Effect of Al on microstructure and impact property of surfacing repair layer of rail

Failed rail can be repaired using self-shielded flux cored wire. Aluminium powder is always added to the flux cored wire to protect the weld pool. However, the Al content affects the microstructure and property of the surfacing layer significantly. Therefore, the microstructure and impact property of the surfacing layer of the rail with different Al contents were analysed. Meanwhile, the formation mechanism of the inclusions was calculated by thermodynamic method. The results show that the pore sensitivity of the surfacing layer is high when the Al content is <0·79 wt-%. The impact energy decreases with the increase in Al content. The thermodynamic calculated results show that the inclusion in the surfacing layer is AlN when the Al content is >1·89 wt-%. In contrast, they are mainly Al₂O₃ when the Al content is <1·45 wt-%. The thermodynamic calculated results are well agreed with the experimental ones.