The effects of load on the microstructure and wear behavior of Co–27Cr–22Fe alloy processed by high-temperature nitriding

In this study, high-temperature nitriding was used to improve the surface hardness and wear resistance of Co–27Cr–22Fe alloy in a thermogravimetric analyzer. The high-temperature nitriding treatments were performed at 1200 °C for 3 and 10 h. Subsequently, at room temperature, the dry sliding wear test was carried out, and the possible effects of load on friction performance and microstructure of different specimens were investigated. The results show that the microstructure of as-received specimens is composed of γ-Co and MC carbides, while the microstructure of the nitrided specimens contains γ-Co, MC carbides, acicular AlN, and granular (Ti, Nb)N. The thickness of the nitriding layer is 375 μm and 708 μm for nitriding 3 h and nitriding 10 h, respectively. An improvement in microhardness (∼425 HV) was attained for nitrided specimens. For the as-received specimens, the wear rate decreases with increasing load. The as-received specimen exhibits better wear resistance than the nitrided specimen under a high load (∼30 N). The wear mechanism under different loads was mainly abrasive wear, accompanied by adhesive wear. For the nitrided specimens, the specimens show different wear mechanisms under varying loads. Under low load (∼5 N and ∼15 N), the high-temperature nitriding improves the wear resistance, and it exhibits abrasive wear and oxidative wear. Under high load (∼30 N), the wear resistance of the nitrided specimen was significantly reduced, and the wear mechanism is mainly abrasive wear, fatigue wear, and oxidative wear.