Effect of Graphene Nanoplatelet Content on Mechanical and Elevated-Temperature Tribological Performance of Self-Lubricating ZE10 Magnesium Alloy Nanocomposites

Magnesium (Mg) and graphene in alloy formulations are of paramount importance for lightweight engineering applications. In the present study, ZE10 Mg-alloy-based nanocomposites reinforced with graphene nanoplatelets (GNPs) having a thickness of 10-20 nm were fabricated via ultrasound-assisted stir casting. The effect of GNP contents (0.25, 0.5, and 1.0 wt.%) on the microstructure, Vickers hardness, and tensile properties of nanocomposites was investigated. Further, tribological studies were performed under a ball-on-disc sliding wear configuration against a bearing ball counterbody, at room and elevated temperatures of 100 degrees C and 200 degrees C, to comprehend temperature-induced wear mechanisms and friction evolution. It was revealed that the GNP addition resulted in grain coarsening and increased porosity rate of the Mg alloy. While the composites exhibited improved hardness by 20-35% at room temperature and 100 degrees C, a minor change was observed in their hardness and tensile yield strength values at 200 degrees C with respect to the GNP-free alloy. A notable improvement in lowering and stabilizing friction (coefficient of friction at 200 degrees C similar to 0.25) and wear values was seen for the self-lubricating GNP-added composites at all sliding temperatures. The worn surface morphology indicated a simultaneous occurrence of abrasive and adhesive wear mode in all samples at room temperature and 100 degrees C, while delamination and smearing along with debris compaction (tribolayer protection) were the dominant mechanisms of wear at 200 degrees C. Inclusively, the results advocate steady frictional conditions, improved wear resistance, and favorable wear-protective mechanisms for the Mg alloy-GNP nanocomposites at room and elevated temperatures.