Abstract: Multi-layer corrosion resistant polymer composite coatings are described wherein a first coating layer is applied by high velocity high temperature spray, thermal spray, plasma spray, fluidized bed, hot melt or electrostatic spray onto an unprepared, particle embedded or alternatively prepared substrate, and the outer surface of the still warm first layer is roughened by embedding particles therein or the outer surface is roughened mechanically, and a second coating layer is applied thereover. Filler powder may be added to one or both of the layers to substantially match the thermal expansion coefficients of the two layers.

Abstract: A method of coating an inner surface of a weapon barrel includes the following steps: introducing a plasma burner into the weapon barrel; producing a plasma flame by the plasma burner; directing the plasma flame against the inner barrel surface to cause impingement thereon; introducing a coating material in powder, wire or ribbon form into the plasma flame for melting the coating material to form a molten liquid and for depositing the molten liquid by the plasma flame on the inner barrel surface; and moving the plasma burner inside the weapon barrel axially thereof and relative thereto while performing the depositing step for obtaining a surface coating on the inner barrel surface.

Abstract: A radial bearing and method for making the same are disclosed. Radial bearings are typically used control the direction of drilling in directional drilling operations. The cuttings flow across the surfaces of the bearings before being removed from the well. The cuttings will contain sand and other hard and/or corrosive substances that will erode the surfaces of the bearings and shorten their useful life. The bearing of this invention is provided with a wear resistant surface to inhibit such erosion. The bearing is made from a bearing blank to which is applied a first overlay of mild steel with dispersed cemented metal carbide pellets. The composition of the cemented metal carbide pellets is disclosed. The first overlay may be applied by any conventional technique. A second overlay of mild steel is applied to the first overlay utilizing a MIG welding process. As the second overlay is applied, a portion of the hard metal particles in the first overlay is dispersed in the weld puddle forming the second overlay.

Abstract: A spray powder which has a particle size of from 6 to 63 &mgr;m and which comprises from 75 to 95 wt % of a ceramic phase made of a WC powder and at least one chromium carbide powder selected from the group consisting of Cr3C2, Cr7C3 and Cr23C6, and from 5 to 25 wt % of a metal phase made of a Ni or Ni-based alloy powder, wherein the mean particle size of primary particles of the WC powder constituting the ceramic phase is from 5 to 20 &mgr;m, and the mean particle size of primary particles of the chromium carbide powder is from 1 to 10 &mgr;m.

Abstract: A soda inclusive glass substrate is coated with a highly tetrahedral amorphous carbon inclusive layer that is a form of diamond-like carbon (DLC). In certain embodiments, the amorphous carbon layer includes at least about 35% sp3 carbon-carbon bonds, more preferably at least about 70%, and most preferably at least about 80% of the sp3 carbon-carbon bonds. The high density (e.g. greater than or equal to about 2.4 gm/cm3) of the amorphous carbon layer prevents soda from exiting the glass and reacting with water at surface(s) of the glass, thereby minimizing visible stains (or corrosion) on the glass. The high density amorphous carbon layer also may repel water. In some embodiments, the highly tetrahedral amorphous carbon layer is part of a larger DLC coating, while in other embodiments the highly tetrahedral layer forms the entirety of a DLC coating on the substrate.

Abstract: A thermal spraying method involves the creation of a coating comprising titanium wire in the presence of nitrogen. The apparatus of the invention comprises a nozzle which has a cylindrical throat, with feedstock guides which guide the feedstock wires to a point of intersection in the throat. A current is passed through the wires to cause an arc in the throat, and a nitrogen rich gas under pressure is forced through the throat, generating a spray of molten particles which is used to coat a substrate. In a variation of the method, one of the feedstock wires comprises a binder metal, which produces a coating having enhanced toughness.

Abstract: The present invention employs a constrained stagnation flow geometry apparatus to achieve the uniform deposition of materials or heat. The present invention maximizes uniform fluxes of reactant gases to flat surfaces while minimizing the use of reagents and finite dimension edge effects. This results, among other things, in large area continuous films that are uniform in thickness, composition and structure which is important in chemical vapor deposition processes such as would be used for the fabrication of semiconductors.

