کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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1662208 | 1517704 | 2006 | 8 صفحه PDF | دانلود رایگان |

A correlation among thermal cycling lifetime, bond coat surface preparation, phase constituents and microstructure of thermally grown oxide (TGO) was examined for electron beam physical vapor deposited (EB-PVD) thermal barrier coatings (TBCs) consisting of ZrO2–7 wt.% Y2O3 (YSZ) ceramic topcoat, NiCoCrAlY bond coats and CMSX-4 superalloy. Variation in the bond coat surface is characterized based on surface roughness modification and pre-oxidation (1100 °C at PO2 of 10− 8 atm up to 4 h) carried out prior to YSZ deposition by EB-PVD. TBC specimens with pre-oxidized bond coats exhibited longer lifetimes than those without pre-oxidation, especially for metallographically polished bond coats. Given a surface roughness of NiCoCrAlY bond coats, TBC lifetime was observed to increase with an increase in the amount of α-Al2O3 in the initial thermally grown oxide (TGO) scale, which was detected by photostimulated luminescence (PL). Using focused ion beam in-situ lift out technique (FIB-INLO), site-specific preparation of thermally cycled TBC specimens for transmission electron microscopy (TEM) was successfully carried out. In addition to the presence of α-Al2O3, a small particulate phase identified as cubic Y2O3 was observed within the TGO scale by electron diffraction analysis on TEM.
Journal: Surface and Coatings Technology - Volume 200, Issues 20–21, 22 May 2006, Pages 5869–5876