Claims
- 1. An article, comprising:
a silicon-containing substrate that is oxidizable by reaction with an oxidant to at least one gaseous product; and an intermediate layer/coating applied onto said substrate, wherein said intermediate layer/coating is oxidizable to form a nongaseous product by reaction with said oxidant.
- 2. The article of claim 1, comprising a silicon-containing substrate and an external environmental/thermal barrier coating, wherein said external environmental/thermal barrier coating is permeable to diffusion of an environmental oxidant and said substrate is oxidizable by reaction with said oxidant to form at least one gaseous product; and
an intermediate layer/coating between said substrate and said environmental/thermal barrier coating that is oxidizable to form a non-gaseous product by reaction with said oxidant.
- 3. The article of claim 1, wherein said substrate is silicon carbide or silicon nitride monolith or composite.
- 4. The article of claim 2, wherein said external environmental/thermal barrier coating comprises yttria-stabilized zirconia, scandia-stabilized zirconia, calcia-stabilized zirconia, magnesia-stabilized zirconia, alumina, alumina silicate or mixtures thereof.
- 5. The article of claim 1, wherein said intermediate layer/coating is silicon or a silicon-containing alloy.
- 6. The article of claim 5, wherein said silicon containing alloy is selected from the group consisting of silicon aluminum (Si—Al), silicon chromium (Si—Cr), silicon magnesium (Si—Mg), silicon calcium (Si—Ca), silicon molybdenum (Si—Mo) and silicon titanium (Si—Ti).
- 7. The article of claim 1, wherein said intermediate layer/coating comprises silicon and an additional phase to enhance thermal or mechanical properties.
- 8. The article of claim 7, wherein said additional phase comprises silicon carbide or silicon nitride.
- 9. The article of claim 1, wherein said substrate comprises silicon carbide (SiC), silicon nitride (Si3N4), silicon carbide (SiC) fiber-reinforced silicon carbide (SiC) matrix composite, carbon fiber-reinforced silicon carbide (SiC) matrix composite or a silicon carbide (SiC) fiber-reinforced silicon nitride (Si3N4) composite.
- 10. The article of claim 1, wherein said substrate comprises a silicon carbide (SiC) fiber-reinforced silicon-silicon carbide (Si—SiC) matrix composite processed by silicon melt infiltration.
- 11. The article of claim 2, comprising a silicon-containing substrate having a lower coefficient of thermal expansion than the coefficient of thermal expansion of said external environmental/thermal barrier coating and said intermediate layer/coating reduces thermal stress between said substrate and said external environmental/thermal barrier coating.
- 12. The article of claim 11, wherein said intermediate layer/coating comprises silicon.
- 13. The article of claim 2, wherein said substrate comprises silicon carbide (SiC) and said intermediate layer/coating comprises a graded layer/coating with higher silicon carbide (SiC) concentration at an intermediate layer/coating-substrate interface than at an intermediate layer/coating-external environmental/thermal barrier coating interface and increasing silicon concentration at an interface between the environmental/thermal barrier coating and the intermediate layer/coating.
- 14. The article of claim 2, wherein said substrate is a silicon-based nonoxide ceramic matrix composition formed by silicon melt infiltration and said intermediate layer/coating is silicon.
- 15. The article of claim 2, comprising a silicon carbide (SiC) fiber-reinforced melt-infiltrated silicon-silicon carbide (Si—SiC) matrix substrate, a mullite-bonded yttria stabilized zirconia external environmental/thermal barrier coating and a silicon intermediate layer/coating.
- 16. The article of claim 1 shaped into an engine part.
- 17. An article comprising a silicon-containing substrate formed into a part and an external environmental/thermal barrier coating, wherein said external barrier coating is permeable to diffusion of an environmental oxidant and said substrate is oxidizable by reaction with said oxidant to at least one gaseous product; and a continuous intermediate layer/coating between said substrate and said environmental/thermal barrier coating that is oxidizable to form a nongaseous product by reaction with said oxidant in preference to reaction of said substrate with said oxidant.
- 18. A method of forming an article, comprising;
forming a silicon-containing substrate that is oxidizable by reaction with an oxidant to at least one gaseous product; and applying an intermediate layer/coating onto said substrate, wherein said intermediate layer/coating is oxidizable to form a nongaseous product by reaction with said oxidant.
- 19. The method of claim 18, comprising applying said intermediate layer/coating by chemical vapor deposition, melt infiltration, thermal spray or solution-based techniques.
- 20. The method of claim 18, further comprising applying an external environmental/thermal barrier coating, onto said intermediate layer/coating, wherein said external environmental/thermal barrier coating is permeable to diffusion of said oxidant.
- 21. The method of claim 20, wherein said substrate is a silicon carbide (SiC) substrate, comprising applying a silicon intermediate layer/coating onto said substrate to reduce thermal stress between said substrate and said external environmental/thermal barrier coating.
- 22. The method of claim 20, comprising applying said silicon intermediate layer/coating as a graded coating with higher silicon carbide (SiC) concentration at an intermediate layer/coating-substrate interface than at an intermediate layer/coating-external environmental/thermal barrier coating interface and increasing silicon concentration at an interface between the environmental/thermal barrier coating and the intermediate layer/coating.
