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Abstract
The effect of aerofoil geometry on the oxidative degradation mechanisms experienced by thermal barrier coatings (TBCs) used on industrial turbine blades has been investigated. Modified aerofoil-shaped samples (CMSX4 coated with high-velocity oxy-fuel sprayed AMDRY 995 and air plasma sprayed TBC) were oxidised at five temperatures in furnaces from 900 to 1000°C. Scanning electron microscopy and energy dispersive X-ray analysis were used to characterise details of the microstructural evolution of the thermally grown oxide and to monitor inter-diffusion between the bond coating and substrate. Additionally, a novel non-destructive examination technique (flash thermography) was used to detect and track the spread of cracks beneath the TBCs. Multiple samples cracking in identical locations suggested an effect of geometry in the failure of coatings. Furthermore, it was observed that coating curvature influenced spinel formation.