Development and optimization of diffusion welding of ODS alloys

To build more efficient, safer and more environmentally compatible reactors, the materials for the future generation IV fission reactors will be subject to even stricter requirements than those for current fission reactors. Major concerns are the resistance against irradiation, corrosion and oxidation as well as high temperatures. One class of materials that combines all those properties are oxide dispersion strengthened chrome steels. The unique properties of this material class are due to homogeneously distributed oxide particles within the steel matrix. The weldability of oxide dispersion strengthened steel, however, is challenging, as conventional welding techniques cause agglomeration of the oxide particles, which results in decreased strength at the welding seam. Fortunately, solid state bonding techniques, such as diffusion bonding, are viable alternatives. The applicability of the diffusion bonding technique for the welding of oxide dispersion strengthened steel is being determined in this work. The aim is to generate a bonding seam without any loss in toughness and strength throughout the material. Furthermore, to obtain a better understanding of the underlying processes and to optimize the technique more efficiently, a novel simulation model based on the work of Hill and Wallach is developed, which describes the diffusion bonding of oxide dispersion strengthened materials. Simulation work supports the development and optimization of the diffusion bonding process of oxide dispersion strengthened steel, because of a better understanding of the physical processes and a more efficient optimization process. The input parameters and boundary conditions are obtained experimentally. Material is characterized mechanically and microstructurally in the as received and heat treated state, respectively, investigate the influence of the temperature during the diffusion bonding process. This optimization process results in a successful diffusion bond with optimal bonding parameters, without considerable loss in strength and toughness of the welding seam.