Basic approach on creep deformation and damage of high temperature structural materials under temperature gradient condition

Abstract

Deformation and failure behavior of a Ni-base superalloy specimen with thermal barrier coating were investigated when it was subjected to external load under a graded temperature condition. The experimental results demonstrated that the crack density in the ceramic top coat was higher at lower temperature side than that at higher temperature side. It was also observed that the inelastic strain rate of the specimen was higher, compared with that of the laboratory creep test without temperature gradient. In order to get basic understanding on the above specific behaviors, a simple two-dimensional creep deformation model was proposed, taking account of the effect of temperature gradient. In the model the stress state was analyzed when the material is uniformly deformed associating with diffusion creep. The numerical calculation result predicted the following noteworthy phenomena: higher stress state would be build up at the lower temperature side than at the higher temperature side, and this state is promoted with time. Cumulative creep strain develops more quickly at the lower temperature side than at the high temperature side. These predictions provided some reasonable explanations to the experimental results.