Acoustic emission analysis on tensile failure of air plasma-sprayed thermal barrier coatings

Abstract

An acoustic emission technique was used to monitor the cracking behavior and fracture process of thermal barrier coatings subjected to tensile loading. Acoustic emission signals were extracted and preformed by fast Fourier transform, and their characteristic frequency spectrums and dominant bands were obtained to reveal fracture modes. Three different characteristic frequency bands were confirmed, corresponding to substrate deformation, surface vertical cracking and interface delamination, with the aid of scanning electronic microscopy observations. A map of the tensile failure mechanism of air plasma-sprayed thermal barrier coatings was established. The fracture strength and interfacial shear strength were estimated as 45.73 ± 3.92 MPa and 20.51 ± 1.74 MPa, respectively, which are well in agreement with available results. Highlights: We established several good correlations between AE data and fracture modes. The correlations can be utilized to reveal cracking profile and coating failure. A tensile failure mechanism of coating system was established. Fracture strength of thermal barrier coating has been obtained by this method. The method has a large advantage to study the failure of coating/film materials.