Growth and mechanical properties of diamond films on cemented carbide with buffer layers

• The hardness and elastic modulus of the diamond films are 38.9 GPa and 380 GPa.
• The diamond film with 800 nm CrN layer and 10 min chemical etching has a good adhesion.
• Reaction between buffer layer and diamond could improve the adhesion of diamond film.

The main hindrance to applications of diamond coatings on cemented carbide cutting tools is poor adhesion between diamond films and the substrates, caused mainly by Co acting as a catalyst for the formation of graphite during the growth of the diamond films. The buffer-layer technique is commonly used to reduce the elemental diffusion or residual stress in the interface between the film and substrate. In this paper, four kinks of buffer layers, namely TiN, CrN, TiC, and SiN, were applied to (111)-textured diamond films grown on mirror-polished cemented carbide substrates using the hot-filament chemical vapor deposition method. The adhesion strengths of different samples are measured by Vickers hardness tests and compared to show the different effects of the buffer layers. The sample with an 800-nm-thick CrN layer and processed by 10-min chemical etching has the best adhesion among the four buffer layers.