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

• The DLC films can be successfully coated on oxynitriding-treated ASP23 steel by PECVD.
• DLC/oxynitriding duplex treatment possesses optimal wear and corrosion resistance.
• DLC/oxynitriding duplex treated specimens with the highest surface hardness (Hv0.01 1931)
• DLC/oxynitriding duplex treatment possesses the lowest wear volume loss (3 × 10− 3 mm3).
• The lowest corrosion current appeared in DLC/oxynitriding duplex treated specimens.

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 (Hv0.01 1931) and the lowest wear volume loss (3 × 10− 3 mm3) can be acquired. In addition, compared with non-treated (polarization resistance Rp = 5 × 103 Ω cm2) and oxynitriding-treated (Rp = 8 × 103 Ω cm2) specimens, the optimal DLC/oxynitriding duplex-treated ASP23 high-speed steel possesses the lowest corrosion current (Icorr = 8 × 10 −6 A cm− 2) and highest polarization resistance (Rp = 1 × 104 Ω cm2) in 3.5 wt.% NaCl solutions. This result confirms that the DLC/oxynitriding duplex treatment enhances optimal wear and corrosion resistance.