Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/41641

Title

Effects of thermal gradient and residual stresses on thermal barrier coating fracture

Author(s)

Qian, G.;  Nakamura, Toshio;  Berndt, Christopher C.

Abstract

Driving mechanisms which lead to internal crack growth and failure in the thermally sprayed coatings are identified using detailed finite element models. Coatings are assumed to contain embedded cracks and they are thermally loaded according to a typical high temperature environment. In order to determine the accurate stress state, the thermal gradient within the coating is calculated from the steady-state heat transfer analysis. Our models take into account various locations of cracks, temperature-dependent and -independent plasticity, thermal conductivities of different layers and thermal insulation across crack surfaces. The results indicate that the energy release rate of large cracks can reach close to fracture toughness of ceramic coatings. We have also studied the effect of residual stresses on the fracture behavior. For a penny-shaped crack located parallel to the coating layers, a limited influence of residual stresses is observed. The effect is more pronounced when the crack orientation is perpendicular to the coating layers where it has shown a beneficial influence. In both cases, the effects of residual stresses are relevant to the cracks close to the ceramic-bond interface. In addition, we have modeled functionally graded material and investigated its mechanical influence on the embedded cracks. The implications of the present work to internal crack initiation and growth, which can lead to coating failure, are also addressed.

Publication type

Journal article

Source

Mechanics of Materials, Vol. 27, no. 2 (Feb 1998), pp. 91-110

Publication year

1998

Keyword(s)

Crack initiation;  Crack propagation;  Failure analysis;  Fracture toughness;  Heat transfer;  Plasticity;  Residual stresses;  Sprayed coatings;  Stress analysis;  TBCs;  Thermal barrier coatings;  Thermal conductivity of solids;  Thermal effects;  Thermal gradients;  Thermal insulating materials

Publisher

Elsevier BV

ISSN

0167-6636

Publisher URL

http://dx.doi.org/10.1016/S0167-6636(97)00042-2

Copyright

Copyright © 1998 Elsevier Science Ltd.

Peer reviewed