GRADIENT WITHIN A THERMAL BARRIER COATING AND METHODS OF THEIR FORMATION

Abstract

Methods are provided for forming a thermal barrier coating having a non-linear compositional gradient and/or a non-linear porosity gradient, along with coated components formed therefrom. The method includes spraying a deposition mixture of a first composition and a second composition via a solution precursor plasma spray apparatus onto a surface of a substrate; while spraying the deposition mixture, adjusting at least one deposition parameter such that the thermal barrier coating is formed with the non-linear gradient.

Description

FIELD OF TECHNOLOGY

This present disclosure generally relates to coatings suitable for use as in coating systems on components exposed to high-temperature environments, such as the hot gas flow path through a gas turbine engine. More particularly, the present disclosure is directed to coating microstructures for use in a thermal barrier coating (TBC) system.

BACKGROUND

The use of TBCs on components such as combustors, high pressure turbine (HPT) blades and vanes of gas turbine engines is increasing. Generally, the thermal insulation of a TBC enables such components to survive higher operating temperatures, increases component durability, and improves engine reliability. In order for a TBC to remain effective throughout the planned life cycle of the component it protects, it is desired that the TBC has a low thermal conductivity throughout the life of the component, including high temperature excursions. Additionally, it is desired that the TBC has a high toughness which reduces the damage due to erosion and impact on rotating components of HPT, combustor components, and static turbine components (e.g., turbine nozzles). Low thermal conductivity TBC can increase efficiency by reducing heat loss and potentially allowing higher temperature operation.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present disclosure, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended FIGS., in which:

FIG. 1 is a cross-sectional schematic diagram of an exemplary coated component;

FIG. 2 is a schematic of an exemplary solution precursor plasma spray apparatus according to various embodiments of the present subject matter;

FIG. 3A is a chart of an exemplary process parameter schedule for forming a TBC with a non-linear porosity gradient;

FIG. 3B is a chart of an exemplary non-linear porosity gradient in the TBC formed by the exemplary process parameter schedule of FIG. 3B;

FIG. 4A is a chart of an exemplary flow rate schedule for forming a TBC with a non-linear concentration gradient;

FIG. 4B is a chart of an exemplary non-linear concentration gradient in the TBC formed by the exemplary flow rate schedule of FIG. 4B;

FIG. 5A is a chart of an exemplary flow rate schedule for forming a TBC with a non-linear concentration gradient;

FIG. 5B is a chart of an exemplary non-linear concentration gradient in the TBC formed by the exemplary flow rate schedule of FIG. 5B;

FIG. 6A is a chart of an exemplary flow rate schedule for forming a TBC with a non-linear concentration gradient;

FIG. 6B is a chart of an exemplary non-linear concentration gradient in the TBC formed by the exemplary flow rate schedule of FIG. 6B;

FIG. 7 is a schematic view of an exemplary controller suitable for use in a solution precursor plasma spray apparatus, such as in FIG. 2; and

FIG. 8 shows a flow chart diagram of an exemplary method of forming a TBC.

Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the present preferred embodiments.

Definitions

As used herein, the word “exemplary” is means “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other implementations. Additionally, unless specifically identified otherwise, all embodiments described herein should be considered exemplary.

The term “gas turbine engine” refers to an engine having a turbomachine as all or a portion of its power source. Example gas turbine engines include turbofan engines, turboprop engines, turbojet engines, turboshaft engines, etc., as well as hybrid-electric versions of one or more of these engines. The term “turbomachine” or “turbomachinery” refers to a machine including one or more compressors, a heat generating section (e.g., a combustion section), and one or more turbines that together generate a torque output.

In the present disclosure, when a layer is being described as “on” or “over” another layer or substrate, it is to be understood that the layers can either be directly contacting each other or have another layer or feature between the layers, unless expressly stated to the contrary. Thus, these terms are simply describing the relative position of the layers to each other and do not necessarily mean “on top of” since the relative position above or below depends upon the orientation of the device to the viewer.

Chemical elements are discussed in the present disclosure using their common chemical abbreviation, such as commonly found on a periodic table of elements. For example, hydrogen is represented by its common chemical abbreviation H; helium is represented by its common chemical abbreviation He; and so forth.

As used herein, “rare earth element” refers to the elements of scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), or deposition mixtures thereof.

As used herein, the term “substantially free” is understood to mean completely free of said constituent, or inclusive of trace amounts of same. “Trace amounts” are those quantitative levels of chemical constituent that are barely detectable and provide no benefit to the functional or aesthetic properties of the subject composition. The term “substantially free” also encompasses completely free.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

Reference now will be made in detail to embodiments of the disclosure, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the disclosure, not limitation of the disclosure. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the preferred embodiments without departing from the scope of the disclosure. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present disclosure covers such modifications and variations as come within the scope of the appended claims and their equivalents.

