Influence of InSitu Formed ZrB2 Particles on Dry Sliding Behavior of ZA Based Metal Matrix Composites

The present work has used pin on disc tribometer at atmospheric conditions to examine dry sliding tribological properties of Zn-Al (ZA) alloy and ZA/ZrB2 composites at varying reinforcement of ZrB2 particles (0, 3, 4.5, 6 and 9 vol%), load (10-50 N) and sliding distance (1000-5000 m). The composites were fabricated using stir cast insitu technique and characterized (in terms of morphological and mechanical) by different techniques. Tribological behaviour of composites has been analyzed in terms of wear volume and frictional coefficient. Scanning electron microscopy, surface profilometer and atomic force microscopy tools were employed to analyze the worn surface to show the mechanism of wear to substantiate the obtained results. Obtained results suggest that the insitu formed ZrB2 particles refine the microstructure and improve the mechanical properties of composites. However, at 9 vol% of ZrB2, the matrix grains are refined by 48% and the hardness value is improved by 68% compared to ZA alloy. As the volume percentage (vol%) of ZrB2 rises, wear rate decreases while coefficient of friction (CoF) surge. However, linear rise in wear and CoF with rise in load and sliding distance. At lower load, wear mechanism is oxidative, while at high load, it converts to oxidative-metallic. Composites with 9 vol% ZrB2 show approximately 80% reduction in wear at load (50 N) and sliding distance (5000 m) compared to ZA alloy. These fabricated composites could be utilized for those applications where less wear and high CoF along with high strength are required.