Multi-layer wear resistant coatings

Abstract

An erosion and corrosion resistant coating is formed of a plurality of alternating layers of metallic and ceramic materials. The two materials selected for the layers have complementary wear resistant characteristics, such that one is relatively ductile and the other is relatively brittle. The concentration of the two materials at the interface between adjacent layers is graded to improve the adhesion of the layers and to provide a more unified coating. Preferably radio-frequency sputtering is employed to deposit the coating, since it does not produce excessive heating which could negate any prior heat treatment of the substrate onto which the coating is deposited.

I claim: 
     
       1. A wear resistant coating on a .Iadd.major .Iaddend.surface of a substrate for protecting against particle induced erosion and water induced erosion and corrosion, said coating comprising at least four layers with layers of a ceramic material alternating with layers of a metallic material .Iadd.in which the layers of metallic material are as thick or thicker than the layers of ceramic material.Iaddend.; .Iadd.and .Iaddend.wherein said metallic material comprises one or more elements selected from the group consisting of titanium, zirconium, hafnium and tantalum; and wherein said ceramic material is a nitride compound of the selected metallic material.   
     
     
       2. The coating as recited in claim 1, wherein each layer has a thickness substantially in the range of 0.1 to 5.0 micrometers. 
     
     
       3. The coating as recited in claim 1, wherein the layers of said metallic material are substantially 2.0 micrometers thick and the layers of said ceramic material are substantially 0.5 micrometers thick. 
     
     
       4. The coating as recited in claim 1 wherein the interface between adjacent layers is a graded transition of the concentration of the two materials. 
     
     
       5. A wear resistant coating on a .Iadd.major .Iaddend.surface of a substrate for protecting against particle induced erosion and water induced erosion and corrosion, said coating having a first set of layers of a ceramic material interleaved with a second set of layers of a metallic material to form a coating with at least four layers, .Iadd.in which the layers of metallic material are as thick or thicker than the layers of ceramic material, and .Iaddend. wherein the interface between adjacent layers is a graded transition of the concentration of the two materials.   
     
     
       6. A wear resistant coating on a surface of a substrate for protecting against particle induced erosion and water induced erosion and corrosion, said coating comprising at least four layers with layers of a ceramic material alternating with layers of a metallic material; wherein said metallic material comprises one or more elements selected from the group consisting of aluminum, silicon, titanium, chromium, magnesium, iron, zirconium, molybdenum, tin, tungsten and tantalum; and   wherein said ceramic material is an oxide compound of the selected metallic material.   
     
     
       7. The coating as recited in claim 6, wherein each layer has a thickness substantially in the range of 0.1 to 5.0 micrometers. 
     
     
       8. The coating as recited in claim 6, wherein the layers of said metallic material are substantially 2.0 micrometers thick and the layers of said ceramic material are substantially 0.5 micrometers thick. 
     
     
       9. The coating as recited in claim 6 wherein the interface between adjacent layers is a graded transition of the concentrations of the two materials. 
     
     
       10. A wear resistant coating on a surface of a substrate for protecting against particle induced erosion and water induced erosion and corrosion, said coating comprising at least four layers with layers of a ceramic material alternating with layers of a metallic material .Iadd.in which the layers of metallic material are as thick or thicker than the layers of ceramic material.Iaddend.; wherein said metallic material comprises one or more elements selected from the group consisting of titanium, zirconium, hafnium, iron and tantalum; and   wherein said ceramic material is a carbide compound of the selected metallic material.   
     
     
       11. The coating as recited in claim 10, wherein each layer has a thickness substantially in the range of 0.1 to 5.0 micrometers. 
     
     
       12. The coating as recited in claim 10, wherein the layers of said metallic material are substantially 2.0 micrometers thick and the layers of said ceramic material are substantially 0.5 micrometers thick. 
     
     
       13. The coating as recited in claim 10 wherein the interface between adjacent layers is a graded transition of the concentrations of the two materials. .Iadd. 
     
     
       14.  The coating as recited in claim 1, wherein each layer of metallic material is at least twice as thick as each layer of ceramic material. .Iaddend. .Iadd.15. The coating as recited in claim 1, wherein each layer of metallic material is at substantially four times as thick as each layer of ceramic material. .Iaddend. .Iadd.16. The coating as recited in claim 6, in which the layers of metallic material are as thick or thicker than the layers of ceramic material. .Iaddend. .Iadd.17. The coating as recited in claim 16, wherein each layer of metallic material is at least twice as thick as each layer of ceramic material. .Iaddend. .Iadd.18. The coating as recited in claim 16, wherein each layer of metallic material is at substantially four times as thick as each layer of ceramic material. .Iaddend. .Iadd.19. The coating as recited in claim 10, wherein each layer of metallic material is at least twice as thick as each layer of ceramic material. .Iaddend. .Iadd.20. The coating as recited in claim 10, wherein each layer of metallic material is at substantially four times as thick as each layer of ceramic material. .Iaddend.