Corrosion resistance of stainless steel joints bonded with a Ni-based amorphous interlayer

Purpose - To study the metallurgical characteristics obtained from the process of diffusion bonding of 316L stainless steel (SS) using a commercial Ni-based amorphous alloy interlayer and its effect on the corrosion resistance of the self-joined SS-amorphous alloy-SS junction zone. Design/methodology/approach - Squared samples of austenitic SS were joined using a brazing metallic foil BMF-15 (R) in a sandwich-like arrangement. The samples were then placed into a resistance furnace with a controlled N-2 atmosphere. The joining process was carried out at 1105 and 1170 degrees C holding the samples in the furnace for periods of 5, 10, 15, 20 and 40 min. The junction zone was evaluated by scanning electron microscopy (SEM) in order to determine the metallurgical structure induced during the process. The corrosion resistance of the SS/BMF-15 (R)/SS joints were evaluated using DC electrochemical methods on joined samples immersed in a 3.5 wt% NaCl solution. Findings - The samples of 316L SS showed self-diffusion bonding at both temperatures which are quality depended upon the holding times. A concentration of second phases was observed by SEM at the BMF-15 (R). The joints developed crevice corrosion at open circuit potential due to a galvanic couple formed between the SS and the amorphous alloy, and presented preferential dissolution of the Ni-amorphous alloy under anodic polarization in 3.5 per cent NaCl solution at room temperature. Originality/value - This work presents a systematic study of the self-diffusion bonding process of SS pieces jointed with an amorphous alloy interlayer and the metallurgical effects on its corrosion resistance of in a 3.5 wt% NaCl solution.