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

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 (-1.5 kV), a coating time of 90 min and duty cycles maintained at 10%. As a result, the DLC/oxynitriding duplex-treated specimens with the highest surface hardness (Hv(0.01) 1931) and the lowest wear volume loss (3 x 10(-3) mm(3)) can be acquired. In addition, compared with non-treated (polarization resistance R-p = 5 x 10(3) Omega cm(2)) and oxynitriding-treated (R-p = 8 x 10(3) Omega cm(2)) specimens, the optimal DLC/oxynitriding duplex-treated ASP23 high-speed steel possesses the lowest corrosion current (I-corr = 8 x 10(-6)A cm(-2)) and highest polarization resistance (R-p = 1 x 10(4) Omega cm(2)) in 3.5 wt.% NaCl solutions. This result confirms that the DLC/oxynitriding duplex treatment enhances optimal wear and corrosion resistance. (C) 2014 Elsevier B.V. All rights reserved.