期刊
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
卷 417, 期 1-2, 页码 322-333出版社
ELSEVIER SCIENCE SA
DOI: 10.1016/j.msea.2005.11.014
关键词
thermal barrier coatings; durability; thermally grown oxide; pre-oxidation displacement instability; oxide grain structure; microstructure; lateral oxide growth; ratcheting
The role of pre-oxidation surface treatments on the oxide microstructure and the failure mechanism of multi-layer thermal barrier systems based on Pt-modified NiAl bond coats and electron beam deposited thermal barrier coatings (TBCs) have been studied. The primary pre-oxidation experimental variable was the partial pressure of oxygen in the pre-oxidizing atmosphere at constant temperature and bond coat composition. The durability of TBCs deposited on surfaces following different pre-oxidation treatments were measured and compared using furnace cycling tests. The oxide layers corresponding to different levels of TBC performance were characterized microstructurally, chemically, and compositionally using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) techniques. TBC performance was enhanced by the formation of a surface oxide having a coarse-grained columnar structure during the pre-oxidation process. Increased TBC durability was consistent with a slower oxide growth rate during exposure of the TBC to high-temperature, cyclic conditions, as was observed for this particular pre-oxidation condition. An oxide microstructure having fewer through-thickness transport pathways (grain boundaries) should also result in slower lateral oxide growth rates, consistent with a slowed rate of ratcheting as was observed in the pre-oxidized samples that had the best TBC performance. The desired surface oxide grain structure was achieved by pre-oxidizing the bond coat prior to TBC deposition at an intermediate partial pressure of oxygen. (c) 2005 Published by Elsevier B.V.
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