Variations in the chemical composition of the surface layers of two alloyed steels are studied in a tribojoint operating according to the “shaft-on-bush“ geometry (bushing test) where the shaft is copper electroplated. Complex interactions are observed during testing in the presence of a molten tin and lead-containing metal lubricant that separates the rubbing surfaces; wear, oxidation, adhesion, and diffusion phenomena are observed in all components of the joint, including the metal lubricant. Comparative studies are performed to study the changes in the surface layer composition of all elements of a ball bearing with a cage fractured due to misuse.