Effects of Different Annealing Heat Treatments on the Microstructure and Mechanical Properties of a Cr-rich High Manganese Hadfield Steel

Hadfield steel exhibits high wear resistance, combined with good toughness, leading to its widespread use in excavators, mineral crushing equipment and other severe mechanical environments. In this study, the mechanical properties of a Cr-rich high manganese Hadfield steel were investigated under different solutionizing heat treatment conditions. The heat treatment consisted of heating to temperatures of 1050, 1100, and 1150 °C with two holding periods of 1.5 and 3 h, followed by the quenching in water or brine. The metallographic examination was performed on all samples and the grain size and the volume percent of carbides were determined. Mechanical properties including the yield strength, UTS, hardness, impact energy, and fracture toughness were also evaluated. It was observed that the quenching in water produced finer grains than the quenching in brine. Increasing the temperature and the holding time caused a decrease in the volume percentage of carbides, as well as the quenching in brine. Indeed, cooling in brine generally produced carbides promoted on the triple junctions of the grains. Meanwhile, blurred dendritic/cellular structures could be observed in interior grains, especially at higher temperatures. It appears that the development of this cellular structure together with the nearly uniform distribution of finely dispersed carbides, has enhanced the mechanical properties. The best hardness was obtained at an annealing temperature of 1150 °C, a holding time of 1.5 h and quenching in water. However, the best fracture toughness and impact value were also obtained at an annealing temperature of 1100 °C, a holding time of 1.5 h, and quenching in brine.