Abstract: The invention relates to a method for applying a coating by means of plasma spraying to a substrate, in which method the beam of a laser is additionally used, it being possible to coat a very wide variety of substrates in order, in particular, to improve the properties on the substrate surface. Moreover, the method according to the invention is to achieve a high coating rate and, in addition to advantageous adhesion and density of the layer, also to influence in a controlled manner the layer structure which is being formed.

Abstract: Precursor solutions are provided to produce thin film resistive materials by combustion chemical vapor deposition (CCVD) or controlled atmosphere combustion chemical vapor deposition (CACCVD). The resistive material may be a mixture of a zero valence metal and a dielectric material, or the resistive materials may be a conductive oxide.

Abstract: A process for creating a coating that protects the underlying article from corrosion and provides a surface that prolongs service life against wear, such as, adhesion, abrasion, erosion, fretting and also can provide non-slip properties for person walking, standing, working on and vehicles traveling on. A hollow wire made of aluminum, or aluminum alloy, or zinc, or zinc alloy, filled with wear resistant particles, such as, oxides or carbides, then thermally metal sprayed onto a substrate of iron alloy, e.g. steel, or aluminum alloy, creates a coating with wear resistant properties that also provides corrosion protection to the substrate. A hollow wire of aluminum or aluminum alloy filled with wear resistant particles then welded to an aluminum alloy, provide a metallurgical compatible coating with wear resistant properties.

Abstract: A method for chemical vapor deposition using a very fine atomization or vaporization of a reagent containing liquid or liquid-like fluid near its supercritical temperature, where the resulting atomized or vaporized solution is entered into a flame or a plasma torch, and a powder is formed or a coating is deposited onto a substrate. The combustion flame can be stable from 10 torr to multiple atmospheres, and provides the energetic environment in which the reagent contained within the fluid can be reacted to form the desired powder or coating material on a substrate. The plasma torch likewise produces the required energy environment, but, unlike the flame, no oxidizer is needed so materials stable in only very low oxygen partial pressures can be formed.

Abstract: A composite steel sheet including a steel base member; an undercoat having opposed surfaces and a thickness of 10-750 .mu.m obtained by spraying one or more spraying materials selected from metals, non-oxide ceramics, oxide ceramics and cermets onto the steel base member. The undercoat has an oxide layer of not less then 0.5 .mu.m in thickness on one of the opposed surfaces positioned away from said steel base member. A fired topcoat is formed on the oxide layer of the undercoat from a vitreous coating having a linear expansion coefficient of 4-11.times.10.sup.-6 /.degree.C.

Abstract: A plasma etch reactor having interior surfaces facing the plasma composed of boron carbide, preferably principally composed of B.sub.4 C. The boron carbide may be a bulk sintered body or may be a layer of boron carbide coated on a chamber part. The boron carbide coating may be applied by thermal spraying, such as plasma spraying, by chemical vapor deposition, or by other layer forming technique such as a surface converting reaction. The boron carbide is highly resistant to high-density plasma etchants such as BCl.sub.3. The plasma sprayed coating is advantageously applied to only a portion of an anodized aluminum wall. The boron carbide may be sprayed over the exposed portion of the aluminum over which the anodization has been removed. A band of the aluminum substrate at the transition between the anodization and the boron carbide is roughened prior to anodization so that the boron carbide sticks to the correspondingly roughened surface of the anodization.

Abstract: A steel bearing member having an erosion resistant surface and a method of making the same is disclosed. The steel bearing member comprising a bearing substrate, a first overlay of hardbanding material having sintered cemented metal carbide pellets in steel and containing hard submicron sized particles, and a second overlay of steel containing hard particles that migrated from the first overlay of hardbanding material during application of the second overlay over the first overlay. A radial bearing member and a method of making the same is disclosed. A composition applied to the bearing substrate to improve the erosion resistance of this surface comprising a steel carrier and carbide pellets composed of submicron hard particles cemented with a metal binder is disclosed.

Abstract: A mass of molybdenum disilicide-silicon carbide composite material is prepared by providing a mixture of molybdenum disilicide-silicon carbide precomposited powder, and plasma spraying the precomposited powder onto a substrate using argon-shrouded plasma spray deposition, to form a plasma-sprayed mass. The plasma-sprayed mass may be subsequently heat treated.

