報告書番号

Q05010

タイトル（和文）

遮熱コーティングの組織変化を用いた温度推定手法およびAl含有量予測手法

タイトル（英文）

Temperature Estimation and Aluminum-content Prediction by means of Microstructural Change in Thermal Barrier Coating

概要 （図表や脚注は「報告書全文」に掲載しております）

遮熱コーティング試験片を用いた大気中高温酸化試験後には、ボンドコート外面が酸化し、それに伴い、特に外面近傍においてAlが豊富な相が消失した層（外面Al低下層と称す）が観察された。この外面Al低下層厚さは、酸化時間の平方根に比例して成長することが明らかとなり、外面Al低下層厚さと酸化時間および温度の関係式を得ることができた。本式を用いて、TBC施工実機部品の外面Al低下層厚さを測定することにより、ボンドコート外面近傍の温度を推定できる可能性が得られた。ただし、ボンドコートの酸化がさらに進展すると、Alが豊富な相はボンドコート全体から消失し、外面Al低下層は判別できなくなる。また、ボンドコート中の平均Al含有量は、外面Al低下層厚さの増加に伴い、直線的に減少する。この関係を用いてAl含有量の低下を予測できる可能性が見出された。ただし、外面Al低下層が判別不能となると、この関係は成立しなくなる。

概要 （英文）

The microstructural change of a CoNiCrAlY bond coat (about 100mm of thickness) in a thermal barrier coating (TBC) was clarified, and temperature estimation and Aluminum-content prediction using it were examined. High-temperature oxidation tests were conducted by means of TBC specimens. After the oxidation tests, an oxide layer grew at the surface of a bond coat. Accordingly, an Al-rich phase disappeared at the vicinity of a bond coat surface, and an Al-decreased outer layer was observed. This results in the diffusion of Al to the surface according to the oxidation of the bond coat. The authors have clarified that, according to the parabolic law, the thickness of the Al-decreased outer layer grows in proportion to the square root of the oxidation time. The relationship between the thickness of the Al-decreased outer layer, the oxidation time and the temperature was achieved. When the oxidation of the bond coat proceeded further, however, the Al-rich phase disappeared from whole area of the bond coat due to the diffusion of Al to the surface and to the substrate, and the Al-decreased outer layer could not be distinguished. Based on this relationship, there is a possibility that the temperature at the vicinity of the bond coat surface is estimated by measuring the thickness of the Al-decreased outer layer in TBC parts of in-service gas turbines. The applicable time limit of this estimation method, however, was determined by the limits of the detection (10mm) and the distinction (50mm) for the thickness of the Al-decreased outer layer. According to the test result, for an example, when the temperature of a TBC part of a gas turbine was 850ｺC, the time limit was estimated as about 2,000 hours to about 40,000 hours. The average Al-content in the bond coat decreased in proportion to the thickness of Al-decreased outer layer. There is a possibility that, by means of the relationship, the time to reach any Al-content be predicted. The decrease of the average Al content, however, was saturated at about half of the initial content when the Al-decreased surface layer could not be distinguished at the thickness of about 50mm, and the above relationship was broken. The applicable time of this method, therefore, is until the content decreases to the half of the initial content.

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