layer has a thickness of at least about 50 microns—e.g., at least about 75 microns, about 100 microns, about 200 microns, about 300 microns, about 400 microns, about 500 microns, about 600 microns, about 700 microns, about 800 microns, about 900 microns, about 1000 microns, or more. In at least one embodiment, the coating material layer has a thickness from about 50 microns to about 1000 microns—e.g., about 75 microns to about 900 microns, about 100 microns to about 800 microns, about 200 microns to about 700 microns, about 300 microns to about 600 microns, about 400 microns to about 500 microns, etc.
The coating material may exhibit improved properties when compared to coating materials that do not comprise an amorphous alloy. In one embodiment, the coating material may exhibit improved hardness and wear resistance. In another embodiment, the coating material may exhibit a decreased friction coefficient. In one embodiment, the coating material may exhibit improved galling resistance or scuffing resistance.
Method of Producing a Coating MaterialProvided in some embodiments herein are methods of producing any of the coatings described above. The following description applies to at least some embodiments of the method of producing a coating material described herein.
In one embodiment, the coating material may be formed over a substrate using a feedstock material. The coating material may comprise an amorphous alloy, and the feedstock material may be adapted to form the amorphous alloy.
During the forming process, the feedstock material may be at a first temperature. The first temperature may depend on the amorphous alloy contained in the coating material. The composition of the amorphous alloy may affect the Tg, crystallization temperature (Tx), and the melting temperature (Tm). The Tg may be lower than Tx, and Tx may be lower than Tm in at least one embodiment.
In one embodiment the first temperature is higher than or equal to the Tg of the amorphous alloy. This embodiment comprises temperatures in the range of about 100° C. to about 1500° C.—e.g., about 100° C. to about 1000° C., about 100° C. to about 900° C., about 100° C. to about 800° C., or about 100° C. to about 700° C. In at least one embodiment the first temperature is at least about 100° C.—e.g., at least about 150° C., about 200° C., about 250° C., about 300° C., about 350° C., about 400° C., about 450° C., about 500° C., about 550° C., about 600° C., about 650° C., about 700° C., or higher. In at least one embodiment, the first temperature is higher than the Tg of the amorphous alloy. For example, the first temperature in at least one embodiment is at least about 0.5° C. higher than the Tg of the amorphous alloy—e.g., at least about 1° C., 2° C., about 3° C., about 4° C., about 5° C., about 10° C., about 15° C., about 20° C., or higher.
The Tg of the amorphous alloy may be in the range of about 100° C. for gold based amorphous alloys, and up to about 700° C. for iron or refractory based amorphous alloys. For zirconium and titanium based amorphous alloy systems the Tg may be in the range of about 300° C. to about 450° C. Depending on the composition of the amorphous alloy, Tg may vary.
In one embodiment, the first temperature is higher than or equal to the Tg of the amorphous alloy, and lower than the degradation temperature of the substrate material. The degradation temperature of the substrate material may be the temperature at which the substrate material begins to react (e.g., chemically react) with the coating material, or in one embodiment may be the melting temperature of the substrate material. In at least one embodiment, utilizing a first temperature lower than the degradation temperature of the substrate material may prevent or reduce undesired chemical reactions between the coating material and the substrate material.
In another embodiment, the first temperature is higher than or equal to the Tg of the amorphous alloy, and lower than the Tx of the amorphous alloy. This embodiment provides at least the advantage of minimizing formation of a crystalline material while allowing the amorphous alloy to flow in a viscous manner during the forming process.
The Tx of the amorphous alloy may be in the range of about 120° C. for gold based amorphous alloys, and up to about 750° C. or 800° C. for iron or refractory based amorphous alloys. For zirconium and titanium based amorphous alloy systems the Tx may be in the range of about 350° C. to about 500° C. Depending on the composition of the amorphous alloy, Tx may vary.
In one embodiment, the first temperature is higher than or equal to the Tx of the amorphous alloy, and lower than the Tm of the amorphous alloy. In this embodiment, it may be important to cool the amorphous alloy at a rate sufficient to form an alloy that is at least partially amorphous. For example, the cooling rate may be at or greater than the critical cooling rate of the amorphous alloy. In one embodiment, the cooling rate is sufficient to produce an alloy consisting at least essentially of an amorphous alloy. The cooling rate may be achieved by employing compressed gas or air blowing, a water bath, a liquid solution bath, a heat sink, a chilling device, or combinations thereof. Active cooling processes may not be needed if a bulk solidifying amorphous alloy is utilized in this embodiment. The first temperature in at least one embodiment is at least about 1° C. higher than the Tx of the amorphous alloy—e.g., at least about 5° C., about 10° C., about 15° C., about 20° C., about 25° C., about 30° C., about 35° C., or higher.
