Effects of Immersion Time in Bright Hardening on the Microstructure and Mechanical Properties of AISI D2 Steel

AISI D2 is a kind of steel that needs double or triple tempering after quenching in oil because of high amount of carbon, alloying elements and retained austenite. In the present study, improving the microstructure and mechanical properties of AISI D2 steel was investigated by means of bright hardening process (using hot alkaline salt bath as a quenching medium). It was found that the tempering process could be eliminated from the heat treatment process or decrease to one step by keeping the samples immersed in hot alkaline salt bath during the quenching stage at temperature and time of 230C and 150 min, respectively. Microstructural examinations of the samples revealed that in comparison with oil quenched samples quenching in hot alkaline salt bath resulted in finer and more uniform distribution of carbides in the matrix. Different microstructure led to different mechanical properties such as hardness and toughness