MECHANICAL PROPERTIES OF CARBURIZED AND NITRIDED MEDIUM CARBON STEEL

Abstract

This work compared hardening of medium carbon steel by carburizing and nitriding. The comparison was done on samples carburized and nitrided for two and three hours respectively. Microstructural analysis of the samples was carried out using the optical microscope and the mechanical properties such as tensile strength, hardness and impact strength of the samples were tested. A control experiment was also performed on the as-received sample. The carburized samples gave an expanded austenite microstructure with highest hardness value while the nitrided samples gave a tempered microstructure with highest ductility value while the as-received samples gave a pearlite microstructure with highest impact energy value. The sample nitrided for 3hours showed very good hardness property very close to the as-received sample with a good ductility far above that of as received sample, making it suitable for application such as automobile gear, ball bearing shafts, valves, discs and cams where hardness and good ductility of the core is required. The sample carburized for 3 hours showed higher hardness with low ductility, making it suitable for application such as tools making where case hardness is the prevailing requirement.