Investigation of the characteristics of DLC films on oxynitriding-treated ASP23 high speed steel by DC-pulsed PECVD process

Abstract

In this study, diamond-like carbon (DLC) films are coated onto oxynitriding-treated ASP23 high-speed steel by DC-pulsed PECVD. The main research parameters of the DC-pulsed PECVD process are the various duty cycles (5%, 10%, 15% and 20%) used to examine the coating characteristics. In order to investigate the DLC film properties, a Raman spectroscopy analysis, wear test, adhesion, and hardness tests are performed. The experimental results show that the duplex coating layers have optimal properties when DLC films are treated with a low-pulse voltage (−1.5kV), a coating time of 90min and duty cycles maintained at 10%. As a result, the DLC/oxynitriding duplex-treated specimens with the highest surface hardness (Hv0.01 1931) and the lowest wear volume loss (3×10−3mm3) can be acquired. In addition, compared with non-treated (polarization resistance Rp=5×103Ωcm2) and oxynitriding-treated (Rp=8×103Ωcm2) specimens, the optimal DLC/oxynitriding duplex-treated ASP23 high-speed steel possesses the lowest corrosion current (Icorr=8×10−6Acm−2) and highest polarization resistance (Rp=1×104Ωcm2) in 3.5wt.% NaCl solutions. This result confirms that the DLC/oxynitriding duplex treatment enhances optimal wear and corrosion resistance.