INVESTIGATION OF LOW-PRESSURE DIAMOND DEPOSITION ON CEMENTED CARBIDES

The main problem of diamond deposition on cemented carbides is the presence of cobalt, a large amount of which on the substrate surface can disturb diamond nucleation and growth. Our research is focused on understanding the mechanism of cobalt influence on diamond coatings grown on cemented carbide substrates. The deposition was carried out using the hot-filament chemical vapor deposition method and a CH4 H2 1% gas mixture. The substrates had the following composition: 91.7% WC, 2.25% TaC, 0.25% NbC and 5.8% Co. In order to study the cobalt effect on diamond film deposition, etched and unetched diamond-ground samples were used. The etching was made to remove cobalt from the surface of the substrates. The substrate surface temperature, which affects cobalt mobility is an important factor in the coating of cemented carbides. It was found that at relatively high temperatures, cobalt strongly attacks diamond crystals. © 1992.