Alloy Oxidation and Porcelain Fused to Alloy Interaction in Noble Alloy Systems

The oxidation and porcelain fusion characteristics of noble alloys containing a variety of minor oxidizable elements, including Cu, Sn, In, Ga, Mn, and Fe were investigated. Four porcelain alloys systems: a Pd-base alloy (Naturelle}, two Pd-Ag-based alloys (Jelstar and Acclaim}, and a high Au-alloy (SMG-3) were examined by scanning electron microscopy and energy dispersive spectroscopy after being heat treated and after being fused with porcelain. Internal oxidation of minor alloying elements occurred within several micrometers from the surface in all four alloys. Surface nodules as detected by other investigators for a Pd-Ag alloy were also detected in this study. Evidence for occ111Tt2lce of such nodules in the high Au-content alloy were also noted. Naturelle, a high Ga and Cu containing alloy, was also characterized by the presence of a 0"203 010 layer beneath Pd-Cu nodules and at grain boundaries. A surface oxide layer, as thin as 100 nm, of F~~ -sno2 was observed in the high Au-alloy. The morphologies for alloy /porcelain interfaces were similar. The presence of minor alloying elements was observed within a distance of several micrometers in the porcelain from the alloy/porcelain interface. These results suggest a predominantly mechanical bond with Pd-Ag base alloys (Jelstar and Acclaim) while a significant contribution by a chemical bond in Pd-base (Naturelle) and high Au-