Effects of SiC additions on the microstructure, compressive strength and wear resistance of Sn-Sb-Cu bearing alloy formed via powder metallurgy

Abstract

Sn base Babbit (Sn-Sb-Cu) has become a material of choice for making sliding bearings and liners because of the anti-friction and excellent embedability properties of Sn while the intermetallics (SnSb, Cu6Sn5) act as the load bearers. However, the load bearing capacity of Sn-Sb-Cu alloy is limited in high speed and heavy load engines. In this work, Sn-Sb-Cu composites reinforced with 3, 6 and 9 wt.% of SiC were fabricated via powder metallurgy (PM) technique. The microstructure, mechanical and tribological properties of the composites were investigated using optical microscopy, scanning electron microscopy (equipped with energy dispersive spectrometer), X-ray diffraction machine, Vickers hardness tester, Instron Universal testing machine and pin-on-disk tribometer. The results were analysed and compared with that of the Sn-Sb-Cu alloy. PM technique was successfully utilised to produce fully dense Babbit alloy and composites with porosity ranging between 1.3% and 6.7%. The microstructure of the alloy revealed the presence of SnSb and Cu-rich angularly shaped phases randomly dispersed in Sn-rich matrix. The composites comprise uniformly dispersed SiC powders in the Sn-base matrix. The volumetric ratio of SnSb:Sn in the composites was found to increase as the SiC composition increased. The hardness, compressive strength and wear resistance properties of the Sn-Sb-Cu alloy increased with the increase in SiC composition. It is found that the addition of 9 wt.% SiC exhibited the highest performance with the improvement of ∼43% in hardness, ∼55% in compressive strength and ∼80% in wear resistance over the Sn-Sb-Cu alloy.