M. Hakovirta, ADHESION OF AMORPHOUS DIAMOND-LIKE FILM ON SPUTTERED HARDMETAL (WC-CO) CUTTING TOOLS, DIAMOND AND RELATED MATERIALS, 5(2), 1996, pp. 186-189
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.