Corrosion resistance of PVD hard coatings for tribological engineering applications

Abstract

The present paper focuses on corrosion resistance of hard coatings deposited on tool steel via Physical Vapour Deposition (PVD) process. Three coating types were investigated - TiN, TiCN and DLC/TiAlN. An immersion corrosion test was performed on the PVD coated tool steels in accordance to ASTM G31 standard. With immersion corrosion test in aggressive media of 3.5% NaCl solution at ambient temperature of 33°C and exposure duration of up to 72 hours, the presence of the PVD coatings on the tool steel surface have improved the corrosion resistance of the tool steel surfaces. The results showed that the DLC/TiAlN coated tool steel has the highest corrosion resistance with corrosion rate of 36.58 mm/year, followed by TiCN and TiN coatings with corrosion rate of 42.10mm/year and 96.86 mm/year, respectively. The uncoated tool steel exhibits the lowest corrosion resistance of 140.61 mm/year. The present study suggests that the DLC coating deposited on SKD11 tool steel substrate has better stability than that of TiCN- and TiN-coated surfaces because the DLC can prevent the corrosion more efficiently than TiCN and TiN.