High temperature oxidation interfacial growth kinetics in YSZ thermal barrier coatings with bond coatings of NiCoCrAlY with 0.25% Hf

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2011-03, Vol.528 (6), p.2223-2230
• Main Authors: Soboyejo, W.O., Mensah, P., Diwan, R., Crowe, J., Akwaboa, S.
• Format: Article
• Language: English
• Subjects: Air plasma; Bonding; Ceramics; Cross-disciplinary physics: materials science; rheology; Electron microscopy; Evolution; Exact sciences and technology; Hafnium; Materials science; Microstructure; Oxidation; Physics; Reaction kinetics; Surface treatments; Thermal barrier coatings; Thermal grown oxide (TGO); Thermally grown oxides; Yttria stabilized zirconia (YSZ)
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2010.11.066

▶ Isothermal oxidation of standard (STD) and vertically cracked (VC) TBCs has been investigated. ▶ The temporal TGO growth kinetics is parabolic in the temperature range between 900 and 1100°C. ▶ Activation energies correspond to growth kinetics controlled by the diffusion of O2 in Al2O3. ▶ Variation in oxidation of TBCs is attributed to its microstructure and in-situ oxygen ingression. ▶ Doping TBC bond coat with Hf appears to have potential for enhancing the development of robust TBCs. The results of an experimental study of the high-temperature isothermal oxidation behavior and microstructural evolution in two variations of air plasma sprayed ceramic thermal barrier coatings (TBCs) are discussed in the paper. Two types of TBC specimens were produced for testing. These include a standard and vertically cracked APS. High temperature oxidation was carried out at 900, 1000, 1100 and 1200°C. The experiments were performed in air under isothermal conditions. At each temperature, the specimens were exposed for 25, 50, 75 and 100h. The corresponding microstructures and microchemistries of the TBC layers were examined using scanning electron microscopy and energy dispersive X-ray spectroscopy. Changes in the dimensions of the thermally grown oxide layer were determined as functions of time and temperature. The evolution of bond coat microstructures/interdiffusion zones and thermally grown oxide layers were compared in the TBC specimens with standard and vertically cracked microstructures.