In order to clarify the refinement behavior of the lamellar spacing and high temperature stability of the lamellae in pearlite by the addition of Cr, the effects of supercooling, the diffusion coefficients of C and Cr and spheroidizing of cementite were investigating using Fe-0.8%C binary and Fe-0.8%C-Cr ternary steels.
The equilibrium transformation temperature of pearlite was increased by the addition of Cr. In comparison with the Fe-0.8%C steel, at a fixed pearlite transformation temperature, the pearlite lamellar spacing of the Cr-added steel was refined by increasing supercooling, and at the same supercooling, the lamellar spacing was refined by increasing the Cr content. This is caused by a decrease of the diffusion coefficient of C in the austenite by addition of Cr.
Spheroidizing of cementite in pearlite at high temperature was inhibited by increasing the Cr content. The spheroidizing rate was reduced by the addition of Cr. Spheroidizing of cementite in pearlite by increasing the Cr content was inhibited due to the increased contribution of Cr diffusion for the coarsening reaction of cementite.