Study of safety science focused on nano-structure for hot section parts of advanced gas turbines

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It is well known that residual stress affects degradation of thermal barrier coatings (TBCs). In this year, we evaluated the residual stress of thickness direction of the TBC by using synchrotron radiation Spring-8 at Japan Synchrotron Radiation Research Institute (JASRI). Moreover, development of high sensitive nondestructive evaluation technique based on results of previous financial year was carried out.Due to different coefficient of thermal expansion between a Ni base superalloy substrate and an yttria stabilized zirconia (YSZ) top coating, thermal stress of the TBC system is induced. Furthermore, due to operation for a long period of time, a thermally grown oxide forms and grows at the interface between the top coating and the bond coating, and then the thermal stress makes progress. It is possible to evaluate the residual stress on the surface of the TBC by using conventional X-ray diffraction (XRD). In this case, however, it can be possible to obtain information about only surface of the TBC. Therefore, the synchrotron radiation was used for evaluation of inside of the TBC. In this study, thermal cycle test, which heats up to 1000 deg.0 and then cool down to room temperature, was carried out. As a result, after 1 cycle, compressive residual stress of 80 MPa acts on inside of the TBC.Furthermore, a new nondestructive inspection (NDI) technique by electro-magnetic wave was developed for evaluation of the thickness of the TGO. By using the technique, we evaluated the TGO quantitatively. As a result, it makes it possible to quantitatively evaluate the TGO thickness by coefficient of reflection and phase angle. Moreover, in order to improve the sensitivity of the detection, wave guide sensor and high frequency (20GHz) signal were used. As a result, resolution of the detection improved with increasing the frequency.