The Tm of the amorphous alloy may be in the range of about 200° C. for gold based amorphous alloys, up to about 1500° C. for iron or refractory based amorphous alloys. For zirconium and titanium based amorphous alloy systems the Tm may be in the range of about 650° C. to about 900° C. Depending on the composition, Tm may vary.
In one embodiment the first temperature is higher than or equal to the Tm of the amorphous alloy. In this embodiment it may be important to cool the amorphous alloy at a rate sufficient to form an alloy that is at least partially amorphous. In one embodiment, the process is sufficiently fast to avoid crystallization. Such a phenomenon may be captured by having a cooling rate sufficiently fast to bypass the crystallization curve of a time-temperature transformation (TTT) diagram of the alloy. In one embodiment, the cooling rate is sufficient to produce an alloy consisting at least essentially of an amorphous alloy. The cooling rate may be achieved by employing compressed gas or air blowing, a water bath, a liquid solution bath, a heat sink or a chilling device. Active cooling processes may not be needed if a bulk solidifying amorphous alloy is utilized in this embodiment. The first temperature in at least one embodiment is at least about 1° C. higher than the Tm of the amorphous alloy—e.g., at least about 5° C., about 10° C., about 15° C., about 20° C., about 25° C., about 30° C., about 35° C., or higher.
In another embodiment, the first temperature is maintained for the minimum amount of time needed for the forming of coating material to occur. Longer times may also be employed. In at least one embodiment, minimizing the time in which the feedstock material is at or above the first temperature may prevent or reduce chemical reactions between the coating material and substrate material. Further, such an approach may prevent the degradation of the substrate material. The first temperature may be maintained for a time that will ensure no (or substantially no) crystalline materials are formed in the amorphous alloy material. For example, the first temperature may be maintained for a time that will not intersect with the crystallization curve on the relevant Time-Temperature Transformation diagram.
The feedstock material may comprise an amorphous alloy. In one embodiment, the feedstock material consists essentially of an amorphous alloy. In another embodiment, the feedstock material consists of an amorphous alloy. In yet another embodiment, the feedstock material is substantially free of an amorphous alloy.
The feedstock material may comprise any material suitable to form a coating material comprising an amorphous alloy as a result of the forming process. In one embodiment, the feedstock material may comprise iron, chromium, silicon, boron, manganese, nickel, molybdenum, niobium, copper, cobalt, carbon, zirconium, titanium, beryllium, aluminum, gold, platinum, palladium, phosphorous, tungsten, yttrium, tantalum, or combinations thereof. In another embodiment, the feedstock material may comprise a crystalline material. In yet another embodiment, the feedstock material may comprise an amorphous alloy. In one embodiment, the feedstock material may be a bulk metallic glass.
In one embodiment the feedstock material may be in any form suitable for use in the forming process—e.g., a powder or a wire. In one embodiment, the feedstock material may further comprise any suitable carrier material.
The feedstock material may be formed by mixing a plurality of materials together. In one embodiment, multiple feedstock materials may be mixed during the forming process to form the coating material containing an amorphous alloy.
The forming process may be any process that produces a coating material comprising an amorphous alloy disposed over the substrate. In one embodiment, the forming process may be a thermal spray process. The thermal spray process may be at least one of Twin-Wire Arc Spraying (TWAS), High Velocity Oxy-Fuel (HVOF) spraying, High Velocity Air Fuel (HVAF) spraying, flame spraying, electric arc wire spraying, high velocity air-fuel spraying, and plasma spraying. In one embodiment the forming process may be a cold spraying process. In another embodiment, the forming process may be a welding process. The welding process may be at least one of Metal Inert Gas (MIG) welding and Tungsten Inert Gas (TIG) welding. In one embodiment, the forming process may be a cladding process. The cladding process may be at least one of laser cladding and electron beam.
The production of the coating material may comprise a heating step. In one embodiment, the feedstock material may be heated before or during the forming process. In one embodiment, the first material is heated to the first temperature before the forming process.
