Friction and wear behaviour of aluminium alloy coconut shell char particulate composites

The friction and wear characteristics of Al-11.8%Si alloys containing 10-25 vol.% (3-8 wt.%) dispersions of coconut shell char particles (average size, 125 μm) were evaluated under dry conditions with a pin-on-disc machine. At the lower sliding speed of 0.56 m s-1, the wear rates and friction coefficients of the composites decreased with increasing volume per cent of dispersed char particles in the aluminium alloy matrix. Scanning electron microscopy observations have revealed the presence of adhering shell char fragments on the worn-out surface of the composites and the average roughness Ra for the worn-out surface of the composite (Al-11.8%Si-8%char) was much less (1.9 μm) than for the worn-out surface of the matrix (3.2 μm). At the higher sliding speed of 5.38 m s-1, the wear rates increased with increasing volume per cent of dispersed char particles in the matrix and the Ra value for the composite (Al-11.8%Si-8%char) was higher (5.2 μm) than for the matrix (4.6 μm). The worn-out surface of the composites did not show the presence of adhering shell char fragments. The reduction in wear rates and friction coefficients of composites at the lower sliding speed of 0.56 m s-1 with respect to the matrix alloy wear was attributed to the presence of adhered fragmented bits of shell char on the wearing composite surface. © 1982.