Effect of grain boundary structure on weld decay of austenitic stainless steel (part 2). Grain boundary structure and carbide precipitation in type 304 stainless steel weld heat affected zone

Grain boundary carbide precipitation in weld heat affected zone of type 304 and 304L austenitic stainless steels was observed using transmission electron microscope to make clear the effects of grain boundary misorientation and structure on carbide precipitation at grain boundaries in stainless steel welds from a crystallographic viewpoint. Grain boundary carbides were detected in grain boundary precipitation region of the 304 steel weld heat affected zone. In that region, some grain boundaries had carbide precipitates, but some were precipitation-free. Kikuchi line analyses showed that grain boundaries with ordered atomic structures had no carbide precipitates. This tendency was valid in 304L steel weld, although grain boundary carbide precipitates were finer in 304L. steel than in 304 steel. These facts have suggested that grain boundary precipitation and corrosion in stainless steel weld heat affected zone depend sensitively on crystallographic character of grain boundary.