NDE assessment of TBCs: an interim report of a photo-stimulated luminescence ‘round-robin’ test

Photo-stimulated luminescence spectroscopy (PSLS) can be used as a non-destructive tool to gain quantitative information about the stress and strain in the thermally grown oxide (TGO) formed beneath a thermal barrier coating (TBC) and possibly assess damage. In response to the increasing popularity of this technique, a ‘round-robin’ test has been initiated to compare methods of luminescence collection using different instruments as well as various spectral analysis methods. The interim results of this ‘round-robin’ are reported here with a series of PSLS measurements and analyses performed at four different laboratories on the same set of electron beam physical vapor deposited (EB-PVD) TBC samples, having undergone various oxidation treatments. In addition, a set of standard electronic spectra (collected from one group) were circulated for analysis in order to compare the curve-fitting methods used by each group. Apart from sample variations, there was very good agreement between the results obtained in the different laboratories, and there were no systematic differences in the data, indicating that present collection and analysis methods are comparable.