K. J. Lawson, Cranfield University, School of Applied Sciences, Bedford, United Kingdom; L. J. Ritchie, Cranfield University,, Bedford, United Kingdom; L. Xie, M. R. Dorfman, Sulzer Metco (US) Inc., Westbury, NY
The monoclinic and tetragonal phase compositions and distribution in air plasma sprayed (APS) yttria-partially stabilised zirconia (YPSZ) thermal barrier coatings were studied. The coatings were produced from powders with varying phase concentrations, chemical purity and powder production processes. Both the powders and coatings were characterised using X-ray diffraction (XRD) and Raman spectroscopy. The use of environmental scanning electron microscopy (ESEM) and X-ray energy dispersive analysis (EDS) added morphological and elemental information to the study. XRD and Raman spectroscopy were shown to be powerful combined tools and showed an overall decrease in the monoclinic phase within the coatings produced from the different powders. The distribution of both the monoclinic and the tetragonal phases could be highlighted both in the coatings and the individual powder particles. This indicated changes in monoclinic concentration in the less dense areas of some of the coatings and a varying distribution across particles in some of the powders. Raman mapping over small areas also showed how phase surface distribution, on the coatings surfaces, could be assessed.
Summary: Phase composition in yttria partially stabilised zirconia powders and air plasma sprayed thermal barrier coatings were characterised using Raman spectroscopy and X-ray diffraction.Comparison was made between coatings produced from powders manufactured through differing process routes.