Current TBC material-8YSZ is known for its high toughness, but also high thermal conductivity. Low thermal conductivity compositions such as 55YSZ lacks high toughness. Thus, further improvements in TBC technology are desirable, particularly as TBC's are employed to thermally insulate components intended for more demanding engine designs.

Methods are generally disclosed for forming a TBC with multiple gradients on a substrate, along with the resulting coated components. In particular, the TBC is formed using a solution precursor plasma spray (SPPS) process while adjusting multiple independent inputs during the spray process. Thus, a unique microstructure may be formed in the TBC that has a non-linear gradient that allows for the combination of characteristics throughout the TBC. These graded microstructures may lead to increased toughness due to mechanisms such as crack deflection, while providing high compositional flexibility.

Referring to FIG. 1, an exemplary coated component 100 is shown. The coated component 100 includes a substrate 102 with an optional bond coat 104 on the surface 103 of the substrate 102. In the embodiment shown, the bond coat 104 is directly on the surface 103 without any layer therebetween. Bond coat materials widely used in TBC systems may include, but are not limited to, oxidation-resistant overlay coatings such as MCrAlX (where M is iron, cobalt and/or nickel, and X is yttrium or another rare earth element), and oxidation-resistant diffusion coatings such as diffusion aluminides that contain aluminum intermetallics.

The substrate 102 may be any suitable material, for example a metal such as steel or superalloys (e.g., nickel-based superalloys, cobalt-based superalloys, or iron-based superalloys, such as Rene N5, N500, N4, N2, IN718, Hastelloy X, or Haynes 188) or other suitable materials for withstanding high temperatures. The TBC 106 may be disposed along one or more portions of the substrate 102 or disposed substantially over the whole exterior of the substrate 102.

A TBC 106 is on the surface 105 of the bond coat 107. In certain embodiments, the TBC 106 is formed as a single continuous phase without individual layers 108 present or detectable therein. For explanation purposes, the TBC 106 includes a plurality of layers 108 shown separated by a period line 110. Although the layers 108 are described as separated by a period line 110, it should be understood that the defining points between adjacent layers may be at other times within the formation process, as described in greater detail below. In one particular embodiment, the plurality of layers 108 are sintered together to form an integrated TBC such that a continuous phase extends throughout the TBC 106. For example, when formed according to a continuous process, such as described below with respect to the schedules shown in FIGS. 3A, 4A, 5A, and 6A, the term “layer” is merely used to describe a period of the process schedule that results in a period within the thickness of the resulting TBC 106, such as shown in FIGS. 3B, 4B, 5B, and 6B. Thus, the term “layer” does not necessarily refer to any physically defined portion of the TBC 106. The TBC 106 has a total thickness, measured perpendicularly from the surface 105 to the outermost surface 107 of the TBC 106, which may be 50 μm to 600 μm in certain embodiments. In the embodiment shown in FIG. 1, a plurality of nonspherical particles 112 (e.g., ceramic fibers) may optionally be embedded in the TBC 106, as discussed in greater detail below.

Generally, the TBC 106 includes multiple gradients. In the remainder of the present disclosure, the TBC 106 is described as having either or both of a non-linear compositional gradient and a non-linear porosity gradient throughout its thickness extending from the surface 105 to the outermost surface 107 of the TBC 106. It is to be understood that the TBC 106 can have any suitable multiple gradients, which may repeat with a substantially similar/same gradient pattern or a different gradient pattern. In one embodiment, each layer 108 is defined by a non-linear compositional gradient and/or a non-linear porosity gradient, which collectively form the non-linear compositional gradient and the non-linear porosity gradient of the TBC 106.

The TBC 106 in the embodiment of FIG. 1 defines a plurality of substantially vertical cracks 114 extending from the outermost surface 107 of the TBC 106. These cracks 114 may be intentionally formed as a result of the method of forming the TBC 106, such as a solution precursor plasma spray (SPPS) process. Generally, the cracks 114 may extend into the thickness from the outermost surface 107 through at least 50% of the thickness of the TBC 106. These plurality of substantially vertical cracks 114 can be referred to as microcracks and allow for flexibility in the TBC 106.

Referring to FIG. 2, an exemplary solution precursor plasma spray apparatus 200 is generally shown for forming a TBC 106 on a substrate 102 and/or the intermediate bond coat 107, such as shown in FIG. 1. The exemplary solution precursor plasma spray apparatus 200 includes a plasma gun 202 and a liquid injector 204 that work together to deposit the TBC 106 on the substrate 102. As stated, the TBC 106 may be deposited via a continuous process, with the resulting deposited TBC 106 formed with any suitable multiple gradients, which may repeat with a substantially similar/same gradient pattern or a different gradient pattern. These gradients may be described as forming layers 108 within the TBC 106, even though no layers 108 are otherwise ascertainable therein. The plasma gun 202 is configured to form a plasma field 206 utilizing a plasma gas 208 that carries a deposition mixture 210 from the liquid injector 204 over the surface 103 of the substrate 102 (including over the bond coat 107, when present).

