The wear characteristics of CeO2 containing nanocomposite coating made by aluminate-based PEO on AM 50 magnesium alloy

This study examined the influence of CeO2 nanoparticles on the wear characteristics of aluminate-based PEO coatings formed on the AM50 magnesium alloy, which was developed for the automotive industry. Sliding wear assessments were conducted on a ball-on-disk tribometer at 2 N, 5 N and 10 N loads (against an AISI 52100 steel ball). It was found that the wear characteristics were greatly affected by the addition of CeO2 nanoparticles, especially under intermediate and high loads. The coatings with and without CeO2 remained intact during the sliding test at 2 N. Under an intermediate load of 5 N, the coating treated in the absence of CeO2 failed, while the one made in the presence of CeO2 offered superior wear resistance without any signs of wear failure. Under the 10 N load, the CeO2-free coating was completely removed and the substrate emerged, which was mainly due to a combined adhesive-abrasive wear damage mechanism; in contrast, the CeO2 -containing coating (PEO-CeO2) offered much superior wear resistance to the Mg alloy, which was consistent with the friction coefficient data. SEM-EDS analysis of the worn surface of the steel balls also indicated that the transfer of the coating fragments to the ball surface was more intensive for the nanoparticle-free coating, as compared to that observed for the PEOCeO2 coating. Also, the appearance of some deep scoring in the worn surface of the balls could be considered as a result of the three-body abrasive wear. The superior wear resistance of the CeO2 embedded nanocomposite coating could be mainly attributed to its lower porosity, lower roughness, and higher hardness.