Microstructural evolution of GCr15 steels with different C and Cr contents during austenitizing and quenching was studied. Thermodynamic analysis of cementite dissolution was implied to obtain the critical temperature. The coordination number x in FexCr3-xC and the volume fraction of undissolved cementite were computed according to element conservation and equilibrium phase diagram. The MS（martensite transformation temperature） was calculated by using empirical formula. The retained austenite content was calculated with further consideration of quenching temperature. The results showed that the coordination number and the undissolved cementite content were promoted by the austenitizing temperature and carbon content of the steel. Increasing Cr element reduced the coordination number.GCr15 steels with different components had nearly the same MS when austenitization at 830 °C to 860 °C. The interaction of C and Cr complicated the evolution of MS and retained austenite content. The results were in good agreement with the literature, which could guide to obtain specified retained austenite and/or carbides.
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