TRIBOLOGICAL EVALUATION OF THERMALLY ACTIVATED CVD DIAMOND-LIKE CARBON (DLC) COATINGS

Diamond-lie carbon coatings have been the subject of expanding technol ogical interest for wear resistance and low friction applications duri ng recent years. In this study diamond-like carbon coatings were depos ited by thermally activated chemical vapour deposition. The deposition temperature was 900 degrees C and CH2I2 was used as a precursor. Trib ological evaluation was performed by surface roughness measurement tog ether with hardness, micro abrasion and friction. Furthermore, the res idual stress of the coating was evaluated by a deflection method. The coating was analysed with nuclear reaction analysis, scanning electron microscopy and atomic force microscopy. The coating was very smooth ( R-a = 1 nm) and free from pores. A high abrasive wear resistance sligh tly worse than physical-vapour-deposited TiN was measured. It exhibit a hardness of 2800 HV and a friction coefficient of about 0.2 in air ( 30-50% relative humididty). Furthermore, the coating has a compressive residual stress of 220 MPa. Hydrogen content and density of the coati ng were 9 at.% and 1.8 g cm(-3), respectively. (C) 1997 Elsevier Scien ce S.A.