Recent Progress of Experimental and Measuring Technology. X-Ray Elastic Constants and Residual Stress Distributions of Zirconia Thermal Barrier Coating.

Abstract

Accurate values of X-ray elastic constants are required for a reliable stress measurement of thermal barrier coating films (TBC films). In this paper, atmosphere and pressureless plasma sprayed TBC films were removed from substrates, then X-ray elastic constants of both TBC films were determained by using newly developed tensile jig. For the atmosphere plasma sprayed film, the value of the mechanical elastic constant was much smaller than the X-ray elastic constant owing to cracks or pores existing in the films. The X-ray elastic constant of the atmosphere plasma sprayed TBC film was nearly equal to that of the pressureless plasma sprayed film. This means that the X-ray elastic constants are little influenced by cracks or pores. Residual stress distributions in both films coated on the substrates were obtained. In the surface region with the depth up 60 μm, residual stresses of both films showed a drastic variation. This variation of the residual stresses was build up during rapid quenching and solidifying of the molten droplet. In deeper regions, residual stresses were nearly constant. These constant values of residual stresses are caused by the thermal strain mismatch between the TBC film and the substrate.