A computational approach to the joining of dissimilar alloys for high temperature heat exchangers

I&EC 117

Paul E. King, Paul.King@netl.doe.gov, Rick D. Wilson, Jarrod Hatem, and Omer N. Dogan. National Energy Technology Lab, 1450 Queen Ave SW, Albany, OR 97321
Optimization of high temperature processes includes the reclamation of waste process heat through the use of high temperature heat exchangers (to 800ºC). However, typical materials that survive these environments are expensive. A combined computational and experimental approach to heat exchanger design is presented in order to indicate how reductions in cost can be achieved. In this work, the heat transfer in a given high temperature heat exchanger is modeled in order to determine regimes where expensive super alloys are required and areas where less expensive, commercial alloys can be utilized. A computational estimation of filler material composition between these disparate alloys is employed, followed by physical testing of the joints at service temperature. Filler materials were identified using equilibrium phase diagrams and thermodynamic simulation software. Experimental weld microstructures were compared to phases predicted by the simulations and recommendations made for the appropriate applications.