Corrosion behavior of additively manufactured AlCrFeNi in lead-bismuth eutectic: dendritic oxides layer facilitate resistance to corrosion spalling

Additive Manufacturing (AM) has promising applications in the nuclear field, offering great design and manufacturing flexibility for miniaturised reactors. 316L, the container material of lead-bismuth eutectic (LBE) coolant, faces severe corrosion resistance challenges in high-temperature and high-pressure environments. This study proposes the selection of AlCrFeNi as a candidate material for the 316L surface corrosion-resistant alloy. AlCrFeNi was prepared using directed energy deposition (DED). The corrosion resistance behaviour and the difference in the properties of the oxide layer-matrix interface between AlCrFeNi and 316L were analysed by comparing the morphology and mechanical properties. The results show that a dendritic oxide layer with non-planar growth characteristics has formed inside the AlCrFeNi alloy, and that the oxide layer penetrates deep into the matrix through the pinning mechanism, while the oxide layer of 316L exhibits characteristics of crack propagation along the grain boundaries. Nanoindentation tests show that the oxide-matrix interface of AlCrFeNi exhibits gradient transition characteristics, effectively reducing the difference in interfacial stress. However, there is a significant abrupt change at the interface of 316L, which causes the oxide layer to be more prone to interfacial spalling in LBE. Dendritic oxide layer in AlCrFeNi is based on the synergistic effect of the pinning mechanism and the gradient interface, which is the essential reason for its excellent corrosion resistance and resistance to spalling.