Adhesion improvement of diamond films on steel substrates using chromium nitride interlayers

Direct deposition of diamond on ferrous materials suffers from adhesion problems due to the build up of a graphitic layer at the interface. A successful solution to this problem was attained through the use of an intermediate layer consisting of 20 mu m thick nitrided chromium film. The initial stage of diamond deposition resulted in the partial carburization of the chromium nitride interlayer onto which a continuous diamond film was deposited. The adhesion of the diamond film to the substrate was enhanced by complicated mechanical building and chemical bonding of the interfacial region and was measured by an indentation test. No delamination events occurred during indentation up to loads of 1000 N. Phase transformation into the interlayer, diamond particle density and quality of obtained films were studied for different times of deposition. The samples were examined by a number of complementary techniques: AES, XRD, Raman Spectroscopy, SEM and EDS. Residual stresses in deposited films were calculated from the shift of the diamond peak in the Raman spectrum and were compared to thermal stresses resulting from mismatch of the thermal expansion coefficients of diamond and the substrate. It is suggested that a chromium nitride interlayer could be employed in the deposition of diamond. films on iron based alloys for industrial purposes. (C) 1997 Elsevier Science S.A.