R. Vassen et al., Development of a micromechanical life prediction model for plasma sprayed thermal barrier coatings, MAT SCI E A, 303(1-2), 2001, pp. 100-109
A widely used method to produce thermal barrier coating (TBC) systems is th
e vacuum plasma spraying of a highly dense bondcoat layer with a defined su
rface roughness and the atmospheric plasma spraying (APS) of a porous (10 -
15%) Y2O3-stabilized zirconia top coat. In thermal cycling operation these
systems often fail by crack initiation and propagation close to the bondco
at-top coat interface. This failure is attributed to stresses arising from
the formation of a thermally grown oxide (TGO) layer on the rough bondcoat
surface. The actual stress situation is rather complex due to TGO formation
, creep effects in both bondcoat and top coat and due to the roughness of t
he bondcoat. All these factors have been take into account in the present w
ork by using a finite element method (FEM) to calculate stress development
during thermal loading. These results can then be introduced into a crack p
ropagation model to estimate crack development during the thermal cycling o
peration. The predictions of this approach are compared to experimental res
ults on the influence of bondcoat roughness on coating life. In these exper
iments TBC systems with bondcoat layers having three different levels of ro
ughness were cycled in a gas burner rig until failure. (C) 2001 Elsevier Sc
ience B.V. All rights reserved.