Oxidative wear assisted enhanced wear performance of spark plasma sintered in situ Fe-based bulk metallic glass composites

Abstract

Current study reports the dry sliding wear behavior of Fe₅₇Cr₉Mo₅B₁₆P₇C₆ (at. %) fully amorphous bulk metallic glass (BMG) and in situ BMG composites, synthesized via spark plasma sintering. Fully amorphous alloy and in situ amorphous-crystalline composites containing various amount of crystallinity with a relative density > 98% were fabricated via optimized sintering conditions. Effect of in situ induced crystalline phase content on wear behavior and wear mechanism was investigated. In situ crystallization of intermetallic phases such as Fe₅PB₂, Fe₂B and Cr₂B led to significant increase in the hardness of the composite samples up to 15.1 GPa from 10.1 GPa in the case of fully amorphous sample. Increase in crystallinity in the studied Fe-based amorphous-crystalline composites was found to have a positive effect on wear performance. In the BMG sample with completely amorphous phase, sliding wear induced debonding of the sintered particles along with surface oxidation. However, in the case of amorphous-crystalline composite samples, sliding wear caused the formation of oxide rich tribolayer that resulted in lower coefficient of friction and significantly lower wear rates compared to the fully amorphous sample. Coefficient of friction values assumed more than 50% decrease in the case of 20% amorphous composite sample in comparison to the fully amorphous sample. Wear rates of the current Fe-based amorphous-crystalline composite samples were found to be in the order of 10⁻⁷ mm³/N.m, which are relatively lower compared to the recently reported Fe-based BMGs.