The deposition mixture 210 is supplied from a plurality of compositions supplied from respective supply units. In a non-limiting example, FIG. 2 shows a first supply unit 212 that includes a first composition 213, a second supply unit 214 that includes a second composition 215, and a third supply unit 216 that includes a third composition 217. Although shown with three compositions, the deposition mixture 210 may be formed from any number of compositions as desired.

At least one process parameter may be adjusted while spraying the deposition mixture to form the TBC 106 in order to form a non-linear porosity gradient within the thickness of the TBC 106. For example, the process parameter may be adjusted according to a parameter schedule during the deposition process. In particular embodiments, the process parameter may be adjusted constantly over time according to a parameter schedule.

Referring to FIG. 3A, an exemplary parameter schedule 300 is generally shown where the process parameter adjusts constantly over time during the deposition process, such as through a peak 302 and a valley 304. As indicated above, each cycle of the exemplary parameter schedule generally defines a layer 108 (FIG. 1) of the TBC 106 for the purposes of describing of the non-linear gradient, whether or not the layers 108 are discernable within the TBC 106. Thus, the TBC 106 may include alternating periods of a relatively high porosity and a relatively low porosity. Referring to FIG. 3B, a non-linear porosity gradient 310 is shown through the thickness of the TBC 106 with a plurality of layers formed within the TBC 106, where each layer 108 is defined by an alternating period of a relatively high porosity 312 and a relatively low porosity 314. Thus, in this embodiment, the plurality of layers defines a substantially repeating porosity gradient within the TBC 106. It is understood that, despite being generally shown as being a substantially repeating porosity gradient within the TBC 106, the non-linear porosity gradient 310 may have a different porosity gradient between the relatively high porosity 312 and a relatively low porosity 314. As shown, the exemplary parameter schedule 300 of FIG. 3A generally corresponds to an exemplary non-linear porosity gradient 310 of FIG. 3B.

In one embodiment, the process parameter is a plasma temperature of the solution precursor plasma spray apparatus such that the parameter schedule is a temperature schedule that adjusts the plasma temperature of the deposition mixture exiting the solution precursor plasma spray apparatus. In FIG. 2, a heating device 230 is generally shown in working proximity to the plasma field 206 so as to control the plasma temperature. Additionally or alternatively, the process parameter is a flow rate of the plasma gas of the solution precursor plasma spray apparatus such that the parameter schedule is a flow rate schedule that adjusts the flow rate of the plasma gas exiting the solution precursor plasma spray apparatus. Although shown with one process parameter adjusting over time in the embodiment of FIG. 3A, multiple process parameters may be adjusted simultaneously during deposition in other embodiments to form the non-linear porosity gradient of FIG. 3B or any other suitable gradient within the TBC 106.

As stated, the TBC 106 may include a non-linear compositional gradient in addition to the non-linear porosity gradient, such as a non-linear compositional gradient of at least one composition of the TBC 106 may have a non-linear compositional gradient through the thickness of the TBC 106.

Referring to FIG. 2, the flow rate of each of the first composition 213, the second composition 215, and the third composition 217 may be individually controlled via a respective valve. For instance, the flow rate of the first composition 213, the second composition 215, and the third composition 217 may be individually controlled via, respectively, a first valve 218, a second valve 220, and a third valve 222. Each of the first valve 218, the second valve 220, and the third valve 222 are positioned downstream of, and in fluid communication with, the first supply unit 212, the second supply unit 214, and the third supply unit 216, respectively. Additionally, in certain embodiments, the total flow rate of the deposition mixture 210 may be controlled by a master valve 224 positioned downstream of each of the first valve 218, the second valve 220, and the third valve 222 but upstream of the liquid injector 204. Similarly, the flow of the plasma gas 208 may be controlled from a plasma supply unit 226 via a plasma valve 228.

Thus, the flow rate of at least one of the first composition 213, the second composition 215, and/or the third composition 217 may be adjusted while spraying the deposition mixture to form the TBC 106 in order to form a non-linear compositional gradient within the thickness of the TBC 106. For example, the flow rate of each of first composition 213, the second composition 215, and the third composition 217 may be adjusted according to a respective flow rate schedule during the deposition process. In particular embodiments, the flow rate of each composition may be adjusted constantly over time according to a respective flow rate schedule. It should be understood that any number of compositions may be included within the deposition mixture and may be adjusted according to a respective flow rate schedule.

