A review of scuffing and running-in of lubricated surfaces, with asperities and oxides in perspective

Abstract

SummaryThe slow progress in the understanding of scuffing (scoring) and runningin of most lubricated surfaces is probably due to an inadequate understanding of the details of asperity deformation and oxide formation. The thickness and properties of oxides influence the stress states imposed on asperities as much as does the liquid lubricant, but the oxides are ignored in theories. Present theories also focus on adhesion as the cause of scuffing and they usually do not take account of the changing surface roughness during sliding. There may indeed be some evidence of adhesion in the later stages of damage but adhesion has not been demonstrated to be the initiating mechanism of scuffing. Plastic fatigue is the more likely explanation, and this can occur without atomic contact between the sliding surfaces.

Testing scuffing resistance of materials for marine 2-stroke engines – Difficulties with lab scale testing of a complex phenomenon

“…Furthermore, scuffing on the local scale, which was called microscuffing by Ludema, could either advance into macroscuffing, i.e. catastrophic failure of the components, or it could be quenched and thereby heal [3]. This is in agreement with observations from marine 2-stroke engines, where a phenomenon called micro-seizure can appear on the surfaces (see section 2).…”

“…Damage accumulation and plastic fatigue are other explanations for initiation of scuffing [3,10,11]. A later suggestion by Ajayi et al is that scuffing is explained by adiabatic shear instability [7].…”

“…Some suggested mechanisms consider how the lubricating film is destroyed, for instance at a critical load or temperature [6]. Others focus on the break down of solid lubricating films, such as oxide layers, which occurs if the wear rate is higher than the rate of film formation [3]. Still others view poor lubrication just as a necessity for scuffing to be initiated and focus on the mechanisms of deformation occurring after lubrication has failed [7].…”

“…According to this theory, scuffing occurs via adiabatic shear when the rate of thermal softening exceeds the rate of work hardening in the sliding contact. Wear particles also play a role in some of the suggested scuffing models [3,12,13].…”

“…Several papers have reviewed scuffing [3][4][5] and many mechanisms of scuffing have been suggested. Some suggested mechanisms consider how the lubricating film is destroyed, for instance at a critical load or temperature [6].…”