Effect of Short-Time Carburizing Treatment on Microstructure and Mechanical Properties of M50 Steel

By using scanning electron microscope (SEM), transmission electron microscope (TEM), X-Ray diffraction (XRD), and hardness and rotational bending fatigue tests, the effect of short-time carburizing treatment on the microstructure and mechanical properties of bearing steel was studied. The results show that when the M50 steel is not carburized, the hardness is 750 HV, the rotational bending fatigue limit is 1100 MPa, and the impact absorption energy is 15.46 J. After short-time carburization with the carbon potential of 0.6%, the maximum hardness in the carburized area, the rotational bending fatigue limit and the impact absorption energy are all increased to be 807.7 HV, 1210 MPa and 16.72 J respectively. When the carbon potential is further enhanced to be 0.8%, the maximum hardness of the carburized area of the steel is further enhanced to be 813.4 HV, but the rotational bending fatigue strength and the impact absorption energy are both decreased to be 1125 MPa and 13.65 J respectively, which has close relations with the increasement of undissolved carbides and the precipitation of acicular carbides.