| Recently, the molten salt reactor (MSR), a generation IV fission reactorcandidate, has drawn much attention because of its intrinsic safety. However, theharsh service environment of the MSR, especially the corrosion environment, raisesmany challenges in terms of applying structural materials, such as intergranularcracking and embrittlement. MAX phases materials are new high temperaturestructural materials that are resistant to irradiation and corrosion. Therefore, MAXphases materials can be promising structural materials used in MSRs. However, thecorrosion behaviour of these materials in molten salt is yet to be evaluated. Thepresent work is a preliminary investigation of the corrosion behaviour of MAX phasematerials in molten fluoride salts. The corrosion mechanism of MAX phases inmolten fluoride salts was deeply discussed. The work was significant to improve thecorrosion resistance of MAX phases in molten fluoride salts.This work choose two common MAX phases: Ti3SiC2and Ti3AlC2as experimentsubject. The corrosion tests were performed in FLiNaK salt. The corrosion of thesetwo MAX phases in molten FLiNaK salt mainly showed as the corrosion of A element.The difference was that Ti3AlC2lost Al entirely, however the loss of Si in Ti3SiC2occured only on the surface. After the loss of A element, the left Ti-C structuretransformed into cubic TiCxdue to a topotactic transformation. The corrosionproducts had a nanolaminated structure that was similar with graphene. The weightloss data showed that Ti3SiC2had a much better corrosion resistance than Ti3AlC2.The corrosion tests at different periods and temperatures were performed. Resultsshowed that corrosion rate was sharply fast in the initial period and then growparabolically with time. This can prove that corrosion in molten fluoride salt wasdominated by element diffusion. The corrosion depth with time indicated that hightemperature can accelerate corrosion, which was due to the larger diffused rateinduced by high temperature. |
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