Dissolution and oxidation behaviour of various austenitic steels and Ni rich alloys in lead-bismuth eutectic at 520 °C

• 10 austenitic steels and Ni rich alloys were tested in LBE at 520 °C with dissolved oxygen content between 10-9 and 5 10-4 wt%.
• It is shown that only thermodynamics cannot explain the Ni rich alloys corrosion behaviour in LBE.
• The role of oxygen on corrosion behaviour in LBE was highlighted.
• An equilibrium line was defined above which only oxidation has occurred on 316L: RTln[O](wt%) = -57584/T(K)-55.876T(K)+254546.
• 18Cr-15Ni-3.7Si, 21Cr-11Ni-1.6Si and 14Cr-25Ni-3.5Al present promising corrosion behaviours in the mixed corrosion domain.
• Against all the odds, austenitic stainless steels can have a good behaviour in mixed domain despite their high Ni content.

Ten austenitic steels and Ni rich alloys were tested in static lead-bismuth eutectic (LBE) at 520 °C in order to obtain a selection of austenitic steels having promising corrosion behaviour in LBE. A test of 1850 h was carried out with a dissolved oxygen concentration between 10−9 and 5 10−4 g kg−1. The combination of thermodynamic of the studied system and literature results leads to the determination of an expression of the dissolved oxygen content in LBE as a function of temperature: RT(K)ln[O](wt%) = −57584/T(K) −55.876T(K) + 254546 (R is the gas constant in J mol−1 K−1). This relation can be considered as a threshold of oxygen content above which only oxidation is observed on the AISI 316L and AISI 304L austenitic alloys in static LBE between 400 °C and 600 °C. The oxygen content during the test leads to both dissolution and oxidation of the samples during the first 190 h and leads to pure oxidation for the rest of the test. Results of mixed oxidation and dissolution test showed that only four types of corrosion behaviour were observed: usual austenitic steels and Ni rich alloys behaviour including the reference alloy 17Cr-12Ni-2.5Mo (AISI 316LN), the 20Cr-31Ni alloy one, the Si containing alloy one and the Al containing alloy one. According to the proposed criteria of oxidation and dissolution kinetics, silicon rich alloys and aluminum rich alloy presented a promising corrosion behaviour.