The structure and oxidation of two palladium ceramic fusing alloys.

The oxides formed at the surface of an alloy during preheating at about 1000 degrees C prior to the firing of ceramic are vital for the formation of a strong chemical bond between alloy and porcelain. Replacing Au used as the basic constituent in the ceramic fusing alloys with Pd seems to have a rather small effect on the behaviour of the elements Sn and In which were found to oxidize internally. However, no external oxidation of the transition metal component Co was found, in contrast to Ni in Au-based alloys. After ceramic firing a zone enriched with Co and In is found in the interaction area between alloy and ceramic. In another alloy Ga was observed to oxidize internally and much more easily than Cu due to its much lower free energy of formation. A solid solution was produced in both the alloys by ceramic firing as shown by SEM studies.