Tribological characteristics of bonded MoS2 films evaluated in rolling-sliding contact in a vacuum

Tribological characteristics of bonded MoS₂ films have been evaluated in air, nitrogen and vacuum using a two-roller type rolling-sliding friction apparatus. Two conventional space-proven films, polyamideimide-bonded and sodium silicate-bonded, designated as film A and film B respectively, were tested at a speed of 998 rev min^-1 under a load of 100 N at slip ratios of 1–100%, the slip ratio being defined as (V₁ - V₂)/ V₁ × 100%, in which V₁ and V₂ was rotational speed of each roller.

The wear life of the film A was more slip ratio dependent than that of the film B. The wear life of the film A tested in a vacuum was the longest at 10% slip ratio but it reduced significantly at 1%. On the contrary, the best durability of the film B was obtained at 100% slip ratio (pure sliding). The wear life of the film A shortened considerably in air and nitrogen.

In general, a solid lubricant film applied to spur gears is subjected to rolling-sliding friction of 0-10% slip ratios. To improve the endurance life of the film A at 1% slip ratio, films prepared by changing content of pigments (MoS₂ and Sb₂0₃) were evaluated. The films with a pigment content of 5-15% showed a marked improvement in wear life at a slip ratio of 1%, while maintaining excellent durability at 10%.

The wear process of an improved film was monitored using a gap sensor. It appears to be dominated by fatigue.