Fretting Damage Behaviors of ER8 Steel Wheel Hub Surface of Motor Car and Trailer

By taking ER8 steel wheel hubs of motor car and trailer of an electric motor train unit operating 1.73×10⁶ km in a windy and sandy environment in northwest China as the research object, the fretting damage behaviors of wheel hub surface of motor car and trailer were analyzed by hardness testing and surface and section damage morphology observation. The results show that the average surface hardness, hardening layer depth and maximum plastic deformation layer thickness of the motor car wheel hub were about 335 HV, 300 μm and 29 μm, respectively, which were greater than 310 HV, 250 μm and 25 μm of the trailer wheel hub. The surface damage of the trailer wheel hub was mainly interlaced shallow furrows; there were many continuous spalling pits and fatigue cracks, and oxidative wear occurred. The section damage of the trailer wheel hub was mainly spalling pits, and there were small-angle long cracks in some areas. The surface damage of the motor car wheel hub was mainly deep furrows in the same direction and a small number of large spalling pits, and there were few surface fatigue cracks; the section damage was mainly long cracks with small angles, and there were cracks propagating inward along the plastic deformation lines on a partial region suface layer.