Microstructure and corrosion behavior of CrAl-coated 316L steel in static and flowing liquid lead-bismuth eutectic

To mitigate the corrosion issue of 316 L steel in lead-bismuth eutectic (LBE) cooled fast reactors, CrAl alloy coating was prepared on 316 L steel by multi-arc ion plating. Its corrosion behavior and microstructure evolution were examined in static and flowing LBE at different temperatures. The results show that the coating exhibited good bonding strength and corrosion resistance in LBE. The microstructure of coating experienced transformation in LBE at 550 degrees C while maintained stable at 350 degrees C. Under 550 degrees C, the coating transformed from Al3Cr7 with columnar grains to AlCr2 with refined equiaxed grains. Meanwhile, the enhanced element interdiffusion at interface of coating and steel also resulted in formation of B2-NiAl, Fe-Cr solid solution, Cr23C6 and (Al0.5Cr0.5)Fe. Although the CrAl coating has good anti-corrosion performance, the phase structure instability might limit its potential application.