Method of forming thermal barrier coating, thermal barrier coating formed thereby, and article comprising same

Abstract

A thermal barrier coating that includes a YAG-based ceramic is prepared by a solution precursor plasma spray method that includes injecting a precursor solution into a thermal jet, evaporating solvent from the precursor solution droplets, and pyrolyzing the resulting solid to form a YAG-based ceramic that is melted and deposited on a substrate. The thermal barrier coating can include through-coating-thickness cracks that improve the strain tolerance of the coating.

1 . A method of forming a thermal barrier coating, comprising:
 injecting a precursor solution into a thermal jet; wherein the precursor solution comprises metal ion precursors to a YAG-based ceramic;   evaporating solvent from the precursor solution in the thermal jet to form unpyrolyzed solid particles;   pyrolyzing at least a portion of the unpyrolyzed solid particles in the thermal jet to form pyrolyzed solid particles comprising a YAG-based ceramic;   melting at least a portion of the pyrolyzed solid particles in the thermal jet to form droplets comprising the YAG-based ceramic; and   depositing the droplets comprising the YAG-based ceramic on a substrate to form a thermal barrier coating.   
     
     
         2 - 4 . (canceled) 
     
     
         5 . The method of  claim 1 , wherein the YAG-based ceramic has the empirical formula Y 3 Al 5-x Fe x O 12 , where x can vary continuously from 0 to 5. 
     
     
         6 . The method of  claim 1 , wherein the YAG-based ceramic comprises yttrium aluminum garnet (Y 3 Al 5 O 12 ). 
     
     
         7 . The method of  claim 1 , wherein the precursor solution is a homogeneous solution. 
     
     
         8 . The method of  claim 1 , wherein the metal ion precursors to the YAG-based ceramic are provided in the form of a salt selected from the group consisting of carboxylate salts, alkoxide salts, carbonate salts, halide salts, nitrate salts, hydrates of the foregoing salts, and combinations thereof. 
     
     
         9 . The method of  claim 1 , wherein the precursor solution comprises yttrium nitrate and aluminum nitrate. 
     
     
         10 . The method of  claim 1 , wherein said depositing the droplets comprising the YAG-based ceramic on the substrate forms splats on the substrate, the splats comprising the YAG-based ceramic; wherein the splats have an average diameter less than or equal to 5 micrometers. 
     
     
         11 . The method of  claim 1 , wherein the thermal barrier coating has a thickness of about 1 to about 5,000 micrometers. 
     
     
         12 . The method of  claim 1 , further comprising incompletely pyrolyzing at least a portion of the unpyrolyzed solid particles in the thermal jet to form incompletely pyrolyzed solid particles; depositing the incompletely pyrolyzed solid particles and/or the unpyrolyzed solid particles on the substrate; and pyrolyzing the incompletely pyrolyzed solid particles and/or the unpyrolyzed solid particles on the substrate. 
     
     
         13 . The method of  claim 1 , wherein said pyrolyzing the unpyrolyzed solid particles and/or incompletely pyrolyzed solid particles on the substrate forms through-coating-thickness microcracks in the thermal barrier coating. 
     
     
         14 . The method of  claim 1 , wherein the thermal barrier coating has a thickness; and wherein the through-coating-thickness microcracks are spaced from each other at a distance, on average, of less than or equal to half the coating thickness. 
     
     
         15 . The method of  claim 1 , wherein the through-coating-thickness microcracks have a width of about 0.1 to about 5 micrometers. 
     
     
         16 . The method of  claim 1 , wherein the thermal barrier coating has a porosity of about 10 to about 40 volume percent based on the total volume of the thermal barrier coating. 
     
     
         17 . The method of  claim 1 , wherein the thermal barrier coating comprises inter-pass boundaries. 
     
     
         18 . The method of  claim 1 ,
 wherein the YAG-based ceramic has the empirical formula Y 3 Al 5-x Fe x O 12 , where x can vary continuously from 0 to 5;   wherein the precursor solution is a homogeneous solution;   wherein the precursor solution comprises yttrium nitrate and at least one of aluminum nitrate and ferric nitrate;   wherein the thermal barrier coating has a thickness of about 50 to about 5,000 micrometers;   wherein the method further comprises depositing incompletely pyrolyzed solid particles and/or the unpyrolyzed solid particles on the substrate and pyrolyzing the incompletely pyrolyzed solid particles and/or the unpyrolyzed solid particles on the substrate;   wherein the thermal barrier coating comprises through-coating-thickness microcracks having a width of about 0.1 to about 5 micrometers;   wherein the through-coating-thickness microcracks are spaced from each other at a distance, on average, of less than or equal to half the coating thickness; and   wherein the thermal barrier coating has a porosity of about 10 to about 40 volume percent based on the total volume of the thermal barrier coating.   
     
     
         19 . A thermal barrier coating prepared by the method of  claim 1 . 
     
     
         20 . A thermal barrier coating having a thickness of about 50 to about 5,000 micrometers and comprising through-coating-thickness microcracks having a width of about 0.1 to about 5 micrometers and spaced from each other at a distance, on average, of less than or equal to half the coating thickness; wherein the thermal barrier coating comprises a YAG-based ceramic. 
     
     
         21 . The thermal barrier coating of  claim 20 , wherein the YAG-based ceramic has the empirical formula Y 3 Al 5-x Fe x O 12 , where x can vary continuously from 0 to 5; and wherein the thermal barrier coating comprises inter-pass boundaries and splats having an average diameter less than or equal to 5 micrometers. 
     
     
         22 . An article comprising the thermal barrier coating of  claim 20 . 
     
     
         23 . The article of  claim 22 , wherein the article is used in the hot section of a gas turbine and selected from turbine blades, turbine vanes, turbine blade outer air seals, and combustor liner segments.