2005 Fiscal Year Final Research Report Summary
Mechanics and Mechanisms on Adhesion of Thermal Barrier Coating : Towards Improvement and Design of Thermal Fatigue Endurance.
| Project/Area Number |
15360046
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Materials/Mechanics of materials
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| Research Institution | Nagaoka University of Technology |
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Principal Investigator |
OKAZAKI Masakazu Nagaoka University of Technology, Dept.Mech.Engg., Professor, 工学部, 教授 (00134974)
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| Co-Investigator(Kenkyū-buntansha) |
KITAMURA Takayuki Kyoto University, Graduate School of Engg., Professor, 大学院・工学研究科, 教授 (20169882)
OGAWA Kazuhiro Tohoku University, Graduate School of Engg., Associate Professor, 大学院・工学研究科, 助教授 (50312616)
IMATANI Katsuzi Kyoto University, Graduate School of Engg., Associate Professor, エネルギー科学研究科, 助教授 (70191898)
YAMAZAKI Yasuhiro Niigata Institute of Technology, Dept.Mech.Engg., Associate Professor, 工学部, 助教授 (70291755)
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| Project Period (FY) |
2003 – 2005
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| Keywords | Thermal barrier coatings (TBCs) / Thermal cycles and fatigue / Mechanical properties / Process variables / Ni-based superalloys / Splat structure / Size effect / Adhesion strength |
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| Research Abstract |
Thermal barrier coatings (TBCs) with high performance have been essential for next generation advanced gas turbines operating at extremely high temperatures. Towards improvement and design of thermal fatigue endurance of TBCs, a series of experimental works have been carried out to get basic understandings on the following articles : how the mechanical properties of ceramic top coat film in TBCs, especially elastic moduli, should be evaluated ; what effect(s) the process variables have ; how high is the adhesion strength of ceramic top coat with Ni-based superalloys substrate and how it should be evaluated ; and how high is the residual stress in TBCs and how it should be evaluated. Elastic stiffness of air plasma sprayed (APSed) YSZ (; ZrO2 stabilized by 8 wt. pct. Y2O3) top coat specimen, which is frequently used for thermal barrier coating (TBC) system for advanced gas turbines, was measured by employing the macro-, micro-, and nano-indentation methods. The elastic stiffness was measured, following the Oliver-Pharr method. It was shown that the elastic stiffness of the YSZ, as well as the microstructure, were significantly influenced by the spraying conditions employed. Especially the size of ceramic powders used were found to have the most pronounced effect. It was also shown that the elastic stiffness revealed significant size effect : that is, there were significant differences in elastic stiffness between the macro-, micro-, and nano-indentation methods. The above size effect was discussed, correlating with some relating phenomena during the indentation process : crackings, sink-in, pile-up and spalling ; as well as with the characteristic microstructures of the sprayed top coat. Based on these knowledge, special discussions have been made on which type of microstructure should be controlled to develop high performance TBCs and how it can be realized through a control of spraying process variables.
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