Molten metal resistant composite coatings

Abstract

Composite coating materials comprising a hard carbide phase and a metallic binder that are resistant to molten metals such as aluminum are disclosed. The hard carbide phase of the composite coatings may comprise tungsten carbide, and the metallic binder may comprise a nickel-based alloy. A thin oxide layer comprising oxides of the binder metal may be provided on the surface of the composite coating. The composite coatings exhibit desirable non-wetting behavior when exposed to molten metals.

1 . A molten metal resistant composite coating comprising:
 a hard carbide phase; and   a metallic binder comprising Ni and Cr.   
     
     
         2 . The molten metal resistant composite coating of  claim 1 , wherein the hard carbide phase comprises from 60 to 70 weight percent of the composite coating. 
     
     
         3 . The molten metal resistant composite coating of  claim 1 , wherein the carbide phase comprises tungsten carbide particles having an average size from 70 to 180 microns. 
     
     
         4 . The molten metal resistant composite coating of  claim 1 , wherein the metallic binder comprises from 30 to 40 weight percent of the composite coating. 
     
     
         5 . The molten metal resistant composite coating of  claim 1 , wherein the metallic binder comprises from 70 to 86 weight percent Ni. 
     
     
         6 . The molten metal resistant composite coating of  claim 5 , wherein the metallic binder further comprises from 7 to 20 weight percent Cr. 
     
     
         7 . The molten metal resistant composite coating of  claim 1 , wherein the metallic binder comprises 70 to 86 weight percent Ni, from 7 to 20 weight percent Cr, from 1 to 5 weight percent Si, from 2 to 5 weight percent Fe, from 1 to 4 weight percent B, and the balance incidental impurities, and has a hardness range of HRC from 33 to 50. 
     
     
         8 . The molten metal resistant composite coating of  claim 1 , further comprising an oxide surface layer over at least a portion of the base layer. 
     
     
         9 . The molten metal resistant composite coating of  claim 8 , wherein the oxide surface layer has a thickness of less than 50 microns. 
     
     
         10 . The molten metal resistant composite coating of  claim 8 , wherein the oxide surface layer is formed by flame oxidation and comprises oxides of the metallic binder metals. 
     
     
         11 . A tool capable of withstanding exposure to molten metal comprising:
 a substrate, and   a composite coating over at least a portion of the substrate, wherein the composite coating comprises a hard carbide phase and a metal binder phase.   
     
     
         12 . The tool of  claim 11 , wherein the hard carbide phase comprises from 60 to 70 weight percent of the composite coating. 
     
     
         13 . The tool of  claim 11 , wherein the carbide phase comprises tungsten carbide particles having an average size from 70 to 180 microns. 
     
     
         14 . The tool of  claim 11 , wherein the metallic binder comprises from 30 to 40 weight percent of the composite coating. 
     
     
         15 . The tool of  claim 11 , wherein the metallic binder comprises from 70 to 86 weight percent Ni. 
     
     
         16 . The tool of  claim 15 , wherein the metallic binder further comprises from 7 to 20 weight percent Cr. 
     
     
         17 . The tool of  claim 11 , further comprising an oxide surface layer over at least a portion of the composite coating. 
     
     
         18 . A method of coating a substrate comprising:
 depositing a composite coating on at least a portion of the substrate, wherein the composite coating comprises a base layer comprising a hard carbide phase and a metallic binder phase.   
     
     
         19 . The method of  claim 18 , wherein the composite coating is deposited on the substrate by plasma transferred arc welding. 
     
     
         20 . The method of  claim 18 , further comprising forming an oxide surface layer over at least a portion of the base layer by flame-oxidation.