Optimization of Process Parameters and Comparative Study on Bi-Metallic Joints Developed by High Temperature Nicrobrazing, Laser and GTAW Joining Processes

Abstract

High Temperature Nicrobrazing of AISI 316 and 316 L stainless steels has been studied by comparing with pulsed laser and gas tungsten arc welding processes. Fabrication of instrumented irradiation capsule for evaluating the irradiation performance of fuel and structural materials in a nuclear reactor requires development of thin wall joints capable of withstanding high temperature and/or internal pressure. Thin wall joints for high temperature (∼550 °C) applications can be made by Laser Beam Welding (LBW), Gas Tungsten Arc Welding (GTAW) and High Temperature Brazing (HTB) methods. Using these methods, joints have been prepared and tests such as helium leak test (HLT) and microhardness test have been carried out. Microstructures were also evaluated. A comparative study has been performed on these joining methods to identify the suitable methods for high temperature applications. No observable leak was found during HLT. Microstructures of joints shows variation in solidification morphology due to difference in heat sources. It has been observed that the joint prepared by high temperature brazing process is having higher microhardness value than the joints prepared by LBW and GTAW processes. Further, it has been observed that LBW joints have better mechanical properties than GTAW joints and HBW joints.