Vacuum Brazing of Tungsten and Fe-Co-Ni Alloy Along with Micro-Structural Evaluation of Joint Interface Using SEM

In the present work, Fe-Co-Ni alloy and tungsten samples (sheet form) have been brazed using Oxygen-Free Electronic (OFE) copper (foil form) as brazing alloy under a vacuum of about 10–5 mbar and the interface has been characterized using scanning electron microscopy (SEM) & energy dispersive spectroscopy (EDS). To ensure proper alignment and uniform flow of brazing filler, uniform compressive force was applied using 25 g weight during brazing process. The joint interface was examined using SEM and is found to be thin, continuous and free from micro-cracks. The joint thickness varies between 25 µm to 40 µm. Further, compositional study using EDS along with Dot Mapping & Line Scan has been carried out across the joint interface and analyzed to correlate the diffusion of various elements across the joint. Micro-hardness variations across brazed interface have also been evaluated and the hardness was found to be lowest in filler region than parent materials which indicates the soundness of interfacial joint using this process. The joint strength has been assessed using Ram Tensile Test and the mean value of joint strength has been found to be 91.7 MPa.