Nondestructive Detection of Delamination of Thermally Sprayed Material Using ESPI

Detection of delamination of a thermally sprayed coating on an SUS304 substrate was carried out nondestructively using electronic speckle pattern interferometry (ESPI) method in both static and cyclic tests at T=298 K and 873 K. