Glass ceramic seals to inconel

A process for forming a seal between a glass having a thermal expansion coefficient .alpha. of 120-160.times.10.sup.-7 /.degree.C. and a nickel base alloy having substantially the same thermal expansion coefficient, comprising the steps of:

• 1. applying a glass having a composition, by weight, of 65-80% SiO.sub.2, 8-16% Li.sub.2 O, 2-8% Al.sub.2 O.sub.3, 1-8% K.sub.2 O, 1-5% P.sub.2 O.sub.5 and 1.5-7% B.sub.2 O.sub.3 to the nickel base alloy, and subjecting the glass to the following processing steps:
• a. heating the glass composition to a temperature sufficient to crystallize lithium metasilicate therein;
• b. holding the glass composition at a temperature and for a time period sufficient to dissolve the lithium metasilicate therein thereby creating cristobalite nucleii;
• c. cooling the glass composition and maintaining the composition at a temperature and for a time period sufficient to recrystallize lithium metasilicate therein;
• and
• d. thermally treating the glass composition at a temperature and for a time period sufficient to cause growth of cristobalite and further crystallization of lithium metasilicate producing a glass ceramic composition having a specific thermal expansion coefficient.