New material brazing

Abstract

This final year project is to test and study a new material to be used for brazing metal pieces together. Current brazing elements give way to Boron which causes boron formation that directly weakens the brazed joint. All obtained results were compared with industry brazes to determine satisfaction level. Nickel-Chromium-Niobium was sandwiched between two Inconel 718 samples as vacuum brazed. The brazed sample was cut in half moulded into a plastic resin and polished to reveal the microstructure. The grinding and polishing were done in multiple stages to reveal obtain the best surface finish possible. The sample was analysed under an optical microscope, scanning electron microscope and energy dispersive x-ray spectrometer to observe the phases and quality of braze. The dispersion of elements throughout the braze zone and diffusive zone was satisfactory. The samples were with very little voids, which already placed it as a superior choice for brazing. The content of Niobium was found to be highest in the braze zone and gradually tapering off with growing distance from the neutral line. The brazed metals underwent a Vickers hardness test and matched with industry standards. The hardness of the sample was found significantly higher at the braze than the rest of the metal. 15 points of varying distance were tested with the diamond pyramid shaped tip. The final test conducted was the tensile test using a Instron machine. Three samples were tested with results having a similar pattern. The braze had an average tensile shear strength of 162.31MPa. It was concluded, that the Nickel-Chromium-Niobium braze was an improvement over the brazes used in industry. The braze had good distribution of elements and the mechanical properties were comparable to the industry standards. However, the reduction in number of void formation gives the new braze material an edge.