Tribological characteristics of nanocrystalline diamond films grown on titanium

摘要

Nanocrystalline diamond (NCD) films on titanium alloys are of importance for tribology and biomedical implants. However, due to the different thermal expansion coefficients of the two materials, the complex nature of the interlayer formed during diamond deposition, and the difficulty in achieving very high nucleation density, it is difficult to deposit adherent thin NCD films on titanium and its alloys. In the present study smooth NCD films were successfully deposited in microwave chemical vapour deposition plasma from CH_4/H_2 mixtures, for the purpose of improving the film's adhesion and the wear resistance of the titanium. An exceptional adhesion of NCD film to the titanium substrate was observed by indentation testing up to 150 kg load. The friction coefficient against a cemented carbide ball of 10 mm in diameter with 20 N load was estimated to be approx 0.05 in dry air. Detailed experimental results of the preparation, characterisation and successful deposition of the NCD film on pure Ti are discussed.