STUDY ON THE MARTENSITE IN LOW CARBON CrNi3Si2MoV STEEL TREATED BY Q&P PROCESS

The martensite in low carbon CrNi3Si2MoV steel treated by Q&P (quenching and partitioning) process was characterized by means of SEM, TEM, EBSD and nano intender. The effect of martensite on uniaxial tension behaviors was discussed. The results showed that initial martensite phase formed at the first quenching step, whose carbon content was lowered due to its carbon diffusion into untransformed austenite during partitioning step. However, the martensite phase formed at the final quenching step consisted of only one single set of packet with lath thickness about 0.1-0.2 mu m, which was thinner than that of the initial martensite lath. It was found that the carbon content and hardness of the martensite formed in the final quenching step were higher than those of initial martensite, which deformed cooperatively with other phases and played a role of strengthening phase during deformation process. In addition, large sized carbonitride and oxide precipitations induced nucleation and expansion of crack during deformation process.