Research On Interface Fracture Behavior Of TBCs/Q345 System Based On Local Approach

TBCs(Thermal Barrier Coatings) is one of the most advanced high temperature protective coatings, which can produce large temperature drop between high-temperature gas and the metal parts as the matrix, Using TBCs can lengthen their service lives and make the machine more effective. So the union intensity between coatings and matrix has become one of most important standards in the applicability of TBCs.This paper begins with the method of assessing the integrity of coating/substrate system. In this paper, interface fracture parameters of coating/substrate system and evaluation of the interface fracture behavior based on Local Approach had been studied.By means of improved tensile test method, the critical interface fracture loads(Pc) of the coatings system with two different prefabricated crack size were obtained. For the purpose of getting stress-strain field, these tests were combined with finite element analysis. The complex stress intensity factor was computed using the definition of complex stress intensity factor. The result showed that the tensile load near the crack tip was dominant, and the tensile load had higher effect than the shear load. The research found the K-dominant zone existed near the crack tip for total specimens in this tensile test.ABAQUS software was used to execute finite element analysis. The JC values of the eight specimens A when the interface fracture occurs were calculated, and found that the JC values of the eight specimens with prefabricated fatigue crack were very dispersive. It's shown that the use of traditional single-J integral fracture parameters to evaluate the interface fracture was not suitable. With experiment datas of interface bond intensity of two different tensile form specimens, the local approach was used to analyze interface fracture behavior of TBCs/Q345 system. In addition, the local approach was used to predict the interface fracture behavior. It was found that the Weibull stress (σW) for all specimen geometries almost were identical under the same fracture probability. Moreover, the interface fracture behavior of another types of specimens with different crack size had been predicted from the test results of pre-crack specimens based on the local approach for interface brittle fracture, and the predicted distribution of the critical load for another specimens gave a good consistent with the test results. In a word, the local approach can not only be used to describe the interface fracture behavior, but also can be used to evaluate the integrity for interface between different materials.