Temperature pre-treatments of hardmetal substrates to reduce the cobalt content and improve diamond deposition

摘要

Temperature pre-treatments of hardmetal substrates were investigated to improve the diamond deposition of tools. In a hot-filament apparatus process parameters were tested to reach substrate temperatures as high as possible at low gas pressures. The aim was to evaporate cobalt from the substrate surface and to increase surface roughness in one single step followed by diamond deposition. The cobalt content at the substrate surface decreased with increasing pre-treatment duration. Changing the gas phase composition from pure hydrogen to argon and/or methane additions showed no further increase in Co evaporation. The surface roughness increased till 2 h pre-treatment duration but then decreased. Diamond nucleation and growth are influenced by the remaining cobalt on the substrate surface. After long pre-treatment times the diamond nucleation decreased but the diamond crystals were better facetted. The diamond adhesion was preliminary tested and showed no flaking.