The tribological performance of selected solid lubricant films in sand-dust environments

Solid lubricant films have received considerable research attention in the last decades owing to their remarkable improved tribological characteristics. In this paper, the abrasive wear behaviour of five types of solid lubricant films (magnetron-sputtered diamond-like carbon, magnetron-sputtered molybdenum disulfide, bonded molybdenum disulfide, bonded polytetrafluoroethylene and bonded graphite) in sand-dust environment has been investigated using a reciprocating pin-on-disc test rig. The effects of applied load, amount of sand and particle size on the tribological performance of these films were systemically studied. Experimental results show that magnetron-sputtered films give excellent anti-friction and wear-resistance performances under sand-dust environments compared to bonded solid lubricant films. The significant differences of surface roughness, hardness, microstructure and intrinsic lubricating property directly lead to the different tribological performances and worn morphology. The formed composite transfer layer plays a vital role in reducing friction and wear due to its anti-friction and shielding action of the film surface from the hard metal asperities. Two main abrasive wear mechanisms (three-body rolling wear and two-body grooving wear) occur simultaneously in the tribological process under sand-dust environments. A transfer layer-hardening composite wear modeling was established to further explain the anti-wear mechanisms and friction-reducing capacity of these solid lubricant films under sand-dust environments.