Effect of space UV irradiation on the mechanical and tribological properties of Cr and B doped hydrogen-containing diamond-like films

Abstract

To promote the wide application of hydrogen-containing diamond-like films (a-C:H) as solid lubricant materials in aerospace environment, a series of a-C:H, a-C:H doped with Cr elements (Cr/a-C:H) and a-C:H doped with B elements (B/a-C:H) were prepared on the GCr15 steel by non-equilibrium magnetron sputtering technique. The effects of ultraviolet (UV) irradiation on the mechanical and tribological properties of the three DLC films were investigated. UV irradiation was found to cause a decline in hardness and modulus of elasticity, and increased residual stress and surface roughness in all three films. UV irradiation has a minor impact to the coefficient of friction of the three films, but leads to a decrease in wear life. The wear life of Cr/a-C:H films was least affected by UV irradiation. UV irradiation can lead to the breakage of sp³C-H bonds in a-C:H film and B/a-C:H film, resulting in the increase of dangling bonds in the films and the decrease of wear life. In the Cr/a-C:H film, the broken sp³ C-H bond is partially reorganized into sp² C-H bond, which further exerts the passivation effect of C-H bond, resulting in a smaller decrease in the wear life of the Cr/a-C:H film.

Keywords:

• Diamond-like films
• elemental doping
• UV irradiation
• frictional wear
• mechanical properties

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This study was supported by the National Natural Science Foundation of China (52122508, 52105200 and 52130509).