Investigation of crack propagation resistance of 304L, 316L and 316L(N) austenitic steels in liquid sodium

Abstract

In order to assess the susceptibility of candidate structural materials to Liquid Metal Embrittlement (LME), the fracture behavior of three grades of austenitic steels was investigated in oxygenated (200 wppm) liquid sodium in the temperature range [473–673 K] on notched axisymmetric tensile specimens. The tests were carried out in an inert glove box at very low concentrations of dioxygen and humidity (<1 ppm) to prevent further contamination after pre-exposure in oxygenated liquid sodium. A decrease in crack propagation resistance of the three austenitic steels (304 L, 316 L(N), 316 L) is observed in oxygenated liquid sodium (200 wppm) from 573, 623 and 673 K respectively after pre-wetting in oxygenated sodium. This reduction is correlated with a ductile to brittle change of the fracture surface. This effect observed with the three austenitic steels is attributed to the onset of LME after significant plastic deformation.