Dissociation of Cr-rich M23C6 carbide in Alloy 617 by severe plastic deformation

In this study, the dissociation of Cr-rich M23C6 carbides in Alloy 617 was investigated using 50% cold rolling. The major carbides in Alloy 617 consisted primarily of M23C6 carbide and a small amount of M6C carbide. The lattice parameters of the carbides were determined as 1.070 nm (M23C6) and 1.121 nm (M6C). The area fraction of the total carbides in Alloy 617 decreased from 3.50% to 1.66% after 50% cold rolling. The M23C6 carbide was dissociated by the carbon traps in dislocations generated during the severe plastic deformation. Alternatively, the area fraction of M6C carbide increased from 0.06% to 0.37% during the dissociation of M23C6 carbide. The area fraction of M6C carbide increased due to the formation of M6C carbide as a result of the relative changes in chemical composition, such as Cr and Mo, during the dissociation of M23C6 carbide.