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

Abstract

PurposeTo 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/approachSquared samples of austenitic SS were joined using a brazing metallic foil BMF‐15® in a sandwich‐like arrangement. The samples were then placed into a resistance furnace with a controlled N2 atmosphere. The joining process was carried out at 1105 and 1170°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®/SS joints were evaluated using DC electrochemical methods on joined samples immersed in a 3.5 wt% NaCl solution.FindingsThe 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®. 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/valueThis 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.

Microstructure and electrochemical properties of the bonding zone of AISI 316L steel joined with a Fe-based amorphous foil

“…In the case of diffusion bonding of AISI 304 stainless steels using amorphous Ni-based alloys, bonding process conducted in the temperature range from 923 to 1123 K (650-850 • C) induced sensitisation of the steel and the joining zone became highly susceptible to intergranular corrosion in 3.5% NaCl solution as reported by González-Sánchez et al (2007). Due to the variety of engineering applications of austenitic stainless steels, research has been done about alternative manufacturing processes including diffusion bonding.…”

“…This assembly was then placed in a graphite die embedded in a boron nitride (99.5% pure) powder bed and subjected to mechanical pressure to keep the assembly together. The experimental set up used has been explained with detail elsewhere by González-Sánchez et al (2007) and by Flores et al (2006). Once each sample was assembled in the graphite die, it was positioned into the furnace filled with argon as shown in Fig.…”

“…However, the actual electrochemical mechanisms of the high corrosion resistance are still not fully understood. González-Sánchez et al (2007) have previously reported that the corrosion resistance of amorphous alloys disappear due to recrystallisation as a consequence of bonding process at temperatures higher than 50% the melting temperature of the alloy.…”

Diffusion Bonding and Transient Liquid Phase (TLP) Bonding of Type 304 and 316 Austenitic Stainless Steel—A Review of Similar and Dissimilar Material Joints

“…If the sample geometry allows it, parts can also be press-fitted and put under pressure into a vacuum furnace where they are then diffusion bonded when the temperature is increased [68][69][70]. If no relevant pressure was applied [67,[71][72][73][74][75][76][77][78][79][80][81][82][83][84][85][86][87], the experiments were not reported here since we considered them brazing rather than diffusion bonding using the definitions introduced earlier. In brazing some pressure is often applied to fix the parts so that a definition between brazing and TLP bonding that only relates to applied pressure is not sufficient.…”

Brazing of Si3N4 with amorphous Ti40Zr25Ni15Cu20 filler

“…Consequently, instead of crystalline alloy fillers, amorphous active alloy has attracted increased attention in the fields of ceramic/ceramic and ceramic/metal joining owing to its unique properties [21]. Amorphous alloy, a material at unsteady state, can accelerate atomic diffusion and surface reaction during high temperature brazing process [22][23][24][25]. In addition, it is expected to decrease brazing temperature so as to reduce residual stress developed in the joint and hence to increase the joint strength.…”