Deposition and friction properties of ultra-smooth composite diamond films on Co-cemented tungsten carbide substrates

To fabricate high-quality chemical vapor deposition (CVD) diamond coated tools or drawing dies, depositing adherent diamond films with fine surface morphology is essential. A novel deposition method combining conventional hot filament CVD (HFCVD) method and polishing technique is proposed, with which an ultra-smooth composite diamond (USCD) film consisting of a layer of fine-grained microcrystalline diamond (MCD) film and multiply layers of nanocrystalline diamond (NCD) films is deposited on Co-cemented tungsten carbide (WC-6 wt.% Co) substrate. The as-deposited USCD films are characterized with scanning electron microscope (SEM), atomic force microscope (AFM), surface profilometer, X-ray diffraction (XRD) and Raman spectrum. Furthermore, Rockwell C indentation tests are conducted to evaluate the adhesion of the USCD film grown onto WC-Co substrate. The friction tests conducted on a ball-on-plate type reciprocating friction tester suggest that the fabricated USCD films exhibit very low friction coefficients of 0.129, 0.091 and 0.173 for dry sliding against ball-bearing steel, alumina ceramic and copper counterfaces respectively. With water lubricating, the friction coefficients of these three contacts further reduce to 0.057, 0.063 and 0.147. (C) 2008 Elsevier B.V. All rights reserved.