Spallation of thermal barrier coatings with real thermally grown oxide morphology under thermal stress. (15th May 2018)

• Record Type: Journal Article
• Authors: Zhu, W.; Zhang, Z.B.; Yang, L.; Zhou, Y.C.; Wei, Y.G.
• Is Part Of: Materials & design. Volume 146(2018)
• Page Start: 180
• Page End: 193
• Publication Date: 2018-05-15
• Subjects: Thermal barrier coatings -- Real thermally grown oxide morphology -- Thermal stress -- Crack propagation -- Failure mechanism; Materials -- Periodicals; Engineering design -- Periodicals; Matériaux -- Périodiques; Conception technique -- Périodiques; Electronic journals; 620.11
• DOI: 10.1016/j.matdes.2018.03.019
• Languages: English
• ISSNs: 0264-1275

Abstract

Abstract: 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 induced by TGO is not clear. In this work, a finite element model with real thermally grown oxide morphology for crack propagation in TBCs is established by taking the advantage of commercial finite element package (ABAQUS) and image processing technique (Coreldraw). The coating failure mechanism under thermal mismatch stress is investigated. Present analysis and discussions 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 are proposed in this paper. Graphical abstract: Unlabelled Image Highlights: Thermally grown oxide morphology influences significantly the stress distribution. Mode I fracture dominates in the interface of the valley region, whilst mode II in other regions. As no horizontal crack existing, the spallation of the ceramic layer occurs due to the development of the interface crack. As horizontal crack existing, the spallation is attributed to the interaction between the horizontal and the interface crack.