The Joining of Alumina to Hastelloy by a TiZrCuNi Filler Metal: Wettability and Interfacial Reactivity

Abstract

A systematic microstructural characterization of alumina joined to Hastelloy C22® by means of a commercial active TiZrCuNi alloy, named BTi-5, as a filler metal is reviewed and discussed. The contact angles of the liquid BTi-5 alloy measured at 900°C for the two materials to be joined are 12° and 47° for alumina and Hastelloy C22® after 5 min, respectively, thus demonstrating good wetting and adhesion at 900 °C with very little interfacial reactivity or interdiffusion. The thermomechanical stresses caused by the difference in the coefficient of thermal expansion (CTE) between the Hastelloy C22® superalloy (≈15.3 × 10−6 K−1) and its alumina counterpart (≈8 × 10−6 K−1) were the key issues that had to be resolved to avoid failure in this joint. In this work, a circular configuration of the Hastelloy C22®/alumina joint was specifically designed to produce a feedthrough for sodium-based liquid metal batteries operating at high temperatures (up to 600 °C). In this configuration, adhesion between the metal and ceramic components was enhanced after cooling by compressive forces created on the joined area due to the difference in CTE between the two materials.

Reusable Cell Design for High-Temperature (600 °C) Liquid Metal Battery Cycling

“…Whenever a ceramic and a metal have to be joined by some means and a tight seal has to be ensured, to avoid its failure, the thermal expansion mismatch between various materials has to be taken into account when designing the feedthroughs. 27 To reduce the risk of joint failure, the heating/cooling rate of the battery should be around 5 K min −1 . 24 Various active cooling designs have been proposed to prevent overheating and further mitigate the risk of the joint rupture.…”