Delamination mechanism and assessment of thermal barrier coating system under thermal cycling
Peishan Ding, Tianshu Cai, Jianwei Sun, Linwei Ma, Xiaotao Zheng, Haofeng Chen
Abstract
Temperature-dependent Linear Matched Method for shakedown and reversed plasticity assessment of thermal barrier coating system is developed to simulate and explain the delamination failure mechanism of thermal barrier coating system with vertical surface crack under thermal cycling. The dimension of vertical surface crack and geometric discontinuity of thermally grown oxide layer are stressed. Results show that comparing with the geometric discontinuity parameters, the depth of vertical surface crack has more significant impact on shakedown boundaries of thermal barrier coating system. Interestingly, the predicted reversed plasticity region initiates at the upper surface of wave valley for the thermally grown oxide layer, which is the delamination failure region verified by microscopic observation. This indicates that the reversed plasticity is the main mechanism for the thermal barrier coating system subjected to thermal cycling and the depth of vertical surface crack obviously accelerates the delamination process. Accordingly, the shakedown limit evaluation approach is proposed for the safety assessment of thermal barrier coating system subjected to thermal cycling.