Laser Beam Welding of Open-Porous Metallic Foams for Application in Cooling Structures of Combined Cycle Power Plants

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, which allows the outflow of the cooling medium over the complete wall area of the combustion chamber, could be realized 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. To join several foams to assemble structural elements, laser beam welding has been used. Different joining strategies have been examined to find out the most suitable method to join 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.