EFFECT OF METHANE CONCENTRATION ON MECHANICAL-PROPERTIES OF HFCVD DIAMOND-COATED CEMENTED CARBIDE TOOL INSERTS

CVD diamond-coated cemented carbide inserts are on the verge of becomi ng the next generation of tools used for high-speed hard-cutting proce sses. Good adhesion of the diamond coating, and consistency on the mic ro-level of the CVD process are the current challenges which to a cert ain extent prevent these coated tools from becoming an off-the-shelf p roduct. In this work, we report preliminary results of the effect of m ethane concentration variation on the surface roughness, adhesion, res idual stress, and turning performance for diamond-coated inserts. Ceme nted carbide inserts with 5% cobalt were coated with diamond films usi ng an inexpensive hot filament CVD system. The methane concentration i n the reaction mixture was varied from 1 to 9%. The results suggest th at the optimal mechanical performance of diamond-coated inserts can be achieved when diamond is deposited at a methane concentration of abou t 3%.