INFLUENCE OF SUBSTRATE ROUGHNESS AND LATERAL SPACING ON MORPHOLOGY AND BRITTLENESS OF DIFFERENT CR-C PVD COATINGS

10 mu m thick, carbon doped (1.1 wt.%) chromium coatings were deposite d by non-reactive magnetron sputtering on steel substrates (XC18) with different surface preparations (electrolytic polishing, SiC grinding, shot peening) and by reactive magnetron sputtering on stainless steel substrates having a deliberately modified surface texture. For each s ubstrate finish, surface topography before and after deposition is cha racterized by scanning stylus profilometry. Fractographs and X-ray dif fraction diagrams show the influence of initial substrate surface morp hology (roughness and lateral spacing) on coating growth mechanisms an d microstructure. High-load Vickers indentation reveals that apparent intrinsic coating brittleness, computed from radial crack lengths, inc reases with perfection of coating microstructure which, in turn, decre ases with increasing ratio of roughness over horizontal spacing, R-tm: S-m. (C) 1998 Elsevier Science S.A.