The influences from CrN transition layer thickness to the tribological and corrosion performance of DLC films

Abstract

The CrN hard interlayer can enhance the performance of DLC (Diamond-Like Carbon) films; however, it simultaneously introduces internal stress and nitrogen (N). To elucidate its effects, this study employs the non-equilibrium magnetron sputtering technique to prepare DLC films on 316 stainless steel substrates with and without CrN transition layers of 0.4, 0.8, and 1.2 μm thicknesses, respectively. The morphology, phase composition, adhesion strength, hardness, wear resistance, and corrosion resistance of the prepared films were systematically investigated using SEM, XRD, TEM, Raman spectroscopy, scratch testing, nanoindentation, micro-hardness, electrochemical workstation, and wear testing. With increasing CrN transition layer thickness, the CrN XRD peak shifts to higher 2θ angles accompanied by a broadening FWHM, indicative of enhanced compressive stress, while residual nitrogen incorporation and elevated deposition temperatures synergistically promote sp² content in DLC films. Comparing among all films, the film with a 0.8 μm CrN transition layer (C3) exhibited the lowest stable friction coefficient and the smallest wear rate (one third of the one without CrN layer), characterized by mild abrasive wear. Additionally, in Tafel curve, the corrosion current density of C3 is 1/4 of that for the C1 sample. However, as the CrN layer thickness increases further from 0.8 to 1.2 μm (C4), the coated surface exhibits the worst tribological performance, likely due to excessive stress concentration and micro-cracking in the CrN layer. This systematic study provides insights into the performance and design of wear- and corrosion-resistance Cr/CrN/DLC films.