Optimization of DLC films on oxynitriding-treated Vanadis 10 tool steel through the various duty cycles of DC-pulsed plasma-enhanced CVD

Abstract

In this study, DLC films were coated on oxynitriding-treated Vanadis 10 tool steel using the DC-pulsed plasma CVD technique. The experimental parameters included different duty cycles (9, 13, 17, and 21 %) with asymmetric bipolar-pulsed voltages of -3 kV, a gas flow of CH4 maintained at 15 sccm, and a deposition time of 90 min. Meanwhile, the properties of DLC films were measured by Raman spectroscopy, Rockwell indentation, wear tests, FT-IR, corrosion tests, water contact angle tests, and four-point probes analysis. The experimental results showed that the optimum properties of DLC films occurred at a duty cycle of 17 %. It had the lowest wear volume loss for loads 2 N and 5 N were 3.49 × 10 −3 mm 3 and 4.08 × 10 −3 mm 3 , respectively. Moreover, the optimal DLC films possessed the lowest corrosion current (Icorr = 7.91 × 10 −5 A cm −2 ) and highest polarization resistance (Rp = 1185.21 Ω cm 2 ) in 3.5 wt.% NaCl solutions. The FT-IR spectrum analysis also found that the characteristic peaks of DLC films were generated at positions of 2852 and 2921 cm −1 , and the water contact angle tests showed that the DLC films had great hydrophobicity (78.33 • ). Consequently, the results confirmed that the duplex surface treatment effectively improved the coating properties of Vanadis 10 tool steel. K e y w o r d s : diamond-like carbon (DLC), oxynitriding, Vanadis 10 tool steel, DC-pulsed plasma-enhanced CVD, wear, corrosion, water contact angle

Improvement of the properties of CrN Films on oxynitriding treated Vanadis 23 high-speed steel by the DC magnetron sputtering

“…In this study, both the lowest corrosion current (8.9×10 − 5 A•cm − 2 ) and highest polarization resistance (822.11 Ω•cm 2 ) appeared in the 325℃ sample. Our previous studies indicated that the samples with a lower corrosion current (I corr ) and a higher polarization resistance (R P ) exhibited better corrosion resistance [4,6,7], thus, the 325℃-deposited CrN lms had the best corrosion resistance. It is speculated that the above phenomenon is mainly caused by the density difference on the surface of the CrN coating (as seen in Fig.…”

“…Generally speaking, the oxynitriding process can form several kinds of nitrides (Fe 2 N, Fe 3 N and Fe 4 N) and oxides (Fe 2 O 3 and Fe 3 O 4 ), which improve the wear, corrosion and erosion properties of the alloy steels [5,6]. Notably, the oxynitriding layer can also effectively improve the adhesive strength as an intermediate layer during the duplex coating treatments [4][5][6][7].…”