Effect of the solid-state transition of Fe–C phase on the friction and wear behavior and mechanism of Cu–(Fe–C) alloys

The effect of solid-state phase transformation during heat treatment on the friction and wear properties of Cu–3Fe–0.18C alloy prepared by vacuum melting was studied. The as-cast structure, deformed structure, Fe–C phase morphology, mechanical properties, and the friction and wear behavior of Cu–Fe–C alloy were studied by optical microscopy (OM), scanning electron microscopy (SEM), nano-mechanical probe analysis, mechanical properties test, and friction and wear experiments, respectively, at room temperature. The results show that micro- and nano-sized Fe–C phases are dispersed in the Cu–(Fe–C) alloy, and the micron-sized Fe–C phase undergoes solid-state transformation during quenching and tempering, which is similar to the martensite transformation and tempering transformation in steel. After quenched at 850 ℃ and tempering at 200, 400 and 650 ℃, the Fe–C phase gradually transforms from acicular martensite to granular tempered sorbite. The corresponding nano-hardness of the Fe–C phase is 9.4, 8, 4.2 and 3.8 GPa, respectively, and the hardness of the strengthening phase is controlled. Through an analysis of tensile fracture, a large number of dissociation surfaces appear on the fracture surface of the quenched alloy. The crack source is located at the interface between the Fe–C phase and the matrix. With an increase in the tempering temperature, the dissociation surface of the fracture surface of the tempered alloy gradually decreases until it disappears, and the crack source gradually transfers to the matrix. The evolution of fracture surface indicates that the bonding between Fe–C phase and matrix in the quenched alloys is poor. With the increase of the tempering temperature, the bonding interface between the Fe–C phase and the matrix is improved. The experimental results of friction and wear at room temperature show that with the increase of tempering temperature, the wear mechanism of the alloy gradually changes from ploughing to adhesion wear and severe plastic deformation, which results in a decrease in the alloy wear resistance. This paper can provide a reference for controlling the friction and wear properties of Cu–(Fe–C) alloys by the solid-state transformation of the Fe-C phase martensitic decomposition.