Localization of Embrittlement in CMAS-Infiltrated Thermal Barrier Coatings via Laser Shock Experiments

Abstract

As the operation temperature of aero-engine increases, the threat of molten deposits, usually caused by volcanic ash or sand ingestion has a major concern to the durability of these systems. In thermal barrier coatings, the ceramic topcoat (TC) layer made of partially stabilized zirconia is highly sensitive to such corrosive attack by means of infiltration, causing their premature failure. Infiltration causes either a decrease in toughness and adhesion or an increase in stiffness of the TC layer. As a local method to assess the interface strength of TBCs, the Laser Shock Adhesion Test (LASAT) is investigated for the first time to a columnar ceramic coating with and without infiltration by a CMAS deposit. LASAT clearly shows the location of the minimum toughness zone within TC layer, which is associated with either the zone of infiltration, the infiltration depth limit or the TGO/topcoat interface. This is key to assessing the mechanical weakening from such corrosive attack.