Effect of Bifilm Oxides on the Dry Sliding Wear Behavior of Fe-Rich Al-Si Alloys

The effect of bifilm oxides on the dry sliding wear behavior of Fe-rich (1.5 wt.%) F332 Al-Si alloy under as-cast and T6 heat-treated conditions was investigated. Toward this end, the surface oxides were intentionally incorporated into the molten alloy by surface agitation. The results showed that, after sliding under the applied load of 75 N, due to the presence of bifilms, the wear rate of base (0.2 wt.% Fe) and 1.5 wt.% Fe-containing alloys increased by almost 22% and 14%, respectively. The results also indicated that, despite the positive effect on the hardness, T6 heat treatment adversely affected the wear resistance of alloys made under surface turbulence condition. This negative effect can be attributed to the expansion of bifilms which, during heat treatment, are converted to the potential sites for initiation and propagation of subsurface microcracks. However, the strengthening effect exerted by the thermally modified beta-Al5FeSi platelets showed that it can compensate the negative effects of bifilm oxides because it improves the wear rate of 1.5 wt.% Fe-containing F332-T6 alloy by about 5% under the applied load of 75 N.