TY - JOUR
T1 - Effects of phase constituents/microstructure of thermally grown oxide on the failure of EB-PVD thermal barrier coating with NiCoCrAlY bond coat
AU - Liu, J.
AU - Byeon, J. W.
AU - Sohn, Y. H.
PY - 2006/5/22
Y1 - 2006/5/22
N2 - 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.
AB - 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.
KW - Photoluminescence
KW - Surface modification
KW - Thermal barrier coatings
KW - Thermal cycling
KW - Thermally grown oxide
UR - https://www.scopus.com/pages/publications/33645832380
U2 - 10.1016/j.surfcoat.2005.08.140
DO - 10.1016/j.surfcoat.2005.08.140
M3 - Article
AN - SCOPUS:33645832380
SN - 0257-8972
VL - 200
SP - 5869
EP - 5876
JO - Surface and Coatings Technology
JF - Surface and Coatings Technology
IS - 20-21
ER -