Characterization of laser sealed coatings of yttria partially stabilized zirconia

Abstract

Abstract The present paper reports an experimental investigation based on X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), and wavelength dispersive spectroscopy (WDS) analyses of phases formed after laser sealing of plasma sprayed coatings of 8.5 wt% yttria partially stabilized zirconia (YPSZ). X-ray diffraction and X-ray step-scanning analyses showed that the plasma sprayed and sealed coatings consisted mainly of t ′ phase with a very small amount of monoclinic phase ( m phase) in the plasma sprayed coatings. It was also found that the small amounts of m and cubic phases ( c phase) present in the sealed coatings were dependent on laser processing specific energies (specific energy is equal to laser power/traverse speed x beam diameter). It was also found that rhombohedral ( r ) phase formed after laser sealing of coatings at higher specific energies. A direct relationship between c / a ratio of transformable tetragonal phase ( t phase) produced by thermal treatment of sealed coatings and nontransformable tetragonal phase ( t ′ phase) and the amount of Yttria was obtained. A new equation was derived, which describes the relationship between Yttria concentration and the c / a ratio of tetragonal phases ( t or t ′).