The study of diffusion brazing of stainless steel 304 using pure copper foil interlayer

Abstract

Diffusion brazing is employed to join stainless steel 304 using pure copper foil interlayer. The bonding process was carried out in a vacuum furnace at various temperatures for various diffusion times. Microhardness test was applied to determine the mechanical properties of the joints. Besides, microstructures of bonds were studied with optical and scanning electron microscopy and energy dispersive spectrometry elemental analyses to determine the mechanical properties of the joints. In order to determine the corrosion resistance of the joints, Tafel test was conducted in 3.5% NaCl solution. It was observed that yFe + eutectic Cu + Cr accumulated along the diffusion zone. The highest microhardness result was obtained at the diffusion zone and hardness value decreased gradually as the distance from the joint increased. The brazed joints developed crevice corrosion due to a galvanic couple formed between stainless steel and copper interlayer and presented preferential dissolution of copper interlayer under anodic polarization in 3.5% NaCl solution at room temperature. In addition, intergranular stress corrosion cracking also found on the copper region. After immersed the brazed joints for 12 hours, pitting attack was concentrated on the copper surface.