Hot deformation behavior and microstructure evolution of 18CrNiMo7-6 gear steel

doi:10.13251/j.issn.0254-6051.2023.02.016

Abstract

Abstract: Isothermal single-pass compression test of the 18CrNiMo7-6 gear steel was carried out by Gleeble-3500 thermal simulation testing machine. The hot deformation behavior of the tested steel was studied under the conditions of deformation temperature of 900-1150 ℃, strain rate of 0.01-5 s^-1 and strain of 0.76, and the microstructure after hot deformation was analyzed by optical microscope. The Arrhenius constitutive equation is established, and the predicted peak stress is in good agreement with the experimental data. The hot deformation process at high temperature is a competitive process between work hardening and dynamic recovery and dynamic recrystallization. In the process of hot deformation, four types of microstructure including deformed grains, recrystallized grains, equiaxed grains and grown grains are observed. When the strain rate is 0.01 s^-1, the higher the temperature, the more sufficient the dynamic recrystallization. However, when the deformation temperature exceeds 1050 ℃, the deformation energy transforms into the driving energy of grain growth, which makes the grains coarsen. When the deformation temperature is constant (1050 ℃), with the increase of strain rate, the dynamic recrystallization occurs incompletely, the resulted grains are mixed of refined, distorted and incompletely recrystallized ones. The larger the deformation degree, the smaller the grain size.

Key words: 18CrNiMo7-6 gear steel, isothermal single-pass compression, constitutive equation, dynamic recovery, dynamic recrystallization

CLC Number:

TG316

Xie Yikui, Wang Qicheng, Chen Zikun, Wu Xiaodong, Wang Zhongying. Hot deformation behavior and microstructure evolution of 18CrNiMo7-6 gear steel[J]. Heat Treatment of Metals, 2023, 48(2): 103-109.

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