Hot corrosion-resistant coatings for gas turbine components

Abstract

A gas turbine component for use in a gas turbine engine includes a substrate a ceramic-based thermal barrier coating (TBC), and a diffusion chromide bond coat between the base material and the TBC. A thermally grown oxide (TGO) layer can be formed on the bond coat prior to application of the TBC. The TBC and the TGO include a common metal oxide. The oxide can be sacrificially in use and soluble in a molten sulfate salt, make the coating system particularly suitable for use in a marine environment.

1 . A gas turbine component for use in a gas turbine engine, comprising:
 a substrate comprising a metal base material;   a ceramic-based thermal barrier coating disposed over the substrate, the thermal barrier coating defining at least a portion of an outer surface of the gas turbine component; and   a bond coat disposed between the base material and the thermal barrier coating, the bond coat comprising a chromide diffusion coating.   
     
     
         2 . A gas turbine component as defined in  claim 1 , wherein the bond coat comprises a platinum diffusion coating. 
     
     
         3 . A gas turbine component as defined in  claim 1 , wherein the bond coat comprises an aluminide diffusion coating. 
     
     
         4 . A gas turbine component as defined in  claim 1 , wherein the bond coat further comprises hafnium, silicon, zirconium, or any combination thereof. 
     
     
         5 . A gas turbine component as defined in  claim 1 , wherein the bond coat is a diffusion coating comprising chromium, platinum, aluminum, and at least one of hafnium, silicon or zirconium. 
     
     
         6 . A gas turbine component as defined in  claim 5 , wherein the base material is a Ni-based superalloy having a gamma phase and a gamma prime phase distributed within the gamma phase, the platinum of the diffusion coating residing in the gamma prime phase and the chromium of the diffusion coating residing in the gamma phase. 
     
     
         7 . A gas turbine component as defined in  claim 1 , wherein the component is a gas turbine blade comprising an airfoil that is exposed to combustion gases of a gas turbine engine when in use, the bond coat and the thermal barrier coating being located along the airfoil. 
     
     
         8 . A method of making a gas turbine component having a thermal barrier coating defining at least a portion of an outer surface of the gas turbine component, the method comprising the step of forming a diffusion bond coat on a component substrate, the diffusion bond coat comprising chromium interdiffused with a metal substrate material of the component substrate, wherein the thermal barrier coating is subsequently coated over the bond coat. 
     
     
         9 . The method of  claim 8 , wherein the diffusion bond coat comprises a Pt-aluminide coating. 
     
     
         10 . The method of  claim 8 , wherein the step of forming the diffusion bond coat comprises vapor phase deposition of the chromium on the metal substrate material. 
     
     
         11 . The method of  claim 8 , wherein the diffusion bond coat comprises hafnium, silicon, zirconium, or any combination thereof. 
     
     
         12 . The method of  claim 8 , wherein the step of forming the diffusion bond coat comprises the steps of coating a slurry comprising a platinum-group metal over the substrate material and heat treating the slurry-coated substrate material to interdiffuse the platinum-group metal with the substrate material. 
     
     
         13 . The method of  claim 12 , wherein the slurry further comprises hafnium, silicon, zirconium, or any combination thereof. 
     
     
         14 . The method of  claim 12 , wherein the step of forming the diffusion bond coat further comprises vapor phase deposition of the chromium on the metal substrate material before the step of coating the slurry over the substrate material. 
     
     
         15 . The method of  claim 12 , wherein the slurry comprises the chromium of the bond coat, the chromium being interdiffused with the substrate material during the step of heat treating. 
     
     
         16 . The method of  claim 12 , further comprising the step of vapor phase aluminide coating the component substrate after the step of heat treating, whereby the diffusion bond coat further comprises an aluminide coating. 
     
     
         17 . The method of  claim 8 , further comprising the step of forming a thermally grown oxide layer over the diffusion bond coat, wherein the thermal barrier coating is subsequently coated over the thermally grown oxide layer. 
     
     
         18 . A gas turbine component for use in a gas turbine engine, comprising:
 a substrate comprising a metal base material;   a metal bond coat formed on the base material;   a thermally grown oxide layer formed on the bond coat and comprising an oxide of a metal element of the bond coat; and   a ceramic-based thermal barrier coating disposed over the substrate and defining at least a portion of an outer surface of the gas turbine component, wherein the thermal barrier coating further comprises the oxide of the metal element of the bond coat.   
     
     
         19 . A gas turbine component as defined in  claim 18 , wherein the oxide of the metal element is alumina or chromia. 
     
     
         20 . A gas turbine component as defined in  claim 18 , wherein the bond coat comprises a diffusion coating comprising chromide, Pt-aluminide, and at least one of hafnium, silicon, or zirconium. 
     
     
         21 . A method of making a gas turbine component comprising the step of coating a turbine component substrate with a coating system comprising a ceramic-based thermal barrier coating comprising a sacrificial oxide that is soluble in a molten sulfate salt.