Influence of copper on amorphous nickel based brazing alloy

Braying of stainless steel easing nickel based alloys has sometimes been av oided, in spite of its various advantages, because it is a somewhat unrelia ble process in terms of the mechanical characteristics arid corrosion resis tance of the brazed joints. Addition of copper to amorphous Ni-Cr-B-Si braz ing alloys has been shorn to be a promising method of improving the perform ance of joints. Because copper cart forma a solid solution with nickel at a rty concentration, addition of copper has a great effect on the microstruct ures of the nickel based filler metal and bra-a seam, by improving the volu me ratio of nickel based solid solution to the embrittled intermetallic com pounds. As a result, a significant increase in the critical brazing clearan ce (CBC) was obtained in the present work. Furthermore, copper might increa se the electrode potential of nickel based solid solution, so that addition of copper could improve the corrosion resistance of the brazed joints. The results show that can appropriate copper addition to the present Ni-Cr-B-S i group amorphous brazing foil provides an effective method of overcoming t he weaknesses of joints brazed using conventional nickel based filler metal s, such as low value of CBC and low corrosion resistance.