Effect of Co Content on the Microstructure and Tribological Properties of Fe-Ni-Co Electroplated Coatings

Abstract Abnormal wear is a major cause of crankshaft failure, and replacing worn crankshafts usually results in high maintenance costs. Electroplated alloy technology provides a promising and cost-effective approach for the surface repair of damaged crankshafts and the surface strengthening of new crankshafts. In this work, Fe-Ni-Co electroplated coatings with different Co contents were prepared, and the effects of Co content on the surface morphology, microstructure, mechanical properties, and tribological performance of the coatings were investigated. The results showed that Co incorporation improved the overall performance of the Fe-Ni-Co coatings. When the Co concentration in the bath was 7.5 g/L, the coating exhibited a relatively smooth surface, a moderately dense reticulated texture, and better wear resistance. Compared with the Co-free coating, the coating prepared at 7.5 g/L Co exhibited a 10.5% increase in hardness and a 25.4% reduction in wear rate. Under dry friction conditions, the dominant wear mechanisms were oxidative wear and abrasive wear, accompanied by slight adhesive wear. The enhanced mechanical and tribological properties were mainly attributed to the combined effects of solid-solution strengthening and grain-refinement strengthening. These findings provide useful guidance for the practical application of Fe-Ni-Co electroplated coatings in crankshaft surface repair.