Methods for fabricating protective coating systems for gas turbine engine applications

A method of applying a protective coating to a substrate includes the steps of:

• providing a substrate formed of a silicon carbide—silicon carbide (SiC—SiC) material, wherein the substrate has an exterior surface exhibiting a degree of valley/hill surface irregularity comprising a plurality of hills and a plurality of valleys;
• forming a first coating layer comprising two or more sol-gel coating layers including a sol-gel of a silicate of zirconium over the substrate, each of the sol-gel coating layers comprising a colloidal suspension, wherein the first coating layer is characterized as an oxygen barrier material, the first coating layer is formed directly on to the exterior surface of the substrate and conforms to the exterior surface of the substrate such that the first coating layer has a non-uniform coating thickness over the substrate, the first coating layer has a thickness within the plurality of valleys that is greater than its thickness over the plurality of hills;
• forming a second, porous coating layer directly on to the exterior surface of the first coating layer and characterized as a thermal barrier material, the second coating layer further comprises a plurality of pores within the second coating layer and the second coating layer comprises a silicate of yttrium;
• and
• forming a third coating layer partially directly on to an exterior surface of the second coating layer and partially within at least some of the plurality of pores within the second coating layer, the third coating layer forming an exposed surface of the protective coating, wherein the third coating layer coats walls of at least some of the plurality of pores but does not completely fill the at least some of the plurality of pores, the third coating layer infiltrates the second coating layer to a depth of 70% or less of a total thickness of the second coating layer and the third coating layer comprises a silicate of zirconium.

A method of applying a protective coating to a substrate includes the steps of:

• providing substrate formed of a silicon carbide—silicon carbide (SiC—SiC) material, wherein the substrate has an exterior surface exhibiting a degree of valley/hill surface irregularity comprising a plurality of hills and a plurality of valleys;
• forming a first coating layer comprising two or more sol-gel coating layers including a sol-gel consisting of a silicate of zirconium over the substrate, each of the sol-gel coating layers comprising a colloidal suspension, wherein the first coating layer is characterized as an oxygen barrier material, the first coating layer is formed directly on to the exterior surface of the substrate and conforms to the exterior surface of the substrate such that the first coating layer has a non-uniform coating thickness over the substrate, the first coating layer has a thickness within the plurality of valleys that is greater than its thickness over the plurality of hills;
• forming a second, porous coating layer directly on to the exterior surface of the first coating layer and characterized as a thermal barrier material, the second coating layer further comprises a plurality of pores within the second coating layer such that the second coating layer comprises a porosity of about 10% to about 70%, the second coating layer consists of a silicate of yttrium;
• and
• forming a third coating layer partially directly on to an exterior surface of the second coating layer and partially within at least some of the plurality of pores within the second coating layer, the third coating layer forming an exposed surface of the protective coating and the substrate has a use temperature of 3000 degrees Fahrenheit with the protective coating, the third coating layer consists of a silicate of zirconium, the third coating layer coats walls of at least some of the plurality of pores but does not completely fill the at least some of the plurality of pores, the third coating layer infiltrates the second coating layer to a depth of 70% or less of a total thickness of the second coating layer, thereby creating a porosity gradient in the second coating layer, and 30% or more of the total thickness of the second coating layer comprises pores that remain uncoated.