Effect of intercritical quenched and tempered microstructure on fatigue properties of 18CrNiMo7-6 gear steel

doi:10.13251/j.issn.0254-6051.2020.11.005

Abstract

Abstract: Taking 18CrNiMo7-6 gear steels (marked as IQ-T-1, IQ-T-2) produced by two different manufacturers as the research object, the effect of microstructure after intercritical quenching and tempering (IQ-T) on the mechanical properties, rotating bending properties and fatigue crack propagation behavior was analyzed. The results show that the IQ-T-1 tested steel has better strength and fatigue properties than that of the IQ-T-2 tested steel, with the strength and fatigue strength increased by about 97 MPa and 96 MPa respectively. The microstructure of the IQ-T-1 tested steel is composed of fine ferrite+small martensite+tempered martensite, while that of the IQ-T-2 tested steel is composed of coarse ferrite+tempered martensite. Fine ferrite+small martensite in the IQ-T-1 tested steel make the crack branching, crack closure and stress shielding phenomena more significant, giving rise to more inhibition of crack initiation and propagation.

Key words: intercritical quenching, microstructure, rotating bending fatigue, crack propagation, crack closure effect

CLC Number:

TG142.1

Li Yunkun, Zhou Yun, Shi Jie, Yu Wenchao, He Xiaofei, Hu Fangzhong, Wang Maoqiu. Effect of intercritical quenched and tempered microstructure on fatigue properties of 18CrNiMo7-6 gear steel[J]. Heat Treatment of Metals, 2020, 45(11): 19-25.

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