Thin films comparable with WC-Co cemented carbides as underlayers for hard and superhard coatings: The state of the art

A new method for deposition of barrier underlayers, which completely prevent Co penetration to the substrate surface and are highly compatible with WC-Co cemented carbides, has been developed. It allows deposition of thin hard continuous, highly adherent and defect-free TiCN-based films by the use of high energy titanium ions. The method ensures deposition without any damage of the cemented-carbide substrate or its decarburization, leading to formation of the eta phase near the surface layer. As a result, CVD TiC, TiCN, TiN etc. coatings can be deposited onto cemented carbides preliminarily plated with barrier underlayers almost without a decrease in transverse rupture strength. Special additional interlayers are applied for enhancement of the adhesion between the underlayers and plasma CVD diamond coatings, resulting in excellent resistance of the near-surface layer of the cemented-carbide substrate with these coatings to high static loading when subjected to indentation.