Nondestructive evaluation of residual stress for thermal barrier coated turbine blades by Cr3+ photoluminescence piezospectroscopy

The role of beam dispersion in Raman and photo-stimulated luminescence piezo-spectroscopy of yttria-stabilized zirconia in multi-layered coatings

“…The signal from the alumina decays exponentially to zero at a YSZ thickness of ∼250 µm. This is consistent with values reported in the literature between 175 µm [35], [40] and [41] and 300 µm [42]. This variation of laser penetration depth in the YSZ layer depends on the microstructure, specifically the distribution and size of scattering sites such as grain boundaries, splat boundaries, cracks and pores in the translucent oxide.…”

The non-destructive and nano-microstructural characterization of thermal-barrier coatings

“…5,6,[17][18][19][20][21][22][23][24][25][26] The governing principles and the applicability of PSLS has been extensively reported, 5,6,[17][18][19][20][21][22][23][24][25][26] particularly for the determination of residual stress of the α-Al 2 O 3 in the TGO scale, and polymorphic phase constituents of Al 2 O 3 (e.g., γ, θ, and α phases). Figure 2 represents a typical evolution of photoluminescence spectra as a function of 1 h thermal cycling at 1,121°C (10 min.…”

Residual stresses in environmental and thermal barrier coatings on curved superalloy substrates: Experimental measurements and modelling

“…Two piezospectroscopic stress analysis techniques, Raman spectroscopy (RS) and photostimulated luminescence piezo-spectroscopy (PLPS) have been used to measure residual stresses within the ceramic top coat and TGO layer of various TBC systems [12,[34][35][36]. The procedure and calibration for the Raman spectroscopy measurements are described in [37,38].…”