The influence of different power supply modes on the microstructure, mechanical, and corrosion properties of nc-TiC/a-C:H nanocomposite coatings

Titanium carbide (TiC) coatings have attracted wide attention from researchers and industry due to their high hardness, wear and corrosion resistance. In this study, a plasma emission monitoring system was adopted to feedback control the target poisoning status of 70% in a gas mixture of acetylene using four different power supply modes including superimposed HiPIMS-MF, HiPIMS, MF, and DC. The nanocrystalline TiC/a-C:H nanocomposite coatings containing NaCl-type TiC nanocrystallites (3–7 nm in diameter) embedded in a hydrogenated amorphous carbon (a-C:H) matrix microstructures were fabricated by four different power supply modes. The corrosion resistance of 304 stainless steel substrate against the sulfuric acid attack was greatly improved by the four nc-TiC/a-C:H nanocomposite coatings. Although the deposition rate of the coating prepared by the DC power supply was the highest, the film quality was inferior to other films due to its higher oxygen content and larger TiC grain size. On the other hand, the nc-TiC/a-C:H coating fabricated by the superimposed HiPIMS-MF power mode exhibited a featureless microstructure with the highest hardness of 27.5 GPa and the highest H3/E2 ratio of 0.38. The nc-TiC/a-C:H nanocomposite film grown by superimposed HiPIMS-MF became a promising protective coating in severe environment applications due to its high hardness, good adhesion, adequate tribological properties, and excellent corrosion resistance against sulfuric acid.