Properties of tin-based matrix composite bearing materials by powder metallurgy
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Date
2019-05
Authors
Muhammad Ammar Izzat Bin Azlan
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Abstract
This work aims to investigate the lead-free Sn-based alloy bearing material using powder metallurgy technique. Compositions of Sn-Sb-Cu with the variation of addition of 3 wt.%, 6 wt.% and 9 wt.% SiC composites were fabricated to reveal the contribution of the ceramic reinforcement on the alloy properties. The powder mixture was performed by mechanical alloying. First, the powder is weighed according to its weight percent, then it will be milled at 220 rpm using planetary mill for 1 hour and 30 minutes. The powder then pressed at 300 MPa for 2 minutes and sintered at 160 °C using vacuum sintering oven. X-ray-diffraction technique reveal that the Sn, SnSb, Cu and SiC phase was detected. The lamellae formation of -Sn becomes the major phase for the matrix. For the composites, SiC particles are observed dispersed uniformly and protruded from the matrix surface. Composite with 9 wt.% SiC has the highest hardness (15.27 Hv) than Sn-Sb-Cu alloy (10.67 Hv) while the compressive strength improved significantly to (618.07 MPa) for 9 wt.% SiC composite as a comparison to (340.96 MPa) Sn-Sb-Cu alloy. Protruded hard SiC particles minimise the surface of the soft tin matrix from making a direct contact with the iron disc during wear test and resulting in the increasing of the coefficient of friction (COF). 9 wt.% SiC composite display higher average of coefficient of friction (0.71) compared to Sn-Sb-Cu alloy (0.46). Observation under SEM discover the formation of delamination wear on SnSb-Cu alloy and abrasive wear is experienced by the composites. Lower specific wear rate 9 wt.% SiC composite (0.02125 𝑚𝑚2 𝑁𝑚 ) composites as compared to (0.03950 𝑚𝑚2 𝑁𝑚 ) for Sn-Sb-Cu alloy confer better wear resistance is attributed to the protruded SiC particles during in contact with iron disc.