Three-dimensional studies of intergranular carbides in austenitic stainless steel

Abstract

A large number of morphological studies of intergranular carbides in steels have always been carried out in two dimensions without considering their dispersion manners. In this article, focused ion beam serial-sectioning tomography was carried out to study the correlation among the grain boundary characteristics, the morphologies and the dispersions of intergranular carbides in 347 austenitic stainless steel. More than hundred intergranular carbides were characterized in three dimensions and finally classified into three different types, two types of carbides probably semi-coherent to one of the neighboring grains with plate-type morphology, and one type of carbides incoherent to both grains with rod-type morphology. In addition, the rod-type carbide was found as the largest number of carbides among three types. Since large numbers of defects, such as misfit dislocations, may be present at the grain boundaries, which can be ideal nucleation sites for intergranular rod-type carbide precipitation.

Advances in Focused Ion Beam Tomography for Three-Dimensional Characterization in Materials Science

“…Maetz investigated the effect of ageing in 2101 lean duplex stainless steel [152]. The correlation between grain boundary characteristics, morphology, and dispersion of intergranular carbides in 347 austenitic steel was obtained in the work of Ochi [153], who identified three different types of carbides: two planar types, with an orientation relationship with one of the neighboring grains, and a rod type, probably associated with the defects of the steel. The same author also described the intra-and inter-granular precipitates, consisting mainly of Cr 2 N and Cr 3 Ni 2 Si(N), for the nitrogen-added austenitic stainless steel SUSXM15J1 [154].…”