Referring to FIG. 4A, an exemplary flow rate schedule 400 is generally shown where the first flow rate 402 of the first composition 213 adjusts constantly over time during the deposition process, where the second flow rate 404 of the second composition 215 adjusts constantly over time during the deposition process, and where the third flow rate 406 of the optional third composition 406 adjusts constantly over time during the deposition process. As indicated above, each cycle of the exemplary flow rate schedules generally defines a layer 108 (FIG. 1) of the TBC 106 for the purposes of describing of the non-linear gradient, whether or not the layers 108 are discernable within the TBC 106. While the first composition, second composition, and third composition are each shown as being adjusted cyclically throughout each layer, it is to be understood that this need not be the case and that one or more of the compositions may be adjusted according to any desired schedule. In fact, one or more of the compositions may remain steady (i.e., a substantially unchanging schedule) throughout TBC 106.

Referring to FIG. 4B, a non-linear compositional gradient 410 is shown through the thickness of the TBC 106 with a plurality of layers formed within the TBC 106, where each layer 108 is defined by an alternating period of a relatively high concentration and a relatively low concentration of a respective composition. For example, the TBC 106 may include a first compositional gradient 412 of alternating periods of a relatively high first concentration 414 of the first composition and a relatively low first concentration 416 of the first composition, a second compositional gradient 418 alternating periods of a relatively high second concentration 420 of the second composition and a relatively low second concentration 422 of the second composition, and a third compositional gradient 424 alternating periods of a relatively high third concentration 426 of the optional third composition and a relatively low third concentration 428 of the third composition. It is understood that, despite being generally shown as being a substantially repeating compositional gradient within the TBC 106, any of the non-linear compositional gradients 412, 418, 424 may have a different compositional gradient between their respective relatively high and low concentrations. Thus, in this embodiment, the substantially repeating compositional gradient within the TBC 106. It is understood that, despite being generally shown as being substantially repeating compositional gradients within the TBC 106, the non-linear compositional gradients 412, 418, 424 may have a different compositional gradient between its respective high concentration and low concentration. As shown, the exemplary flow rate schedule of FIG. 4A generally corresponds to an exemplary non-linear compositional gradient of FIG. 4B.

Each of the first flow rate 402, the second flow rate 404, and the third flow rate 406 are controllable independently from each other. As such, each of the non-linear compositional gradients 412, 418, 424 may have an independently selected compositional gradient that is unrelated to other non-linear compositional gradients within the TBC 106. For example, FIG. 5A shows another exemplary flow rate schedule of a first compositional flow rate 502 and a second compositional flow rate 504, resulting in a non-linear compositional gradient 510 that includes a first compositional gradient 506 of the first composition and a second compositional gradient 508 of the second composition of FIG. 5B, respectively. In the embodiment shown in FIG. 5A, the peaks and valleys of the first compositional flow rate and the second compositional flow rate are misaligned from each other.

FIG. 6A shows still another exemplary flow rate schedule 600 of a first compositional flow rate 602 and a second compositional flow rate 604, resulting in a non-linear compositional gradient 610 that includes a first compositional gradient 606 of the first composition and a second compositional gradient 608 of the second composition of FIG. 6B, respectively. In the embodiment shown in FIG. 6A, the rate of change of the first compositional flow rate 602 and the second compositional flow rate 604 are different from each other.

The deposition mixture may be sprayed according to the parameter schedule and the respective flow rate schedules such that the TBC 106 includes a desired number of layers, such as 10 layers to 25 layers. For example, each layer of the TBC 106 may be formed to a thickness of 2 μm to 50 μm, and the TBC 106 may be formed to a thickness of 50 μm to 600 μm.

Referring again to FIG. 1, the TBC 106 generally includes a plurality of nonspherical particles 112. As used herein, the term “nonspherical” refers to a particle having a shape other than a sphere, and particularly as a shape having at least one dimension that is greater than another dimension. For example, nonspherical particles 112 may have an irregular shape, an ellipsoidal shape, a flake-like shape, etc. The plurality of nonspherical particles 112 may be randomly dispersed within the TBC 106 such that the thermal barrier coating 106 includes a generally equal distribution of the nonspherical particles 112 therein.

In the embodiment shown, the TBC 106 has a columnar microstructure that includes surface-connected voids or cracks 114. As shown, the cracks 114 are generally elongated such as having an aspect ratio greater than 1 measured as the longest depth (from the surface 115 to its deepest point within the thermal barrier coating 106) divided by the greatest width within the crack 114 parallel to the surface 107. In particular embodiments, the cracks 114 have an aspect ratio that is 10 to 100. Without wishing to be bound by any particular theory, it is believed that these cracks 114 may help increase the cyclic life of the thermal barrier coating 106 by accommodating thermal expansion strains on the TBC 106 over a series of heating and cooling cycles. In some embodiments, cracks 114 include substantially vertically oriented (from the perspective of a cross-sectional view as in FIG. 1, that is extending generally perpendicular from the surface 103 of the substrate 102) cracks and/or boundaries of grains or other microstructural features. The elongated surface-connected cracks 114 may be present due to inherent characteristics of deposition processes used to deposit the thermal barrier coating 106; some elongated surface-connected cracks 114 may also form after deposition due to normal wear and tear during operation.

The plurality of nonspherical particles 112 may be generally included the TBC 106 to increase the fracture toughness and optionally add other functionality to the TBC 106. Without wishing to be bound by any particular theory, it is believed that the nonspherical particles 112 embedded within the TBC 106 may inhibit crack propagation therein. For example, the nonspherical particles 112 may inhibit expansion of the plurality of surface-connected microporosity cracks 114 and/or cracks 114 introduced by impact or thermal cycling during use of the coated component 100.

When present, the plurality of nonspherical particles 112 may generally include a CMAS resistant material. For example, the CMAS resistant material of the nonspherical particles 112 may be a stabilized ceramic material that can sustain a fairly high temperature gradient and may be compatible with theTBC 106. For example, the nonspherical particles 112 may be formed from materials suitable for the TBC 106. For instance, the stabilized ceramic material of the nonspherical particles may be one or more of yttria stabilized zirconia (YSZ, such as 8YSZ) and other rare-earth-stabilized zirconia compositions, lanthanide aluminates, yttria aluminates, mullite (3Al₂O₃-2SiO₂), alumina, ceria (CeO₂), lanthanide rare-earth zirconates, aluminosilicates, rare-earth oxides (e.g., La₂O₃, Nb₂O₅, Pr₂O₃, CeO₂), alkaline earth-lanthanide-silicates and metal-glass composites, and combinations thereof (e.g., alumina and YSZ or ceria and YSZ). Besides its high temperature stability, YSZ also has a good combination of high toughness and chemical inertness, and the thermal expansion coefficient of YSZ is a comparatively suitable match to that of the TBC 106.

In one embodiment, the plurality of nonspherical particles 112 may include a fluorescing compound, such as being doped with a fluorescing compound. For example, suitable fluorescing compounds may include, but are not limited to, cerium, neodymium, praseodymium, europium, samarium, terbium, dysprosium, erbium, titanium, manganese, or bismuth doped rare earth containing materials, such as rare earth zirconates or rare earth oxides. The presence of the fluorescing compound within the nonspherical particles 112 may allow for the measurement of the thickness of the TBC 106, at deposition and after use. For instance, the TBC 106 may have an initial fluorescent intensity after deposition, which may be monitored throughout the use of the coated component 100. A measurement of reduced fluorescent intensity after use indicates that there is some loss of the TBC 106. Thus, the thickness of the TBC 106 may be monitored for abrasion and other losses.

Generally, the nonspherical particles 112 have an elongated configuration to inhibit crack proliferation through the TBC 106. That is, the nonspherical particles 112 define a longest dimension and a shortest dimension that may be utilized to define an aspect ratio by dividing the longest dimension by the shortest dimension. In one embodiment, at least 50% of the plurality of nonspherical particles 112 have an aspect ratio that is greater than 5 (e.g., 5 to 100,000), such as an aspect ratio that is 10 to 10,000. In one particular embodiment, a great majority of the nonspherical particles 112 have such an aspect ratio. For example, at least 90% of the plurality of nonspherical particles 112 may have an aspect ratio that is greater than 5 (e.g., 5 to 100,000), such as an aspect ratio that is 10 to 10,000.

The thermal barrier coating 106 shown in FIGS. 1 and 2 generally includes a thermal barrier material 113. Suitable thermal barrier material 113 may include, but is not limited to, various types of oxides, such as hafnium oxide (“hafnia”) or zirconium oxide (“zirconia”), in particular stabilized hafnia or stabilized zirconia, and blends including one or both of these. Examples of stabilized zirconia include without limitation yttria-stabilized zirconia, ceria-stabilized zirconia, calcia-stabilized zirconia, scandia-stabilized zirconia, magnesia-stabilized zirconia, india-stabilized zirconia, ytterbia-stabilized zirconia, lanthana-stabilized zirconia, gadolinia-stabilized zirconia, as well as mixtures of such stabilized zirconia. Similar stabilized hafnia compositions are known in the art and suitable for use in embodiments described herein.

In certain embodiments, the thermal barrier material 113 includes yttria-stabilized zirconia. Suitable yttria-stabilized zirconia may include from 1 weight percent to 60 weight percent yttria (based on the combined weight of yttria and zirconia), and more typically from 3 weight percent to 10 weight percent yttria. An example yttria-stabilized zirconia thermal barrier coating includes 7% yttria and 93% zirconia. These types of zirconia may further include one or more of a second metal (e.g., a lanthanide or actinide) oxide, such as lanthana, ytterbia, samaria, dysprosia, erbia, europia, gadolinia, neodymia, praseodymia, urania, and hafnia, to further reduce thermal conductivity of the thermal barrier material. In some embodiments, the thermal barrier material may further include an additional metal oxide, such as, titania.

Suitable thermal barrier material 113 may also include pyrochlores of general formula A₂B₂O₇ where A is a metal having a valence of 3+ or 2+(e.g., gadolinium, samarium, cerium, lanthanum or yttrium) and B is a metal having a valence of 4+ or 5+(e.g., hafnium, titanium, cerium or zirconium) where the sum of the A and B valences is 7. Representative materials of this type include gadolinium zirconate, lanthanum titanate, lanthanum zirconate, yttrium zirconate, lanthanum hafnate, cerium hafnate, and lanthanum cerate. Additionally, perovskite materials, following the formula ABO₃, can also be used, where the A or B site can contain a single cation or multiple.

It is noted that each of these compositions discussed herein for the TBC 106 may be utilized, independently, as the first composition 213, the second composition 215, the third composition 217, etc. For example, in one embodiment, a rare earth stabilized zirconia (e.g., YSZ) may form the TBC 106 with the concentration of the rare earth having a gradient through the thickness of the TBC 106 (e.g., varying from 8 wt. % to 55 wt. %). In one embodiment, for instance, the rare earth stabilized zirconia (e.g., YSZ) may include hafnium substitutions where there is a gradient from pure 8YSZ to a stabilized zirconia with up to 50% Hf substituted. Such an embodiment could also be achieved with 20YSZ, 55YSZ, etc, (instead of 8YSZ). The rare earth stabilized zirconia (such as YSZ) may, in another embodiment, have a gradient up to a (Y, Lanthanide)SZ composition. For example, something similar to the example of 8YSZ that varies to a higher YSZ, although in this embodiment, Ln substitution has a gradient in the higher YSZ for lower thermal conductivity.

Aspects of the present disclosure allow for graded microstructures to form coatings with composite properties to enable both low thermal conductivity and high toughness. For example, for a TBC 106 having a total coating thickness of 75 μm to 635 μm, the TBC 106 may have a thermal conductivity of 1 W/mK @1000° C. or less (particularly if the thermal barrier material 113 includes 60% to 70% by weight of 8YSZ), may have a fracture toughness of 20 J/m² or greater (particularly if the thermal barrier material 113 includes 50% by weight of 8YSZ), may have an interfacial toughness of 250 J/m² or greater (particularly if the thermal barrier material 113 includes 50% by weight of 8YSZ), may have a density varying between 15-50% porous with regions of relatively high density and low density, and/or may have a compositional gradient (i.e., a chemical gradient) that does not differ by more than 5% by weight in composition.

Referring again to FIG. 2, an exemplary controller 700 is in operable communication with the valves and/or heater(s) present in the plasma spray apparatus 200 so as to control the respective flow rate and plasma temperature. For example, the controller 700 may be configured to make control decisions for the respective valves and heaters based on a predetermined schedule and/or any received data from sensors (not shown) within the plasma spray apparatus 200.

In one or more exemplary embodiments, the controller 700 may be a stand-alone controller 700. Referring particularly to the operation of the controller 700 as shown in FIG. 7, in at least certain embodiments, the controller 700 can include one or more computing device(s) 710. The computing device(s) 710 can include one or more processor(s) 710A and one or more memory device(s) 710B. The one or more processor(s) 710A can include any suitable processing device, such as a microprocessor, microcontroller, integrated circuit, logic device, and/or other suitable processing device. The one or more memory device(s) 710B can include one or more computer-readable media, including, but not limited to, non-transitory computer-readable media, RAM, ROM, hard drives, flash drives, and/or other memory devices.

The one or more memory device(s) 710B can store information accessible by the one or more processor(s) 710A, including computer-readable instructions 710C that can be executed by the one or more processor(s) 710A. The instructions 710C can be any set of instructions that when executed by the one or more processor(s) 710A, cause the one or more processor(s) 710A to perform operations. In some embodiments, the instructions 710C can be executed by the one or more processor(s) 710A to cause the one or more processor(s) 710A to perform operations, such as any of the operations and functions for which the controller 700 and/or the computing device(s) 710 are configured, the operations for the system 200 (FIG. 2), as described herein, and/or any other operations or functions of the one or more computing device(s) 710. The instructions 710C can be software written in any suitable programming language or can be implemented in hardware. Additionally, and/or alternatively, the instructions 710C can be executed in logically and/or virtually separate threads on processor(s) 710A. The memory device(s) 710B can further store data 710D that can be accessed by the processor(s) 710A. For example, the data 710D can include data indicative of flow schedules, temperature schedules, system operating conditions, and/or any other data and/or information described herein.

The computing device(s) 710 can also include a network interface 710E used to communicate, for example, with the other components of the system 200. The controller 700 and the system 200 are operably coupled together through, e.g., the network interface, such that the computing device(s) 710 may receive data indicative of various operating parameters sensed by the one or more sensors during operation and/or send instructions to control various operating parameters. The network interface 710E can include any suitable components for interfacing with one or more network(s), including for example, transmitters, receivers, ports, controllers, antennas, and/or other suitable components.

