Elastic constants of LPPS stabilized-zirconia coatings

The elastic constants of yttria stabilised-zirconia coatings produced by a recently developed Low Pressure Plasma Spraying system were measured by in-situ diffraction in a four- point bending device. The anisotropic nature of the cubic zirconia coatings was investigated by collecting diffraction data under increasing load along two crystallographic directions ([440] and [620]). The four point bending was such to add compression to the measured coating surface, in order to progressively increase the compressive (residual) stress already present in the material. Unlike conventional Plasma Spray ceramic coatings, the elastic constants and the anisotropy of the studied LPPS coatings are comparable with those of the corresponding bulk materials. Average compressive residual stress in excess of –500 MPa was found in ~24 µm thick coatings.