The forming process may produce a layer of the coating material disposed on the substrate. The coating material layer has a thickness of at least about 50 microns—e.g., at least about 75 microns, about 100 microns, about 150 microns, about 200 microns, about 250 microns, about 300 microns, about 350 microns, about 400 microns, about 450 microns, about 500 microns, about 550 microns, about 600 microns, about 650 microns, about 700 microns, about 750 microns, about 800 microns, about 850 microns, about 900 microns, about 950 microns, about 1000 microns, about 2 microns, about 5 microns, or higher. In at least one embodiment, the coating material layer has a thickness from about 50 microns to about 1 cm—e.g., about 100 microns to about 5 mm, about 200 microns to about 1 mm, about 300 microns to about 900 microns, about 400 microns to about 800 microns, or about 500 microns to about 700 microns.
The forming process may be conducted in air, an ambient atmosphere, a controlled gas atmosphere, an inert gas atmosphere, a pressurized atmosphere, or a vacuum.
A property is considered to be improved when in comparison to another material the property is more desirable for any given application. For example, in the case of tensile strength, improvement may refer to an increase in magnitude.
NON-LIMITING WORKING EXAMPLESThe following non-limiting examples were produced and analyzed.
Example 1A coating material comprising amorphous alloy A was formed over an aluminum alloy substrate by a HVOF thermal spraying process. The amorphous alloy A was an Fe-based alloy, and was formed from a feedstock material with the same composition. The feedstock material was fully amorphous, and the coating material was also fully amorphous. The feedstock material was in powder form. The coating material formed a layer on the substrate with a thickness of about 350 microns to about 750 microns.
As shown in
A coating material B, was formed over an aluminum alloy substrate by a HVOF thermal spraying process. The coating material B was an Fe-based alloy, and was formed from a feedstock material with the same chemical composition. The feedstock material was almost fully crystalline, and the coating material B formed therefrom comprised both an amorphous alloy and crystalline phases. The feedstock material was in powder form. The coating material formed a layer on the substrate with a thickness of about 350 microns to about 750 microns.
As shown in
A coating material was immersed in a 95 to 98 w % H2SO4 solution for two minutes. A micrograph of the surface of a pre-existing coating material is depicted in
A coating material was immersed in a H2SO4 solution, and micrographs of cross-sections of the material were taken after two minutes and after five minutes of exposure.
A coating material was immersed in a solution of 2.5% HF, 1.25% HCl, 1.25% HNO3, and 95% H2O for a period of twenty minutes. A micrograph of the surface of a pre-existing coating material before exposure is depicted in
A coating material was immersed in a solution of 2.5% HF, 1.25% HCl, 1.25% HNO3, and 95% H2O, and micrographs of cross-sections of the material were taken before exposure and after twenty minutes of exposure. A micrograph of a cross-section of a pre-existing coating material before exposure is depicted in
An Fe-based amorphous alloy containing coating material was immersed in a saltwater solution as shown in
The appearance of the coating material after 1, 2, 3, and 4 days of exposure is depicted in
The weight loss of the samples of the coating material were measured at the conclusion of the saltwater immersion test, as reported in the table below.
An Fe-based amorphous alloy containing coating material was immersed in a zinc solution at a temperature of 480° C.
Accordingly, as should be understood by the description, Figures, and examples, sliding metal-to-metal surface which is coated with an amorphous alloy (or formed of an amorphous alloy) will not be marred or scored by any of the debris as the debris will, in all instances, be softer than the amorphous alloy surface. However, it is necessary to minimize the debris between the contacted metal-to-metal surfaces as such debris would tend to increase the frictional drag which may cause sufficient heat to be generated that would exceed the crystalization temperature of the amorphous alloy. Therefore, in both configurations, structure is provided to accommodate and remove from continuous recirculation, the debris from between the contacted metal-to-metal surfaces.
Depending upon the fabrication technique, a particular alloy may be entirely amorphous or only partly amorphous. It is understood that both fully and partially amorphous materials are within the scope of the present disclosure. In one embodiment, the hardness of amorphous portion exceeds about 1000 VHN and crystallization temperature exceeds 600 C. Amorphous materials having hardness greater than about 1000 VEIN and a crystallization temperature in excess of 600 combination, provides a wear resistance significantly greater than that of other lower VHN amorphous materials and of commonly used non-amorphous materials. Such amorphous materials are fabricable into surface-protective materials with good strength, ductility, and corrosion resistance. Further such material has a sufficiently low coefficient of friction and elevated crystallization temperature that heat developed in contacted metal-to-metal surface is insufficient to initiate galling.
