Effect of Si content on impact-abrasive wear resistance of Al₂O₃p/steel composites prepared by squeeze casting

The 40Cr steel matrix composites were reinforced with Al₂O₃ particulates (Al₂O₃p) through Si adding to improve the impact-abrasive wear resistance, in which Si powder ranging up to 25% of the Al₂O₃p weight was added into the Al₂O₃p preforms; then, the composites were fabricated by squeeze casting. For all composites, alumina particles are evenly distributed, and Si powder is dissolved in the matrix. Without Si powder addition, the 40Cr steel matrix contains only pearlite; however, ferrite appears and increases with Si powder addition. In the impact-abrasive wear tests, the impact frequency is 80 min^–1 and the impacting energy is 2 J. With increasing Si powder, the wear of the composites first decreases obviously, reaches the minimum at 10% and then increases. The effect of Si addition on the wear resistance can be attributed to two reasons: one is increasing the hardness of the matrix, and the other is improving the interfacial bonding between Al₂O₃p and steel. The wear mechanism of the composites is abrasive wear when the Si powder is < 10 wt%. Otherwise, it is a mixed mode of abrasive and delamination wear.