Effect of microstructure on the spalling damage in a 20Mn2SiCrMo bainitic rail

The effect of microstructure on the spalling damage in a heavy-haul 20Mn2SiCrMo bainitic wing rail was investigated. The results show that spalling damage is strongly correlated to the detailed microstructure factors which contribute to the crack propagation resistance at different levels. It is demonstrated that comparing with blocky martensite/austenite (M/A) constituents, film-like M/A constituents have better performance to retard crack propagation. Moreover, the type and proportion of M/A constituents are affected by the isothermal holding temperature during heat treatment, where typical blocky M/A constituents are found in the temperature range from 360 °C to 400 °C.