Liquation cracking and chromium depletion in austenitic welds of light water reactors

Abstract

Different types of austenitic stainless CrNi-steels were tested in hot tensile and weld simula-tion tests including two melts of niobium stabilized austenitic steel, three melts of titanium stabilized austenitic steel and one melt of an unstabilized austenite. The stabilized austenites were tested in conventional versions and in optimized nuclear grade versions. The unstabi-lized austenite was tested in a conventional version. The hot tensile tests revealed the conventional Nb-stabilized austenites to have the strongest susceptibility to intergranular liquation cracking followed by the unstabilized material A 304. The titanium stabilized qualities (conventional and optimized ones) exhibited no relevant susceptibility to intergranular liquation cracking. The optimized Nb-stabilized austenite showed no relevant susceptibility to intergranular liquation cracking. The weld simulation tests revealed with respect to the heat affected zone (HAZ) close to the fusion line the unstabilized austenite A 304 to be most sensitive to intergranular stress cor-rosion cracking (IGSCC) under Boiling Water Reactor (BWR) conditions. The titanium stabilized austenites (conventional and optimized ones) showed a significantly lower suscep-tibility to IGSCC. Furthermore, the conventional Nb-stabilized austenites proved to be less sensitive to IGSCC than the Ti-stabilized ones. According to the actual state presented here, the optimized Nb-stabilized austenite shows no susceptibility to IGSCC.