Abstract: An object of the invention is to provide a window for an optical use having excellent transmission property over a wide range of from infra-red to vacuum ultraviolet as well as excellent baking resistance and capable of being fitted to an ultra-high vacuum apparatus and a process for the production of the same.This object can be attained by a window for an optical use comprising a diamond as a window material, a flange for a vacuum apparatus, a frame for bonding the diamond to the flange and the specified adhesive material for bonding the frame and diamond, and a process for the production of the window for an optical use comprising a step of preparing a diamond plate, a step of fitting a frame to a flange and bonding the diamond plate to the frame through an adhesive material. The benefits can be enlarged by suitably selecting the shape, material, etc. of the frame.

Abstract: In a method of coating easily oxidisable materials by plasma powder build-up welding of additive materials in powder form using alternating current or direct current with superimposed alternating current to produce a plasma transferred arc for powder build-up welding in accordance with patent application No 196 26 941.5 a CuNi-alloy is used as an additive welding material with additions (in % by weight) of:______________________________________ Fe below about 10; Cr below about 5; B below about 4; Si below about 4; C with about 1.5; ______________________________________with a degree of mixing of more than 40% by volume.

Abstract: A method for lubricating glass contacting surfaces of glass forming equipment is disclosed. The method comprises the steps of delivering MAPD gas to a venturi at a low pressure, preferably below 10 p.s.i., and delivering oxygen to the venturi at a lower pressure, usually half or less than half of the pressure at which the MAPD gas is delivered to the venturi. The MAPD gas and the oxygen are mixed in the venturi and delivered to and through a nozzle which is directed toward a glass contacting surface. The mixture is ignited as it leaves the nozzle; its flow is controlled so that the temperature of the flame is between approximately 1500 and 1800 degrees K. By controlling the temperature of the flame, the method is operable to deposit on the glass contacting surface a lubricating coating of graphite including a substantial percentage of flat plate graphite.

Abstract: A method for the growth of diamond on a substrate combines an ECR (Electron cyclotron resonance) MPCVD (Microwave plasma chemical vapor deposition) method with a MPCVD method in one system. A two-step diamond growing method comprises firstly etching and nucleation performed by the ECR method and then diamond grown by the microwave plasma CVD method. Not only are high quality continuous polycrystalline diamond films on silicon wafer obtained but also heteroepitaxial growth has been achieved in the present invention. Auger electron spectroscopy (AES), scanning electron microscopy (SEM) and Raman spectroscopy have been used to characterize the structure and morphology of the synthesized diamond films.

Abstract: A high temperature and highly corrosive resistant structure and method of fabricating the structure. In one embodiment of the present invention, vacuum plasma spray or other materials deposition techniques are used to fabricate the structure on a removable support member in the form of a gradient or composite structure that sequentially consists of a 100% ceramic interior layer, a first transition layer of ceramic/refractory metal, a layer of 100% refractory metal, a second transition layer of ceramic/refractory metal, and an outer layer of 100% ceramic material. In a second embodiment, the ceramic/refractory metal/ceramic cartridge is formed without transition layers between the ceramic and metal layers. In another embodiment of the invention the structure is fabricated on a removable support member by depositing an outer layer of ceramic material on a refractory metal. No transition layers of ceramic material/refractory metals are used.

Abstract: A method of forming a film of boron carbide on a substrate is provided, which comprises the steps of forming the boron carbide film on a surface of a substrate by plasma spraying, and heating the film at 1100.about.2400.degree. C. in a non-oxidizing atmosphere, whereby boron oxide contained in the boron carbide film is removed.

Abstract: A method for applying a functionally gradient coating on a component, having a surface and subjected to one or more of rolling, sliding, abrasion and bending contacts, including the step of thermally spraying a functionally gradient material (FGM) on said surface that forms an FGM coating, said FGM coating having a thickness, a plurality of material compositions and a plurality of elastic modulus profiles. Each elastic modulus profile consists of a plurality of elastic modulii at a plurality of corresponding points within that thickness. The elastic modulii are in the range from about 28 Mpsi to about 60 Mpsi. Optionally, there is also a plurality of carbon content profiles.

Abstract: This invention relates to methods whereby reprocessed nanoparticle powder feeds, nanoparticle liquid suspensions, and metalorganic liquids are used in conventional thermal spray deposition for the fabrication of high-quality nanostructured coatings. In one embodiment of this invention, the nanostructured feeds consist of spherical agglomerates produced by reprocessing as-synthesized nanostructured powders. The method is applicable to as-synthesized nanostructured powders made by a variety of liquid chemical processing methods. In another embodiment of this invention, a fine dispersion of nanoparticles is directly injected into a combustion flame or plasma thermal spray device to form high-quality nanostructured coatings.

