Joining strategies for open-porous metallic foams

Abstract

Abstract Within the Collaborative Research Centre 561 “Thermally highly loaded, porous and cooled multilayer systems for combined cycle power plants” open porous and high-temperature stable Ni-based structures are being developed for the requirements of effusion cooling. A two-dimensional cooling strategy for the walls of combustion chambers, that allows the outflow of the cooling medium over the complete wall area of the combustion chamber, could be realised by an open porous metallic foam structure. The open porous metallic foam is produced by the “Slip Reaction Foam Sintering” process, a powder metallurgical process. For joining several foams to assemble structural elements laser beam welding and capacitor discharge welding have been used. Different joining strategies have been examined for both processes to find out the most suitable method for joining these foams. In this paper the process setups, settings of the different strategies and results of trials (seam geometry and strength tests) are discussed. The need for graded structures to combine the essential permeability and adequate weldability is also shown.