Analysis Of Tensile Failure And Mechanical Properties Of EB-PVD Thermal Barrier Coating System By Using Digital Image Correlation Technique

As a kind of thermal protection structure system, thermal barrier coatings in demanding different service environment tests and experiments can effective improve the service temperature of turbine blade and reduce high temperature service environment for turbine blade metal base damage. High-temperature environment is difficult to predict the thermal barrier coating system interface failures and shedding problem, those greatly limits its wide application and reliability evaluation. Therefore, it is urgent to develop new experimental techniques and laboratory testing equipment to improve the mechanical properties of high-temperature thermal barrier coating system for the effective control over their failure mechanism. Based on improved traditional test equipment and developed a new method which can realize 1600 °C range of material mechanical properties testing. And the traditional system of EB-PVD thermal barrier coatings was analyzed in different working environment temperature tests and crack failure mechanism. The main contents are as follows,Firstly, the conventional DIC test equipment was upgraded, autonomous configuration the two high-temperature magnifying lens and blue filter, introduced specifically for the experiments on high temperature compensation light source. Fully solve the problem of the high temperature of the experiment, the lack of amplification, thermal radiation and the lack of light and other factors, and developed a new method which can achieve 1600 °C range of material mechanical properties testing and in the displacement field and strain field of benchmark to validate its feasibility. Improved the high-temperature speckle preparation method and successfully obtained the invention patents(CN103792117A).Secondly, based on the improved equipment and method, the evolution of the surface displacement field and the strain field of the adhesive layer in the whole tensile test was obtained by tensile test at room temperature and 800 °C~1000 °C. By extracting the accurate data of critical stage and initial crack, obtained that with the increase of temperature the critical fracture strain gradually decreased from 0.35% to 0.21%. The critical fracture strength gradually reduced from 700 MPa to 252 MPa. The critical shear strength gradually reduced from 117.6 MPa to 42.4 MPa. The failure mechanism under tension was summarized by using these strain mappings and scanning electron microscope observations.Thirdly, the Raman spectra obtained residual EB-PVD thermal barrier coating system of ceramic layer on the surface of the stress value. Then use the high temperature test platform, the temperature as the only variable tensile test at room temperature and 800 °C~1000 °C temperature range. Accurate access to the whole process of tensile test in EB-PVD thermal barrier coating system of surface displacement field and strain field evolution, and through the extraction of accurate data on key stage and key crack, the critical fracture strain of EB-PVD thermal barrier coating system of ceramic layer gradually decreased from 0.45% to 0.12%. Corresponding to the critical fracture strength gradually decreased from 239.7 MPa to 74 MPa. Critical the shear strength is gradually reduced from 53.8 MPa to 20.5 MPa. Similarly, the possible failure modes of EB-PVD TBCs system under tension at service temperature were summarized by using these strain mappings and scanning electron microscope observations.