Corrosion and scratch resistance of DLC coatings applied on chromium molybdenum steel

Diamond-like carbon (DLC) coatings found many industrial applications in various fields, such as in aerospace, automotive bearing and electronic applications. DLC coatings performances are strictly correlated to their structure and composition which can be optimized controlling the substrate bias voltage (SBV). In this research, the corrosion and scratch resistance of DLC coatings applied on chromium molybdenum steel has been evaluated by electrochemical, microscopical and spectroscopical techniques. It has been observed that increasing the SBV leads to harder and more protective coatings, but decreases the resistance to delamination during scratch testing. Corrosion was always triggered at local defects of the Cr/C gradient interlayer, where the DLC layer was easily delaminated, exposing the chromium molybdenum steel substrate. The results of this study suggest that a better control of the Cr/C deposition parameters are necessary to further enhance corrosion resistance.