Tribological characteristics of AA7075 composites reinforced with rice husk ash and carbonized eggshells

This paper investigates dry sliding friction and wear behavior of AA7075 composites reinforced with rice husk ash and carbonized eggshells. Composites with varying weight percentages of rice husk ash and carbonized eggshells in the range of 0-5 wt.% were fabricated through stir-casting technique. Density, porosity content, and microhardness were computed before tribological testing. Friction and wear tests were conducted on pin-on-disc type tribometer at room temperature. The samples were tested at different loads (10-50 N) with constant speed of 1 m/s and constant sliding distance of 1500 m. Samples were also tested at different sliding speeds (3 and 5 m/s) with constant normal load of 30 N. The addition of natural reinforcements decreased the density of composites. Microhardness of sample having 5 wt% rice husk ash increased by 15.08% over base composition. Maximum wear resistance was shown by sample with 5 wt% rice husk ash. Highest coefficient of friction was shown by sample with 3.75 wt% rice husk ash and 1.25 wt% carbonized eggshells. Wear loss varied directly with increasing load and sliding speeds for all composites, whereas coefficient of friction increased with increasing load and decreased with increasing sliding speed for all composites. Delamination and ploughing are dominant wear mechanisms at low speed whereas ploughing is the dominant wear mechanism at high speed as depicted by scanning electron microscopic images of worn surfaces. Composites with improved wear-resistant properties can be used for different tribological applications particularly in automotive industry.