Studies On Preparation And Properties Of Novel Cr₂O₃ Composite Coating As Tritium Permeation Barriers

Cr2O3 coating is regarded as one of candidate materials in tritium permeation barriers due to its thermal stability,chemical inertness,low permeability of hydrogen isotopes,and good adhesion to metal substrate.However,in order to ensure the microstructure stability of the stainless steel substrate,a low sintering temperature of Cr2O3 coating is required,which leads to some microcracks and pores in the coating.So that,the actual barrier permeability of the coating is far lower than that of the theoretical value.Therefore,it is necessary to improve the density of Cr2O3 coating for improving its barrier properties.In view of the above problems,in this paper,we fabricate another coating on the surface of Cr2O3 coating to further improve the compactness of the coating and increase the internal interface of the material to prevent the diffusion of hydrogen and its isotopes.Al2O3/Cr2O3composite coating and GO-AlPO4/Cr2O3 composite coating were obtained by electrophoretic deposition and impregnation-lifting respectively.The effects of key process parameters such as deposition times,heat treatment temperature,dipping-lifting times and GO content on the morphologie,microstructure and properties of the composite coating were investigated.The main findings are as follows:1.A flat and dense Al2O3/Cr2O3 composite coating can be obtained by electrophoretic deposition combined with heat treatment.There is no obvious interface between Al2O3 layer and Cr2O3 layer.Al2O3 plays two roles:part of Al2O3 is filled in the pores of Cr2O3 coating,which improves the compactness of the coating;another part of Al2O3 is dissolved into Cr2O3 caoting,which improves the interfacial adhesion between the coatings.2.The heat treatment temperature has a great influence on the microstructure and properties of the Al2O3/Cr2O3 composite coating.The Al2O3/Cr2O3 composite coating heat-treated at 750°C has the best mechanical properties and barrier properties.The Al2O3/Cr2O3composite coating heat-treated at 750°C exhibits a high microhardness of 219.4 HV500g,a bonding strength of 46.5 MPa,good anti-corrosion(corrosion current is 6.64×10^-10 A cm^-2,corrosion potential is 224.0 mV).The D-PRF（Deuterium-Permeation Reduction Factor）value of the coated samples are evaluated 302 at 600°C,which is greater than the D-PRF of Cr2O3 coating（236）.3.The GO-AlPO4/Cr2O3 composite coating was successfully prepared by the dipping-lifting method.The interface between the graphene reinforced AlPO4 layer and the Cr2O3layer is well bonded,no pores and cracks are observed,and the structure is dense and uniform.4.With the increase of GO content,the microhardness and electrochemical corrosion resistance of the sample increased,and the friction coefficient decreased,but the binding force increased firstly and then decreased.0.05 GO-AlPO4/Cr2O3 sample has the best comprehensive ability and it exhibits the high microhardness of 317.3 HV500g,a bonding strength of 21.5 MPa,the friction coefficient of 0.7,corrosion voltage of-77 mV,corrosion current of 3.92×10^-9 A cm^-2.