Sliding wear behavior of AZ91/B4C surface composites produced by friction stir processing

Abstract

In the present study, the surface of AZ91 Mg alloy was modified by incorporating boron carbide (B4C) particles using friction stir processing (FSP). Sliding wear behavior of these developed AZ91/B4C surface composites was investigated against AISI 52100 steel ball using linear reciprocating tribometer. Hardness tests reveal that the hardness of the fabricated surface composite (∼137.47 HV) is significantly increased compared to the base metal (∼95.5 HV) due to the presence of B4C particles. Wear tests were conducted on the samples at two different sliding velocities; 0.06 m s−1 and 0.12 m s−1. It was observed that at higher sliding velocity of 0.12 m s−1, AZ91/B4C surface composite exhibited lower friction coefficient value in comparison to that of the base metal, whereas it is vice versa at the low sliding velocity of 0.06 m s−1. However, surface composites exhibited superior wear resistance at both the sliding velocities, in comparison to that of the base metal. Scanning electron microscopy and energy-dispersive spectroscopy analysis of the wear tracks were carried out to understand the wear mechanisms. From the observations, a combination of abrasive, adhesive, and oxidative wear mechanisms were found to be prominent.