Deposition of DLC/oxynitriding Films onto JIS SKD11 Steel by Bipolar-pulsed PECVD

Abstract

In this study, diamond-like carbon (DLC) films are coated by bipolar-pulsed PECVD onto oxynitriding-treated JIS SKD11 steel. In order to evaluate the properties of the DLC/oxynitriding films on SKD11 steel, Raman spectroscopy analysis, wear tests, adhesion tests, hardness tests and corrosion resistance inspections are performed. The experimental results show that the DLC/oxynitride duplex layers possess ideal wear and corrosion resistance when DLC films are deposited by unbalanced bipolar-pulsed voltage, with a coating time of 90 min and duty cycles maintained at 15%. The highest surface hardness (Hv_0.025 2830.7) and lowest wear volume loss (when the load of 2 N and sliding speed of 0.05 m·s⁻¹ is 4.07 × 10⁻³ mm³ and the load of 5 N and sliding speed of 0.25 m·s⁻¹ is 5.83 × 10⁻³ mm³, respectively) are obtained. In addition, the optimal DLC/oxynitride films also possess the lowest corrosion current (I_corr = 2.66 × 10⁻⁶ A·cm⁻²) and highest polarization resistance (R_p = 1.57 × 10⁴ Ω·cm²) in 3.5 wt% NaCl solutions.