| LIU Kun,WANG Jiusi,DU Kangping,GUO Xiaoman,ZHANG Lei,HE Wenbing,DU Jinguang,MING Wuyi.Crack Growth in GZO/8YSZ Functionally Graded Thermal Barrier Coatings during Thermal Shock[J],54(7):189-202 |
| Crack Growth in GZO/8YSZ Functionally Graded Thermal Barrier Coatings during Thermal Shock |
| Received:August 07, 2024 Revised:December 02, 2024 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2025.07.016 |
| KeyWord:functionally graded thermal barrier coatings extended finite element method response surface methodology vertical crack horizontal crack |
| Author | Institution |
| LIU Kun |
Henan Key Lab of Intelligent Manufacturing of Mechanical Equipment,Zhengzhou , China;School of Mechanical and Electrical Engineering, Zhengzhou University of Light Industry, Zhengzhou , China |
| WANG Jiusi |
Henan Key Lab of Intelligent Manufacturing of Mechanical Equipment,Zhengzhou , China;School of Mechanical and Electrical Engineering, Zhengzhou University of Light Industry, Zhengzhou , China |
| DU Kangping |
School of Mechanical and Electrical Engineering, Zhengzhou University of Light Industry, Zhengzhou , China |
| GUO Xiaoman |
School of Mechanical and Industrial Engineering, University of Toronto, Toronto M5S2E8, Canada |
| ZHANG Lei |
School of Material Science and Engineering, Taiyuan University of Science and Technology, Taiyuan , China |
| HE Wenbing |
Henan Key Lab of Intelligent Manufacturing of Mechanical Equipment,Zhengzhou , China;School of Mechanical and Electrical Engineering, Zhengzhou University of Light Industry, Zhengzhou , China |
| DU Jinguang |
Henan Key Lab of Intelligent Manufacturing of Mechanical Equipment,Zhengzhou , China;School of Mechanical and Electrical Engineering, Zhengzhou University of Light Industry, Zhengzhou , China |
| MING Wuyi |
Henan Key Lab of Intelligent Manufacturing of Mechanical Equipment,Zhengzhou , China |
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| Abstract: |
| In the pursuit of enhancing the performance and longevity of thermal barrier coatings (TBCs) in harsh operating environments, functionally graded thermal barrier coatings (FG-TBCs) have garnered significant attention as a promising alternative to traditional design. FG-TBCs exhibit a unique ability to mitigate the detrimental interfacial effects that often plague the integration of dissimilar materials, achieving a harmonious blend of thermophysical properties across their compositional gradient. This integration not only alleviates thermal stresses, but also significantly improves the overall durability and service life of the coating system. The fundamental difference in the layer-by-layer composition of FG-TBCs leads to distinct crack propagation and failure mechanisms that are markedly different from those observed in conventional TBCs. Therefore, a meticulous investigation into the crack propagation mechanisms within FG-TBCs is imperative for the development of high-performance coatings with enhanced reliability and longevity. The present study delves into the microstructural intricacies of an 8% YSZ/Gd2Zr2O7 gradient TBC, utilizing advanced computational modeling techniques to simulate its behavior under operational conditions. By incorporating the UMAT subroutine within a finite element analysis (FEA) framework, a sophisticated model that captures the thermally and mechanically graded material properties of the top coat (TC) layer across a wide range of temperatures is constructed. This model incorporates realistic features such as porosity and lamellar structures, ensuring a high degree of fidelity in simulating the coating's response to thermal and mechanical stimuli. The model comprises four distinct layers:substrate (SUB), bond coat (BC), thermally grown oxide (TGO) layer, and ceramic top coat (TC). Each layer is meticulously defined based on its material properties and geometric dimensions, ensuring that the simulation accurately reflects the coating's actual structure and composition. To investigate the crack propagation behavior at the TGO/TC interface, an advanced technique, the extended finite element method (XFEM) is employed to simulate the growth and evolution of pre-existing horizontal and vertical cracks within the complex microstructural environment of the coating. By incorporating the Box-Behnken Design (BBD) methodology, the influence of various stress components — including radial (S22), axial (S11), and shear (S12) stresses — on the crack propagation patterns is systematically analyzed. The findings reveal several intriguing insights into the crack propagation mechanisms within FG-TBCs. Firstly, it is observed that the propagation length of cracks at the TGO/TC interface inversely correlates with the thickness of the TGO layer. As the TGO layer thickens, the crack propagation length and associated damage severity decrease, indicating that a thicker TGO layer can provide better resistance to crack propagation. Furthermore, the TGO/TC interface amplitude is identified as the most critical factor influencing crack propagation length, followed by TGO thickness and crack inclination angle. An interesting trend emerges, where crack propagation initially decreases with increasing interface amplitude before reversing at a critical value of λ=13.6 μm. This finding suggests that there is optimal interface amplitude that minimizes crack propagation, providing valuable insights for the design and optimization of FG-TBCs. In terms of crack initiation and propagation, the simulations indicate that the primary driving force for crack growth during the initial heating phase of thermal shock is thermal stress arising from temperature gradients within the coating.As the coating undergoes subsequent thermal cycles, crack growth and damage accumulation become increasingly dependent on the cumulative effects of stress. This understanding of the crack propagation mechanisms within FG-TBCs has significant implications for the development of advanced coating systems with enhanced resistance to thermal fatigue and improved service life. |
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