Comparative analysis of pack carburizing, flame hardening, and quenching techniques used for surface hardening of AISI 1020 steel

Abstract

AISI 1020 steel is widely utilized in various fabrication processes, construction works, and automobile assemblies. Sometimes, hardness and toughness become very important for different machine parts. The surface hardening techniques, like pack carburizing and flame hardening, are two important approaches to enhance the hardness of the low-carbon steel while maintaining a good amount of toughness. In the present work, a comparative analysis has been carried out among pack carburizing, flame hardening, and quenching methods done on AISI 1020 steel. The analysis has been made based on hardness, toughness, and microstructural characterization. The quenching phenomenon is a different approach from surface hardening. The microstructural changes occur throughout the sample during the quenching process. Standard-shaped AISI 1020 steel samples were subjected to air quenching, pack carburizing, and flame hardening. The microstructural and phase changes were analysed using optical microscopy and X-ray diffraction (XRD) analysis. In addition, the Rockwell hardness (B scale) test and Charpy impact test were conducted to check the steel's variation in hardness and toughness after heat treatment. According to the analysis, the as-received sample exhibits an excellent mix of hardness and toughness, with a toughness of 209.25 J that rises to 268 J following water quenching. With a hardness of 225.5 J, the pack carburized sample outperforms the as-received sample by 8%. Additionally, the flame-hardened sample exhibits a reasonable balance between surface hardness and toughness.