Microstructural and Mechanical Evaluations of Transient Liquid Phase Bonded In X-750/BNi-3/SAF 2205

In this study, dissimilar joining between SAF 2205 duplex stainless steel and Inconel X-750 superalloy produced by TLP process was investigated. This process was done at temperature of 1100 degrees C for different bonding times of 1, 15, 30, 45 and 60 min. The effect of different bonding times on the microstructure and mechanical properties of the welded samples was studied. Microstructure of the samples was analyzed by optical microscopy and scanning electron microscopy equipped with energy-dispersive x-ray spectroscopy. X-ray diffraction analysis was used to determine the formed phases in the bonding area. Microhardness and shear strength tests were done to evaluate the mechanical properties of the joints. It was found that the joint area contains the gamma-Ni solid solution, eutectic compounds with intermetallic phases beside precipitated secondary phases. The gamma-Ni solid solution, BN, BCN, CrB, Ni3Si and Ni3B were the main phases in the joining area. Maximum microhardness was found in athermally solidified zone, due to the presence of hard and brittle intermetallic and boride phases. The maximum shear strength (368 MPa) was obtained for the sample with the bonding time of 45 min, due to the completion of isothermal solidification and removal of eutectic compounds.