Abstract
The purpose of this study was to understand the effects of thermal exposure on residual stress in thermal grown oxide (TGO) on CoNiCrAlY coatings, which were fabricated by air plasma spraying (APS), high velocity oxygen fuel spraying (HVOF) and low pressure plasma spraying (LPPS) on a nickel base alloy, respectively. The thermal exposure tests were conducted in air at 1000 ℃ and 1100 ℃ for up to 1000 hours using an electric furnace. X-Ray Diffraction (XRD) shows the presence of the γ phase and β phase in the coating. The residual stresses in the TGO layer were measured by photo-stimulated luminescence spectrum. It was shown that the residual stress in the TGO layer on APS coating was the highest and on LPPS coating was the lowest. The residual stress in the TGO layer decreased with an increase in thermal exposure time up to 300h.
