Microstructure and tribological characteristics of aged Co–28Cr–5Mo–0.3C alloy

In this study, an attempt to investigate the role of isothermal aging on the microstructure and tribological characteristics of Co–28Cr–5Mo–0.3C alloy was made. Regarding the results, isothermal aging at 850 °C and 950 °C for at least 16 h contributed to the formation of lamellar-type carbides at the grain boundary regions. Moreover, at higher aging times (over 16 h), the amount of lamellar-type carbides decreased. The wear properties of as-cast and heat treated samples were determined at 0.5 ms−1 speed several under normal applied loads such as 50, 80, and 110 N. At the lowest applied load (50 N), the samples were isothermally aged at 850 °C for 8 and 16 h and also the ones were aged at 950 °C for 16 h had higher wear resistance probably due to more volume fraction of lamellar-type carbides when compared to as-cast and the other aged samples, but, at higher applied loads (80 and 110 N) due to the formation of adhesive oxide layer on the as-cast sample surface, the wear rate of as-cast samples is lower compared with all heat treated ones.