Hybrid Thermal Barrier Coating and Process of Making Same

Abstract

A thermal barrier coating is applied to a turbine engine component having a substrate. The thermal barrier coating has a first layer which has a strain tolerant columnar microstructure at an interface with the substrate for spallation resistance and a second layer which is porous conduction and radiation thermally resistant at an outer surface of the thermal barrier coating.

What is claimed is: 
     
         1 . A thermal barrier coating applied to a turbine engine component having a substrate, said coating comprising:
 a first layer which has a strain tolerant columnar microstructure at an interface with the substrate for spallation resistance; and   a second layer which is porous conduction and radiation thermally resistant at an outer surface of the thermal barrier coating.   
     
     
         2 . The thermal barrier coating of  claim 1 , wherein said first and second layers are formed from the same material. 
     
     
         3 . The thermal barrier coating of  claim 1 , wherein said first and second layers are formed from different compositions. 
     
     
         4 . The thermal barrier coating of  claim 1 , wherein said second layer has a porosity in the range of from 10 to 40%. 
     
     
         5 . The thermal barrier coating of  claim 1 , wherein each of said first and second layers is formed from 7 wt % yttria stabilized zirconia. 
     
     
         6 . The thermal barrier coating of  claim 1 , wherein said first layer is formed from 7 wt % yttria stabilized zirconia and the second layer is formed from gadolinia stabilized zirconia. 
     
     
         7 . The thermal barrier coating of  claim 1 , wherein said first layer has a first thermal conductivity and said second layer has a second thermal conductivity which is at least 10% lower than the first thermal conductivity. 
     
     
         8 . A process for applying a thermal barrier coating to a turbine engine component comprising:
 forming a first layer which has a strain tolerant columnar microstructure at an interface of the first layer and a substrate using a suspension plasma spray technique; and   forming a second layer which is porous and radiation thermally resistant at an outer surface of the thermal barrier coating using one of said suspension plasma spray technique and an air spray plasma technique.   
     
     
         9 . The process of  claim 8 , further comprising:
 forming a continuously graded microstructure from said interface to said outer surface.   
     
     
         10 . The process of  claim 8 , wherein said first layer forming step comprises suspending a powder feedstock in a liquid suspension and injecting said powder feedstock and said suspension into a plasma jet under conditions where said first layer is formed with said strain-tolerant columnar microstructure. 
     
     
         11 . The process of  claim 10 , wherein said second layer forming step comprises changing spray parameters so as to form said porous and radiation thermally resistant second layer. 
     
     
         12 . The process of  claim 8 , wherein said first and second layer forming steps comprises forming said layers from the same material. 
     
     
         13 . The process of  claim 8 , wherein said first layer is formed from a first material having a first composition and said second layer is formed from a second material having a second composition which is different from said first composition. 
     
     
         14 . The process of  claim 8 , wherein said second layer is formed using said air spray plasma technique. 
     
     
         15 . The process of  claim 8 , wherein said second layer forming step comprises forming said second layer so as to have a porosity of from 10 to 40%. 
     
     
         16 . The process of  claim 8 , wherein said second layer forming step comprises forming said second layer so as to have a thermal conductivity which is at least 10% lower than a thermal conductivity of said first layer. 
     
     
         17 . The process of  claim 8 , wherein said first and second layer forming steps comprise using a powdered feedstock having a particle size in the range of from 10 nm to 10 microns. 
     
     
         18 . The process of  claim 8 , wherein said first and second layer forming steps comprises using a powdered feedstock having a particle size in the range of from 10 nm to 2.0 microns.