Wetting of substoichiometric YSZ2-x by molten Sn-based active alloys at 800–900 °C

Abstract

The wetting of Sn–8Zr, Sn–4Zr–4Ti, and Sn–8Ti on a substoichiometric YSZ2-x (yttria-stabilized substoichiometric zirconia) substrate was studied using a modified sessile drop method at 800–900 °C. The Sn–4Zr–4Ti/YSZ2-x system had the best final wettability (approximately 32°, 27°, and 22° at 800, 850, and 900 °C, respectively), satisfying the brazing wetting requirements. When Zr-containing alloys contacted the YSZ2-x substrate, the decomposition of YSZ2-x induced the formation of Sn2Zr and more non-metallic YSZ2-y. The final wettability was determined using Sn2Zr, YSZ2-y, and the adsorption of Zr (and/or Ti). Titanium in the Sn–8Ti/YSZ2-x system inhibited the massive decomposition of YSZ2-x, maintained the original metallicity, and, together with the adsorption of Ti, contributed to the final wettability. A scalar law analysis indicated that the wetting activation energies of the Sn–4Zr–4Ti/YSZ2-x and Sn–8Ti/YSZ2-x systems were 197 and 243 kJ/mol, corresponding to the formation of Sn–Zr and Ti–Zr chemical bonds during the liquid-solid interface formation, respectively.