LARGE-AREA DIAMOND DEPOSITION AND BRAZING OF THE DIAMOND FILMS ON STEEL SUBSTRATES FOR TRIBOLOGICAL APPLICATIONS

Diamond films were successfully deposited on molybdenum substrates as large as 100 mm in diameter at a high deposition rate of 30 mum h-1 by the r.f. induction thermal plasma chemical vapour deposition (CVD) method. Besides the uniformity of the film thickness, the surface morphology and the film quality were confirmed to be homogeneous over the deposited area by scanning electron microscopy and Raman spectroscopy. Self-standing diamond films of 30 mm diameter were obtained when the films were deposited on mirror-finished molybdenum substrates by the r.f. thermal plasma CVD method. One of the self-standing diamond film surfaces (originally substrate side) was as smooth as the mirror-finished substrate surface. The self-standing diamond films were brazed in vacuum on steel substrates so that the smooth surface of the film became the top of the brazed materials. The adhesive strength of the brazed diamond film on the steel substrate was found to be rather high, and the as-brazed diamond film with the smooth surface had a low friction coefficient of 0.1 against steel and a high wear resistance without oil lubrication in an ambient atmosphere.