Preparation And Properties Of Al₂O₃/Cr₂O₃ Composite Tritium Permeation Barrier By Pack Cementation

Controlled nuclear fusion is an ideal new energy source.Hydrogen isotopes deuterium and tritium are used as raw materials for nuclear fusion energy.They are easy to diffuse and infiltrate in the cladding structure of the fusion reactor,resulting in the consequences of radioactive fuel tritium leakage and structural material embrittlement.How to prevent tritium penetration has become one of the key issues in nuclear fusion research.At present,the preparation of tritium barrier coating on the surface of structural materials is an effective method to solve the problem of tritium penetration.Alumina has excellent tritium resistance performance,thermodynamic stability,and good compatibility with tritium multiplication agents.It is one of the main candidate tritium materials,but due to its large difference in thermal expansion coefficient from the steel substrate,the coating is prone to peeling and failure Is difficult to solve.This paper combines the embedding method and the heat treatment process of the base steel to explore the preparation of Al₂O₃/Cr₂O₃composite tritium coating on the surface of RAFM steel.By preparing a Cr₂O₃transition layer between the Al₂O₃coating and the substrate,a thermal expansion gradient is formed to alleviate the thermal mismatch between alumina and the substrate;and the template effect of Cr₂O₃can also be used to effectively reduce the formation temperature ofα-Al₂O₃.This paper studies the preparation process and performance of the composite coating,and finally draws the following conclusions:（1）By combining packing cementation co-infiltration technology and subsequent heat treatment process,an oxide layer with a thickness of 32μm and a transition layer with a thickness of 55μm are obtained,in which the oxide layer is an Al₂O₃/Cr₂O₃composite coating,and the transition layer consists of Al and Cr elements Formed by diffusion in steel.The surface and cross-sectional morphology of the Al₂O₃/Cr₂O₃composite coating are good,and the bonding with the base steel is good.Adding a small amount of Y₂O₃to the penetrant will cause the quality of the composite coating to seriously deteriorate,and a large area will fall off,which is not in line with expectations（2）The subsequent heat treatment has an important influence on the coating morphology.Using the same packing cementation process,the infiltrated layer was separately nitrided and oxidized pretreated during the first tempering.Microscopic analysis showed that the infiltrated layer nitriding pretreatment can refine the coating grains and make the coating more uniform and dense.（3）The Al₂O₃/Cr₂O₃composite coatings obtained by nitridation and oxidation treatment have good thermal shock resistance,wear resistance and high Vickers hardness.The composite coating has good chemical corrosion resistance,and the corrosion current density reached 5.023×10^-9A cm^-2.