The technology discussed herein makes reference to computer-based systems and actions taken by and information sent to and from computer-based systems. One of ordinary skill in the art will recognize that the inherent flexibility of computer-based systems allows for a great variety of possible configurations, combinations, and divisions of tasks and functionality between and among components. For instance, processes discussed herein can be implemented using a single computing device or multiple computing devices working in combination. Databases, memory, instructions, and applications can be implemented on a single system or distributed across multiple systems. Distributed components can operate sequentially or in parallel.

For example, the controller 700 may be configured to perform a method, such as a method of forming a thermal barrier coating having a non-linear compositional gradient and a non-linear porosity gradient. In one embodiment, such as depicted in FIG. 8, an exemplary method 800 is provided. At 802, a deposition mixture may be sprayed via a solution precursor plasma spray apparatus onto a surface of a substrate, as described in greater detail above. At 804, at least one deposition parameter is adjusted (e.g., according to an adjustment schedule, such as described above).

Further aspects of the disclosure are provided by the subject matter of the following clauses:

1. A method of forming a thermal barrier coating having a non-linear compositional gradient and a non-linear porosity gradient, the method comprising: spraying a deposition mixture of a first composition and a second composition via a solution precursor plasma spray apparatus onto a surface of a substrate; while spraying the deposition mixture, adjusting at least one deposition parameter such that the thermal barrier coating is formed with the non-linear gradient.

2. The method of any preceding clause, wherein adjusting the at least one deposition parameter comprises adjusting a first flow rate of the first composition to the solution precursor plasma spray apparatus according to a flow rate schedule, wherein the flow rate schedule is configured such that the thermal barrier coating is formed with a non-linear compositional gradient of the first composition.

3. The method of any preceding clause, wherein the non-linear compositional gradient is defined by alternating periods of a relatively high concentration of the first composition and a relatively low concentration of the first composition in the thermal barrier coating.

4. The method of any preceding clause, wherein the first composition comprises a rare earth stabilized zirconia with a concentration of the rare earth having a gradient through the thermal barrier coating.

5. The method of any preceding clause, wherein the concentration of the rare earth varies from 8 wt. % to 55 wt. % within the thermal barrier coating.

6. The method of any preceding clause, wherein adjusting the at least one deposition parameter further comprises adjusting a second flow rate of a second composition to the solution precursor plasma spray apparatus according to the flow rate schedule, wherein the flow rate schedule is configured such that the thermal barrier coating is formed with the non-linear compositional gradient of the second composition.

7. The method of any preceding clause, wherein the non-linear compositional gradient is defined by alternating periods of a relatively high concentration of the second composition and a relatively low concentration of the second composition in the thermal barrier coating.

8. The method of any preceding clause, wherein the deposition mixture further comprises a third composition; wherein adjusting the at least one deposition parameter further comprises: adjusting a third flow rate of the third composition to the solution precursor plasma spray apparatus according to the flow rate schedule, wherein the flow rate schedule is configured such that the thermal barrier coating is formed with the non-linear compositional gradient of the third composition.

9. The method of any preceding clause, wherein the third composition comprises a plurality of nonspherical particles such that the thermal barrier coating is formed with the non-linear compositional gradient of the plurality of nonspherical particles.

10. The method of any preceding clause, wherein adjusting the at least one deposition parameter comprises adjusting a process parameter of the solution precursor plasma spray apparatus according to a parameter schedule, wherein the parameter schedule is configured such that the thermal barrier coating is formed with a non-linear porosity gradient.

11. The method of any preceding clause, wherein the non-linear porosity gradient is defined by alternating periods of a relatively high porosity and a relatively low porosity in the thermal barrier coating.

12. The method of any preceding clause, wherein the process parameter is a plasma temperature of the solution precursor plasma spray apparatus such that the parameter schedule is a temperature schedule that adjusts the plasma temperature of the deposition mixture exiting the solution precursor plasma spray apparatus.

13. The method of any preceding clause, wherein the process parameter is a plasma gas flow rate of the solution precursor plasma spray apparatus such that the parameter schedule is a plasma gas flow rate schedule that adjusts the plasma gas flow rate of a plasma gas exiting the solution precursor plasma spray apparatus.

14. The method of any preceding clause, further comprising: after spraying a deposition mixture, sintering the thermal barrier coating to form an integrated coating such that a continuous phase extends throughout the thermal barrier coating.

15. The method of any preceding clause, wherein the thermal barrier coating has a thickness of 75 μm to 635 μm.

16. The method of any preceding clause, wherein the thermal barrier coating includes a thermal conductivity of 1 W/mK @1000° C. or less.

17. The method of any preceding clause, wherein the at least one deposition parameter is continuously adjusted such that the thermal barrier coating is formed with the non-linear gradient that has a continuously changing non-linear gradient therein.

18. The method of any preceding clause, further comprising: prior to spraying a deposition mixture, forming a bond coat on the surface of the substrate, wherein the deposition mixture is sprayed onto the bond coat.

