Failure of Solid Lubricant W-S-C Coatings under Boundary Lubrication Conditions

A boundary lubrication regime imposes a significant challenge on mechanical systems in terms of both friction and wear. A standard approach to the boundary lubrication regime problems involves coating the contacting parts and lubrication with additivated lubricant. The presented paper explores the application of TMD-based coatings combined with a base oil and an organic-based friction modifier to provide a more environmentally friendly and cheaper solution. An investigation has been performed using a reciprocating tribometer across a range of applied loads, with post-test characterisation performed by a 3D optical profilometer, Raman microscopy, SEM, and TEM. Results show that the coating with higher hardness performs better and that the organic friction modifier increases coefficient of friction but decrease wear in the boundary lubrication regime. Moreover, it was established that without an external source of sulphur TMD-based coatings do not have a satisfactory performance in the boundary lubrication regime.