Effect of heat and cryogenic treatment on wear and toughness of HSS AISI M2

Abstract

Despite the promising results obtained with cryogenic treatment of tool steels, there are still contradictions regarding its benefits, and there is no consensus regarding its mechanisms in the steel microstructure. The goal of this work is to investigate the optimum heat treatment process parameters together with the cryogenic treatment. Samples of AISI M2 steel were austenitized at 1170, 1200 or 1230°C and quenched in salt bath. The cryogenic treatment was performed through nitrogen nebulization with a cooling/heating rate of 0.3°C/min, 24-h holding time at −190°C, before, after or between the double tempering. The influence of cryogenic treatment in AISI M2 steel was dependent on the previous austenitization temperature. No significant reduction in retained austenite was observed by deep cryogenic treatment. The benefits achieved in the resistance to abrasive wear and toughness are associated with lower amount of carbon in the martensite together with finer and more homogeneous carbide precipitation.