Interfacial reactions between lithium silicate glass-ceramics and Ni-based superalloys and the effect of heat treatment at elevated temperatures

Two lithium silicate glasses (S- and BPS-glass) were sealed to four different Ni-based superalloys (Inconel 600, Inconel 718, Haynes 230, and Hastelloy C-276) and the effects of long-term heating at 700–900°C on the chemical, microstructural, and mechanical properties of sealed interfaces were studied. The presence of a small amount of ZnO in the BPS-glass leads to the formation of a thin interfacial second phase layer and a less rough alloy interface compared to the ZnO-free S-glass. Inconel 718 was found to be the most reactive of the alloys, with Cr and Nb diffusing into the glass and forming a coarse glass-ceramic microstructure at the interface. Heat treatment of all the reaction assemblies at 900°C for 100 h in air resulted in degradation of the seals and their spontaneous failure. Heat treatments at 700 or 800°C did not cause any interfacial coarsening in BPS sealed to Inconel 600, Haynes 230, and Hastelloy C-276 alloys and did not alter the bond strength of Haynes 230 bars, sealed with a thin layer of BPS-glass, demonstrating the potential of these material combinations for applications up to 800°C.