Effects of local gas shielding on induction brazing of stainless steel: an experimental approach

Abstract Ni-based brazing fillers are primarily utilized in vacuum furnaces or continuous furnaces. However, the application of such furnace techniques imposes technical and economic limitations on the size of brazeable components. Induction brazing offers an alternative to overcome these limitations, enabling the brazing of large components by means of localized heating and gas shielding. This study aims to improve the understanding of process control and required gas quality for effective brazing by conducting experiments on tube-to-tube joints using Ni-based brazing alloys. To determine their impact on brazing outcomes, process gases with varying oxygen contents were systematically tested. The microstructure of the brazed joints was analyzed by light microscopy. The influence of process gas quality on corrosion behavior was examined using a capillary microcell. High residual oxygen contents in the process gas led to a shift in the corrosion potentials. Additionally, the mechanical properties of the joints are affected. Therefore, the monotonic mechanical properties were investigated at ambient temperature. The findings of this research offer practical recommendations and present a newly developed shielding gas nozzle for industrial applications. These insights support the optimization of induction brazing processes and highlight the potential for increasing the quality and efficiency of brazing large components.