Gradient within a thermal barrier coating and methods of their formation

Abstract

Methods are provided for forming a thermal barrier coating having a non-linear compositional gradient and/or a non-linear porosity gradient, along with coated components formed therefrom. The method includes spraying a deposition mixture of a first composition and a second composition via a solution precursor plasma spray apparatus onto a surface of a substrate; while spraying the deposition mixture, adjusting at least one deposition parameter such that the thermal barrier coating is formed with the non-linear gradient.

What is claimed is: 
     
         1 . A method of forming a thermal barrier coating having a non-linear gradient therein, the method comprising:
 spraying a deposition mixture of a first composition and a second composition via a solution precursor plasma spray apparatus onto a surface of a substrate; and   while spraying the deposition mixture, adjusting at least one deposition parameter such that the thermal barrier coating is formed with the non-linear gradient.   
     
     
         2 . The method of  claim 1 , wherein adjusting the at least one deposition parameter comprises adjusting a first flow rate of the first composition to the solution precursor plasma spray apparatus according to a flow rate schedule, wherein the flow rate schedule is configured such that the thermal barrier coating is formed with a non-linear compositional gradient of the first composition. 
     
     
         3 . The method of  claim 2 , wherein the non-linear compositional gradient is defined by alternating periods of a relatively high concentration of the first composition and a relatively low concentration of the first composition in the thermal barrier coating. 
     
     
         4 . The method of  claim 2 , wherein the first composition comprises a rare earth stabilized zirconia with a concentration of the rare earth having a gradient through the thermal barrier coating. 
     
     
         5 . The method of  claim 4 , wherein the concentration of the rare earth varies from 8 wt. % to 55 wt. % within the thermal barrier coating. 
     
     
         6 . The method of  claim 2 , wherein adjusting the at least one deposition parameter further comprises adjusting a second flow rate of a second composition to the solution precursor plasma spray apparatus according to the flow rate schedule, wherein the flow rate schedule is configured such that the thermal barrier coating is formed with the non-linear compositional gradient of the second composition. 
     
     
         7 . The method of  claim 6 , wherein the non-linear compositional gradient is defined by alternating periods of a relatively high concentration of the second composition and a relatively low concentration of the second composition in the thermal barrier coating. 
     
     
         8 . The method of  claim 6 , wherein the deposition mixture further comprises a third composition; wherein adjusting the at least one deposition parameter further comprises: adjusting a third flow rate of the third composition to the solution precursor plasma spray apparatus according to the flow rate schedule, wherein the flow rate schedule is configured such that the thermal barrier coating is formed with the non-linear compositional gradient of the third composition. 
     
     
         9 . The method of  claim 8 , wherein the third composition comprises a plurality of nonspherical particles such that the thermal barrier coating is formed with the non-linear compositional gradient of the plurality of nonspherical particles. 
     
     
         10 . The method of  claim 1 , wherein adjusting the at least one deposition parameter comprises adjusting a process parameter of the solution precursor plasma spray apparatus according to a parameter schedule, wherein the parameter schedule is configured such that the thermal barrier coating is formed with a non-linear porosity gradient. 
     
     
         11 . The method of  claim 10 , wherein the non-linear porosity gradient is defined by alternating periods of a relatively high porosity and a relatively low porosity in the thermal barrier coating. 
     
     
         12 . The method of  claim 10 , wherein the process parameter is a plasma temperature of the solution precursor plasma spray apparatus such that the parameter schedule is a temperature schedule that adjusts the plasma temperature of the deposition mixture exiting the solution precursor plasma spray apparatus. 
     
     
         13 . The method of  claim 10 , wherein the process parameter is a plasma gas flow rate of the solution precursor plasma spray apparatus such that the parameter schedule is a plasma gas flow rate schedule that adjusts the plasma gas flow rate of a plasma gas exiting the solution precursor plasma spray apparatus. 
     
     
         14 . The method of  claim 1 , further comprising:
 after spraying a deposition mixture, sintering the thermal barrier coating to form an integrated coating such that a continuous phase extends throughout the thermal barrier coating.   
     
     
         15 . The method of  claim 1 , wherein the thermal barrier coating has a thickness of 75 μm to 635 μm, and wherein the thermal barrier coating includes a thermal conductivity of 1 W/mK @1000° C. or less. 
     
     
         16 . The method of  claim 1 , wherein the at least one deposition parameter is continuously adjusted such that the thermal barrier coating is formed with the non-linear gradient that has a continuously changing non-linear gradient therein. 
     
     
         17 . The method of  claim 1 , further comprising:
 prior to spraying a deposition mixture, forming a bond coat on the surface of the substrate, wherein the deposition mixture is sprayed onto the bond coat.   
     
     
         18 . A coated component formed according to the method of  claim 1 , wherein the thermal barrier coating includes a non-linear compositional gradient therein, a non-linear porosity gradient therein, or both. 
     
     
         19 . The coated component of  claim 18 , wherein the thermal barrier coating includes a thermal conductivity of 1 W/mK @1000° C. or less. 
     
     
         20 . The coated component of  claim 18 , wherein the thermal barrier coating has a fracture toughness of 20 J/m 2  or greater.