Abstract: A process for the deposition of thick coatings with a thickness >1 mm on products made of copper or alloys thereof, wherein said products are subjected to the following operations: surface activation of the product made of copper or alloys thereof; optional heat stabilization to a temperature below the ones causing deterioration of the chemical and physical properties of the copper or alloys thereof; deposition of a first layer, for example of Ni or alloys thereof; optional interdiffusion heat treatment; optional activation of the surface of the first layer; thermal stabilization of said product at a temperature of between 20.degree. and 400.degree. C.

Abstract: A method for chemical vapor deposition using a very fine atomization or vaporization of a reagent containing liquid or liquid-like fluid near its supercritical temperature, where the resulting atomized or vaporized solution is entered into a flame or a plasma torch, and a powder is formed or a coating is deposited onto a substrate. The combustion flame can be stable from 10 torr to multiple atmospheres, and provides the energetic environment in which the reagent contained within the fluid can be reacted to form the desired powder or coating material on a substrate. The plasma torch likewise produces the required energy environment, but, unlike the flame, no oxidizer is needed so materials stable in only very low oxygen partial pressures can be formed.

Abstract: A granular composition is applied to tips of rotor blades utilized in a gas turbine engine wherein the blade tips rub against an abradable ceramic layer. Individual grains each have a core of silicon carbide and a layer of aluminum nitride on the core. A layer of a cladding metal may be bonded to the aluminum nitride. The composition also may include particles of cubic boron nitride and/or particles of metal alloy blended with the grains of silicon carbide.

Abstract: Structural ceramic matrix composite material to be employed as automotive engine parts and the like is provided with erosion-resistant qualities in several ways. For one, an erosion-resistant material is applied to the surface as by plasma spraying. The erosion-resistant material can also be mixed with the fibers of the material, particularly near the surface.

Abstract: A process for manufacturing wear and corrosion-protected surfaces on plasticized screws for injection molding machines forms the wear-resistent layers over the entire screw surface in two steps. A laser technique is used to melt additives into the surfaces of the screw rib, flank and top as well as the screw base by high-speed flame spring with hard metallic and/or ceramic substances.

Abstract: A blank mold sooting process in which a lubricating or detaching layer is formed on the internal walls of the blank mold, by igniting an acetylene flow with piezoelectric electrodes, a voltaic arc generator, or an electrical resistance. The process is performed utilizing, for example, a blow mold and an invert, and the invert can be utilized to transfer a collar from the blank mold to the blow mold.

Abstract: The carbonizing furnace of the present invention is capable of effectively making a large amount of carbides and reducing manufacturing cost and maintenance cost. The carbonizing furnace includes a furnace proper being formed into a cylindrical shape, the furnace proper having a first end section, to which a combustible raw material is supplied, and a second end section, from which a carbide is discharged; a spiral member for conveying the raw material from the first end section to the second end thereof; and a burner for burning the raw material to make the carbide, the burner burns the raw material in the second end section whereby the raw material is carbonized therein, wherein a surface of the raw material is coated with an inorganic binder.

Abstract: In order to improve the wear resistancy--including adherence behaviour, ductility and shearing strength--at a diamond coated multiphase body, an element enrichment is applied in controlled manner in the interphase of base body and diamond layer.

Abstract: A composite ceramic coating having abrasive properties for application to a metallic substrate is provided which includes a ceramic matrix and a plurality of ceramic abrasive particles disposed within said ceramic matrix. The abrasive particles have a shear strength substantially greater than that of the ceramic matrix and possess an angular geometry. A method for providing an abrasive coating on a metallic article is also provided.

Abstract: Apparatus which is disclosed comprises a metal mold, a metal plunger and an annular manifold, and includes means for moving the plunger and the manifold between an open position in which the manifold surrounds the plunger and a gob of softened glass can be introduced into the mold and a closed position in which the manifold surrounds the plunger and the latter forms, with the mold and the manifold, a cavity in which a glass part can be formed. The manifold and the plunger have facing walls which are above the mold cavity, have portions which are in close fitting sliding engagement, and, thereabove, portions which diverge away from one another and form an annular space.

