A comparative study of the elevated temperature wear characteristics of A356-15wt. % SiC p functionally graded composite under unidirectional and reciprocating sliding contacts

This paper aims to present a comparative tribological evaluation of A356–15 wt.% SiC _p functionally graded composite (FGM) in unidirectional (USC) and reciprocating sliding contacts (RSC) under ambient (33°C) and elevated (350°C) temperatures. A broader range of operating parameters was considered: 15–45 N load, 1 m/s sliding velocity, and 350 m sliding distance. FGMs were prepared using vertical centrifugal casting. Brinell hardness was measured for both as-cast and T6-treated specimens. Tribological tests were conducted using a Pin-on-disc and a patented Pin-on-reciprocating plate setup, under similar operating conditions. Two wear test pins - matrix (MRP) and particle-rich (PRP) - were evaluated. At ambient temperature, wear increased with load for both MRP and PRP in USC and RSC, with higher wear observed in RSC. At 350°C, MRP in RSC exhibited an early mild-to-severe wear transition above 30 N, while USC showed a gradual increase in wear. PRP exhibited lower wear for both contact modes. Additionally, at 350°C, MRP in USC showed a steep rise in coefficient of friction (COF), whereas PRP exhibited a decrease. COF for both test pins was lower in RSC across all load ranges. At high load conditions, SEM/EDS analysis of MRP in RSC revealed temperature-induced transition wear, while USC showed no such transition. Higher oxidative wear was observed for MRP in RSC and PRP in USC. Wear debris analysis showed higher three-body abrasion in USC. This study delineates the wear behaviour of functionally graded materials (FGMs) at ambient and elevated temperatures during dry sliding against EN31 steel, comparing USC and RSC under identical sliding conditions. Furthermore, it reveals distinct wear characteristics between the two contact modes.