Metal bonding glass-ceramic compositions having improved hardness

A method of bonding a glass-ceramic material to a metal member comprising the steps of:

• A. forming a fluid glass composition consisting essentially of about 60 to 80 weight percent SiO.sub.2 12 to 20 weight percent Li.sub.2 O, 2 to 14 weight percent MgO, 1.5 to 6 weight percent P.sub.2 O.sub.5, 1 to 7 weight percent of an alkali oxide selected from the group consisting of K.sub.2 O and Na.sub.2 O and their mixtures, 0 to 2 weight percent of a transition metal oxide selected from the group consisting of Co.sub.3 O.sub.4, MnO.sub.2, Fe.sub.2 O.sub.3, V.sub.2 O.sub.5 and WO.sub.3 and their mixtures, 0 to 5 weight percent PbO, 0 to 2 weight percent Al.sub.2 O.sub.3 and 0 to 1 weight percent As.sub.2 O.sub.3 ;
• B. applying the glass composition directly to a metal member;
• C. cooling the glass to a temperature of below about 600.degree.C;
• D. heating the glass and metal member up to a temperature of about 900.degree.C at a rate of about 10.degree.-80.degree.C per hour, to form a glass-ceramic from the glass composition which intimately bonds directly to the metal member, said glass-ceramic being a substantially homogeneous microcrystalline mass of ceramic having a Knoop handness value of over about 660 in a glass matrix;
• E. maintaining the temperature of the glass-ceramic bonded metal member for about 1/2-10 hours;
• F. cooling the glass-ceramic bonded metal member to room temperature.