Abstract: A high temperature thermal sprayable material, such as a metal or metal oxide, is adhered to the surface of a thermal sprayable plastic particle to form a cladding layer thereon. The high temperature material cladding layer provides a thermal barrier that allows use of the plastic in a high temperature thermal spray process to create a duplex coating containing plastic.

Abstract: A carbon coated metal powder depositable by thermal spray techniques to form a metal coating is disclosed. The carbon coated metal powder has a composition comprising a metal powder and carbon adhered to the metal powder. The metal powder is coated with carbon to form a carbon coated metal powder. The carbon coated metal powder, after being thermally sprayed on to a substrate and after being formed into a metal coating on the substrate, has an oxygen content at least 20% by weight less than the oxygen content in the carbon coated metal powder prior to being thermally sprayed.

Abstract: A method for producing an atomized powder of chromium carbide particles dispersed in a nickel chromium matrix in which chromium in the powder is from 55 to 92 weight percent of the powder.

Abstract: Known thermal spray apparatus are modified to achieve thermal spray coatings of increased hardness. Thermal spray apparatus operate to develop a plasma stream for introduction to a nozzle, for eventual application to the surface of a substrate. Upon entering the nozzle, the plasma stream is passed through a plasma cooling zone defined by a plasma cooling passageway, to a plasma accelerating zone defined by a narrowed passageway that expands into a plasma/particle confining zone for the discharge of material from the apparatus. The narrowed passageway of the apparatus is cooled, and the powder material to be applied by the apparatus is introduced into the plasma stream along the cooled, narrowed passageway.

Abstract: In a method of forming a mold release film on the surface of a glass blank from which an optical element is made by press molding, a carbon film having a thickness of less than 50 angstroms or, preferably, less than 10 angstroms is formed on the surface of the glass blank, thereby improving the releasability of the mold and the molded article with respect to each other. A glass blank (1) is subjected to ashing with an oxygen plasma so as to remove organic dirt attached to the glass blank (1). Then, plasma cleaning with an argon plasma is effected so as to remove inorganic dirt attached to the glass blank (1). Thereafter, the glass blank (1) is subjected to methane plasma processing such that a carbon film (2) having a thickness of less than 50 angstroms is formed on the surface of the glass blank (1) from which the dirt has been removed.

Abstract: A method of stabilizing a strained flame in a stagnation flow reactor. By causing a highly strained flame to be divided into a large number of equal size segments it is possible to stablize a highly strained flame that is on the verge of extinction, thereby providing for higher film growth rates. The flame stabilizer is an annular ring mounted coaxially and coplanar with the substrate upon which the film is growing and having a number of vertical pillars mounted on the top surface, thereby increasing the number of azimuthal nodes into which the flame is divided and preserving an axisymmetric structure necessary for stability.

Abstract: Disclosed is a bearing unit which can be used in a drainage pump operated without supply of clean water or a hydraulic pump, which exhibits excellent wear resistance against water containing earth and sand and satisfactory assembling facility, and a method of manufacturing the bearing unit.The contact surface of a bearing made of stainless steel and/or that of a sleeve is applied with a sprayed coating, the main component of which is WC, and which contains one or more elements selected from a group consisting of nickel, chromium and cobalt as a binder material thereof, or a sprayed coating, the main component of which is Cr.sub.3 C.sub.2, and which contains NiCr as a binder material, after the sprayed coating has been formed, heating at from 300.degree. C. to 550.degree. C. is performed for one hour or longer so that hardness and wear resistance equivalent to those of a WC-12% sintered article is attained.

Abstract: A method and apparatus for reactive plasma surfacing includes at least two electrodes between which reactive gases are passed. The reactive gases are ionized by the arc between the electrodes, creating a plasma of heated, ionized, reactive gases. The plasma is then applied to a surface to be treated, causing a chemical reaction between the plasma and the surface and resulting in a new diffusional substrate surface on the treated object. The process occurs at substantially atmospheric pressure, and may include an inert gas to shield the process from the surrounding environment.

Abstract: Cluster particles including a plurality of molecules or atoms are prepared by a gas cluster method, are accelerated, and are then irradiated onto a diamond in a low pressure atmosphere, so that the unevenness surfaces of the diamond are smoothed with no damages in the diamond. The cluster particles are prepared by the steps of forming, ionizing, mass-separating, and accelerating cluster particles. The cluster particles with a certain energy are irradiated onto the surface of the diamond. Irradiated cluster particles collide with the surface of the diamond, and then break apart into each molecule or atom while changing momentum (direction and speed) or energy. Thus, the surface of the diamond is efficiently smoothed and etched.

