Influence of heat treatments applied on the microstructural and microhardness behavior of ASTM A131 ABS DH36 steel

This study analyzed the impact of heat treatments on ASTM A131 ABS DH36 steel's microstructure and hardness behavior. In its initial state, we characterized the chemical composition, microstructure, tensile strength, and hardness. Several samples underwent heat treatments, with heating temperatures of 500 °C, 750 °C, and 1000 °C, followed by cooling in brine at 1 °C and 29 °C. Microstructure analysis including optical microscopy, scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD), and Vickers microhardness profiling. At 500 °C, the microstructure remained mostly unchanged, with ferrite and pearlite colonies, and no significant hardness alterations. At temperatures of 750 °C and above 1000 °C, martensite formation during cooling dominated, resulting in higher hardness as it increased. The highest average hardness of 364 HV, a 127% increase from the initial state, was observed in samples treated at 1000 °C. Except for quenching at 500 °C, heat treatments significantly impacted microstructure and hardness, with minimal differences between cooling temperatures applied.