Vakuumdichte feuerfeste Metall-Keramik-Verbindung und Verfahren zu ihrer Herstellung

摘要

Bonding a refractory ceramic member to a refractory metal surface includes forming on the ceramic member a tightly adhering spongy porous layer of tungsten and/or molybdenum, then coating the layer with a refractory metal and brazing the refractory metal surface to the metallized ceramic, the refractory metal coating consisting of rhenium, molybdenum-rhodium alloy or molybdenum ruthenium alloy. A body of alumina 1 has applied thereto a suspension of molybdenum oxide or tungsten oxide or mixtures thereof in a solution of nitrocellulose in amyl acetate and the body is then heated in hydrogen to reduce the oxides and sinter a spongy layer 2 to the body. The powdered metals instead of their oxides may be employed. An aqueous solution of rhenium heptoxide is applied to the sponge and heated in hydrogen to reduce the heptoxide to rhenium metal 3 which covers the surfaces of the spongy layer without filling the pores of the sponge. To the rhenium coated sponge layer a molybdenum body 5 is brazed. In a modification the sponge layer is coated with a suspension of 40% ruthenium oxide balance molybdenum oxide in a solution of nitrocellulose in amylacetate and the assembly fired in hydrogen to form a eutectic ruthenium-molybdenum alloy coating on the sponge which fills the pores. Instead of a ruthenium and molybdenum alloy a rhodium-molybdenum alloy may be used. The coated ceramic is then brazed to a tungsten, molybdenum or rhenium plate. If the material for coating the sponge and for brazing are of the same composition the coating and brazing may take place simultaneously. The metals or alloys may be used instead of the oxides.