Study on Multi-Field Coupled Evolution Mechanism of Laser Irradiated 40Cr Steel Quenching Process Based on Phase Change Induced Plasticity

40Cr is essential to steel for the manufacture of hardened gears, and optimizing its laser quenching process will be of great significance for gear wear and life extension. However, the complete reliance on the experimental trial-and-error approach does not effectively reveal the mechanism of the evolution of the laser quenching process in disk laser. Numerical simulation provides an effective way to obtain the transient evolution of the laser quenching process. In this paper, the temperature changes physical parameters of the quenched material are calculated based on the CALPHAD method. Establish a thermo-elastic-plastic multi-field coupling model for the laser hardening process of the disk laser 40Cr gear steel. Perform the numerical calculations on the transient temperature, martensite phase fraction, and the transformation-induced plasticity stress evolution of the 40Cr laser hardening process. Focus on the mechanism of the mutual coupling between phase change behavior and plastic strain. Calculations show that there is heat accumulation during quenching, with a peak temperature of 1448 K. Plastic stress has a "hump" distribution, with a peak value of 834 MPa, which is 1.25 mm from the center of the focal point. The experimental analyses of the 40Cr gear steel quenching microstructure and hardness distribution state by the Axioskop2 scanning electron microscope, the KEYENCE VH-Z100R super depth of field 3D microscope, and the Q10M microhardness tester reveal the mechanical behavior of the material and the phase hardening law during the quenching process. That provided an essential theoretical basis for effective prediction on quenching residual stress and optimizing industrial production parameters.