Sn/Graphite/Cu reinforced aluminum: An experimental study on fabrication of hybrid surface composite as journal bearing material by friction stir processing

Friction stir processing (FSP) is an energy-efficient and environmentally friendly technique that provides tailored manufacturing possibilities for surface composites in solid-state conditions. This study focuses on manufacturing solid lubricant-reinforced aluminum matrix surface composite (AMSC) through FSP, which can be used as a journal-bearing material. Composite fabrications are performed utilizing Sn, Cu, and graphite particles (hybrid powder) with four passes of FSP. The cross-sectional macro and microstructures of obtained surface composites are investigated via optical microscopy (OM) and scanning electron microscopy (SEM). The stir zone (SZ) chemistry is analyzed with energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The microhardness measurements show the effects of hybrid powder as reinforcement and FSP parameters on the mechanical features of the composite cross-sections. Wettability and tribological tests are also conducted to determine the surface properties of the fabricated composites. According to the findings, the wear rate is decreased by 8 % with the reduction of average CoF to 0.75, while a hardness increment is achieved over similar to 35 % in manufactured surface composites compared to the base material. It is observed that the content and amount of the hybrid powder and FSP parameters employed can ensure the fabrication of desired characteristics compatible with the aim in surface composites.