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.