Vacuum induction brazing for heterogeneous joining of tantalum to stainless steel

摘要

Tantalum is used in chemical industry due to its refractory and corrosion resistance properties. Because of its high cost, joining tantalum to stainless steel can be useful for less solicitated parts. As fusion welding is possible only using a filler metal, solid state joining is preferable to limit structural deterioration. Brazing is a good compromise when using a suitable filler metal regarding corrosion resistance. The eutectic alloy Au/Ni (82/18 wt%) offers in addition good wettability and mechanical property. Its melting temperature is 955℃. This communication presents the experimental procedure and metallurgical analysis of the brazes. Induction is preferred as a localized heat source with high dynamics. Vacuum brazing is required to protect tantalum against oxidation and makes simplified surfaces preparation possible. The braze matrix shows a refined lamellar structure favorable in terms of mechanical properties. Rapid heating limits the extension of reacting phenomena between filler alloy and base metals. Dispersed areas of Ni{sub}8Ta compound are localized near tantalum erosion zones. An additional phase rich in nickel is located at grains boundaries.