| Budget Amount *help |
¥2,700,000 (Direct Cost: ¥2,700,000)
Fiscal Year 2006: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 2005: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
The residual stresses in the zirconia thermal barrier coatings (TBCs), which were made by EB-PVD (electron beam-physical vapor deposition), were analyzed in order to improve reliability and thermal efficiency of a gas turbine. The TBCs as nano-coating were made by the EB-PVD method with rotating a substrate. The rotation of the substrate were 0rpm, 5rpm, 10rpm and 20rpm. The EB-PVD zirconia has strong preferred orientation and complicated structure. As a result, a conventional X-ray stress measurement is not applicable. The EB-PVD coating without rotation has columnar structure of <111> preferred orientation normal to the substrate. On the other hand, the TBCs with rotations of 5rpm, 10rpm and 20rpm have columnar structure of preferred orientation of <100>. The column structure with rotating EB-PVD is feather-like structure and its top is pyramidal shape made by (111) lattice plane.
The specimen was rotated on the in-plane spinner mounted on a Psi-goniometer and the in-plane stress was
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measured by a sine square method. The out-of-plane strain was measured by a strain scanning method with hard synchrotron X-rays. Combining between the in-plane stress and out-of-plane strain, the distributions of the out-of-plane stresses were obtained. The out-of-plane stresses in the TBCs with a rotation were very small.
For the in-plane stress, the TBC without rotation had a large compressive residual stress, and its compressive stress promoted the fracture of the coating. The compressive residual stress in the TBC decreased with the increase in rotation of the substrate. In addition to the above, the effect of oxidization on the distributions of the residual stresses in the TBC was investigated. The residual stress decreased due to sintering.
On the other hand, the behavior of internal stress with a thermal cycle was in-situ measured by hard synchrotron X-rays. The change in the internal stress of the 10rpm specimen was smaller than that of 5rpm. The rotation in the EB-PVD process is useful for the reduction of the residual stress. Less
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