Carbide Precipitation of TBM Cutter Ring Steel During Tempering

In this comparative study, the carbides of TBM cutter ring steel at different tempering temperatures of 530 and 560 °C, were studied using ASPEX inclusion automatic analyzer and EPMA, respectively. The results show that the number of carbides increased by about 180% at the tempering temperature of 530 °C. The inclusions of test steels were characterized through the carbides and carbides with the core of Al₂O₃. The thermodynamics results indicate that Al₂O₃ inclusions were generated in the liquid phase, and carbides started to form in the solid–liquid two-phase region. Al₂O₃ inclusion promoted the formation of carbides through serving as preferred nucleation sites. A lower temperature in the solid phase increases the difference value of actual solubility product and equilibrium solubility product, thus it is beneficial to the formation of carbide. The thermodynamic calculations are in accordance with the experimental results.