Abstract:The tribological behaviour of gravity die stir cast LM6 alloy with graphite (Gr) and silicon nitride nanoparticles was investigated. Al-Gr-Si₃N₄ hybrid composite, Al-Si₃N₄ nanocomposite and Al-Gr nanocomposites were separately fabricated to investigate their frictional and wear characteristics under dry sliding conditions. EDS was used to ensure the uniform presence of nano Si₃N₄ and graphite in the cast. L9 orthogonal array method was chosen to conduct the experiments to study the effect of different applied loads (20, 30 and 40 N) and sliding distances (1, 2 and 3 km). The results showed that the respective wear rate and coefficient of friction (COF) decreased by 25% and 15% for hybrid composite when compared with those of Al-Si₃N₄ nanocomposite whereas the wear rate and COF of Al-Gr was found to be very minimal. The micro Vickers hardness of the hybrid composite was 14% more than that of the simple nanocomposite and there was not much notable variation for Al-Gr and Al-Si₃N₄ nanocomposite materials. Scanning electron microscope was used to analyze the worn surface and subsurface, from which it was noted that the predominant wear mechanisms observed were abrasive for nanocomposite and both abrasive and adhesive mechanism for hybrid composite. Analysis of variance (ANOVA) and F-test were used to check the validity model and to determine the significant parameters affecting the wear rates.

Key words: abrasive wear; Si₃N₄; graphite; hybrid composite; load; sliding distance; ANOVA