In situ deposition behavior of SiO₂ on YSZ-TBC-coated IN738LC during a burner rig test

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• 作者：Min Tae Kim^a ; ^{mtkim@kepri.re.kr} ; ^{jasmint@paran.com} ; Yong Chan Jung^a ; Dongyi Seo^b ; ^{Dongyi.Seo@nrc-cnrc.gc.ca}
• 关键词：Gas turbine ; Burner rig ; In situ deposition ; Thermal barrier coating ; SiO2
• 刊名：Surface and Coatings Technology
• 出版年：2012
• 期刊代码：106_02578972
• 类别：ms
• 出版时间：25 June, 2012
• 卷：206
• 期：22
• 页码：4539-4545
• 文件大小：2083 K

摘要

This work was planned as a preliminary test to obtain an optimal condition for in situ deposition of SiO₂ on zirconia-based thermal barrier coating (TBC)-coated IN738LC specimens using a burner rig. The effect of the in situ deposited SiO₂ on the long-term reliability of TBCs upon cyclic burner rig operations will be tested in the next study. Tetraethylorthosilicate (TEOS), the precursor for the deposition, was fed admixed with methanol into the combustion chamber of the burner rig at an exhaust flame temperature of 1530 掳C. All five coating processes were selected by varying the concentration of TEOS in the mixture and applied to hollow type pin specimens infixed to the rotating carousel to face the downstream exhaust gas vertically. A total of 1500 cc of the mixture at a given vol.%TEOS was fed evenly to the burner rig for 54 min during the coating process.

After the process, TBC spallation was observed on the front side of the specimens processed with 10, 5, and 2 vol.%TEOS, while the specimen of 0.5 vol.%TEOS was coated with a ~ 5 渭m thick SiO₂ layer without any macroscopic damages. The surface of the coatings consisted of fractal-structured nodules at 10 vol.%TEOS, and of smooth grains at 0.5 vol.%TEOS. The spallation of SiO₂-coated TBC was attributed to the thermal mismatch due to the difference in the thermal expansion coefficients of the two materials. Based on these results, the mixing ratio of TEOS to methanol was reduced to 0.3 vol.%, which produced a 1-2 渭m thick, smooth and homogenous SiO₂ coating without any spallation of TBC. This deposition condition was chosen for the planned test to evaluate on the effects of the in situ deposition of SiO₂ on the long-term durability of TBC-coated IN738LC specimens upon cyclic burner rig operations.