An investigation of factors influencing the mechanical strength of glass-to-metal seals.

The mechanical strength of two widely used types of glass-to-metal seals, 29/17/54 nickel-cobalt iron alloy with borosilicate glass and 50/50 nickel-iron alloy with lead glass, have been examined. Controlled variations were made in the Oxidation treatment of the alloy component prior to sealing and the time for which the seal was held at temperature following the glassing operation. These variations in the fabrication process were found to have a marked effect on the mechanical strength and the results are reported. The glass-metal interface of the seals were studied by electron microprobe and microscopic means. The structures observed are discussed in relation to the mechanical strength of the seals. Whilst the results of this investigation are in general agreement with the limited amount of work published on this subject, some widely held theories on the mechanisms of adherence between glass and metal are found to be inadequate.