Overview of interfacial fracture toughness testing of ceramic coatings at room and elevated temperatures

Ceramic coatings such as thermal barrier coatings (TBC), environmental barrier coatings (EBC) and electrodes in solid oxide cells (SOCs) are exposed to high temperatures during operation. Due to the harsh operating environments, these types of layered materials go through various types of thermal cyclic loads and stress conditions, which lead to damage and failure. In order to prolong their life span and understand the failure mechanisms of these coatings, the interfacial adhesion between coatings to substrates of these highly configurated systems is essential. Various test methods have been developed to understand the interfacial mechanical properties of these materials. In this comprehensive review, the test methodologies of multilayered ceramic coatings at room and elevated temperatures along with the microstructure, merits and limitations are discussed. Certain criteria are proposed to conduct interfacial fracture tests depending on the applicability of ceramic coatings.