Methods for forming high temperature coating systems and gas turbine engine components including the same

Abstract

Methods for forming high temperature coating systems are provided, as are gas turbine engine components including high temperature coating systems. In embodiments, the coating formation method includes forming a fracture-resistant Thermal Barrier Coating (TBC) layer over a workpiece surface. The fracture-resistant TBC layer is produced from a first coating precursor material containing an amount of zirconia in mole percent (ZrOmol %1) and an amount of tantala in mole percent (TaOmol %1). A Calcium-Magnesium Aluminosilicate (CMAS) resistant TBC layer is formed over the fracture-resistant TBC layer from a second coating precursor material, which contains an amount of zirconia in mole percent (ZrOmol %2), an amount of tantala in mole percent (TaOmol %2), and an amount of one or more rare earth oxides in mole percent (REOmol %2). The first and second coating precursor materials are formulated such that ZrOmol %1 is greater than ZrOmol %2, TaOmol %1 is less than TaOmol %2, and TaOmol %2 is substantially equivalent to REOmol %2.

What is claimed is: 
     
         1 . A method for producing a high temperature coating system over a component, the method comprising:
 forming a fracture-resistant Thermal Barrier Coating (TBC) layer over a surface of the component, the fracture-resistant TBC layer formed from a first coating precursor material containing:   a non-trace amount of zirconia by mole percent (ZrO mol %1 ); and
 a non-trace amount of tantala by mole percent (TaO mol %1 ); 
   forming a Calcium-Magnesium Aluminosilicate-resistant (CMAS-resistant) TBC layer over the fracture-resistant TBC layer, the CMAS-resistant TBC layer formed from a second coating precursor material containing:
 a non-trace amount of zirconia by mole percent (ZrO mol %2 ); 
 a non-trace amount of tantala by mole percent (TaO mol %2 ); and 
 a non-trace amount of at least one rare earth oxide by mole percent (REO mol %2 ); 
   wherein ZrO mol %1  is greater than ZrO mol %2 , TaO mol %1  is less than TaO mol %2 , and TaO mol %2  is substantially equivalent to REO mol %2 .   
     
     
         2 . The method of  claim 1  further comprising selecting the at least one rare earth oxide selected from the group consisting of yttria, ytterbia, gadolinia, and lanthanum oxides, and combinations thereof. 
     
     
         3 . The method of  claim 1  further comprising formulating the first coating precursor material to contain a non-trace amount of the at least one rare earth oxide by mole percent (REO mol %1 );
 wherein REO mol % 1  is less than REO mol %2 . 
 
     
     
         4 . The method of  claim 3  further comprising selecting REO mol %2  to be at least twice REO mol %2 . 
     
     
         5 . The method of  claim 1  further comprising formulating the first coating precursor material to be essentially free of the at least one rare earth oxide. 
     
     
         6 . The method of  claim 1  further comprising selecting ZrO mol % 1  to be at least twice ZrO mol %2 . 
     
     
         7 . The method of  claim 1  wherein forming the CMAS-resistant TBC layer comprises:
 depositing the second coating material directly onto the fracture-resistant TBC layer; and 
 after deposition of the second coating material, heat treating the second coating material to diffuse the at least one rare earth oxide into the fracture-resistant TBC layer and form a rare earth oxide gradient therein. 
 
     
     
         8 . The method of  claim 7  further comprising:
 producing the fracture-resistant TBC layer to include an outer surface to which the CMAS-resistant TBC layer is bonded and an inner surface opposite the outer surface; and 
 formulating the first coating precursor material and heat treating the second coating material such that the rare earth oxide gradient decreases from a maximum value to a minimum value when moving from the outer surface toward the inner surface. 
 
     
     
         9 . The method of  claim 1  further comprising formulating the second coating precursor material such that:
 ZrO wt %2  is between about 0.1% and about 35% by mole percent; 
 TaO wt %2  is between about 30% and about 40% by mole percent; and 
 REO wt %2  is between about 30% and about 40% by mole percent. 
 
     
     
         10 . The method of  claim 1  further comprising:
 producing a base TBC layer over the surface of the component prior to forming the fracture-resistant TBC layer thereover; and 
 formulating the base TBC layer to contain zirconia in an amount exceeding ZrO mol %1  by mole percent. 
 
