ADHESION OF AMORPHOUS DIAMOND-LIKE FILM ON SPUTTERED HARDMETAL (WC-CO) CUTTING TOOLS

Adhesion between (WC-Co) hardmetal (6 wt.% Co) and hydrogen-free, amor phous diamond-like film (78% sp(3)-bondings) produced by the filtered pulsed are-discharge method has been investigated. The poor adhesion b etween cobalt and diamond-like film in the case of WC-Co samples was s olved by etching cobalt (after a Co sputtering on the hardmetal surfac e of 0.8 wt.%) from the hardmetal surface using an argon sputtering io n gun (sputtering yield for cobalt is five times higher than for tungs ten carbide). A conventional scratch tester was used to test adhesion between the diamond-like film and hardmetal substrate. Depending on th e deposition parameters, the samples without etching by sputtering had critical load values (the load at which the coating is stripped from the substrate) from 4.9 to 8.8 N. With similar deposition parameters t he samples etched by argon ion sputtering had critical load values fro m 10.8 to 21.6 N. Wear resistance and coefficient of friction were mea sured with a pin-on-disc tester. Film thickness, the quality of the fi lm and the thickness of the adhesion layer produced with the high-ener gy carbon plasma, were the major factors affecting the adhesion. The b est adhesion values measured with a scratch tester were obtained from diamond-like film of intermediate thickness (similar to 1.0 mu m) and intermediate quality (similar to 68% sp(3)-bondings). In cutting tests on aluminium, (G-AlSi12(Cu)P and AlMgSiT5) diamond-like films deposit ed on cutting tools (critical load > 10 N) showed no delamination or o bservable wear and much lower sticking of aluminium to the tool surfac e than with plain WC-Co cutting tools.