Behaviour of chromium steels in liquid Pb–55.5Bi with changing oxygen content and temperature

The behaviour of protective oxide layers on P122 steel and its welds and of ODS steel in liquid Pb44.5Bi55.5 (LBE) is examined under conditions of changing temperatures and oxygen concentrations. P122 (12Cr) and its welded joints are exposed to LBE at 550 °C for 4000 h with oxygen concentrations of 10−6 and 10−8 wt% (p(O2) = 8.1 × 10−23 bar and 5.2 × 10−27 bar) which change every 800 h. It is found that like in case of constant oxygen concentration of 10−6 wt% a protective spinel layer (Fe(Fe1−xCrx)2O4) was maintained on P122 and also on its welded joint. Two experiments with exposure times of 4800 h are conducted on ODS steel, both with temperatures changing from 550 to 650 °C and back every 800 h, one experiment with 10−6 the other with 10−8 wt% oxygen in LBE. Both experiments show strong local dissolution attack after 4800 h which is in agreement with the behaviour of ODS in LBE at a constant temperature of 650 °C. However, dissolution attack is less in LBE with 10−8 wt% oxygen (p(O2) = 3.0 × 10−25 bar).