Research On Evaluation Of The Integrity Of FeCrAl /Q345 Coating Interface Based On The Local Approach

At present, in astronautics, aviation and so many industry domains, each kind of thermal spraying coating technology has already been widely used in enhancing the performance of the mechanical components and lengthened their service life. The integrity of coating/substrate system is critical for the components'security, and the union intensity of coatings has become one of many important standards in the applicability of coatings. For the purpose of seeking a method to evaluate the integrity of coating/substrate system interface, the applicability of traditional fracture parameter J integral in interface fracture problem and evaluation of interface fracture behavior of FeCrAl coating/Q345 steel substrate based on the local approach have been studied in this paper.In this paper, the statistics theory of brittle material fracture is presented. And the local approach of interface crack is shown.The 3-point bend test has been used to measure interface bond intensity(critical fracture load Pc) of FeCrAl coating/Q345 steel substrate system with prefabricated fatigue crack, and the 4-point bend test had been used to measure interface bond intensity(critical fracture load Pc) of FeCrAl coating/Q345 steel substrate system with prefabricated notch. These experiments provide experiment data for fracture mechanics analysis.ABAQUS software is used in finite element analysis. The JC values of the eight C3PB specimens when the interface fracture occurs are Calculation, and it's seen that the JC values of the eight specimens with prefabricated fatigue crack are very dispersive. It's shown that JC can not be used as the single fracture parameter to evaluate the interface fracture behavior.With experiment data of interface bond intensity of two bend form specimens, the local approach is used to analyze geometry and load dependence of FeCrAl coating/Q345 steel substrate system for interface fracture behavior. In addition, the local approach is used to predict the interface fracture behavior. It is found that the Weibull stress(σW) for all specimen geometries almost are identical under the same fracture probability when the interface fracture initiation occurs for different specimen geometries. Moreover, the interface fracture behavior of one type of specimens with notch has 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 the notched specimens gives a good agreement with the test results. In a word, the geometry dependence of the interface brittle fracture toughness data can be reduced through the local approach's application. It showed that the local approach not only can be used to describe the interface fracture behavior, but also can be used in the integrity evaluation for interface between different materials.In the case of the same constitution of Q345 steel substrate, the fracture failure probability of FeCrAl/Q345 coating system is compared with that of LX88A/Q345 coating system. It's found that the fracture failure probability of FeCrAl/Q345 coating system is higher than that of LX88A/Q345 coating system.