Diamond deposition on hardmetal substrates after pre-treatment with aluminium or aluminium compounds

Diamond coated WC-Co hardmetal alloys are widely used as cutting tools for non-ferrous materials. A disadvantage is the poor adhesion of diamond layers on hardmetal, which is mainly caused by cobalt used as binder material. Various attempts have been made to reduce cobalt on the substrate surface either by etching or by forming stable compounds (especially silicides and borides). This paper deals with the possibility of forming cobalt-aluminium-compounds such as aluminides or aluminates during substrate pre-treatment with metallic aluminium or solutions, respectively, suspensions of aluminium-salts. Diamond deposition was carried out in a hot-filament-CVD-reactor. The diamond levers were examined with respect to growth rate, morphology and adhesion. Some improvements concerning the reduction of cobalt migration and diffusion were detected leading to increased layer adhesion, as compared to untreated hardmetal substrates. (C) 2001 Elsevier Science B.V. All rights reserved.