Effects of hydrogen plasma etching on adhesive strength of diamond coating with cemented carbide substrate

One of the most important problems that obstructed the industrialization of chemical vapor deposited (CVD) diamond coated cutting tools is the insufficient coating adhesion and subsequent coating delamination. Therefore, we choose the hydrogen plasma to etch the surface of cemented carbide substrate (also known as "decarburized") before deposition to enhance the adhesive strength of CVD diamond films. Meanwhile, we analysis the impact of different hydrogen plasma etching time on the micro structure, ingredients of the substrate, and the adhesive strength between substrate and coatings. It was found that when use the hydrogen plasma to etch the substrate,the surface of substrate forming a rough active surface. During deposition, the surface will transfer to WC transition layer, which will not only prevent the diffusion of Co but also increase the mechanical lock effects between the substrate and coatings. When the etching time is 120 min, it can effectively improve the adhesive strength of diamond coating and the cemented carbide, thus extend the life of the tools, which is of great significance for the production and application of diamond coated cutting tools.