Optimization of solid-state diffusion bonding of Hastelloy C-22 for micro heat exchanger applications by coupling of experiments and simulations

The paper presents an optimization of diffusion bonding processes of Hastelloy C-22 based on the coupling of experiments and model simulations for manufacturing of micro heat exchangers for chemical applications. A systematic work is begun with experimental investigations of the influences of the bonding temperature on microstructures and mechanical properties of the material to be bonded. Based on these, the optimal bonding temperature is determined. To predict the remaining bonding parameters, a diffusion bonding model is used. The mechanical properties used as input parameters are provided by tensile and creep tests. The experimental investigations and model calculations yielded an optimized parameter set of 1050 °C, 26 MPa and 3.6 h for a given surface roughness. This is verified by diffusion bonding using sheet material for various compression stresses, bonding durations and surface roughness. Bonding with this parameter set is successfully conducted, which in turn resulted in a sound bonding seam. The tensile strength was comparable to that of the base material and the toughness was higher than 50% of that of the base material.