Studies on Egg Shell and SiC Reinforced Hybrid Metal Matrix Composite for Tribological Applications

The hybrid metal matrix composite is developed through stir casting process. In theAl7075 aluminium matrix material, two different combination of reinforcements are used to make hybrid composite and they are as (i) Al7075 + Al2O3 + SiC and (ii) Al7075 + Al2O3 + egg shell powder. The weight proportion of SiC and egg shell powder varied to study the influence of reinforcement. To validate the hybrid composite developed, electron microscopic imaging, density and hardness measured. Maximum surface hardness of 197 Hv is observed in the composite with 6% egg shell powder. The presence organic egg shell is in the form of calcium oxide which is harder than carbide particle reinforced in the hybrid composite material. It has posse’s natural strength compared to synthetic material and with less in density.The density of egg shell is less compared to SiC and alumina particle reinforcement. Electron images and the corresponding spectroscopic results infer that the reinforcements are equal distributed in the volume of composite. While casting the egg shell has been found in the form of calcium oxide along with aluminium and oxide elements. Since, the composite has less density which is light in weight compared to alumina or silicon carbide. With respect to sliding wear behaviour, the hybrid composite with Sample 1 (3% SiC) and Sample 4 (6% egg shell) has good wear resistance. With increase in hard particle the wear mechanism is abrasion and metal loss trend found increasing. The minimum of 0.25 mm3/min found with less load (10 N) and 0.42 mm3/min for 20 N load. On prolonged exposure more than 40 μm reached for maximum load. Increase in hard particle reinforcement (6% Al2O3 + 6% SiC) has induced severe surface damage due to abrasion on worn surface. Adhesive morphology and minimum wear are noticed with 6% Al2O3 + 6% SiC in hybrid composite. Therefore, it is confirmed that the reduced in hard particle or increase in egg shell may produce expected results on sliding wear behaviour.