Study the Effect of New Rheocast on Tribological Behaviour of ZA27

This paper investigated how casting affects ASTM ZA-27 alloy's tribological performance in dry and lubricated conditions. To this end, varying contact loads and sliding speeds were applied to tribological tests. The ZA-27 alloy was produced using gravity die casting (GDC) and new rheo-casting (NRC) methods. The results showed that the microstructure of GDC ZA-27 alloy is dendritic containing α and η phases. While the NRC alloy microstructure demonstrates a semi-globular structure of fine equiaxed α phase bordered by eutectoid α and η. The NRC alloy achieved an improvement in tensile, hardness, and elongation properties by almost 15%, 20%, and 25%, respectively. Regarding tribological properties, the NRC alloy achieved an enhancement in tribo-behavior by lowering the coefficient of friction (COF) to about 67% than the GDC alloy. Further, the results showed that the wear rate recorded an increment with applied load for both GDC and NRC alloys. Though, the results showed that the wear rate with NRC alloy was lower compared to the GDC alloy with about 84% at 160N normal load. The worn surfaces of NRC alloys were characterized by smooth and shallow wear grooves. While the GDC alloy worn surfaces were rougher and experience deeper grooves and damage.

Keywords:
Gravity Die Casting; New Rheo-Casting; ZA-27; Tribological behavior