Specific features of residual stress measurements in thermal barrier coatings

Abstract

Techniques for measuring the residual stresses in bilayer thermal barrier coatings of a NiCrAlY alloy metal sublayer and 8-wt% stabilized ZrO₂–8Y₂O₃ ceramic upper layer are developed with the inhomogeneous composition and stress relaxation upon removal of the top layers taken into account. The outer ceramic layer is shown to undergo quenching-induced tensile stress up to 200 MPa, whereas the metal sublayer is subjected to compressive stress of 600 MPa which is associated with an increase in the specific volume as a result of the formation of a thermally grown oxide (TGO).