Evaluation of tribological parameters for boron carbide and graphite infused aluminium hybrid composite fabricated by stir casting technique

The present work focuses on suggesting Gr as a valuable self-lubricating reinforcement for hybrid composite samples and offering a minimum wear rate for sliding pairs with fewer mechanical surface defects at the same time. A series of samples were fabricated using the route by stir casting method considering B₄C and Gr as the two reinforcements. The morphology of the sample has been studied using the X-ray diffraction graphs, Energy dispersive X-ray analysis and Scanning electron imaging stating the homogeneity of reinforcement in various composite cast. The theoretical and experimental density of the series of samples has been studied and compared stating the low porosity of the samples fabricated. A maximum wear rate (W_r) of 0.351 × 10^-4 mm³/m. was found for pure aluminium sample against EN31 steel disc with 0.053 as friction coefficient (µ). W_r was somehow seen to reduce up to 0.286 × 10^-4 mm³/m for Al-B₄C composite with µ of 0.48. For hybrid samples, the wear rate was further seen to improve to 0.187 × 10^-4 mm³/m for Al-B₄C and Gr 2.0% weight with µ of 0.38. Least W_r was found for composite having Gr 3.5% weight, of 0.149 × 10^-4 mm³/m. with µ of 0.36. SEM images of the worn surface give evident results for delamination and crack formation on the pin face for the pure-Al sample. Taguchi-ANOVA analysis has been carried out showing the valid contribution of pin type, load and sliding speed on W_r and friction coefficient as the P-value lies below 0.05 for input parameters considering the 95% confidence level of the model developed. An F-value of 44.57 with R² of 0.895 is developed for W_r model and an F-value of 54.2 with R² of 0.934 for the µ model.