Friction transition diagram considering the effects of oxide layer formed on wear track of AISI 1045 steel disk against TiN coated AISI 52100 steel ball in sliding

In this study, the effect of the real contact area on oxide layer formation was investigated by varying coating thickness, surface roughness of counter part and contact load between two materials in order to understand the wear mechanism of a TiN coated ball against a steel disk. After conducting sliding tests under different conditions, the characteristics of the oxide layer that are formed on the sliding surfaces of the two materials and changes in friction signal, which were caused by the oxide layer formation, were examined. For the coated ball specimen, an AISI 52100 steel ball was used and AISI 1045 steel was used for the disk counter part. From the results, the iron oxide layer on the steel disk dominates the friction characteristic between the two materials and induces a friction transition and high friction. The oxide layer, on the sliding surfaces of two materials, begins to form at a point through which friction signal transits from low friction to high friction. Also, the formation on the counter part occurred early as the contact load increased, as the surface roughness of counter part decreased and as the TiN coating thickness decreased.