Abstract: In order to improve the surface hardness and wear resistance of the EA4T axle steel in quenched and tempered state, the surface of the axle was modified by laser quenching. The microstructure, phase transition depth and hardness of the laser quenched layer were characterized by scanning electron microscopy, microhardness tester and nano indentation meter. The results show that when the EA4T axle surface is subjected to different laser quenching processes, the quenched structure in the phase transition layer is mainly composed of fine lath martensite and granular bainite, and the depth varies from 100 μm to 800 μm according to the process. There is a tendency that the depth of the phase change layer gradually increases as the laser quenching power increases and the scanning speed decreases. The microhardness of the quenched phase transition layer is basically maintained at about 450 HV0.2, which is approximately twice the hardness of the matrix, so that the wear resistance of the axle steel is remarkably improved. Due to the overlapping between the quenching passes, the laser quenched layer exhibits a waveform distribution. The martensite content in the valley region is higher than that of the peak region, so that the hardness in the valley region is significantly higher than that of the peak region.

Key words: EA4T axle steel, laser quenching, microstructure, hardness