Measurement of residual stress in air plasma-sprayed Y 2O 3–ZrO 2 thermal barrier coating system using micro-Raman spectroscopy

Abstract

Residual stress in air plasma-sprayed Y 2O 3 stabilized ZrO 2 thermal barrier coating (TBC) has been measured using micro-Raman spectroscopy. The frequency shift of Raman peak from tetragonal phase (≈640 cm −1) is used for determination of local stress in TBC. The relation between Raman peak shift and applied uniaxial stress is measured using a freestanding specimen. The relation is used to determine actual residual stress of the TBC layer coated on a stainless steel substrate. The uniaxial stress, σ ¯ t b c U , and Raman peak shift, Δ ν, on the freestanding TBC layer follows: Δ ν = Π ¯ σ ¯ t b c U ( Π ¯ = 25 c m − 1 GP a − 1 ) . The average in-plane residual stress in this layer is smaller than that obtained from thermal stress, although the trend of measured values versus thickness follows the estimated thermal stress-substrate thickness relation. This experimental evidence suggests that measurement by micro-Raman spectroscopy is an effective tool to determine local and average residual stress in the Y 2O 3 stabilized ZrO 2 TBC layer.