The bonded area growth at diffusion bonding determined by the numerical modelling of Gleeble 3800 experiments and in comparison with the model by Hill and Wallach

Abstract

Diffusion bonding or HIP (Hot Isostatic Pressing) is a common manufacturing process at several ITER components inside the Vacuum Vessel. The key uncertainties during diffusion bonding the unknown surface contaminations, remaining oxides. Diffusion bonding and reference tests were performed on specimens made from 316 L on a Gleeble 3800 Thermal-Mechanical Physical Simulation System. The contact electrical resistance on the bonded surfaces were determined in earlier work, where the decreasing contact electrical resistance predicted the increasing contact area during the welding process. Using the theoretical calculations to the electrical resistance of the surface asperities modelled by Zhang the bonded area growth was determined in time for the cylindrical specimens.A theoretical diffusion bonded model by Hill and Wallach was used to calculate the bonded area grow (a/b) on the examined tests. The results were comparable between the growth rate of (A/B) estimated by the Zhang model and bonded area growth by Hill and Wallach (a/b). The theoretical diffusion bonding models show much faster bonding, where the ideal model and the presumable re-oxidation of the surface gave the explanation to this phenomenon.