The use of synchrotron x-ray micro computed tomography to study the failure mechanisms of thermal barrier coatings

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Khoshkhou, Danial (2017). The use of synchrotron x-ray micro computed tomography to study the failure mechanisms of thermal barrier coatings. University of Birmingham. Eng.D.

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Abstract

Thermal barrier coatings (TBCs) are used to protect high-pressure stage 1 turbine components in aero engines. At present the full potential high-temperature capabilities of TBCs cannot be utilised due to the difficulties in estimating the remaining useful life of in-service TBCs. State of the art non-destructive techniques, such as photo-luminescent piezospectroscopy (PLPS) have aided in furthering the understanding of damage evolution mechanism techniques, but are limited in applicability at temperature. In this work, a new force-balance model is presented for calculating the growth stress in a thermally grown oxide (TGO) layer at oxidation temperatures. Furthermore, a new experimental technique is explored for observation of the full-field strain distribution using synchrotron X-ray microtomography (SX μCT) coupled with digital volume correlation (DVC). The forcebalance method relates the creep in bondcoats of precision-machined cylindrical micro-specimens to the stress acted on the bondcoat by the TGO. These precisionmachined specimens were volumetrically imaged at the I12 JEEP beamline of Diamond Light Source (DLS) to reveal the three-dimensional evolution of TBC microstructure with time at temperature. The time-dependent volumetric image data acquired at DLS were processed using commercial digital volume correlation code to compute full-field displacement and strain distribution.

Type of Work:

Thesis (Doctorates > Eng.D.)

Award Type:

Doctorates > Eng.D.

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