Functionally graded coating

Abstract

In one aspect, composite articles are described comprising multifunctional coatings. A composite article described herein, in some embodiments, comprises a substrate and a coating adhered to the substrate, the coating comprising an inner layer and an outer layer, the inner layer comprising a presintered metal or alloy and the outer layer comprising particles disposed in a metal or alloy matrix.

That which is claimed is: 
     
         1 . A composite article comprising:
 a substrate; and   a coating adhered to the substrate, the coating comprising an inner layer and an outer layer, the inner layer being substantially fully dense and comprising sintered metal or alloy, and the outer layer comprising hard particles disposed in matrix metal or matrix alloy, wherein the matrix metal or matrix alloy does not infiltrate the inner layer.   
     
     
         2 . The composite article of  claim 1 , wherein the inner layer is metallurgically bonded to the substrate. 
     
     
         3 . The composite article of  claim 1 , wherein the hard particles of the outer layer comprise one or more metal carbides, metal nitrides, metal borides, metal silicides, ceramics, cemented carbides, cast carbides or mixtures thereof. 
     
     
         4 . The composite article of  claim 1 , wherein the inner layer has hardness on the Rockwell C scale lower than the outer layer. 
     
     
         5 . The composite article of  claim 4 , wherein the outer layer has an abrasion resistance greater than the inner layer as measured according to ASTM G65-04. 
     
     
         6 . The composite article of  claim 1 , wherein the outer layer further comprises metal carbide tiles or ceramic tiles disposed in the matrix metal or matrix alloy. 
     
     
         7 . The composite article of  claim 1 , wherein the inner layer further comprises particles disposed in the sintered metal or alloy, the particles selected from the group consisting of metal carbides, metal nitrides, metal borides, metal silicides, ceramics, cemented carbides, cast carbides and mixtures thereof. 
     
     
         8 . The composite article of  claim 1 , wherein the coating further comprises at least one layer of refractory material deposited over the outer layer by chemical vapor deposition or physical vapor deposition of a combination thereof. 
     
     
         9 . The composite article of  claim 1 , wherein the inner layer of the coating has corrosion resistant and crack arrest functionalities, and the outer layer of the coating has an abrasion resistant functionality, erosion resistant functionality or combination thereof. 
     
     
         10 . The composite article of  claim 1 , wherein the substrate comprises steel. 
     
     
         11 . The composite article of  claim 1 , further comprising an interfacial transition region between the inner layer and the outer layer. 
     
     
         12 . The composite article of  claim 1 , wherein the inner layer comprises sintered nickel-based alloy. 
     
     
         13 . The composite article of  claim 12 , wherein the nickel-based alloy is of composition 0-15 wt. % cobalt, 1-30 wt. % chromium, 2-28 wt. % molybdenum, 0-5 wt. % tungsten, 0-50 wt. % iron, 0-6 wt. % niobium, 0-1 wt. % silicon, 0-2 wt. % manganese, 0-3 wt. % copper, 0-1 wt. % aluminum, 0-2 wt. % titanium and the balance nickel. 
     
     
         14 . A composite article comprising:
 a substrate; and   a coating adhered to the substrate, the coating comprising an inner layer and an outer layer, the outer layer comprising hard particles disposed in matrix metal or matrix alloy, and the inner layer being substantially fully dense and formed of a porous sintered metal or sintered alloy scaffold infiltrated with the matrix metal or matrix alloy of the outer layer.   
     
     
         15 . The composite article of  claim 14 , wherein the inner layer is metallurgically bonded to the substrate. 
     
     
         16 . The composite article of  claim 14 , wherein the particles of the outer layer comprise one or more metal carbides, metal nitrides, metal borides, metal silicides, ceramics, cemented carbides, cast carbides or mixtures thereof. 
     
     
         17 . The composite article of  claim 14 , wherein the inner layer has hardness on the Rockwell C scale lower than the outer layer. 
     
     
         18 . The composite article of  claim 17 , wherein the outer layer has an abrasion resistance greater than the inner layer as measured according to ASTM G65-04. 
     
     
         19 . The composite article of  claim 14 , wherein the substrate comprises steel. 
     
     
         20 . The composite article of  claim 14 , wherein the inner layer of the coating has corrosion resistant and crack arrest functionalities, and the outer layer of the coating has an abrasion resistant functionality, erosion resistant functionality or combination thereof.