Investigation of the chemical composition of the thermally grown oxide layer in thermal barrier systems with NiCoCrAlY bond coats

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• 作者：C. Mercer ; S. Faulhaber ; N. Yao ; K. McIlwrath and O. Fabrichnaya
• 关键词：Thermal barrier coatings ; Thermally grown oxide ; NiCoCrAlY ; Energy-dispersive spectroscopy ; Hafnia ; Fluorite
• 刊名：Surface and Coatings Technology
• 出版年：2006
• 期刊代码：106_02578972
• 类别：ms
• 出版时间：5 October 2006
• 卷：201
• 期：3-4
• 页码：1495-1502
• 文件大小：1020 K

摘要

The morphology and composition of the thermally grown oxide (TGO) layer in a thermal barrier system with a NiCoCrAlY bond coat are characterized by a combination of scanning and transmission electron microscopy, focused ion beam sectioning and energy-dispersive spectroscopy (EDS) element mapping. The investigation has revealed a complex TGO that exhibits numerous thickness inhomogeneities (‘pegs’), and a sizable distribution of nano-scale second phase particles. These particles have been determined to be of two types: regions of entrained bond coat and oxides based on Y₂O₃ and HfO₂. The most probable phase makeup of the oxides is a cubic fluorite of approximate composition 4HfO₂–Y₂O₃. Diffusion of Hf and Y from the bond coat or entrapment of bond coat elements during TGO growth are the most likely mechanisms for the formation of these oxide particles.