Numerical and Experimental Analysis on Low-pressure Carburizing Process of M50NiL Navy C-Ring

During case hardening of precision transmission components, distortion reduction and residual stress control are crucial to achieve high efficiency and reliable service performance. This work studied the effects of carbon content distribution on the distortion behavior during a carburizing and quenching treatment of an M50NiL steel. A multi-physics model integrated into commercial software DEFORM-3D was developed to predict the temperature, microstructure, stress and carbon content distribution. The kinetic parameters for carburizing and quenching were modified by fitting the experimental data. The calculated results showed that quenching distortion increased with the increase in case depth and surface carbon concentration. The quenching distortion of the M50NiL steel C-ring increased by 115% with the total case depth increasing from 0.93 mm to 2.35 mm. On the other hand, as the surface carbon concentration increased, the residual stress on the part surface transformed from compressive stress to tensile stress.