Tribological and mechanical properties of HFCVD diamond-coated WC-Co substrates with different Cr interlayers

Abstract

Chromium interlayers between WC-Co substrates and diamond coating by hot filament chemical vapor deposition (HFCVD) process were produced by two different techniques: using pack chromization and bipolar symmetry pulsed DC reactive magnetron sputtering processes. Both chromium surfaces were found partially transformed into carbide compound layers by energy dispersive X-ray spectrometer (EDS) and X-ray diffractometer (XRD). Daimler–Benz Rockwell-C indentation tests were conducted to evaluate the adhesion properties of diamond coatings with interlayers created by these two techniques. Delamination outside the indentation zones was also observed by a scanning electron microscopy (SEM). Wear resistance of both coatings were investigated by pin-on-disk wear tests. Rather low wear volumes revealed their excellent anti-wear behavior. Good diamond adhesion on chromized interlayers has been attributed to chromium carbide formation on pack chromized film surfaces as well as on PVD ones during the HFCVD process. It is concluded that the adhesion properties and tribological performance of CVD diamond coatings are significantly improved by the proposed two chromium interlayers. However, chromium interlayer produced by pack chromization is more beneficial to the adhesion of diamond coating than that, by PVD process. One reason is the former interlayer's role as a diffusion barrier of cobalt binder, the other is the low cost of the facilities for the pack chromization technique.