Degradation of Thermal Barrier Coated Superalloy Component During Service

Lee, Han-sang; Yoo, Keun Bong; Kim, Eui Hyun; Kim, Sung Chul; Ryou, Sangsoo

doi:10.1007/s11668-007-9045-1

Cited by 1 publication

(1 citation statement)

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“…4(c)) acting as aluminum reservoir in bond coat were totally exhausted in both specimens. Many studies attribute TBC failure to surface oxidation on bond coat, and thickness of TGO and β depleted zone in bond coat as a function of time and temperature have been suggested for evaluating the remaining time of TBC [6,8,9]. The β phase depletion occurs at the outer surface of bond coat due to TGO formation, and at the bond coat / substrate interface due to interdiffusion [10].…”

Section: Methodsmentioning

confidence: 99%

Degradation of thermal barrier coated superalloy component during service

et al. 2009

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The time dependent degradation of first-stage blades for gas turbine was investigated. First, Two used blades were prepared from the operating facilities, and their operating hours were 25,000 and 52,000 hrs, respectively. Microstructural comparison of coating surfaces showed that exposure to the environment increased thickness of TGO (Thermally Grown Oxide) and β depletion region, and then debonding and spallation of TBC (Thermal Barrier Coating) occurred finally. In the case of substrate, Ni-based superalloy, the shape and size of γ` were changed with increasing operating time. Especially, in the leading and trailing edges of blades, the size of γ` was bigger and the shape was more elliptic than other region. It can be thought that the leading and trailing edges of blades can be the starting point of degradation in first-stage blades. Second, TBC failed blade used for 22,000 hrs was prepared and compared with other two blades. Large interfacial cracks were formed between top and bond coat, and TGO was not uniform and continuous. The chemical composition analysis on bond coat showed that low chromium content is responsible for the formation not only of Al oxide but also of Co, Cr, Ni oxides.

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Section: Methodsmentioning

confidence: 99%