Method of forming a multilayer ceramic coating

A method of forming a multilayer ceramic coating system on a substrate, the method comprising the steps of:

• forming a first mixture comprising, in weight percent, 5 to 75% solvent, 0 to 10% surfactant, 5 to 70% of a first alumina powder, 0 to 25% of a second alumina powder that is finer than the first alumina powder, 5 to 70% of a third alumina powder that is finer than the second alumina powder, 3 to 35% silicone binder, 0.5 to 25% dibutyl pthalate, and 1 to 50% silicone binder/plasticizer;
• forming a second mixture comprising, in weight percent, 5 to 75% solvent, 0 to 10% surfactant, 0 to 25% of a first alumina powder, 5 to 85% of a second alumina powder that is finer than the first alumina powder, 0 to 25% of a third alumina powder that is finer than the second alumina powder, 3 to 35% silicone binder, 0.5 to 25% dibutyl pthalate, and 1 to 50% silicone binder/plasticizer;
• forming a multilayer tape to contain a first layer of the first mixture and a second layer of the second mixture;
• drying the multilayer tape to evaporate the solvents;
• applying the multilayer tape to a substrate so that the first layer directly contacts the substrate and the second layer is most remote from the substrate;
• applying pressure to the second layer to modify the surface finish and geometry thereof;
• heating and applying pressure to the multilayer tape to attach the multilayer tape to the substrate;
• and then
• sintering the multilayer tape at a temperature below the melting temperature of the substrate so that the first and second layers of the multilayer tape form innermost and outermost ceramic layers, respectively, on the substrate, the innermost ceramic layer having submicron voids therein to yield a porosity of at least 10%, the outermost ceramic layer having a surface roughness of less than 20 μinches Ra and a porosity of less than 10%.