Tribological properties of steel sheet with epoxy-based enamel coating under dry and lubricated conditions for stamping applications

In the automotive industry, steel sheets used for stamping into laminations are often coated with various enamel coatings to enhance product performance. However, the impact of these coatings on the tribological behavior of the steel sheets has not been given sufficient attention. This research evaluates the tribological performance of steel sheet with epoxy-based enamel coating in contact with a WC-Co ball under dry and lubricated conditions. The lubricated conditions included the use of water, two low-viscosity (LV) oils (paraffinic LV and naphthenic LV) and two high-viscosity (HV) oils (paraffinic HV and naphthenic HV). The Raman spectra of the wear track show that the epoxy-based enamel coating remains in contact during the initial testing cycles for all the tested conditions, keeping the coefficient of friction low and resulting in only a small variation in the coefficient of friction between the dry and lubricated conditions. Even though the chosen lubricants slightly decrease the hardness of the epoxy-based enamel coating, they (with the exception of the high-viscosity paraffinic oil) prolong the presence of the enamel coating in the contact compared to dry conditions. After the coating is removed, the difference in the coefficient of friction between the different lubricants and the dry contact becomes significant, being much lower under lubricated conditions, especially with HV oils.