Study On Hydrogen Resistance Of Chromium Oxide Based Coating And TiZrNbCr_0.9Al_0.1 High Entropy Alloy Passivation Film

One extremely important issue of fusion structure materials in the field of controlled nuclear fusion is the permeation of hydrogen and its isotopes,which generally results in structural material embrittlement,nuclear fuel loss,and radioactive contamination.At present,the mainstream practice in the world is to prepare a high permeation reduction factor（PRF）material layer on the surface of structural materials to reduce the diffusion of hydrogen and its isotopes in structural materials.Studies have shown that ceramic materials can largely inhibit the hydrogen permeation,and some metal carbide also has great potential in inhibiting hydrogen permeation.In this work,the preparation and hydrogen permeation resistance performance of Cr₂O₃/SiC composite coating,Cr₂O₃/HeVm composite coating high-entropy alloy passivation film were studied.（1）The preparation and hydrogen permeation resistance performance of Cr₂O₃/SiC composite coating.The Cr/SiC composite coating was prepared on the iron-nickel alloy substrate by unidirectional pulse electrodeposition.The composite coating is oxidized under low oxygen partial pressure to obtain Cr₂O₃/SiC composite coating.The morphological characterization results show that the introduction of SiC nanoparticles refines the grains during the electroplating process,so that a dense oxide layer was formed on Cr coating in the subsequent oxidation process.From the electrochemical analysis,the Cr₂O₃/SiC composite coating has higher impedance value and lower carrier concentration than the single Cr₂O₃ layer,which means that the composite coating has better hydrogen barrier properties and better stability in a hydrogen environment.（2）The preparation and hydrogen permeation resistance performance of Cr₂O₃/He_nV_m composite coating.The Cr₂O₃ layer with a relatively simple chemical composition is formed on the surface of pure chromium by oxidation under ultra-low oxygen partial pressure environment.The Cr₂O₃ layer is relatively stable in a hydrogen environment.On the basis of the prepared oxide layer,a layer of helium bubble was formed under the oxide layer by helium ion implantation.Through the cross-section analysis of the sample prepared by FIB,it was found that the oxide film was completely dense,no bulge,cracks etc.,the transition between oxide film and He bubble layer is gentle.TDS analysis of the samples with different He ion implantation doses showed that the hydrogen barrier effect of the composite hydrogen barrier layer decreased first and then increased with the increase of the implant dose,that is,there is an optimal value for the implant dose,and the hydrogen barrier performance will decrease beyond this dose.In this subject,the implantation dose of 10¹⁶ shows superior hydrogen barrier properties.Through the electrochemical analysis,the reason why the He ion implantation dose has the optimal value is explained to some extent.There may be a certain competition relationship between the increased impedance value of He ion implantation and the damage caused by it.The proper amount of He ion implantation helps to improve the hydrogen barrier effect of the composite coating,but when a larger dose of helium is injected into the coating,the increased impedance is insufficient to compensate for the damage introduced by the irradiation;the hydrogen barrier effect of the coating is lowered.（3）The preparation and hydrogen permeation resistance performance of high-entropy alloy passivation film.High-entropy(TiZrNbCr_0.9AI_0.1)alloy is prepared using a non-consumable vacuum melting furnace,and C ions are implanted into the high-entropy alloy at about 200 nm by ion implantation.The ion-implanted sample is oxidized in an ultra-low oxygen pressure environment to form an oxide layer on the surface of the high-entropy alloy,thereby protecting the underlying MnCm（M=Ti,Zr,Nb,Cr,Al）.)do not oxidized.Electrochemical analysis shows that the passivation film formed on the surface of high-entropy alloy is not stable in hydrogen environment.It is speculated that it may be due to the existence of a variety of phases in the high-entropy alloy,which leads to the obvious boundary of the passivation film formed after oxidation and the poor structural integrity of the passivation film,which needs further study.