抄録
To produce a diamond-coated cutting tool with a smooth surface and high adhesive capability, a diamond film is deposited on a mirror-polished Co cemented tungsten carbide (WC-Co) substrate. Adhesion is usually better for substrates with high surface roughness, but a smooth substrate provides a sharp edge for cutting tools.
For this study, the diamond film was deposited at 970 K on a mirror-polished WC-Co substrate (Ra=7 nm) treated using a nano-size diamond seeding process. The adhesive ability of the diamond film differs according to the nano-size diamond concentration in the seeding dispersion. A high adhesive diamond film that withstands a cavitation test for 240 min can be produced with 0.01 mass% nano-sized diamond dispersion. The diamond film surface roughness is Ra = 148 nm.
To smooth the diamond films, deposition temperatures are examined. Using two-step deposition, which changes the substrate temperature from 970 K to 1070 K during deposition, the diamond film surface roughness decreased to Ra = 74 nm.
When the deposition temperature becomes higher than 1070 K, Co segregation from WC-Co substrates occurs. Furthermore, the adhesive ability is reduced by the amorphous carbon layer formed at the interface as the diamond reacts with Co.
