Carburization-based optimization of AISI 8620 steel using rice husks and charcoal as carburizers

Abstract

This study was centered on improving the mechanical properties of AISI 8620 steel using the carburization technique. The failure in service conditions of many steel components such as cams, gears, and shafts necessitated the research as it demands that they possess both high wear-resistant surfaces and tough shock-resistant cores. Standard test samples prepared from the steel material were subjected to a pack carburization process using rice husk and charcoal as carburizers, and the energizer – calcium trioxocarbonate (IV) at temperatures of 800, 850, 900, and 950 °C, and held for 60, 90, and 120 minutes. The samples were quenched in water and tempered at 500 °C for 60 minutes. After the pack hardening process, the test samples were subjected to tensile, impact, and hardness tests. From the data obtained, ultimate tensile strength (UTS), Hardness, Young’s Modulus, engineering strain, and impact strength were calculated. The case and core hardness of the carburized samples were noted, and an optical microscope was used to observe the microstructural features of the case-hardened, quenched, and tempered samples. The responses (mechanical properties of steel) were optimized using response surface methodology to obtain the optimum carburizing conditions-temperature and holding time. Results showed that the sample’s microhardness core and microhardness case increased from 253 to 327 HV and from 243 to 339 HV as the holding time increased from 60 to 120 minutes, indicating an appreciable increase in the mechanical property of the samples. The optimum carburizing conditions were at a temperature of 885 °C and a holding time of 120 minutes. Hence, the carburization of AISI 8620 steel using rice husk and charcoal as carburizers improved the steel material’s case, core, and mechanical properties.