19. A coated component formed according to the method of any preceding clause.

20. The coated component of any preceding clause, wherein the thermal barrier coating includes a non-linear compositional gradient therein, a non-linear porosity gradient therein, or both.

21. The coated component of any preceding clause, wherein the thermal barrier coating includes a non-linear compositional gradient therein and a non-linear porosity gradient therein.

22. The coated component of any preceding clause, wherein the thermal barrier coating comprises a rare earth stabilized zirconia with the concentration of the rare earth having a gradient through the thickness of the thermal barrier coating.

This written description uses exemplary embodiments to disclose the disclosure, including the best mode, and also to enable any person skilled in the art to practice the disclosure, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the disclosure is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

Claims

1. A method of forming a thermal barrier coating having a non-linear gradient therein, the method comprising:

spraying a deposition mixture of a first composition and a second composition via a solution precursor plasma spray apparatus onto a surface of a substrate; and

while spraying the deposition mixture, adjusting at least one deposition parameter such that the thermal barrier coating is formed with the non-linear gradient.

2. The method of claim 1, wherein adjusting the at least one deposition parameter comprises adjusting a first flow rate of the first composition to the solution precursor plasma spray apparatus according to a flow rate schedule, wherein the flow rate schedule is configured such that the thermal barrier coating is formed with a non-linear compositional gradient of the first composition.

3. The method of claim 2, wherein the non-linear compositional gradient is defined by alternating periods of a relatively high concentration of the first composition and a relatively low concentration of the first composition in the thermal barrier coating.

4. The method of claim 2, wherein the first composition comprises a rare earth stabilized zirconia with a concentration of the rare earth having a gradient through the thermal barrier coating.

5. The method of claim 4, wherein the concentration of the rare earth varies from 8 wt. % to 55 wt. % within the thermal barrier coating.

6. The method of claim 2, wherein adjusting the at least one deposition parameter further comprises adjusting a second flow rate of a second composition to the solution precursor plasma spray apparatus according to the flow rate schedule, wherein the flow rate schedule is configured such that the thermal barrier coating is formed with the non-linear compositional gradient of the second composition.

7. The method of claim 6, wherein the non-linear compositional gradient is defined by alternating periods of a relatively high concentration of the second composition and a relatively low concentration of the second composition in the thermal barrier coating.

8. The method of claim 6, wherein the deposition mixture further comprises a third composition; wherein adjusting the at least one deposition parameter further comprises: adjusting a third flow rate of the third composition to the solution precursor plasma spray apparatus according to the flow rate schedule, wherein the flow rate schedule is configured such that the thermal barrier coating is formed with the non-linear compositional gradient of the third composition.

9. The method of claim 8, wherein the third composition comprises a plurality of nonspherical particles such that the thermal barrier coating is formed with the non-linear compositional gradient of the plurality of nonspherical particles.

10. The method of claim 1, wherein adjusting the at least one deposition parameter comprises adjusting a process parameter of the solution precursor plasma spray apparatus according to a parameter schedule, wherein the parameter schedule is configured such that the thermal barrier coating is formed with a non-linear porosity gradient.

11. The method of claim 10, wherein the non-linear porosity gradient is defined by alternating periods of a relatively high porosity and a relatively low porosity in the thermal barrier coating.

12. The method of claim 10, wherein the process parameter is a plasma temperature of the solution precursor plasma spray apparatus such that the parameter schedule is a temperature schedule that adjusts the plasma temperature of the deposition mixture exiting the solution precursor plasma spray apparatus.

13. The method of claim 10, wherein the process parameter is a plasma gas flow rate of the solution precursor plasma spray apparatus such that the parameter schedule is a plasma gas flow rate schedule that adjusts the plasma gas flow rate of a plasma gas exiting the solution precursor plasma spray apparatus.

14. The method of claim 1, further comprising:

after spraying a deposition mixture, sintering the thermal barrier coating to form an integrated coating such that a continuous phase extends throughout the thermal barrier coating.

15. The method of claim 1, wherein the thermal barrier coating has a thickness of 75 μm to 635 μm, and wherein the thermal barrier coating includes a thermal conductivity of 1 W/mK @1000° C. or less.

16. The method of claim 1, wherein the at least one deposition parameter is continuously adjusted such that the thermal barrier coating is formed with the non-linear gradient that has a continuously changing non-linear gradient therein.

17. The method of claim 1, further comprising:

prior to spraying a deposition mixture, forming a bond coat on the surface of the substrate, wherein the deposition mixture is sprayed onto the bond coat.

18. A coated component formed according to the method of claim 1, wherein the thermal barrier coating includes a non-linear compositional gradient therein, a non-linear porosity gradient therein, or both.

19. The coated component of claim 18, wherein the thermal barrier coating includes a thermal conductivity of 1 W/mK @1000° C. or less.

20. The coated component of claim 18, wherein the thermal barrier coating has a fracture toughness of 20 J/m2 or greater.