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7069 |
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Wednesday, June 22, 2022, Saal Brüssel 9:20 AM Diffusion bonding |
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On the relation of bonding temperature, contact pressure and deformation on the mechanical properties of diffusion bonded AISI 304 |
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Thomas Gietzelt* / KIT/IMVT, Germany Mario Walter / KIT, Institute for Micro Process Engineering, Germany Volker Toth/ KIT, Institute for Micro Process Engineering, Germany |
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The main process parameters for diffusion bonding are bonding temperature T, dwell time t and contact pressure p. Temperature and contact pressure have opposite effects on deformation and act nonlinearly. Other factors such as geometrical dimensions, internal structures and the materials microstructure affect deformation too. For this reason, it is difficult to specify the process parameters for diffusion bonding in advance for any given component in such a way that a specific target deformation or property such as high-vacuum tightness is guaranteed. Here, the impact of temperature on deformation was investigated in the range of 1015 to 1135 °C for constant contact pressure of 16 MPa and dwell time of 4 h on AISI 304. For 925 to 995 °C, reduced values for elongation at fracture were obtained due to imperfect bonding at a contact pressure of 16 MPa. At 850 °C bonding was investigated at higher contact pressures. The values for elongation at fracture were significantly lower, regardless of the deformation obtained. Obviously, the diffusion coefficient is significantly reduced, which prevents bonding at the atomic scale and filling of pores by volume diffusion. It can be concluded that deformation is a necessary criteria to deform surface asperities at the initial state of diffusion bonding but not sufficient to derive mechanical soundness of the bond. A diffusion bonding process is proposed to limit deformation for arbitrary geometries. |