CVDダイヤモンド膜合成のための超硬合金の表面改質

抄録

CVD diamond (CVDD) films have many excellent characteristics and hold potential as a coating material for use in various fields. Applications in cutting tools are well known, but sufficient utility in practice has not been achieved. One of the largest technical problems is delamination caused by strong impact when cutting work-piece materials. In the case of cemented carbide tools, in particular, removal of Co contained as a binder from the surface of substrate is indispensable, because, in the first stage of CVD, C dissolves into Co and a brittle substrate/CVDD interface is formed. This paper describes a novel surface design technique that optimizes the surface of cemented carbides for improvement of the adhesion strength of CVDD films. With the specific surface treatment of cemented carbide in a plasma atmosphere, extremely favorable surface conditions for the synthesis of CVDD can be obtained in a short period. That is, this reformed surface promotes removal of Co from the uppermost surface and also has roughness formed by recrystallization of WC grains that results in an anchoring effect and increase of the contact area.