Influence of H2S addition during diamond deposition on hardmetal substrates

Diamond deposition on hardmetal substrates is an industrial process to increase the wear resistance of tools during machining operations. but till now an increase in diamond layer adhesion is desirable. The main problem during diamond deposition on hardmetal substrates is the Co content in the binder phase. H2S was used for immobilizing the cobalt on the substrate surface. The H2S should react with the metallic Co covering its surface with CoS. Because of this the diamond nucleation occurs easier and the Co vapour pressure is also reduced. Similar mechanisms were observed using silicon and boron vapour during substrate pre-treatment. Positive effects of H2S addition were achieved if the H2S is added only during the diamond nucleation period. The experiments with continuous H2S addition were not successful. For comparison diamond deposition on Murakami/Carrot pre-treated substrates were carried out. (C) 2008 Elsevier B.V. All rights reserved.