Development of Ti/Ti-DLC multilayers on magnesium alloys — Part 2: Corrosion and wear resistance

Abstract

To improve corrosion and wear resistance of magnesium alloy, the Ti-DLC monolayer and Ti/Ti-DLC multilayer films were deposited on AZ31 magnesium alloys by filter cathodic vacuum arc deposition technology. All coatings showed good corrosion and wear resistance, and low friction coefficient. The corrosion resistance of the coated samples, from high to low, was Ti/Ti-DLC)2 multi coated-, Ti-DLC mono coated-, and Ti/Ti-DLC)4 multi coated samples. That is because the good toughness and film/substrate deformation coordination of multilayer films were beneficial for improving the corrosion resistance of coating, but the thinner Ti sublayer increased the risk of corrosion liquid penetrating the coating. Under friction test under 5 N load for 30 min, the Ti-DLC monolayer film showed best wear resistance with lowest wear rate as its combination effects of high hardness and good toughness. Whereas, under higher load, the higher toughness and film/substrate deformation coordination of multilayer films played a more positive role in its wear life. Under load of 10 N, comparing to the Ti-DLC monolayer film, the (Ti/Ti-DLC)4 multi and (Ti/Ti-DLC)2 multi films improved wear life by 15 % and 36 %, respectively. The (Ti/Ti-DLC)2 multi film had the best corrosion resistance and wear life.