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EP-4737429-A1 - POROUS MACHINED COATINGS

EP4737429A1EP 4737429 A1EP4737429 A1EP 4737429A1EP-4737429-A1

Abstract

A method of fabricating a porous machined coating for a ceramic matrix composite, comprising the steps of providing a ceramic matrix composite; optionally depositing on the ceramic matrix composite at least one bond coat; depositing on the at least one optional bond coat at least one ceramic powder to form at least one ceramic coat; and, machining the at least one ceramic coat to form at least one machined ceramic coat, wherein the at least one machined ceramic coat comprises a porosity gradient of approximately 5 percent by volume to approximately 30 percent by volume, the porosity gradient comprising an average fine pore size range of approximately 1 µm to approximately 25 µm, to an average coarse pore size range of approximately 30 µm to approximately 55 µm.

Inventors

  • KOLE, MOLLY
  • ALIDOOST, JALIL

Assignees

  • RTX Corporation

Dates

Publication Date
20260506
Application Date
20251027

Claims (15)

  1. A method of fabricating a porous machined coating for a ceramic matrix composite (500), comprising the steps of: providing a ceramic matrix composite (500); optionally depositing on the ceramic matrix composite (500) at least one bond coat (600); depositing on the at least one optional bond coat (600) at least one ceramic powder to form at least one ceramic coat (700); and machining the at least one ceramic coat (700) to form at least one machined ceramic coat (700), wherein the at least one machined ceramic coat (700) comprises a porosity gradient of approximately 5 percent by volume to approximately 30 percent by volume, the porosity gradient comprising an average fine pore size (800) range of approximately 1 µm to approximately 25 µm, to an average coarse pore size (900) range of approximately 30 µm to approximately 55 µm.
  2. The method of claim 1, wherein depositing the at least one ceramic powder comprises air plasma spraying the at least one ceramic powder.
  3. The method of claim 2, wherein air plasma spraying includes adjusting one or more of the following parameters: a distance between a nozzle of an air plasma spraying apparatus and a surface of the ceramic matrix composite (500); a voltage of the air plasma spraying apparatus; a powder feed rate of the air plasma spraying apparatus; and a temperature of the surface of the ceramic matrix composite (500), optionally wherein adjusting the temperature of the surface of the ceramic matrix composite (500) includes heat treating the surface of the ceramic matrix composite (500) prior to depositing the at least one ceramic powder.
  4. The method of any preceding claim, wherein, prior to depositing the at least one ceramic powder, further comprising providing the at least one ceramic powder comprising a mixture of one or more ceramic powders and one or more polymeric powders, optionally wherein the at least one ceramic powder comprises one or more of the following: mullite, hafnium silicate, ytterbium disilicate, yttrium disilicate, and combinations thereof.
  5. The method of claim 4, wherein the polymeric powders include at least polyester; and/or wherein the polymeric powder is present in an amount of approximately 1 percent by weight of the mixture to approximately 10 percent by weight of the mixture.
  6. The method of claim 4 or 5, further comprising heat treating the at least one deposited mixture of one or more ceramic powders and one or more polymeric powders at a temperature of approximately of 1,400°F (760 °C) to approximately 2,700°F (1482 °C), to form the at least one ceramic coat (700) comprising the porosity gradient.
  7. The method of any preceding claim, wherein the at least one deposited ceramic coat (700) includes a thickness of approximately 30 mil (0.76 mm) to approximately 100 mil (2.54 mm); and/or wherein the at least one machined ceramic coat (700) comprises a thickness of approximately 30 mil (0.762 mm) to approximately 50 mil (1.27 mm).
  8. The method of any preceding claim, further comprising: pre-heating the ceramic matrix composite (500) prior to optionally depositing the at least one bond coat (600); and/or pre-heating the ceramic matrix composite (500) and the at least one optional bond coat (600) prior to depositing the at least one ceramic powder.
  9. A gas turbine engine component, comprising: a ceramic matrix composite (500) having at least one optional bond coat (600), and the at least one machined ceramic coat (700) comprises a porosity of approximately 5 percent by volume to approximately 30 percent by volume, the porosity comprising a gradient having an average fine pore size (800) range of approximately 1 µm to approximately 25 µm, to an average coarse pore size (900) range of approximately 30 µm to approximately 55 µm.
  10. The method or gas turbine engine component of any preceding claim, wherein the average fine pore size (800) range of the gradient is proximate to an interface between the at least one optional bond coat (600) and the at least one machined ceramic coat (700); the average coarse pore size (900) range of the gradient is proximate to an exterior surface (1000) of the at least one machined ceramic coat (700); and, an average pore size of the gradient increases from the interface to the exterior surface (1000).
  11. The method or gas turbine engine component of any preceding claim, wherein the average coarse pore size (900) range of the gradient is proximate to an interface between the at least one optional bond coat (600) and the at least one machined ceramic coat (700); and the average fine pore size (800) range of the gradient is proximate to an or the exterior surface (1000) of the at least one machined ceramic coat (700); and, an average pore size of the gradient decreases from the interface to the exterior surface (1000).
  12. The gas turbine engine component of any of claims 9 to 11, wherein the at least one ceramic coat (700) comprises an at least one air plasma-sprayed layer ceramic coat (700).
  13. The gas turbine engine component of any of claims 9 to 12, wherein the at least one ceramic coat (700) comprises a thickness of approximately 30 mil (0.762 mm) to approximately 100 mil (2.54 mm).
  14. The gas turbine engine component of any of claims 9 to 13, wherein the at least one ceramic coat (700) comprises one or more of the following: mullite, hafnium silicate, ytterbium disilicate, yttrium disilicate, and combinations thereof.
  15. The method or gas turbine engine component of any preceding claim, wherein the at least one optional bond coat (600) comprises one or more of silicon, silicon-containing material, silicon oxycarbide, mullite, and combinations thereof.

