Effect of cold working on the corrosion resistance of JPCA stainless steel in flowing Pb-Bi at 450 degree C

Development of a high performance proton beam window material is one of the critical issues for the deployment of the accelerator-driven transmutation system (ADS) with liquid Pb-Bi eutectic as a spallation target and coolant. In the present study, we applied 20% cold work treatment to JPCA austenitic stainless steel and investigated it from the corrosion behavior viewpoint. The corrosion test of 20% cold-worked JPCA SS has been carried in the JLBL-1 (JAEA Lead-Bismuth Loop-1) apparatus. The maximum temperature, the temperature difference, the flow velocity and the exposure time of the liquid Pb-Bi were 450 degree C, 100 degree C, 1 m/s, and 1000 h, respectively. For comparison analysis, JPCA SS without cold working was also tested in the same time and conditions with the 20% cold-worked JPCA SS. The results showed a different corrosion behavior between the JPCA SS without and with cold working. As for the JPCA SS without cold working, Pb-Bi penetrated into the matrix through a ferrite layer which was formed because of constituent metals dissolution from the matrix into Pb-Bi. As for the 20% cold-worked JPCA SS, dissolution attack occurred only partially and formed localized superficial pitting corrosion. It was found that the different corrosion behavior occurred because the cold working induced a structure transformation from gamma -austenite to alpha '-martensite and affected the corrosion resistance of the JPCA SS in flowing Pb-Bi at 450 degree C.