High Temperature Sliding Wear Behavior of Al 4032-ZrB₂in situ Composite

Aluminum matrix composites (AMCs) reinforced by ZrB₂ particles were fabricated from Al 4032- x wt% ZrB₂ (x=5, 10, 15, 20) by in situ reaction from mixtures of K₂ZrF₆ and KBF₄ with molten Al alloy. The sliding wear behavior of these composites were analyzed at high temperatures (200°C & 400°C) using a high temperature pin on disc apparatus according to ASTM G99-95a standards. The results indicate that the volumetric wear rate is decreased with the increase in the weight percentage of ZrB₂, while it is increased with the increase of the applied load. Higher wear rates were registered at 400°C than at 200°C. The SEM analysis of the wear scar indicates the fragmentation of ZrB₂ particles into smaller ones orienting themselves along the sliding direction. The phenomenon of ploughing of the metal was found at lower temperature, while presence of oxides and fine micro cracks were found at higher temperature. The results indicate that ZrB₂ particles markedly improve the wear performance of the Al 4032 alloy.