Joining of Brass/Copper/Nickel with Stainless Steel by Powder Metallurgy Process

Abstract

Joining of dissimilar material is very attractive for many applications because of special performance requirements of materials in different areas like light-weight automotivebstructures, improving methods for energynproduction, creating next generation medical products and consumerndevices, and numerous other manufacturingnand industrial uses. Joining dissimilar materials by conventional welding processes have too many issues. One major problem is the direct change in properties ofjbase metals at the welding interface diminishes the quality of joints. In this joining method, two different metals/alloys in powder form are joined by the mechanism of plastic flow of the powder particles and diffusion of interface atoms using powder metallurgy process. The process was started with the blending of 304L Stainless Steel powder in a Ball mill. Then compaction was carried out by pouring 1gm of milled stainless steel (SS) powder and 1gm of copper powder into the die cavity and applying varying load (4 and 5 ton) by the mechanical press. By using same process Brass (1 gm) and Nickel (1 gm) powders were compacted with Stainless Steel (1 gm) powder at 4 and 5 ton load. The compacts were in the shape of solid round disc. After compaction compacts were subjected to the sintering process. This process involved the heating of compacts in Tubular Furnace (using argon atmosphere) below the melting point temperature of both the metals. Cu-SS and Ni-SS were sintered at 1000°C and Brass-SS was at 800°C with a heating rate of 10 k/min, and holding time was 2 hours. The sintered specimens were cross-sectioned by using the hand saw and then mounted and polished for macroscopic and microscopic observation. To study macro and microstructures of the specimen optical microscope and scanning electron microscope (SEM) were used. From the microstructure, it was observed that there is no presence of cracks in all the joints and even at higher magnification there is no appearance of intermetallic in the microstructures. Vickers micro hardness test showed that the increase in compaction load there was a better bonding between the joints. From the compression test, it was observed that Ni-SS and Cu-SS joint have shown improved strength compared to BrassSS.