Enhanced Tribocorrosion Resistance of Superhard Ti-C-N Ceramics Coatings

Abstract Cubic transition-metal nitride coatings have been regarded as promising candidates for of marine engineering components in seawater environments. However, the excellent seawater lubrication is hard to achieve due to contradictory relations of hardness and toughness, as well as unstable behaviors at sliding contact surface. As discussed in our previous work about the enhanced tribological behaviors of hard yet tough CrN/Si3N4 multilayer coatings[14], superhard yet tough coatings are highly desired to improve wear resistance and durability in aggressive solutions. Here we report Ti-C-N coatings with Ti(C,N) and small sp2-C phases deposited by high power impulse magnetron sputtering exhibit simultaneously superhardness of 40.2 GPa and favourable toughness (without radial cracks in HRC indentations). Superhard yet tough Ti-C-N coatings show excellent seawater-lubricating behaviors with extremely low friction coefficient of 0.03 and smooth wear morphologies in 3.5wt.% NaCl aqueous solution. The enhanced tribocorrosion performance are attributed to superhard yet tough properties resulting in the increased resistance of crack initiation and propagation, which restrains synergistic actions of wear and pitting corrosion. In addition, stable self-lubricating amorphous carbon phase at sliding contact surface reduce friction and wear in seawater.