Electrochemical Behaviour and Surface Studies on Austenitic Stainless Steel and Nickel-Based Superalloy Dissimilar Weld Joints

Development on austenitic stainless steel and nickel-based superalloys have played vital role in the field of manufacturing of engineering components. The selection of materials depends upon working environment and operating conditions. In some cases, the combination of two different materials is used to join and apply them for specific working conditions. Joining of stainless and super alloys for turbine power shaft and high temperature steam pipe lines are the two major examples of this. Challenges in current research are to join dissimilar materials without disturbing the properties of parent metals. Materials joining process either may be at fusion state or solid state. Extensive research articles are available to discuss about the joining process of similar materials. While considering the dissimilar materials, individual conditions has to be satisfied depending upon the choice of joining process. Sample thickness, weld energy required, filler material, weld speed, weld design, etc. are the pre-requisite for completion of the process. The weld zone heat transformation (thermal gradient) thickness and its metallurgical quality are the major outcome in welding process. In this chapter, the research is focused on joining of two different metals using laser and electron beam welding (EBW) process. The metallurgical changes in the weld zone are studied. Further, the electrochemical behaviour of austenitic stainless steel and nickel-based superalloy dissimilar weld has been studied using 3.5% NaCl solution. The samples exposed to corrosion medium are followed with metallurgical characterization techniques such as: Optical imaging, SEM, EDS and XRD. Results from the investigation indicate that the EBW sample is superior than laser beam welded sample. The heat convention under laser welding has induced the samples to metallurgical deficiency.