Transition from the boundary lubrication to scuffing - The role of metallic surfaces morphology

The experimental investigations examined the morphological changes of pairs of cooperating surfaces, from "freshly" machined to scuffed states. The frictional process was systematically carried out on a specifically adapted tribometer (a “block-on-ring” system). Explicitly wear-resistant materials (e.g. AISI 4130 steel/EN-GJL-300 cast iron and AISI W1-81/2A steel/EN-GJS-450-10 cast iron) were selected for this investigation, using the same load to cause the transition to scuffing and employing different combinations of more or less efficient lubricants in the boundary regime: either reclaimed naphthenic oil or a chemically-active oil containing a particular additive (an olefin sulphide). The double-blind protocol of these experiments was employed in order to achieve a higher standard of scientific rigour. The strategy was to apply the concept of a morphological precursor to scuffing to the identification of the transition conditions from the boundary lubricating regime to scuffing. The quantification of the morphological transition based on the scientific examination of selected parameters (EN-ISO 25178 and EUR 15178, ISO 16610, ISO 13565-2 and ISO 13565-3, ISO 12085 motifs' parameters), from normal boundary lubrication to the scuffing wear regime, is presented.