Description

FIELD OF THE INVENTION The subject matter disclosed herein relates to coatings and, in particular, to porous machined coatings. BACKGROUND OF THE INVENTION Gas turbine engines include sections such as a fan, a low-pressure compressor, a high-pressure compressor, a combustor and a turbine. During operation, at least one of these sections may achieve high internal temperatures. Those gas turbine engine components located in the "hot sections" may comprise ceramic matrix composites ("CMC"). These CMC gas turbine components may come in contact with metallic or metal-containing gas turbine engine components. Those CMC components in contact with metallic or metal-containing components may further include a ceramic coating applied to the surface of the CMC component. The ceramic coating may be sufficiently thick to be machined down, through contact with the metallic or metal-containing components during operation, and create a seal between the CMC component and metallic or metal-containing component. During operation, the difference in temperature between the CMC component and metallic or metal-containing component may be drastic, e.g., up to 2,500°F (1371 °C). As a result, a thermal gradient may be exhibiting through the thickness of the ceramic coating. This resultant thermal gradient may cause stress(es) that may potentially lead to premature failure of the CMC component. In addition, the elevated operating temperatures may result in phase changes within candidate material systems, leading to volumetric changes and associated stresses in the ceramic coating. For example, the observed stress(es) may lead to cohesive cracking within the coating, or premature delamination between coating layers on the exterior surface of the CMC component. There exists a need to mitigate the aforementioned stress(es) throughout the ceramic coating. SUMMARY OF THE INVENTION The present disclosure is directed, in a first aspect, to a method of fabricating a porous machined coating for a ceramic matrix composite, comprising the steps of providing a ceramic matrix composite; optionally depositing on the ceramic matrix composite at least one bond coat; depositing on the at least one optional bond coat at least one ceramic powder to form at least one ceramic coat; and machining the at least one ceramic coat to form at least one machined ceramic coat, wherein the at least one machined ceramic coat comprises an porosity gradient of approximately 5 percent by volume to approximately 30 percent by volume, the porosity gradient comprising an average fine pore size range of approximately 1 µm to approximately 25 µm, to an average coarse pore size range of approximately 30 µm to approximately 55 µm. In another aspect, the present disclosure is directed to a gas turbine engine component, comprising a ceramic matrix composite substrate having at least one optional bond coat, and the at least one machined ceramic coat comprises an porosity of approximately 5 percent by volume to approximately 30 percent by volume, the porosity comprising a gradient having an average fine pore size range of approximately 1 µm to approximately 25 µm, to an average coarse pore size range of approximately 30 µm to approximately 55 µm. In yet another aspect, which the Applicant expressly reserves the right to claim independently, the present disclosure is directed to a gas turbine engine, comprising at least one rotatable gas turbine engine component; at least one stationary gas turbine engine component disposed opposite the at least one rotatable gas turbine engine component, the at least one stationary gas turbine engine component comprises a ceramic matrix composite substrate having at least one optional bond coat, and the at least one machined ceramic coat comprises an porosity of approximately 5 percent by volume to approximately 30 percent by volume, the porosity comprises a gradient having an average fine pore size range of approximately 1 µm to approximately 25 µm, to an average coarse pore size range of approximately 30 µm to approximately 55 µm. In further examples of the present disclosure, including further examples of the above, the average fine pore size range of the gradient is proximate to an interface between the at least one optional bond coat and the at least one machined ceramic coat; the average coarse pore size range of the gradient is proximate to an exterior surface of the at least one machined ceramic coat; and, an average pore size of the gradient increases from the interface to the exterior surface. In further examples of the present disclosure, including further examples of the above, the average coarse pore size range of the gradient is proximate to an interface between the at least one optional bond coat and the at least one machined ceramic coat; and the average fine pore size range of the gradient is proximate to an exterior surface of the at least one machined ceramic coat; and, an average pore size of the gradient decreases from the i