It is noted that any and all noted ASTM standards in the description above are hereby incorporated by reference in their entireties herein.
While the principles of the disclosure have been made clear in the illustrative embodiments set forth above, it will be apparent to those skilled in the art that various modifications may be made to the structure, arrangement, proportion, elements, materials, and components used in the practice of the disclosure.
It will thus be seen that the features of this disclosure have been fully and effectively accomplished. It will be realized, however, that the foregoing preferred specific embodiments have been shown and described for the purpose of illustrating the functional and structural principles of this disclosure and are subject to change without departure from such principles. Therefore, this disclosure includes all modifications encompassed within the spirit and scope of the following claims.
Claims
1. A method of increasing galling resistance of a substrate comprising coating a material over at least a portion of a surface of a substrate, wherein the coating material comprises an amorphous alloy.
2. The method according to claim 1, wherein the coating material withstands testing according to the ASTM G 98-02 standard.
3. The method according to claim 1, wherein the coating is performed using a thermal spray process.
4. The method according to claim 1, wherein the coating comprises utilizing at least one of: a flame spray, electric arc wire spray, plasma spray, high velocity oxy-fuel spray, high-velocity air-fuel spray, cold spray, welding, or a cladding deposition process.
5. The method according to claim 1, wherein the substrate is a vehicle component or a machine component.
6. The method according to claim 1, wherein the substrate is at least a part of a piston ring, a synchronizer ring, a synchronizing assembly, a shift fork, a differential shaft, a differential pin, a transaxle assembly, a differential assembly, a fuel injector, a cam follower, a gear, a valve, a pump component, and a lathe bedway.
7. The method according to claim 1, wherein the material is applied in the form of a layer over the surface of the substrate, and wherein the layer has a thickness of between about 50 microns and about 1000 microns.
8. The method according to claim 1, wherein the material has a friction coefficient of about 0.1 or less.
9. The method according to claim 1, wherein the material has a wear resistance characterized by a volume loss of less than about 10 mm3.
10. The method according to claim 1, wherein the material is resistant to temperature induced degradation at temperatures up to about 1000° C.
11. The method according to claim 1, wherein the material has a hardness of between about 600 HV and about 1500 HV.
12. The method according to claim 1, wherein the material has a hardness of greater than about 1000 HV and a crystallization temperature of greater than about 600° C.
13. The method according to claim 1, wherein the substrate exhibits improved galling resistance when compared to another component in the absence of the coating material.
14. The method according to claim 1, wherein the substrate exhibits improved sliding properties when compared to another component in the absence of the coating material.
15. An article comprising:
- a substrate, and
- a coating material disposed over at least a portion of a surface of the substrate;
- wherein the coating material comprises an amorphous alloy.
16. The article according to claim 15, wherein the coating material withstands testing according to the ASTM G 98-02 standard.
17. The article according to claim 15, wherein the substrate is a vehicle or machine component.
18. The article according to claim 15, wherein the substrate is at least a part of a piston ring, a synchronizer ring, a synchronizing assembly, a shift fork, a differential shaft, a differential pin, a transaxle assembly, a differential assembly, a fuel injector, a cam follower, a gear, a valve, a pump component, and a lathe bedway.
19. The article according to claim 15, wherein the coating material is in the form of a layer over the substrate, and wherein the layer has a thickness of between about 50 microns and about 1000 microns.
20. The article according to claim 15, wherein the coating material has a friction coefficient of about 0.1 or less.
21. The article according to claim 15, wherein the coating material has a wear resistance characterized by a volume loss of less than about 10 mm3.
22. The article according to claim 15, wherein the coating material is resistant to temperature induced degradation at temperatures up to about 1000° C.
23. The article according to claim 15, wherein the coating material has a hardness of between about 600 HV and about 1500 HV.
24. The article according to claim 15, wherein the coating material has a hardness of greater than about 1000 HV and a crystallization temperature of greater than about 600° C.
25. The article according to claim 15, wherein the article exhibits improved galling resistance when compared to another component in the absence of the coating material.
26. The article according to claim 15, wherein the article exhibits improved sliding properties when compared to another component in the absence of the coating material.
Type: Application
Filed: Oct 6, 2017
Publication Date: Feb 20, 2020
Inventors: Choongnyun Paul KIM (Lake Forest, CA), Lance UNDERWOOD (Lake Forest, CA), John KANG (Lake Forest, CA)
Application Number: 16/339,822
