Materials & Design (Apr 2021)
Contributions of mechanical bonding and chemical bonding to high-temperature hermeticity of glass-to-metal compression seals
Abstract
The present work compares the contributions of mechanical bonding and chemical bonding to high-temperature hermeticity of glass-to-metal (GTM) compression seals and explores their temperature-dependent failure behaviors. The GTM compression seals were fabricated using pre-oxidized AISI 304 and borosilicate glass with different thermal expansion coefficients (TECs). The variation of TEC was investigated by changing the alkali oxides contents. The chemical bonding strength between the glass and the pre-oxidized AISI 304 was evaluated using shear strength test and fracture surface analysis. And the mechanical compressive stress was analyzed by fiber Bragg grating technology at elevated temperature. In addition, the seal hermeticity with varying temperature under high pressure helium was also recorded. The results show that the hermeticity failure temperature increases as compressive stress attenuation reduces. But the contribution of increasing chemical bonding strength to high-temperature hermeticity is covered up by that of compressive stress decay. This demonstrates that mechanical bonding has a stronger influence on high-temperature hermeticity of the seals than chemical bonding. The findings of this work will guide the development and optimization of GTM compression seals towards further improvement of the high-temperature tolerance.
