Thermo-mechanical Treatment for Improving Grain Boundary Structure and Corrosion Resistance of RAFM Steel

Aiming at the intergranular embrittlement of structural materials caused by irradiation and coolant corrosion in fusion reactors, this paper investigated the effects of different ratios via thermo mechanical treatments on the microstructure of reduced activation ferritic/martensitic steel CLF 1. High temperature steam corrosion tests were performed to verify the feasibility of grain boundary engineering. The results showed that at ratio below 9%, both the prior austenite grain (PAG) size and the fraction of coincidence site lattice (CSL) boundaries along prior austenite grain boundaries increased with increasing ratio. Conversely, further increasing ratio led to reductions in PAG size and the fraction of CSL boundaries. High temperature steam corrosion experiments demonstrated that the thickness of the corrosion induced oxide layer first decreased and then increased with increasing ratio, and it decreased as the fraction of CSL boundaries increased. Accordingly, thermo mechanical treatments can enhance the corrosion resistance of CLF 1 steel by optimizing grain boundary structures.