     
     
         11 . The method of  claim 1  wherein the component comprises a Gas Turbine Engine (GTE) component; and
 wherein the method further comprises forming the CMAS-resistant TBC layer as an outermost layer of the high temperature coating system such that the CMAS-resistant TBC layer is directly exposed to core gas flow during GTE operation. 
 
     
     
         12 . A method for producing a high temperature coating system over a component, the method comprising:
 forming a fracture-resistant Thermal Barrier Coating (TBC) layer over a surface of the component, the fracture-resistant TBC layer comprising:
 about 25% to about 75% zirconia by weight percent; and 
 about 1% to about 30% tantala by weight percent; 
   forming a Calcium-Magnesium Aluminosilicate-resistant (CMAS-resistant) TBC layer on the fracture-resistant TBC layer, the CMAS-resistant TBC layer comprising:
 0% to about 25% zirconia by weight percent; 
 about 35% to about 55% tantala by weight percent; and 
 about 25% to about 40% of at least one rare earth oxide by weight percent. 
   
     
     
         13 . The method of  claim 12  further comprising selecting the at least one rare earth oxide from the group consisting of yttria, ytterbia, gadolinia, and lanthanum oxides, and combinations thereof. 
     
     
         14 . The method of  claim 12  further comprising:
 producing the fracture-resistant TBC layer to include an outer surface to which the CMAS-resistant TBC layer is bonded and an inner surface opposite the outer surface; and 
 diffusing the at least one rare earth oxide into the fracture-resistant TBC layer such that the fracture-resistant TBC layer contains a rare earth oxide gradient, which decreases from a maximum value to a minimum value when moving from the outer surface toward the inner surface of the fracture-resistant layer. 
 
     
     
         15 . The method of  claim 14  further comprising:
 selecting the at least one rare earth oxide to comprise gadolinia; and 
 diffusing the at least one rare earth oxide into the fracture-resistant TBC layer such that the fracture-resistant TBC layer contains a gadolinia gradient, which decreases from a maximum gadolinia concentration to a minimum gadolinia concentration when moving from the outer surface toward the inner surface of the fracture-resistant layer, the minimum gadolinia concentration substantially equivalent to  0 % by mole percent. 
 
     
     
         16 . A coated GTE component, comprising:
 a component body having a surface;   a fracture-resistant Thermal Barrier Coating (TBC) layer overlying the surface of the component body, the fracture-resistant TBC layer comprising:
 a non-trace amount of zirconia by mole percent (ZrO mol %1 ); and 
 a non-trace amount of tantala by mole percent (TaO mol %1 ); 
   a Calcium-Magnesium Aluminosilicate-resistant (CMAS-resistant) TBC layer over the fracture-resistant TBC layer, the CMAS-resistant TBC layer comprising:
 a non-trace amount of zirconia by mole percent (ZrO mol %2 ); 
 a non-trace amount of tantala by mole percent (TaO mol %2 ); and 
 a non-trace amount of at least one rare earth oxide by mole percent (REO mol %2 ); 
   wherein ZrO mol %2  less than ZrO mol %1 ; and   wherein the at least one rare earth oxide is selected from the group consisting of yttria, ytterbia, gadolinia, and lanthanum oxides, and combinations thereof.   
     
     
         17 . The coated GTE component of  claim 16  wherein TaO mol %1  is less than TaO mol %2 . 
     
     
         18 . The coated GTE component of  claim 16  wherein TaO mol%2  is substantially equivalent to REO mol %2 . 
     
     
         19 . The coated GTE component of  claim 16  wherein the CMAS-resistant TBC layer comprises:
 about 0.1% to about 35% zirconia by mole percent; 
 about 30% to about 40% tantala by mole percent; and 
 about 30% to about 40% of the at least one rare earth oxide by mole percent. 
 
     
     
         20 . The coated GTE component of  claim 16  wherein the at least one rare earth oxide comprises gadolinia;
 wherein the fracture-resistant TBC layer comprises an outer surface to which the CMAS-resistant TBC layer is bonded and an inner surface opposite the outer surface; 
 wherein the fracture-resistant TBC layer contains a maximum gadolinia concentration adjacent the outer surface; and 
 wherein the fracture-resistant TBC layer is essentially free of gadolinia concentration adjacent the inner surface.