Effect of microstructure and mechanical properties on the tribological and electrochemical performances of Si/DLC films under HCl corrosive environment

Abstract

Si-doped diamond-like carbon (Si/DLC) films appear very attractive due to their superior mechanical and tribological properties and chemical inertness. In the present work, Si/DLC films with silicon concentration from 1.64 to 15.32 at.% were fabricated on 304 stainless steel by adjusting Si target current using unbalanced magnetron sputtering system. The microstructure, surface morphology and mechanical properties of the films with different Si concentration, as well as the tribological and electrochemical properties of the films under HCl corrosive environment were systematically investigated. Results showed that Si doping increased the sp3 CC content, hardness, and elastic modulus of as-fabricated films, lowered the residual stress, but deteriorated the adhesion strength. At the same time, the appropriate Si concentration was conducive to low surface roughness and dense microstructure. The Si/DLC films presented good tribological performances in 1 M HCl solution, including low friction coefficient and wear rate. The degradation of tribological properties was attributed to the synergistic effect of less solid lubrication, declined adhesion strength, worse resistance to elastic and plastic deformation. The wear mechanism was mainly dominated by abrasive wear. Furthermore, the Si/DLC film with 15.32 at.% Si provided the best corrosion resistance, which benefited from its dense structure, higher thickness, and the highest sp3 CC content.