Effect of Copper on the Corrosion of High-Carbon Bearing Steels

Abstract

Roller bearings are one of the most important industrial components with a large variety of challenging environmental applications. Under water-contaminated lubricant conditions, a pro- tective layer of oxide forms on the surface of the most used 100Cr6 bearing steel, which helps suppress the corrosion rate, while adding corrosion-resistant alloying elements can improve this corrosion resistance further. Recent research suggests that the Cu alloying element in high- carbon steels contains numerous carbide precipitates, which can help to form a stronger passive layer and, thus, more effective in protecting the steel against corrosion. Meanwhile, the accu- mulation of Cu as a tramp element can degrade the quality and performance of scrap-based steel. This limits the proportion of scrap that can be used in new products and may require adding ore-based steel to dilute the copper content and maintain the required properties. This study investigates the effect of incorporating copper in high-carbon bearing steel manufactured from scrap on enhancing long-term atmospheric corrosion resistance. The effective usage of this tramp element will contribute to boosting the circular economy of steel.
In this project, high-carbon bearing steel containing a high amount of Cu (0.5 wt %) was hardened using martensitic or bainitic hardening and compared with the baseline hardened steel with no excessive Cu. The microstructures of the steel were characterized by LOM, SEM (EDS), XRD and XPS to study the retention/segregation of Cu. Electrochemical corrosion tests were used to validate the prediction. Finally, LOM, SEM (EDS), XRD and XPS were utilised to characterise the corroded surfaces.