Further Developments in Boron Free Nickel-Chromium-Phosphorus-Silicon Brazing Filler Metals

Ni-Cr-Si-P brazing filler metals are widely used and are of particular importance in the manufacture of Exhaust Gas Recirculation (EGR) units, Heat Exchangers and Catalytic Convertors.  The latest design of these parts invariably involves thinner wall sections and more variable gap tolerances than previous models. Consequently, it is essential that the braze filler metal provides good flow, gap filling performance with minimal erosion. Corrosion resistance and mechanical strength are fundamental requirements of the braze filler metal. The current work investigates the influence of solid solution strengthening additions such as molybdenum, tungsten and cobalt within boron-free BFMs and assesses the wetting properties, gap filling ability, corrosion resistance and tensile strength at elevated temperatures. Comparisons will be made against traditional and recently developed BFMs such as Nicrobraz® LM (BNi-2) and Nicrobraz® 33 respectively.