Development of High Temperature Mechanical Rig for Characterizing the Viscoplastic Properties of Alloys Used in Solid Oxide Cells

• Published in: Journal of testing and evaluation 2018-09, Vol.46 (5), p.1918-1929
• Main Authors: Molla, Tesfaye Tadesse, Greco, Fabio, Kwok, Kawai, Zielke, Philipp, Frandsen, Henrik Lund
• Format: Article
• Language: English
• ISSN: 0090-3973; 1945-7553
• DOI: 10.1520/JTE20170046

Analyzing the thermomechanical reliability of the solid oxide cell (SOC) stack requires precise measurement of the mechanical properties of the different components in the stack at operating conditions of the SOC. It is challenging to precisely characterize the time-dependent deformational properties of metallic components in the SOC stacks at the required level of stress and operational conditions (high temperature and controlled atmosphere). This work presents an improved methodology for characterizing the time-dependent, or viscoplastic, properties of metallic alloys used in the SOC stacks at a high temperature and in a controlled atmosphere. The methodology uses a mechanical loading rig designed to apply variable and constant loads on samples within a gas-tight high temperature furnace. In addition, a unique, remotely installed length measuring setup involving a laser micrometer is used to monitor deformations in the sample. Application of the methodology is exemplified by measurement of stress relaxation, creep, and constant strain rate behaviors of a high-temperature alloy used in the construction of SOC metallic interconnects at different temperatures. Furthermore, measurements using the proposed methodology are also verified by the literature and experiments conducted using other machines.