Research On Transient Liquid Phase Bonding Of Stainless Steel For MS-SOFC

The metal-supported solid oxide fuel cell(MS-SOFC)is the third-generation fuel cell,which uses metal as the anode support.MS-SOFC effectively reduces the operating temperature of the battery and has a very broad application prospect.However,the connection problem restricts its industrial application,so this research developed a transient liquid phase connection method based on the Sn intermediate layer to meet the connection requirements for connection at low temperature and work at high temperature.The main research contents are as follows:In order to protect the ferritic stainless steel,and at the same time for the connection needs,the nickel layer was plated on the surface of the ferritic stainless steel by electroplating method.The three-dimensional sheet shape of the surface was observed,and the phase of the electroplated nickel layer was analyzed.The influence of process parameters was explored: with the increase of the plating time,the plating thickness also increased linearly.When the plating time was 7 minutes,the nickel plating layer was uniform and dense,which is suitable for transient liquid phase connection.In order to improve the bonding strength of the coating,it was subsequently heat treated.The sheet morphology of the coating changed significantly when the heat treatment temperature was above 400?;the structure of the nickel plating layer roughened and even disappeared when the heat treatment was held for more than 1h.Therefore,in this research,the electroplating time is 7min,the heat treatment temperature is 400?,and the holding time is 1h.A pure Sn intermediate layer was used to connect Ni-plated Crofer ferritic stainless steel,and a Ni3Sn4 compound joint was formed under the parameters of 400 ? and 60 min.The SEM morphology observation and line scan distribution of whole IMC joints were carried out;the morphology observation of transmission electron microscope was carried out,and the diffraction spot analysis was carried out at the same time.The calculation confirmed that the reaction product was Ni3Sn4 and the reaction layer product was Ni3Sn2.The effect of process parameters on the connection joints was explored: the effect of different insulation times on the joints at 300°C was obtained,and the best insulation time was 60 minutes,and the thickness of the intermetallic compound was over 10 ?m;then the different connection temperatures were explored when the insulation time was 60 minutes The effect on the connection joints is that the connection temperature of whole IMC joints is 400°C.The mechanism of element diffusion between Fe,Ni and Sn and the formation of intermetallic compounds were investigated.The ABAQUS is a finite element analysis software,which is used to simulate the finite element simulation of the residual stress distribution.The simulation analysis is on stress changes at different connection temperature and operating temperatures.The research established a finite element analysis model based on the joint and divided the mesh.As the connection temperature increases,the residual stress of the joint increases linearly.At different operating temperatures,as the temperature increases,the residual stress in the joint is increasing.