Effect of Y₂O₃ stabilized ZrO₂ coating with tri-model structure on bi-layered thermally grown oxide evolution in nano thermal barrier coating systems at elevated temperatures

Mohammadreza Daroonparvar¹，Muhamad Azizi Mat Yajid¹，Noordin Mohd Yusof¹，Hamid Reza Bakhsheshi-Rad¹，Z.Valefi²，Esah Hamzah¹

1. Department of Materials, Manufacturing and Industrial Engineering, Faculty of Mechanical Engineering, Universiti Teknologi Malaysia2. School of Metallurgy and Materials, College of Engineering, University of Tehran

摘 要：Bi-layered thermally grown oxide（TGO） layer plays a major role in the spallation of Y2 O3 stabilized ZrO2（YSZ） layer form the bond coat in the thermal barrier coating（TBC） systems during oxidation. On the other hand, bi-layered TGO formation and growth in the TBC systems with nanostructured YSZ have not been deeply investigated during cyclic oxidation. Hence, Inconel 738/NiCrAlY/normal YSZ and Inconel 738/NiCrAlY/nano YSZ systems were pre-oxidized at 1000 °C and then subjected to cyclic oxidation at 1150 °C. According to microstructural observations, nanostructured YSZ layer over the bond coat should have less micro-cracks and pinholes, due to the compactness of the nanostructure and the presence of nano zones that resulted in lower O infiltration into the nanothermal barrier coating system, formation of thinner and nearly continuous mono-layered thermally grown oxide on the bond coat during pre-oxidation, lower spinels formation at the Al2 O3 /YSZ interface and finally, reduction of bi-layered thermally grown oxide thickness during cyclic oxidation. It was found that pre-heat treatment and particularly coating microstructure could influence microstructural evolution（bi-layered TGO thickness） and durability of thermal barrier coating systems during cyclic oxidation.

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