THERMAL SHOCK RESISTANCE OF MULTI-LAYERED CERAMIC COMPONENTS

摘要

Resistance to thermal shock is a key design requirement for thin ceramic components which operate at elevated temperature. This paper describes a methodology developed for the prediction of the thermal shock behaviour of multi-layer ceramic systems. Application to Solid Oxide Fuel Cells (SOFCs) will be demonstrated. An experimental procedure based on an air flow cooling method has been devised to typify the flow of a gas stream over the surface of a multi-layered ceramic system. Such conditions are typical of SOFCs operation, in particular during transient phases including start-up and shut-down. Temperatures on the surface of the tested multilayer system have been carefully monitored to calculate the corresponding stress fields. Detailed investigations of the fractured samples are presented and representative fracture patterns and crack initiation sites reported. A failure prediction methodology is presented which relies on failure diagrams constructed from a combination of experimental and analytical studies. For a given probability of failure, a failure diagram indicates permitted thermal shock conditions (i. e. temperature histories) and geometric characteristics.