Compact heat exchangers have high compactness and efficiency, which is achieved by joining the stack of plates through diffusion bonding. In the diffusion bonding process, compressive stress is applied on plates at elevated temperature for specified time period. These conditions leads to atomic diffusion which results in to joining of all plates in to solid block. The diffusion bonding temperatures are above recrystallization temperatures, which changes the mechanical and microstructural properties of bonded metal. Hence, diffusion bonded material need mechanical and microstructural property evaluation. In this study, Alloy 800H is selected to study the influence of diffusion bonding process on mechanical and microstructure properties of base metal. A series of tensile, fatigue, creep and creep-fatigue experiments are conducted on base metal 800H (BM 800H) and diffusion bonded 800H (DB 800H) to explore the mechanical properties. Up to this point microstructure evolution during diffusion bonding is studied and presented in the paper. The mechanical and microstructural observations indicated ductile fracture at room temperature and brittle failure with bond delamination at elevated temperatures. The microstructure evolution during diffusion bonding is studied through tensile, fatigue, creep and creep-fatigue tests and the implied root causes for the mechanical property changes are formulated. Efforts are made to correlate the microstructure change with mechanical property change in DB 800H.


Mechanical and Microstructural Characterization of Diffusion Bonded 800h

Division / Sponsors: 
Pressure Vessels & Piping (PVP)


Paper Proceedings: https://asmedigitalcollection.asme.org/PVP/PVP2020/volume/83815

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