Improvement of creep-fatigue life by the modification of carbide characteristics through grain boundary serration in an AISI 304 stainless steel

The modification of carbide characteristics through grain boundary serration and its subsequent effect on the creep-fatigue property at 873 K have been investigated, using an AISI 304 stainless steel. It was found that the grain boundaries are considerably serrated when a specimen is furnace-cooled. The grain boundary serration leads to a change in the carbide characteristics as well as grain boundary configuration, i.e., morphology of carbide from an acute triangular to a planar form and a lowered density. Additionally, an array of carbide particles is changed from a consistent to zigzag pattern, in terms of their preference to one grain to share the coherency. Planar carbides on serrated grain boundaries have a lower interfacial energy than that of triangular carbides on straight grain boundaries. It is suggested that the modification of carbide characteristics through the grain boundary serration has a remarkable influence on the improvement of creep-fatigue resistance.