Damage processes and substrate surface design for CVD diamond films

Experimental results on the development of damage processes for CVD diamond (hereafter referred to as CVDD) films and substrate surface design are presented with the purpose of application to cutting tools. The initial stage of damage was investigated with a mechanically scanned acoustic microscope. It is shown that the damage is formed by development of cracks, which extends to the top surface. Delaminations around the cracks finally result in peeling off from the substrate. These facts suggest that interface structures inhibiting the extension of cracks and delamination around the cracks are advantageous for adhesion enhancement of CVDD films. Accordingly, the phase transformation of cemented carbide was investigated. As a result, it is demonstrated that by a specific surface treatment under H2 plasma atmosphere, a surface structure, which is best suitable for the synthesis of CVDD films, can be obtained.