Potential of grain boundary engineering to suppress welding degradations of austenitic stainless steels

Abstract

Grain boundary phenomena strongly depend on grain boundary structure and characteristics, i.e. coincidence site lattice (CSL) boundaries, as contrasted with random boundaries, are highly resistant to intergranular degradation. Grain boundary engineering (GBE) primarily intends to prevent the initiation and propagation of intergranular degradation along random boundaries by frequent introduction of CSL boundaries into the grain boundary networks in materials. A high frequency of CSL boundaries by GBE processing leads to high resistance to grain boundary degradations. Annealing twins bring CSL boundaries into austenitic stainless steels. By twin induced GBE utilising optimised single step thermomechanical processing consisting of a slight strain followed by annealing, a very high frequency of CSL boundaries was introduced into austenitic stainless steels. The resulting steels indicated remarkably high resistance to intergranular corrosion even to weld decay and knife line attack during welding. Grain boundary engineering could have a high potential to suppress a variety of grain boundary related degradations of welded austenitic stainless steels.