Deposition of TiN/CrN hard superlattices by reactive d.c. magnetron sputtering

Multilayer superlattice coatings of TiN/CrN were deposited on silicon substrates using a reactive d.c. magnetron sputtering process. Superlattice period, also known as modulation wavelength (?), was controlled by controlling the dwell time of the substrate underneath Ti and Cr targets. X-ray diffraction (XRD), nanoindentation and atomic force microscopy (AFM) were used to characterize the films. The XRD data showed 1st and 2nd order satellite reflections along the principal reflection for films having 132 A? ? ? ? 84 A?, thus confirming the formation of superlattice. The multilayer coatings exhibited hardness (H) as high as 3200 kg/mm2, which is 2 times the rule-of-mixtures value (i.e. HTiN = 2200 kg/mm2 and HCrN = 1000 kg/mm2). Detailed investigations on the effect of various process parameters indicated that hardness of the superlattice coatings was affected not only by modulation wavelength but also by nitrogen partial pressure and ion bombardment during deposition.