Shear strength and interfacial characterization of borosilicate glass-to-metal seals

In this work, we present the shear strength and interfacial characterization of 304 stainless steel (304SS) to borosilicate glass seals, with the aim of obtaining the best chemical bonding of seals. Different microstructures and chemical compositions of the interface transition region were achieved by employing various pre-oxidation processes of 304SS, which were conducted in a low oxygen partial pressure environment at 1000, 1050, and 1100 degrees C for a duration of 30, 45, and 60 min. The results of X-ray diffraction (XRD) reveal that the oxide layer is mostly composed of Cr2O3 and Mn1.5Cr1.5O4, and martensitic transformation occurs in the surface of 304SS substrate. Shear strength test shows that the bonding strength formed by dissolution of oxides is far higher than that formed by interfacial redox (reduction-oxidation) reaction directly between metal and glass. The seals to 304SS pre-oxidized at 1050 degrees C for 45min exhibit the highest shear strength, yielding an average failure strength of 27 +/- 0.5 MPa. The correlations between bubble-free region, element diffusion, interfacial defects, fractured surfaces, and the shear strength were qualitatively discussed, leading to new insights into interfacial bonding properties of the glass-to-metal seals. (C) 2020 Elsevier B.V. All rights reserved.