[15p-P2-1~15] 6.2 Carbon-based thin films

[15p-P2-8] Application of Ultrananocrystalline Diamond/Nonhydrogenated amorphous Carbon Composite Films to Hard Coating on Cemented Carbide

〇Tsuyoshi Yoshitake¹, Mohamed Egiza^1,2, Hiroshi Naragino¹, Aki Tominaga¹, Kouki Murasawa³, Hidenobu Gonda³, Masatoshi Sakurai³ (1.Kyushu Univ., 2.Kafrelsheikh Univ., 3.OSG Corporation)

Keywords:nanocrystalline diamond, hard coating, coaxial arc plasma gun

Ultrananocrystalline diamond(UNCD)/nonhydrogenated amorphous carbon (a-C) composite (UNCD/a-C) films were deposited on cemented carbide containing Co by coaxial arc plasma deposition. The film deposited at room temperature exhibited the maximum hardness of 51.3 GPa and Young’s modulus of 520 GPa, which evidently indicates that graphitization induced by Co in the WC substrates and thermal deformation from sp³ to sp² bonding are suppressed. The hard UNCD/a-C films can be deposited at a thickness of approximately 3 µm, which is an order larger than that of comparably hard a-C films. The internal compress-stress of the 51.3-GPa hardness film is 4.5 GPa, which is evidently smaller than that of comparably hard a-C films. This is a reason for the thick deposition. The presence of a large number of grain boundaries in the film, which is a structural specific to UNCD/a-C films, might play a role in releasing the internal stress of the films.