Study On The Preparation And Properties Of α-Al₂O₃/SiO₂ Composite Oxide Hydrogen Permeation Barrier

In the fields of nuclear fusion and hydrogen energy,hydrogen and its isotopes,deuterium and tritium,easily penetrate into metal structural materials such as stainless steel,causing hydrogen damage and hydrogen embrittlement.Coating the surface of structural materials with tritium permeation barrier（TPB）is an economically effective means,but most of the preparation methods for tritium permeation barrier are not easy to promote in industry,especially for the inner wall coating of small-diameter stainless steel pipes.To solve this problem,this paper refers to the mature ceramic sintering process and preparesα-Al₂O₃/SiO₂ composite oxide ceramic coatings on the inner wall and disk surface of 316L stainless steel pipes.The influence of different process parameters and component ratios on the morphology and performance of the composite coatings is studied to determine the preparation process parameters of the coatings.At the same time,the influence of adding rare earth metal oxides such as La₂O₃ on the performance of the composite coatings is studied.The main research results are shown as follows:（1）The influence of different sintering temperatures and the content of oxide,glass powder and inorganic silica gel adhesives on the surface morphology ofα-Al₂O₃/SiO₂ composite coatings is studied.It is determined that under the formulation of mass ratio ofα-Al₂O₃:SiO₂:low-temperature glass powder=1:2:1,the mass ratio of mixed powder and inorganic silica gel adhesive is 1:4,and the sintering process is carried out at 850℃to prepare coatings with excellent surface quality,and the coating thickness is about 61.8μm.The composite coating with high gloss is smooth and dense,without defects such as cracks and holes.（2）The relevant properties ofα-Al₂O₃/SiO₂ composite coatings are studied.The microhardness of the composite coating is 519.91 HV,much higher than that of the316L stainless steel substrate and theα-Al₂O₃ single-component coating.At the same time,the composite coating has good adhesion to the substrate,and the bonding force tested by the acoustic emission method is 37.95 N.In terms of thermal shock resistance,after 10 thermal cycles at 850℃,the coating surface did not produce cracks and holes except for some edge shrinkage.The hydrogen resistance performance of the coating is excellent,with a PRF of up to 46340 at 650℃.（3）Furthermore,attempts were made to add rare earth oxides such as La₂O₃,Ce O₂and Er₂O₃ to the existingα-Al₂O₃/SiO₂composite coating system,and only La₂O₃ was found to be more compatible.Based on this,α-Al₂O₃/SiO₂/La₂O₃ composite coatings were prepared.The morphology of this composite coating system is slightly rougher than that of theα-Al₂O₃/SiO₂ composite coating,and the thickness on the axial and longitudinal directions of the inner wall of the pipeline is between 50～70μm,with a relatively uniform distribution.The microhardness of the coating surface reaches 599.2HV,and the improvement is significant.The bonding force between the coating and the substrate is 25.70 N,which is lower than that of theα-Al₂O₃/SiO₂ composite coating.Its hydrogen resistance performance has a PRF of 955 at 650℃and exhibits different permeation characteristics from theα-Al₂O₃/SiO₂ composite coating at different temperatures.