16 - Joining of heat sink with structural material for ITER like divertor application

Abstract

This article summarizes the challenges in the joining of copper alloy to structural materials at elevated temperatures. Joining of copper alloy material with structural material has been considered in the development of plasma facing component of ITER like tokamak application. Dissimilar material joining is known to be problematic as the parent materials are having different thermal properties. Popular joining techniques for CuCrZr to SS316L are (i) vacuum brazing, (ii) diffusion bonding, such as explosive bonding, and Hot Isostatic Press, (iv) Electron beam Welding. For the joining of copper alloy with SS316L material, vacuum brazing technique and uniaxial diffusion bonding are chosen in the present study. Joining of copper alloy (CuCrZr) to SS316L (as structural material) has been performed by vacuum brazing technique using Gleeble machine using selective brazing fillers at different temperatures. Selection of suitable brazing filler and proper brazing cycle/diffusion cycle, compressive loading and suitable environment are the key factors for the dissimilar material joining. This type of CuCrZr/SS316L dissimilar joint is particularly used in divertor Plasma facing component (PFC) of ITER like tokamak. The dissimilar brazed and diffusion bonded joint are characterized by Non-destructive testing (NDT) particularly Ultrasonic Testing (UT), microstructural examination and destructive testing such as shear strength measurement and micro hardness measurement. The brazed joint has been finally tested for thermal cyclic tests at 450 °C in Gleeble system. The results of the experimental and characterization will be discussed in this chapter.