Sintered cemented carbide body coated with two layers

Abstract

A sintered hard metal body (e.g., a cutting insert) is provided as to wear resistance by depositing thereon an intermediate thin coating of a metallic carbide or metallic nitride free from binder metal and applying over this intermediate coating a thin ceramic coating free from binder metal.

We claim: 
     
       1. Compound body consisting of a core or substratum of sintered cemented carbide containing a small quantity of a binder metal, on which core or substratum is a very thin and extremely uniform surface coating with higher wear resistance than that of the core or substratum, in which said thin coating consists of two layers applied one above the other by chemical vapor deposition, neither of the layers containing binder metal, the outer layer having a thickness of 0.2-20 μm and consisting of at least one extremely wear resistant deposit consisting essentially of ceramic material selected from the group consisting of aluminum oxide and zirconium oxide and the inner layer lying next to the core or substratum having a thickness of 1-10 μm and consisting of at least one coat of at least one member selected from the group consisting of the carbides and nitrides of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Si and B. 
     
     
       2. Compound body as defined in claim 1, wherein said core or substratum is formed of WC, cubic carbides and Co and said inner layer is formed of titanium carbide and has a thickness of about 2 μm and said outer layer is formed of Al 2  O 3  and has a thickness of about 2 μm. 
     
     
       3. Compound body as defined in claim 1, wherein said bore or substratum is formed of WC, cubic carbides and Co and said inner layer is formed of titanium nitride with a minor amount of TiC and has a thickness of about 3 μm and said outer layer is formed of ZrO 2  and has a thickness of about 5 μm. .Iadd. 4. Compound body consisting of a core or substratum of sintered cemented carbide containing a small quantity of a binder metal, on which core or substratum is a very thin and extremely uniform surface coating with higher wear resistance than that of the core or substratum, in which said thin coating consists of two layers applied one above the other by chemical vapor deposition, neither of the two layers containing binder metal, the outer layer having a thickness of 0.2-20 μm and consisting of at least one extremely wear resistant deposit consisting essentially of a member of the group consisting of aluminum oxide, titanium oxide and zirconium oxide, and the inner layer lying next to the core or substratum having a thickness of 1-10 μm and consisting of at least one coat of at least one member selected from the group consisting of the carbides and nitrides of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Si and B. .Iaddend.