Grant-in-Aid for Scientific Research (B).
|Allocation Type||Single-year Grants|
Materials/Mechanics of materials
|Research Institution||The University of Tokyo(1999-2000)|
Nagaoka University of Technology(1998)
OKAZAKI Masakazu The University of Tokyo, Schoool of Engg., Assoc.Prof., 大学院・工学系研究科, 助教授 (00134974)
KAKEI Koji Tokyo Metro. Univ., Assoc.Prof., 工学部, 助教授 (70185726)
SAKANE Masao Ritsumeikan Univ., Schoool of Engg., Prof., 理工学部, 教授 (20111130)
KITAMURA Takayuki Kyoto University, Schoool of Engg., Prof., 大学院・工学研究科, 教授 (20169882)
YAMADA Yasuhiro Niigata Inst.Tech., Research Assoc., 工学部, 助手 (70291755)
TADA Yaoya Kyoto University, Schoool of Engg., Research Assoc., 工学部, 助教授 (70243053)
|Project Period (FY)
1998 – 2000
Completed(Fiscal Year 2000)
|Budget Amount *help
¥12,500,000 (Direct Cost : ¥12,500,000)
Fiscal Year 2000 : ¥600,000 (Direct Cost : ¥600,000)
Fiscal Year 1999 : ¥2,500,000 (Direct Cost : ¥2,500,000)
Fiscal Year 1998 : ¥9,400,000 (Direct Cost : ¥9,400,000)
|Keywords||Industrial Gas Turbines / Coatings / Thermo-Mechanical Fatigue / Life Prediction / Medelling / Single Crystal Ni-base Superalloy / DS Superalloy / Pollycrystalline Alloys / Ni基超合金 / 単結晶 / 疲労強度|
Collaborative research, which cover the themo-mechanical fatigue (TMF) and isothermal low-cycle fatigue (ILCF) strengths of Ni-Base superalloys and the protective coatings at elevated temperatures, has been carried out. Based on the observations of the crack initiation, the fracture surface and the dislocation structures, the effects of the substrate alloy and the coating on the TMF and ILCF lives are presented in this paper. The correlation between the TMF and ILCF are also discussed.
The results obtained by the collaborative research are summarized as follows :
(1) The TMF lives, as well as the ILCF, were strongly dependent of the substrate alloys. The single crystal and directionally-solidified alloys and their coatings generally exhibited the most excellent properties, compared with those of the traditional pollycrystalline alloy.
(2) The observation of dislocation structures indicated that the controlling and deformation mechanisms were intrinsically different between TMF and ILCF in
the Ni-base superalloys. Accordingly, it must be unreasonable in principle to reproduce and to estimate the TMF failure of the Ni-base superalloys by the ILCF tests.
(3) Remarkable reductions in the TMF life of the Ni-base superalloy coatings under the out-of-phase condition was found to occur, compared with that of the substrate. It was shown by the investigation of the crack density that this was due to the low ductility of the coating film at the temperatures at which the maximum tensile strain was reached in the TMF tests, resulting in severe crackings. Hence, it is essential for the TMF life prediction of Ni-base superalloy coatings to get understandings not only on the substrate but also the coating film.
(4) Regarding as the TMF failure of the coatings, attention should be paid to the results by ILCF tests which can provide us a somewhat misleading information : e.g., the TMF lives under the out-of-phase condition were significantly reduced by the coating, although the ILCF one at 900℃ was improved. Less