Effect of subcritical heat treatment on microstructure and properties of high chromium cast irons

doi:10.13251/j.issn.0254-6051.2024.10.001

Abstract

Abstract: Aiming at the problem of high energy consumption in conventional quenching and tempering process of high chromium cast irons, the subcritical heat treatment tests of three kinds of high chromium cast irons were carried out. Moreover, the effect of the process on the microstructure, hardness and surface wear resistance was studied. The results show that the microstructure of high chromium cast irons is primarily composed of retained austenite, M₇C₃ carbide, (Fe, Cr)₂₃C₆ carbide, Mo₂C carbide and pearlite when subjected to holding temperatures ranging from 500 ℃ to 650 ℃ for 1 h to 14 h. A peak value in hardness is observed for the three high chromium cast irons when holding at 550 ℃ to 600 ℃ for 6 h to 12 h, with the highest peak hardness being 57.4 HRC. The hardness is most significantly influenced by the Mo element. During the insulation process, the pearlite phase transformation of austenite is promoted by the precipitation of secondary carbides in high chromium cast irons. The effects of pearlite transformation strengthening and precipitation strengthening of secondary carbides gradually decrease with prolonged holding time. The eutectic high chromium cast iron with the highest carbon content exhibits the best wear resistance when holding at 600 ℃ for 8 h. It can be seen that the first step to improve the wear resistance of high chromium cast irons is to increase the amount of eutectic carbides, and then to add elements such as Mo to enhance the precipitation strengthening effect.

Key words: high chromium cast irons, subcritical heat treatment, wear resistance, retained austenite, carbide

CLC Number:

Yuan Zhizhong, Liu Haiming, Ju Yulin, Chen Lu, Niu Zongran, Wang Zhiyuan, Cao Fuyang, Cheng Xiaonong. Effect of subcritical heat treatment on microstructure and properties of high chromium cast irons[J]. Heat Treatment of Metals, 2024, 49(10): 1-7.

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