摘要
Experimental observations display that there exist two types of cracks induced by thermally grown oxide(TGO) in electron beam physical vapor deposition(EB-PVD) thermal barrier coatings(TBCs),which will lead to the coating spallation.Up to now,the failure mechanism is not clear.In the present research,based on the analysis for the experimental observations of the previous researches,a model for crack propagation and failure in TBCs is established,which covers the constitutive equation and the crack propagation criterion.Based on the model,a finite element method is developed,which is specifically for the failure of TBCs with real TGO morphology and with an image processing technique.Using the finite element method the coating failure mechanism under thermal mismatch stress is investigated.Present analysis and discussion show that the horizontal crack tends to propagate through the top coat layer toward the interface during the cooling stage,while the interface crack initiates at the points located in the middle region and then propagates in two side directions simultaneously,and mode II fracture plays a dominant role in the whole crack propagation process.Finally,two failure mechanisms of the TC/TGO interface at EB-PVD TBCs are proposed in this paper.
Experimental observations display that there exist two types of cracks induced by thermally grown oxide(TGO) in electron beam physical vapor deposition(EB-PVD) thermal barrier coatings(TBCs),which will lead to the coating spallation.Up to now,the failure mechanism is not clear.In the present research,based on the analysis for the experimental observations of the previous researches,a model for crack propagation and failure in TBCs is established,which covers the constitutive equation and the crack propagation criterion.Based on the model,a finite element method is developed,which is specifically for the failure of TBCs with real TGO morphology and with an image processing technique.Using the finite element method the coating failure mechanism under thermal mismatch stress is investigated.Present analysis and discussion show that the horizontal crack tends to propagate through the top coat layer toward the interface during the cooling stage,while the interface crack initiates at the points located in the middle region and then propagates in two side directions simultaneously,and mode II fracture plays a dominant role in the whole crack propagation process.Finally,two failure mechanisms of the TC/TGO interface at EB-PVD TBCs are proposed in this paper.
引文