Nanoindentation, Scratch Resistance, and Elevated Temperature Tribological Behavior of AZ31-B4C Composites

Abstract The present study investigates the outcome of the incorporation of different amounts of B4C particles (0–2 wt%) in AZ31 alloy on nanohardness, elastic modulus, scratch resistance, and elevated temperature tribological behavior. AZ31-B4C composites are produced by an ultrasonic stir casting technique. Mechanical properties of synthesized materials are evaluated by conducting nanoindentation tests following a constant depth method for a loading–unloading rate of 10 mN/min. The nanoindentation test reveals that the AZ31-2B4C composite possesses 98.25% and 27% enhancement in nanohardness and elastic modulus, respectively, compared to the AZ31 matrix. Scratch behavior (scratch hardness, wear loss, and friction coefficient (COF)) is studied under ramp loading conditions (20–30 N, 20–40 N, and 20–50 N) using a diamond indenter. Composite samples exhibit better scratch resistance at all experimental conditions. Experimental results disclose that AZ31-2B4C possesses around a 24% decrement in scratch width compared to AZ31 alloy. It is also observed that the wear-rate decreases linearly with an increase in wt% of B4C while COF increases moderately. The pin-on-disc type tribo-meter is utilized to study the tribological behavior of AZ31 alloy and AZ31-B4C composites at elevated temperatures (50–250 °C) under varying loads (20–40 N). The wear-rate of the base alloy increases continuously following a steep slope with respect to an increase in temperature while wear-rate composite samples do not possess any significant change up to a transition temperature after which the wear-rate increases significantly. Finally, scratch track and worn surfaces of samples tested under elevated temperature conditions are examined under SEM to evaluate dominant wear mechanisms.