Welding of Martensitic Stainless Steel AISI 440C by means of TransientLiquid Phase Bonding (TLP-DB) and the Assessment of its Microstructure andCorrosion Behaviour Hamidreza Vahabi Hr.vahabi@ma.iut.ac.ir Date of submission: Spetember …, 2020 Department of Materials Engineering Isfahan University of Technology, Isfahan 84156-83111, Iran Degree: M.Sc Language:Farsi Supervisors: Morteza Shamanian : shamanian@cc.iut.ac.ir Ali Ashrafi : ashrafi@cc.iut.ac.ir In this study,the similar connection of 440 C martensitic stainless steel was investigated bythe transient liquid phase process and the optimization of the parameters ofthis process. For this purpose, samples with dimensions of 40 × 10× 5 mm were prepared and the surfaces of these samples were prepared bysanding and ultrasonic washing. AWS BNi-2 foil was used as the connectioninterface layer. The foil was placed between two pieces of base metal and theirassembly was placed very tightly inside a holder. The retainingmaterial is selected from St52 carbon steel with a thickness of 10 mm, which isleveled and tightened by two bolts. Samples were bonded at 1050 and 1100 ° C at60 and 120 minutes in a vacuum furnace. Due to the fact that after thetransition operation of the transient liquid phase, the martensitic structureof 440 C steel was changed to a perlite ferrite structure with coarse carbidesin the base metal ferrite field. To approach the initial structure of the basemetal before bonding, quench-temper heat treatment was performed on thesamples. The given connection samples were cut for cross-sectionalmetallography. A more detailed microstructure study of thescanning electron microscope was performed. Using an electron microscopeequipped with an energy separation analyzer, changes in the concentration ofalloying elements in the bonding area as well as the chemical composition ofthe bonding phases and the base metal were studied. Changes in joint stiffnessand shear strength of the specimens were investigated. With the exception ofthe bonded specimen at a temperature of 1050 ° C and a time of 60 minutes,which was observed with a very small amount of non-isothermal freezing zone,the rest of the specimens have the structure of the bonded zone under completeisothermal freezing. With increasing temperature and bonding time, theconcentration concentration of the elements in the interface layer of the bondand the base metal changed due to the penetration phenomenon. Iron and chromium in the base metal penetrated very much into the interfacelayer and nickel, boron and silicon in the interface layer penetrated into thebase metal. The binding phase phases indicate the presence of a nickel-richproectotic solid solution phase in the isothermal freezing zone. Investigationof microhardness changes in different regions of the sample according todifferent bonding conditions shows an increase in hardness from the heataffected area to the base metal, which was done with a steep slope. Thestiffness increased from the center of the joint area to the end of theheat-affected area with a very gentle slope. The stiffness of the bondedspecimens in the base metal and heat affected areas increased sharply in theheat treated specimens. The shear strength of the specimens increased withincreasing temperature, but the shear strength of the bonded specimen decreasedat higher temperatures even after heat treatment. In order to investigate thecorrosion behavior of the bonded samples by the transient liquid phase process,corrosion tests were performed on the bonded specimens. Showed itself. key words : Transient liquid phase connection process, 440 Cmartensitic stainless steel, vacuum atmosphere, heat treatment of samples