Diamond-like carbon film coatings on soft metal substrates

Application of segment-structured tetrahedral amorphous carbon (ta-C) film on soft metal substrate is proposed to improve wear resistance of mechanical parts. It was generally considered that continuous structure ta-C film was effective when applied to hard materials because it could not follow deformation of substrate material and the film tended to delaminate. In contrast, by applying segment structure on ta-C film, tribological properties of ta-C film coated on soft substrate were further improved, and sliding surface exhibited excellent wear resistance even under high sliding loads. Effectiveness of the use of brass substrate in improving wear resistance was demonstrated through large-scale wear resistant test of valve-plate used in oil pump of construction machine. Segment-structured ta-C coated brass valve-plate reduced maximum wear by approximately 80 % as compared with uncoated brass plate.