Abstract: Thermally sprayed coatings made from carbides of metals having greater carbon affinity than Cr in the presence of free carbon, or thermally sprayed coatings made from carbides of metals having smaller carbon affinity than Cr are heat treated in a chromium halide containing atmosphere which also contains hydrogen gas, whereby activated metallic Cr is precipitated in a fine particulate form, which is allowed to act on the thermally sprayed coatings, whereupon a Cr.sub.23 C.sub.6 -form carbide is created not only on the coating surface but also in its interior, particularly within pores, to form a modified layer, thereby compositing the thermally sprayed coatings.

Abstract: A high quality shaped article of silicon carbide is efficiently produced by using a carbon substrate suitable for the production of a silicon carbide film without generating cracking or breakage. In a method of producing a shaped article of silicon carbide while using a carbonaceous material as a deposition substrate by decomposing halogenated organic silicone compound by a reduction pyrolysis at a high temperature, forming a silicon carbide film layer on a surface of the substrate by CVD and removing the carbon substrate, the carbon substrate is formed of a composite of graphite and amorphous carbon obtained by shaping and firing a mixture of a powdery graphite and an organic substance.

Abstract: A composite material comprising a matrix including chromium carbide particles, and a solid lubricant mixed with the matrix and including barium fluoride and calcium fluoride. The composite material is spray deposited onto a substrate using a high velocity oxy-fuel (HVOF) spray technique to provide an HVOF spray coating.

Abstract: Heat transfer device (30) dissipates and removes heat energy from a heat source and delivers the heat energy to a heat sink. Heat transfer device (30) includes diamond substrate (32) for receiving the heat energy from the heat source. Interconnect point (36) connects to diamond substrate (32). Fiber (34), such as a carbon fiber, connects at interconnect point (36) to receive the heat energy from diamond substrate (32) and conduct the heat energy to the heat sink.

Abstract: A glass making apparatus adapted to deposit a lubricating/detaching layer of carbon black obtained from acetylene cracking on the internal walls of a blank mold (1, 18). The glass making apparatus includes a blank mold (1, 18) having an open top and an open bottom (10); a collar (6) sized, shaped, and positioned to selectively plug the open bottom (10) of the blank mold (1, 18) during a glass forming process and to disengage from the open bottom (10) of the blank mold (1, 18) during a blank mold sooting process; a ring (7) disposed in the collar (6); a plunger (8, 14) sized, shaped, and positioned to selectively move up into the collar (6) and down out of the collar (6); and a sleeve (9) surrounding the plunger (8, 14).

Abstract: A process for reducing oxygen content in thermally sprayed metal coatings comprises the following steps. A metal powder is provided. The metal powder has a particle size in the range of from about 10 .mu.m to about 500 .mu.m. Carbon is adhered and coated to the metal powder to form a carbon coated metal powder. The carbon is present in the range of from about 0.1% to about 2.0% by weight of the carbon coated metal powder. The carbon coated metal powder is thermally sprayed onto a substrate and a metal coating is deposited on the substrate. The metal coating has a lower oxygen content compared to the oxygen content of the carbon coated metal powder.

Abstract: A dielectric image receiving member is disclosed which comprises a substrate layer, a porous plasma-sprayed dielectric layer formed on the surface of the substrate layer, and a dielectric polymeric coating material filling at least those pores opening at the surface of the oxide layer. Most preferably, the plasma-sprayed layer is a metal oxide and the coating material is a glass resin.

Abstract: An abrasive material is proposed which is useful for the precision treatment of surfaces. This material may be in the form of an abrasive layer adhered by chemical and/or physical bonds to a carrier, the latter preferably made of a flexible material such as plastic. Alternatively, the abrasive material may be in the form of a free abrasive without a carrier. The abrasive material may be in the form of a vacuum condensate consisting of at last 80 atomic percent of an ultradispersed composite superhard diamond-like substance, preferably containing carbon, and including not more than 0.1 atomic percent hydrogen and oxygen, combined. The abrasive material is preferably obtained from the pulse-flows of an accelerated electroerosive plasma.