Intergranular Corrosion of High Temperature Ni-based Alloy GH3535 Induced by Fission Product Tellurium
In molten salt reactors,the interaction between fission products dissolved in the fuel salt with the structural alloys is a critical issue.Notably,the presence of tellurium(Te)poses a significant chal-lenge by inducing intergranular cracks(IGC)for high temperature Ni-based alloys.Herewith,the corro-sion behavior of high temperature Ni-based alloy GH3535 exposed to Te vapor(i.e.the test alloy with nominal doses of 1,6,and 10 mg/cm2 Te powders respectively were vacuum sealed in a quartz tube)at 700℃ for 150 h was assessed by means of scanning electron microscope(SEM),electron probe micro-analyzer(EPMA),and transmission electron microscope(TEM),in terms of corrosion products and Te dif-fusion behavior.Results reveal that a dual-layered corrosion product was observed on the alloy surface after being exposed to Te vapor for 150 h at 700℃.The outer telluride layer comprised Ni3Te2,Ni3Te2.07,and Cr2Te3,exhibiting a thickness directly proportional to the Te concentration.The inner ones represent-ed a diffusion layer containing elongated Te-rich phases resulting from the inward diffusion of Te into the alloy matrix.Te diffusion was observed predominantly along grain boundaries(GB),penetrating to deeper regions and segregating there.It follows that the findings may provide a meaningful reference for under-standing the Te-induced IGC,namely,this diffusion process led to a conspicuous depletion of Ni,Fe,and Cr at GB,thereby facilitating significantly the occurrence of IGC.
Molten salt reactorNickel alloyTelluriumIntergranular corrosion
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