Interfacial toughness evaluation of thermal barrier coatings by bending test

• Main Authors: Qi Zhu, Wei He, Lei Chen, Jianguo Zhu, Wenfeng Hao
• Format: Article
• Language: English
• Published: Elsevier 2018-01-01
• Series: Theoretical and Applied Mechanics Letters
• Online Access: http://www.sciencedirect.com/science/article/pii/S2095034917301058

ABSTRACT: Determining the interfacial properties of thermal barrier coatings (TBCs) is imperative for their durability evaluation and further improvements. A ceramic coating (topcoat) and a NiCoCrALY bondcoat were atmospheric-plasma-sprayed (APS) on a stainless steel substrate. A modified three-point bending test was adopted to initiate and propagate the topcoat/bondcoat (TC/BC) interfacial crack. After a complete delamination, the fracture surfaces were examined by an optical microscope, which shows that the cracking plane was merely on the TC/BC interface. Based on the experimental results of load–displacement and crack length–displacement, the strain energy release rate G for crack propagation was calculated, and the averaged magnitude was 77.1 J/m2. Repeatable results have indicated that the method can be used for the evaluation of interfacial fracture toughness in thermal barrier coatings and other multi-layer structures. Keywords: Thermal barrier coatings, Three-point bending, Interfacial fracture toughness