Effect of Carburizing Temperature and Post Carburizing Treatments on Microhardness and Microstructural Evolution of Carburized Low-Carbon Steel

This paper reports the results of an experimental investigation of the effect of carburizing temperature and post carburizing heat treatments on the structural and hardness properties of pack carburized low-carbon steel. The carburizing processes were performed at temperatures of 900°C and 1035°C for 6 hours. After that, two hardening procedures were carried out. In the first hardening procedure, the specimens were directly quenched in oil from carburizing temperatures, while in the second procedure, a double quenching method using brine as a quenching medium was applied. The resultant changes in surface hardness values, carbon content, case depth, microhardness profiles, and microstructural evolution during all processes were tracked and reported. The study showed that the hardness values and carbon content of the carburized specimens increased significantly compared to an untreated specimen, also case depth values increased by two times in some hardened specimens, the increasing in these values were correlated to the changes in microstructures. The obtained results indicated that the structure and the properties of the carburized components are strongly influenced by carburizing temperature and by post carburizing heat treatments; therefore, both variables can be used to altering or modifying surface and core characteristics of the carburized steel, which make it more suitable for engineering components that require a combination of hard surface along with ductile and tough core.