Methods of forming coatings on substrates

Abstract

Methods are provided for forming coatings on substrates. In an embodiment, a method includes forming a first metal layer on the substrate, the first metal layer comprising a first precious metal, electrodepositing an active element over the first metal layer to form an active element layer, the active element selected from the group consisting of yttrium, scandium, and a lanthanide series element, applying a second metal layer over the active element layer, the second metal layer consisting essentially of a metal selected from a group consisting of a second precious metal, nickel, and cobalt, heating the substrate including the first metal layer, the active element layer, and the second metal layer to form a diffusion-alloyed layer over the substrate, adding aluminum to the diffusion-alloyed layer, and heating the substrate to diffuse and react the aluminum with the diffusion-alloyed layer to form a modified precious metal aluminide coating on the substrate.

1 . A method of forming a coating on a substrate, the method comprising the steps of:
 forming a first metal layer on the substrate, the first metal layer comprising a first precious metal;   electrodepositing an active element over the first metal layer to form an active element layer, the active element selected from the group consisting of yttrium, scandium, and a lanthanide series element;   applying a second metal layer over the active element layer, the second metal layer consisting essentially of a metal selected from a group consisting of a second precious metal, nickel, and cobalt;   heating the substrate including the first metal layer, the active element layer, and the second metal layer to form a diffusion-alloyed layer over the substrate;   adding aluminum to the diffusion-alloyed layer; and   heating the substrate to diffuse the aluminum into the diffusion-alloyed layer to form a modified precious metal aluminide coating on the substrate.   
     
     
         2 . The method of  claim 1 , wherein the step of forming the first metal layer comprises depositing platinum onto the substrate. 
     
     
         3 . The method of  claim 1 , wherein the step of forming a first metal layer comprises electroplating the first metal layer onto the substrate. 
     
     
         4 . The method of  claim 1 , wherein the step of electrodepositing comprises:
 providing a bath comprising a primary alcohol and a tertiary alcohol, and an electrolyte comprising an yttrium salt; and   electrodepositing yttrium from the yttrium salt onto the first metal layer.   
     
     
         5 . The method of  claim 4 , wherein the electrolyte comprises yttrium nitrate. 
     
     
         6 . The method of  claim 5 , wherein the electrolyte comprises Y(NO 3 ).3H 2 O. 
     
     
         7 . The method of  claim 1 , wherein the step of applying a second metal layer comprises applying nickel to form the second metal layer. 
     
     
         8 . The method of  claim 1 , wherein the step of applying a second metal layer comprises applying cobalt to form the second metal layer. 
     
     
         9 . The method of  claim 1 , wherein the step of applying a second metal layer comprises applying platinum to form the second metal layer. 
     
     
         10 . The method of  claim 1 , wherein the step of applying a second metal layer comprises electrodepositing nickel onto the active element layer to form the second metal layer. 
     
     
         11 . The method of  claim 10 , wherein the step of electrodepositing nickel comprises placing the substrate in an electrolytic bath including nickel chloride and boric acid. 
     
     
         12 . The method of  claim 10 , wherein the step of electrodepositing nickel comprises placing the substrate in an electrolytic bath including nickel fluoroborate, nickel chloride, and boric acid. 
     
     
         13 . A method of forming a coating on a substrate, the method comprising the steps of:
 forming a platinum layer on the substrate;   electrodepositing yttrium over the platinum layer to form an yttrium layer;   applying a nickel layer over the yttrium layer;   heating the substrate to form a diffusion-alloyed layer over the substrate, the diffusion-alloyed layer comprising platinum, yttrium, and nickel;   adding aluminum to the diffusion-alloyed layer; and   heating the substrate to diffuse the aluminum into the diffusion-alloyed layer to form a platinum-yttrium-nickel-aluminide coating on the substrate.   
     
     
         14 . The method of  claim 13 , wherein the step of electrodepositing comprises:
 providing a bath comprising a primary alcohol, a tertiary alcohol, and an electrolyte comprising an yttrium salt; and   electrodepositing yttrium from the yttrium salt onto the platinum layer.   
     
     
         15 . The method of  claim 14 , wherein the tertiary alcohol comprises alpha-terpineol. 
     
     
         16 . The method of  claim 14 , wherein the primary alcohol comprises ethanol. 
     
     
         17 . The method of  claim 16 , wherein the step of applying the nickel layer comprises electrodepositing nickel onto the yttrium layer to form the nickel layer. 
     
     
         18 . A method of forming a coating a substrate, the method comprising the steps of:
 electrodepositing an active element over the substrate to form an active element layer, the active element selected from the group consisting of yttrium, scandium, and a lanthanide series element;   applying a second metal layer over the active element layer, the second metal layer consisting essentially of a metal selected from a group consisting of a second precious metal, nickel, and cobalt;   heating the substrate including the active element layer and the second metal layer to form a diffusion-alloyed layer over the substrate;   adding aluminum to the diffusion-alloyed layer; and   heating the substrate to diffuse the aluminum into the diffusion-alloyed layer to form a modified platinum aluminide coating on the substrate.   
     
     
         19 . The method of  claim 18 , further comprising the step of:
 forming a first metal layer on the substrate, before the step of electrodepositing, the first metal layer comprising nickel or cobalt.   
     
     
         20 . The method of  claim 18 , wherein the step of electrodepositing comprises:
 providing a bath comprising a primary alcohol, a tertiary alcohol, and an electrolyte comprising an yttrium salt; and   electrodepositing yttrium from the yttrium salt onto the substrate.