Measurements and understanding of the stiffness of an air plasma sprayed thermal barrier coating

Abstract

In this work, the stiffness of an air plasma sprayed thermal barrier coating (APS TBC) was studied using the three-point bending technique. Various measurements over different time periods were made on detached TBC beams, prepared by acid etching, in both as-deposited states and after heat treatment. Monotonic and cyclic loading were conducted to understand the mechanical behaviour of the TBCs in detail. The TBC beams during bending show nonlinear behaviour, inelastic deformation and hysteresis loops. The derived global in-plane elastic modulus, at first increases and then decreases with thermal exposure, and is of the range 14–18 GPa. This behaviour is a result of competition between sintering and development of microstructural damage. Direct microstructural observations during In-situ mechanical testing show that intra-splat opening/closure and inter-splat sliding give rise to the relatively low elastic modulus of the APS TBC.