Adhesion and tribological performances enhancement for a-C:Ta coatings by adjusting the Ar gas pressure

Abstract In this study, the adhesion property of the a-C:Ta coatings on 9Cr18 substrates prepared by magnetron sputtering technology was tailored by modifying the working pressure via adjusting the Ar flow. The effects of the working pressure on the microstructure, mechanical and tribological properties of the prepared coating were analyzed. The results indicated that the average growth rate of the coating was first improved when the working pressure appropriately increased, but then declined due to the etching effect at the further increasing flow rate. With the working pressure increasing, the sp 3 C content, hardness and elastic modulus of coatings showed a trend of first increasing and then decreasing. By the modulation of working pressure, the adhesion forces between the substrates and coatings were tuned with the optimized value of 23 N, while the friction coefficient ranged from 0.1 to 0.2 without serious changes. The wear rate showed a trend of first decreasing and then increasing with enlarging the working pressure. The coating possessed the most stable friction coefficient and lowest wear rate when the working pressure was 0.23Pa, attributed to the highest adhesion force, resistance to plastic deformation, and stable graphitization transfer film formed during the friction process. This approach can provide systematic guidance for enhancing the adhesion and tribological properties of amorphous carbon coatings, which could be widely applied as protective layers on moving mechanical components in the future.