On the Dissolution of Spheroidized Carbides into Austenite in 0.8%C and 0.8% C-Cr Steels

Dissolution of spheroidized carbides into austenite was studied in 0.8% C steels containing 0, 2 and 5% Cr. M3C carbides was observed in 0.8% C and 0.8% C-2% Cr steels and M7C3 in 0.8% C-5% Cr steel. It was found that the larger particles required longer times for dissolution into austenite than smaller ones. Marked acceleration of carbides dissolution was also observed with increasing austenitizing temperature.Activation energies of dissolution of carbides into austenite were obtained to be 90 kcal/mol in 0.8% C steel and 80 kcal/mol in 0.8% C-Cr steels. The variation of mean particle size of dissolving carbides was calculated under the assumption of diffusion model. From these results it was concluded that the dissolution of carbides into austenite would be controlled by diffusion of Cr atoms in 0.8% C-Cr steels.