The development of Generation IV nuclear reactors and accelerator driven systems (ADS) is supporting a wide range of work on the compatibility of stainless steels with heavy liquid metals (HLM).The austenitic steel DIN 1.4970 (also known as 15-15Ti) is being qualified for use in heavy liquid metals because of its lack of sensitivity to Liquid Metal Embrittlement. The aim of this study is to look into cracking modes and their main characteristics in order to reach a clear idea of mechanisms.Flat tensile, tapered specimens were loaded in PbBi at 300 °C with low oxygen content and, for comparison in air, up to the Ultimate Tensile Stress, UTS, point and rupture. The specimens had one ground and one polished surface, to highlight also the effect of the surface finish.The behaviour of the steel was not notably affected by the environment, when compared to testing in air. In both cases, the cracking mode was mainly ductile and affected only by the presence of large precipitates in the steel matrix.Post-tests examinations were carried out with SEM and EBSD. The role of microstructure towards crack initiation and propagation is here described.The 1.4970 steel, in this experimental conditions, was not affected by the environment, as small plastic cracks were observed around the Ti-rich precipitates in both air and PbBi.Keywords: Crack initiation, austenitic steel, lead-bismuth eutectic, metallography
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