The carburizing–quenching–tempering process is generally conducted on heavy-duty gear in order to obtain favorable comprehensive mechanical performance. Different mechanical properties could be produced by carbon partition and precipitation. In this study, the carburizing–quenching–tempering process was carried out on low-carbon alloy steel in order to investigate the influence of microstructure evolution and precipitate transition on mechanical behavior and wear resistance under different carburizing/tempering durations. Favorable comprehensive mechanical property and wear resistance could be obtained in favor of long durations of carburizing/tempering. A fatigue-wear model was proposed to describe fatigue crack evolution and damage mechanism on the basis of wear features.

The effect of different heat treatment processes (as-cast, annealing, forging, and annealing after forging) on the microstructure transition and mechanical property evolution of Fe50Mn30Co10Cr10 alloys with different carbon contents (0, 0.2, 0.5 wt.%) was investigated, and a potential strengthening–toughening mechanism was revealed. With 0.5 wt.% carbon added, the interstitial carbon atoms provided a great deal of strength and the highest hardness was obtained. Meanwhile, the high carbon content generated a large amount of stacking fault energy and inhibited the transition of a face-centered cubic (FCC) to a hexagonal close-packed phase (HCP); as such, the TRIP and TWIP effects were induced during deformation and a favorable ductility with the largest elongation to fracture (of 141%) was achieved. The forged-annealed specimen with 0.2 wt.% carbon obtained favorable comprehensive mechanical properties, with an ultimate tensile strength of 795 MPa and an elongation of 104%. After forging, the grains were refined and several dislocations were generated; as such, the yield strength was greatly improved. With subsequent annealing, a good phase distribution of FCC and HCP was achieved, inducing the TRIP and TWIP effects during deformation and producing favorable ductility.