Methods of improving surface roughness of an environmental barrier coating and components comprising environmental barrier coatings having improved surface roughness

A method for reducing a surface roughness of an environmental barrier coating, the method comprising:

• providing a component having a plasma sprayed environmental barrier coating having a surface characterized by a surface roughness of greater than 5 micrometers Ra;
• applying an outer layer repair slurry to the surface of the environmental barrier coating of the component;
• drying the applied outer layer repair slurry;
• and
• sintering the applied outer layer repair slurry to form a sintered outer repair layer that defines an outer surface having a surface roughness of 1 to 5 micrometers Ra;
• wherein the outer layer repair slurry comprises:
• water;
• a primary outer material comprising barium-strontium-aluminosilicates (BSAS) in an amount in the outer layer repair slurry to constitute a solids loading in the outer layer repair slurry of greater than 10% and up to 55% by volume;
• and
• a slurry sintering aid selected from the group consisting of rare earth nitrate, rare earth acetate, rare earth chloride, rare earth oxide, and combinations thereof;
• and
• wherein the sintering step forms a secondary material in the sintered outer repair layer as a reaction product of the primary outer material and the slurry sintering aid, wherein the slurry sintering aid increases a rate of diffusion of the primary outer material such that the surface area reduction occurs within the sintered outer repair layer at lower temperatures than would occur absent the slurry sintering aid, and the secondary material is chosen from the group consisting of rare earth oxides, rare earth disilicates, rare earth monosilicates, rare earth elements, rare earth containing aluminosilicate glasses, rare earth and alkaline earth containing aluminosilicate glasses, rare earth aluminates, and combinations thereof.