Tribological behavior and wear mechanism of Ti/MoS2 films deposited on plasma nitrided CF170 steel sliding against different mating materials

To improve the load-bearing capacity and tribological properties of CF170 steel, a duplex treatment including plasma nitriding and Ti/MoS2 films was carried out on CF170 steel. The morphology, structure and composition of the films were characterized by SEM, XRD, AFM and XPS. The mechanical and tribological behaviors of the films sliding against different mating materials were investigated by hardness tester, scratch tester and ball-ondisc tribometer, respectively. The results indicated that the Ti/MoS2 film deposited on plasma nitrided substrate was composed of MoS2, gamma-Fe4N, epsilon-Fe2,3N and alpha-Fe phases, and the MoS2 phase had a strong (002) preferred orientation. The load-bearing capacity and critical adhesion load of the duplex-treated samples were significantly improved compared to the single Ti/MoS2 film. The duplex-treated samples exhibited different wear behaviors against different mating materials, the contact pressure and formation of the valid MoS2 transfer film on the friction pairs were notable in determining the tribological behavior. The duplex-treated sample sliding against the SiC ball under air showed a lower friction coefficient and wear rate than that of others, indicated an excellent wear resistance.