Tensile and cracking behavior of thin-walled 316Ti austenitic steel after exposure to 550 °C lead-bismuth eutectic with different oxygen concentration

Abstract

The corrosion evolution of 316Ti steel in 550 °C lead-bismuth eutectic (LBE) with oxygen concentrations (Co) of 5 × 10−6 wt% and 5 × 10−8 wt% and their impact on the tensile behavior were investigated in this study. The steel primarily underwent oxidation at Co of 5 × 10−6 wt%, slightly influencing the tensile strength and elongation of specimen within 1000 h exposure. In contrast, the structural integrity and tensile strength of specimen were significantly deteriorated at Co of 5 × 10−8 wt% where the steel mainly experienced dissolution corrosion. The cracking behaviors of oxide layer and ferrite layer, and their influences on the failure of thin-walled specimen were discussed. Special concerns should be raised on the detrimental effect of localized corrosion, such as intergranular oxidation, LBE-wetted precipitate bands and dissolution pits, since cracks are expected to initiate easily in these zones and propagate into steel matrix under tension, potentially leading to the premature failure of thin-walled components.

Keywords

• Lead-bismuth eutectic
• Stainless steel
• Oxidation
• Ferritization
• Tensile behavior