FACTORS INFLUENCING THE ADHESION OF DIAMOND COATINGS ON CUTTING TOOLS

CVD diamond coatings can greatly extend the tool life of cemented carbide cutting tools when machining abrasive non-ferrous materials. However, reliable tool performance is difficult to obtain due to the problem of controlling coating adhesion. In this work, diamond coatings have been deposited on cemented carbide tool inserts with variation of substrate chemical composition and surface pre-treatment. The coatings have been characterized with respect to nucleation density, crystallinity, non-diamond material content and residual stresses. The adhesion and wear resistance of the coatings were investigated by machining tests in Al-18%Si alloy. The diamond deposition process and the resulting coating adhesion are both strongly influenced by the surface characteristics of the substrate surface. Formation of voids and non-diamond material at the coating-substrate interface in combination with high compressive stresses in the coating are believed to be the main reasons for poor adhesion. © 1990.