Corrosion Resistance of 15-15ti and 316ti Austenitic Steels as Fuel Cladding in Liquid Lead-Bismuth Eutectic at 550  ℃: The Dominant Role of Grain Structure

Abstract

The corrosion mechanism of 15-15Ti and 316Ti austenitic stainless steels exposed to liquid lead-bismuth eutectic (LBE) at 550 ℃ with dissolved oxygen 5×10-7 mass% was investigated. The oxides formed on steels have a dual- or triplex-layered structure. The higher content of Cr in oxides, the better inhibiting effect on Ni diffusion. The local dissolution attack left a Ni-rich recrystallization area with fcc-phase fine grains. The preferential intergranular oxidation (PIO) in random GBs of 15-15Ti induced intergranular cracking while the annealing twin boundaries were more resistant to crack. The 316Ti with smaller grains presented higher resistance to corrosion and intergranular cracking.

Keywords: Fuel cladding, LBE Corrosion, grain boundary, Preferential intergranular oxidation, Intergranular cracking