Growth and erosive wear performance of diamond coatings on WC substrates

Adherent diamond coatings up to similar to 30 mu m thick have been grown by microwave plasma CVD on WC substrates and their erosive wear properties in vestigated under high velocity air-sand erosion testing. Coating properties , particularly residual stress and adhesion, are sensitive functions of sur face pre-treatment and deposition procedures. Adherent coatings offer signi ficantly better erosion resistance compared to uncoated substrates, with th e erosion rate being lower by up to a factor of similar to 5 based on the r esults obtained to date. Also films with low residual stress appear to exhi bit longer lifetimes under testing. Failure tends to occur catastrophically along the coating-substrate interface. The grain boundaries do not appear to represent an easy route for crack propagation. Their strength appears to be comparable to that of the grains themselves. (C) 1999 Elsevier Science S.A. All rights reserved.