2016 Volume 56 Issue 12 Pages 2276-2283
In this study, diamond-like carbon (DLC) films are prepared by DC-pulsed plasma-enhanced chemical vapor deposition (PECVD) after the oxynitriding treatment of PM60 high-speed steel. The chief study of the parameters of a DC-pulsed PECVD process includes various power densities (200, 400, 600, 800 and 1000 mW·cm−2) with unipolar negative-pulsed voltage. In order to evaluate the properties of the DLC films for DLC/oxynitriding-treated PM60 high-speed steel, Raman spectroscopy analysis, wear tests, hardness tests, Rockwell indentation and corrosion resistance inspections are performed. The experimental results show the duplex coating layers to have the ideal properties when the DLC films are treated by the unipolar negative-pulsed voltage, a deposition time of 90 min and duty cycles maintained at 11%, with an appropriate power density (400 mW·cm−2), respectively. The DLC/oxynitriding duplex treatment results in the highest surface hardness (Hv0.2 2516.4) and lowest wear volume loss (when the load of 2 N and 5 N is 2.36 × 10−3 mm3 and 5.67 × 10−3 mm3, respectively). In addition, when the DLC/oxynitriding duplex film is treated by a power density of 200 mW·cm−2, it possesses the lowest corrosion current (Icorr = 7.24 × 10−5 A·cm−2) and highest polarization resistance (Rp = 6.26 × 102 Ω·cm2) in 3.5 wt% NaCl solutions. The test results confirm that the optimal wear and corrosion resistance can be acquired by the DLC/oxynitriding duplex treatments.
