Abstract: In response to the surface magnetic detection cracks on railway freight car axles during maintenance, the chemical composition, mechanical properties, fracture morphology, microstructure, and microhardness of the axles were analyzed using spark discharge atomic emission spectrometer, electronic universal testing machine, scanning electron microscope, metallographic microscope, and energy dispersive spectrometer. The causes and mechanisms of surface cracks on the axles were studied. The results indicate that the nature of train axle cracks is fatigue cracking formed by martensitic transformation at the transition fillet, which belongs to the cracks caused by local burns during the grinding process of the axle surface due to improper grinding technology.

Key words: axles, fatigue, cracks, martensite