JOINING OF CU TO SS304 BY MICROWAVE HYBRID HEATING WITH NI AN INTERLAYER

The joining of dissimilar Pure Copper (Cu) to Stainless Steel (SS304) is necesilated in many industrial applications such as heat exchangers and electrical contacts. Advantages of both the materials such as high electrical conductivity of copper and better corrosion resistance of SS304 can be harnessed by way of joining both the metals. However, joining to Cu to itself or other materials is a challenge since the input heat is dissipated rapidly. Most of the conventional welding methods such as arc and gas are incompetent and unconventional methods such as Explosion Welding, EBW, Diffusion Bonding are very expensive.In this study a new economical process of joining of dissimilar metals i.e. Cu to SS304 by microwave hybrid heating is investigated. Microwave joining is made possible by applying a powder (in this work Nickel metal powder) as an interlayer and exposing to microwave surrounding the interlayer with a susceptor. In this study the interlayer of Ni powder having average size 200nm and 45μm was used. On exposure to microwave, the interlayer meal powder heats up [1] and then it promotes melting and thereby bonding to facilitate dissimilar joint. The microstructure of the joint is studied by optical microscope and scanning electron microscope. The joints formed with 200nm Ni powder were observed to have a defect free microstructure as illustrated in Fig. 1. The EDS and XRD analysis determines the formation of solid solution between Cu-Ni interface and an intermetallic compound at Fe-Ni interface. The diffusion of elements across the joint was further analyzed by EDS line scan. The hardness variation was studied by Vickers’ micro-hardness. It can be concluded that smaller size Ni heat up faster in microwave and produce stronger joint of Cu to SS304 by microwave hybrid heating.  References 1.           M. S. Srinath, A. K. Sharma, et al. ,Materials & Design , 2011, 32, 2685–2694