Influence of substrate roughness and lateral spacing on morphology and brittleness of different Cr-C PVD coatings

10 μm thick, carbon doped (1.1wt.%) chromium coatings were deposited 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 substrate finish, surface topography before and after deposition is characterized by scanning stylus profilometry. Fractographs and X-ray diffraction diagrams show the influence of initial substrate surface morphology (roughness and lateral spacing) on coating growth mechanisms and microstructure. High-load Vickers indentation reveals that apparent intrinsic coating brittleness, computed from radial crack lengths, increases with perfection of coating microstructure which, in turn, decreases with increasing ratio of roughness over horizontal spacing, R tm: S m.