Influence of Cryogenic Treatment on As-Cast AZ91+1.5 wt%WC Mg-MMNC Wear Performance

Abstract

In this work, the enhancement of wear performance of cryogenic treated (CT) as-cast AZ91 reinforced with 1.5 wt% WC magnesium metal matrix nano-composite (Mg-MMNC) had been explored using pin-on-disc tribometer and scanning electron microscope (SEM). AZ91 with 1.5 wt% WC reinforcement was prepared with stir casting process and the cryogenic treatment was carried out at −190 °C. The wear test parameters were the applied normal loads of 20 and 40 N, sliding velocities of 1.0, 1.6, 2.1 and 3.1 m/s and a constant slipping distance of 1200 m with tribo-couples of aluminium disc and Mg-MMNC pin at atmospheric conditions. At lower loads, almost all the samples had showed the similar wear loss. But in higher loads, there was significant reduction in wear loss for cryogenic treated Mg-MMNC. The presence of reinforcement and increased Mg₁₇Al₁₂ phase particles volume fraction due to CT had significantly enhanced the wear resistance of composite. There was also wear loss in counter-part aluminium disc. The SEM analyses of worn surface indicate that there was abrasion and oxidation. And a changeover occurred from oxidation wear to delamination wear and abrasion wear while the applied load was increased from 20 to 40 N. Adhesion wear took place at the sliding condition of load 40 N and speed 3.1 m/s.