Correlation between characteristics of grain boundary carbides and creep–fatigue properties in AISI 321 stainless steel

The effects of the interfacial relationships between grain boundary carbides and neighboring grains on the creep–fatigue behaviors have been investigated in AISI 321 stainless steel. The contacting interfacial planes between grain boundary TiC and neighboring grains are found to have lower Miller indices than those between Cr23C6 and neighboring grains. From this observation, it is suggested that the interfacial free energy between grain boundary TiC and grains is lower than that between Cr23C6 and grains. Creep–fatigue life of TiC aged AISI 321 stainless steel is observed to be longer than that of Cr23C6 aged AISI 321 stainless steel. The differences in creep–fatigue life are based on the stronger cavitation resistance of TiC compared with that of Cr23C6. From the interfacial relationships between the grain boundary carbides and the neighboring grains, it is verified that formation and growth of grain boundary cavities at TiC carbides are more retarded than those at Cr23C6 carbides, thus extending the creep–fatigue life of the steel.