- 23. The method of claim 20, wherein said substrate has a lower coefficient of thermal expansion than the coefficient of thermal expansion of said external environmental/thermal barrier coating, comprising applying an intermediate layer/coating onto said substrate to reduce thermal stress between said substrate and said external environmental/thermal barrier coating.
- 24. The method of claim 23, wherein said intermediate layer/coating comprises silicon.
- 25. A method of improving the bond strength of an article, comprising: providing a silicon-based nonoxide substrate for application of an external environmental/thermal barrier coating, wherein said external environmental/thermal barrier coating is permeable to diffusion of an environmental oxidant and said substrate is oxidizable by reaction with said oxidant to form at least one gaseous product; and
applying an intermediate layer/coating onto said substrate, wherein said intermediate layer is oxidizable to a nongaseous product by reaction with said oxidant in preference to reaction of said substrate with said oxidant.
- 26. A method of forming an article, comprising:
providing a silicon-silicon carbide substrate containing silicon carbide-containing fibers and said substrate having an external yttria-stabilized zirconia coating; and
applying a silicon intermediate layer/coating onto said substrate, wherein said intermediate layer is oxidizable to a nongaseous product by reaction with said oxidant in preference to reaction of said substrate with said oxidant.
- 27. A method according to claim 26 where the external environmental/thermal barrier coating further comprises a bond coat.
- 28. A method according to claim 27 where the bond coat is mullite, modified mullite or MCrAlY where M is nickel, iron, cobalt, or mixtures thereof.
- 29. A method according to claim 28 where the mullite coating comprises a modifier component.
- 30. A method according to claim 29 where the modifier component is selected from the group consisting of alkaline earth aluminosilicate having a formula MO.Al2O3.2SiO2, where M is an alkaline earth element, yttrium silicates (YS), calcium aluminates, aluminum titanates, cordierite, fused silica, silicon, NaZr2P3O12, Ba1.25Zr4P5.5Si0.5O24, Ca0.5Sr0.5Zr4(PO4)6, Ca0.6Mg0.4Sr4(PO4)6 and mixtures thereof.
- 31. A method according to claim 30 where the formula MO.Al2O3.2SiO2 includes barium feldspar (BaO.Al2O3.2SiO2), strontium feldspar (SrO.Al2O3.2SiO2), and combinations of barium feldspar (BaO.Al2O3.2SiO2), and strontium feldspar (SrO.Al2O3.2SiO2).
- 32. A method according to claim 30 where the aluminosilicates include (BaO)0.75(SrO)0.25.Al2O3.2SiO2 (BSAS) and CaO.Al2O3.2SiO2 (CAS) or combinations thereof.
- 33. The article of claim 4 where the external environmental/thermal barrier coating further comprises a bond coating.
- 34. The article of claim 33 where the bond coating comprises mullite, modified mullite or MCrAlY where M is nickel, iron, cobalt, or mixtures thereof.
- 35. The article of claim 34 where the mullite coating comprises a modifier component.
- 36. The article of claim 35 where the modifier component is selected from the group consisting of alkaline earth aluminosilicate having a formula MO.Al2O3.2SiO2, where M is an alkaline earth element, yttrium silicates (YS), calcium aluminates, aluminum titanates, cordierite, fused silica, silicon, NaZr2P3O12, Ba1.25Zr4P5.5Si0.5O24, Ca0.5Sr0.5Zr4(PO4)6, Ca0.6Mg0.4Sr4(PO4)6 and mixtures thereof.
- 37. The article of claim 36 where the formula MO.Al2O3.2SiO2 includes barium feldspar (BaO.Al2O3.2SiO2), strontium feldspar (SrO.Al2O3.2SiO2), and combinations of barium feldspar (BaO.Al2O3.2SiO2), and strontium feldspar (SrO.Al2O3.2SiO2).
- 38. The article of claim 37 where the aluminosilicates include (BaO)0.75(SrO)0.25.Al2O3.2SiO2 (BSAS), CaO.Al2O3.2SiO2 (CAS) or combinations thereof.
- 39. An article, comprising:
comprising a silicon carbide (SiC) fiber-reinforced melt-infiltrated silicon-silicon carbide (Si—SiC) matrix substrate, a mullite bond coating, a yttria stabilized zirconia external environmental/thermal barrier coating and a silicon intermediate layer/coating.
- 40. The article of claim 39 where the mullite coating comprises a modified component.
- 41. The article of claim 40 where modified component comprises (BaO)0.75(SrO)0.25.Al2O3.2SiO2 (BSAS), CaO.Al2O3.2SiO2 (CAS) or combinations thereof.
Government Interests
[0001] This invention was made with government support under Contract No. NAS3-26385 awarded by NASA. The government may have certain rights in the invention.
Provisional Applications (1)
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Number |
Date |
Country |
|
60083207 |
Apr 1998 |
US |
Divisions (1)
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Number |
Date |
Country |
Parent |
09299418 |
Apr 1999 |
US |
Child |
09846548 |
May 2001 |
US |