Patent ID: 7910225
Filing Date: 2011-03-22
Classification: C23C,Y10T

Abstract:
1. A low thermal expansion bondcoat for thermal barrier coatings, said bondcoat comprising: (i) an inner layer comprising an inner layer alloy of MCrAlM′ wherein M is an element selected from nickel, cobalt, iron and mixtures thereof, and M′ is an element selected from yttrium, zirconium, hafnium, ytterbium and mixtures thereof, and wherein said inner layer has a composition based on the thermal expansion of said inner layer that is determined by the equation: in which the indicated element is its weight percent based on the total weight of said inner layer; said inner layer alloy thermally sprayed from a powder having a mean particle size of 50 percentile point in distribution of from about 5 microns to about 50 microns; and (ii) an outer layer comprising an outer layer alloy of MCrAlM′ wherein M is an element selected from nickel, cobalt, iron and mixtures thereof, and M′ is an element selected from yttrium, zirconium, hafnium, ytterbium and mixtures thereof, and wherein said outer layer has a composition based on the thermal expansion of said outer layer that is determined by the equation: in which the indicated element is its weight percent based on the total weight of said outer layer; said outer layer alloy thermally sprayed from a powder having a mean particle size of 50 percentile point in distribution of from about 30 microns to about 100 microns, and said outer layer having a surface roughness of at least 200 micro-inches; wherein said bondcoat has a thermal expansion of about 6.5 millimeters per meter or less between a temperature of from about 25° C. to about 525° C.; wherein an alpha-Cr phase is present in said inner layer and said outer layer in an amount sufficient to control thermal expansion of said bondcoat to about 6.5 millimeters per meter or less between a temperature of from about 25° C. to about 525° C.; and wherein the bondcoat is heat treated to stabilize equilibrium phases of said bondcoat, and the alpha-Cr phase is in equilibrium in said bondcoat composition that has been thermally stabilized at a temperature of about 800° C. and said alpha-Cr phase does not dissolve upon heating to a temperature of at least about 1000° C.