Sliding Wear Studies on Heat-Treated Functionally Graded Cu–Ni–Si/TiC Composite

Abstract

Centrifugally cast functionally graded Cu–11Ni–4Si/10 wt% TiC composite of dimension Oout100 × Oin70 × 100 mm was heat treated to enhance the mechanical and tribological characteristics. Samples from inner zone (9–15 mm) were initially solution treated (850 °C/1 h), water quenched, and aged at varying temperatures (450, 500, and 550 °C) and ageing time (4, 6 and 8 h). The highest hardness (192 HV) displayed by the specimen aged at 550 °C/6 h was chosen for dry sliding tribological studies performed at varying applied loads (10–30 N), sliding velocities (1–3 m/s) and sliding distances (500–1500 m). An improvement of 65% was observed on comparing the micro-hardness values of heat-treated and non-heat-treated composites, while a decrease of 54.8% was observed on comparing the wear rate of heat-treated alloy and composite at optimum parameters. The wear rate increased with applied load, decreased initially and then increased with sliding distance and sliding velocity. Analysis of variance predicted applied load as the major influential parameter, followed by sliding distance and sliding velocity. Worn surface analysis revealed increase in delamination along with mild to severe wear transition with increase in applied load, and the formation of a mechanically mixed layer with increase in sliding velocity. This composite having high wear rate and hardness could be utilized for automotive load bearings, cylinder liners and brake drum applications.