Claims
- 1. A coating system on a surface of a component, the coating system comprising a thermal-insulating layer, the thermal-insulating layer comprising a matrix of a first material, particles of at least a second material dispersed in the matrix, and microcracks originating at interfaces between the particles and the matrix and emanating in directions substantially parallel to the surface of the component, the first and second materials having sufficiently different coefficients of thermal expansion to develop the microcracks in the thermal-insulating layer when subjected to thermal cycling.
- 2. A coating system according to claim 1, wherein the first material is yttria-stabilized zirconia or alumina.
- 3. A coating system according to claim 1, wherein the second material is barium strontium aluminosilicate, mullite, barium feldspar, strontium feldspar, a calcium aluminate, an aluminum titanate, a zirconate phosphate material, and/or cordierite.
- 4. A coating system according to claim 1, wherein the first material is yttria-stabilized zirconia and the second material is barium strontium aluminosilicate.
- 5. A coating system according to claim 1, further comprising an intermediate layer between the thermal-insulating layer and the surface of the component, the intermediate layer having a coefficient of thermal expansion between the coefficients of thermal expansion of the matrix and the component.
- 6. A coating system according to claim 5, wherein the intermediate layer is formed of at least one material selected from the group consisting of yttria-stabilized zirconia, mullite and barium strontium aluminosilicate.
- 7. A coating system according to claim 1, wherein the thermal-insulating layer is the outermost layer of the coating system.
- 8. A coating system according to claim 1, further comprising an outermost ceramic layer overlying the thermal-insulating layer.
- 9. A coating system according to claim 1, wherein the thermal-insulating layer is formed of splats so as to have a microstructure characterized by irregular flattened grains.
- 10. A coating system according to claim 1, wherein the particles are sized in a range of about 0.5 to about 50 micrometers in diameter and constitute about 5 to about 50 volume percent of the thermal-insulating layer.
- 11. A coating system according to claim 1, wherein the first material has a coefficient of thermal expansion that is at least 40% greater than that of the second material.
- 12. A coating system according to claim 1, wherein the component is formed of a material selected from the group consisting of superalloys and silicon-containing materials.
- 13. A coating system on a surface of a gas turbine engine component, the coating system comprising a bond coat and a multilayer barrier coating, the barrier coating comprising an intermediate layer on the bond coat and a thermal-insulating layer on the intermediate layer, the thermal-insulating layer comprising a matrix of yttria-stabilized zirconia, particles of barium strontium aluminosilicate and/or, mullite dispersed in the matrix, and microcracks originating at interfaces between the particles and the matrix and emanating in directions substantially parallel to the surface of the component, the matrix and the particles being formed of splats so that the thermal-insulating layer has a microstructure characterized by irregular flattened grains.
- 14. A coating system according to claim 13, wherein the particles are sized in a range of about 0.5 to about 50 micrometers in diameter and constitute about 5 to about 50 volume percent of the thermal-insulating layer.
- 15. A coating system according to claim 13, wherein the thermal-insulating layer is the outermost layer of the coating system.
- 16. A coating system according to claim 13, further comprising an outermost ceramic layer overlying the thermal-insulating layer.
- 17. A coating system according to claim 13, wherein the component is formed of a material selected from the group consisting of superalloys and ceramic matrix composite materials containing silicon or a silicon compound.
- 18. A method of reducing the thermal conductivity of a coating system, the method comprising the steps of:
forming a thermal-insulating layer on a surface of a component, the thermal-insulating layer being formed to comprise a matrix of a first material and particles of at least a second material dispersed in the matrix material, the first and second materials having different coefficients of thermal expansion; and heating and then cooling the thermal-insulating layer to form cracks that propagate from interfaces between the particles and matrix material in directions substantially parallel to the surface of the component.
- 19. A method according to claim 18, wherein the first material is yttria-stabilized zirconia or alumina.
- 20. A method according to claim 18, wherein the second material is barium strontium aluminosilicate, mullite, barium feldspar, strontium feldspar, a calcium aluminate, an aluminum titanate, a zirconate phosphate material, and/or cordierite.
- 21. A method according to claim 18, wherein the first material is yttria-stabilized zirconia and the second material is barium strontium aluminosilicate.
- 22. A method according to claim 18, further comprising the step of forming an intermediate layer between the thermal-insulating layer and the surface of the component, the intermediate layer having a coefficient of thermal expansion between the coefficients of thermal expansion of the matrix and the component.
- 23. A method according to claim 22, wherein the intermediate layer is formed of at least one material selected from the group consisting of yttria-stabilized zirconia, mullite and barium strontium aluminosilicate.
- 24. A method according to claim 18, wherein the thermal-insulating layer is the outermost layer of the coating system.
- 25. A method according to claim 18, further comprising an outermost ceramic layer overlying the thermal-insulating layer.
- 26. A method according to claim 18, wherein the thermal-insulating layer is formed by plasma spraying so as to have a microstructure characterized by irregular flattened grains.
- 27. A method according to claim 18, wherein the particles are sized in a range of about 0.5 to about 50 micrometers in diameter and constitute about 5 to about 50 volume percent of the thermal-insulating layer.
- 28. A method according to claim 18, wherein the first material has a coefficient of thermal expansion that is at least 40% greater than that of the second material.
- 29. A method according to claim 18, wherein the component is formed of a material selected from the group consisting of superalloys and silicon-containing materials.
- 30. A method of reducing the thermal conductivity of a coating system, the method comprising the steps of:
depositing a bond coat on a surface of a component; depositing an intermediate layer on the bond coat; plasma spraying a thermal-insulating layer on the intermediate layer so that the thermal-insulating layer is formed of splats and has a microstructure characterized by irregular flattened grains, the thermal-insulating layer comprising a matrix of yttria-stabilized zirconia, and particles of barium strontium aluminosilicate and/or mullite dispersed in the matrix; and then subjecting the coating system to multiple heating and cooling cycles, wherein microcracks are created in the thermal-insulating layer with each cycle, the microcracks originating at interfaces between the particles and the matrix and emanating in directions substantially parallel to the surface of the component.
- 31. A method according to claim 30, wherein the particles are sized in a range of about 0.5 to about 50 micrometers in diameter and constitute about 5 to about 50 volume percent of the thermal-insulating layer.
- 32. A method according to claim 30, wherein the thermal-insulating layer is the outermost layer of the coating system.
- 33. A method according to claim 30, further comprising an outermost ceramic layer overlying the thermal-insulating layer.
- 34. A method according to claim 30, wherein the component is formed of a material selected from the group consisting of superalloys and ceramic matrix composite materials containing silicon or a silicon compound.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
[0001] This invention was made with Government support under F33615-98-C-2893 awarded by the United States Department of the Air Force. The Government has certain rights in this invention.