3 - Oxidation behavior of the bondcoat and associated lifetime of thermal barrier coating systems

• Published in: Thermal Barrier Coatings pp. 43 - 86
• Main Authors: Song, Peng, Huang, Taihong, Naumenko, Dmitry, Quadakkers, Willem Josef
• Format: Book Chapter
• Language: English
• Published: Elsevier Ltd 2023
• Edition: Second Edition
• Subjects: Alumina scale; Crack propagation; Cyclic oxidation; Lifetime; MCrAlY bondcoats; Lifetime; MCrAlY bondcoats; Cyclic oxidation; Alumina scale; Crack propagation
• ISBN: 0128190272; 0128190280; 9780128190289; 9780128190272
• DOI: 10.1016/B978-0-12-819027-2.00003-1

The oxidation behavior of the bond coat is an important factor determining the lifetime of thermal barrier coatings (TBC) in advanced gas turbine components. Various testing parameters, such as hot/cold dwell time, heating/cooling rate, and atmosphere composition, play an important role in the bondcoat oxidation and associated TBC lifetime. The range of coating systems includes Electron Beam-Physical Vapor Deposited (EB-PVD) and Air Plasma Sprayed (APS) TBCs with MCrAlY (M=Ni, Co) and NiPtAl-type bondcoats. The effect of the testing parameters strongly depended on the type and properties of the studied system. The lifetime of EB-PVD TBC systems with conventional MCrAlY and NiPtAl bondcoats forming uniform, flat alumina scales was found to be limited by critical scale thickness, upon which a rapid crack propagation at the scale/bondcoat interface results in macroscopic failure. For APS TBC systems the bondcoat oxidation is only one of several factors determining the ceramic topcoat lifetime. The cracks initiated at the oxide scale/bondcoat interface and propagated through the APS TBC to cause macroscopic failure.