Effect of nano-carbide formation on hydrogen-delayed fracture for quenching and tempering steels during high-frequency induction heat treatment

► Addition of Cr and Mo contents increased the spheroidization rate of carbides. ► The main trapping sites of diffusible hydrogen were identified as the grain boundaries of martensite. ► The 0.2C-Cr steel has the largest spheroidization rate and superior HDF property. ► HDF surface confirmed the trapping site of diffusible hydrogen to be the grain boundary.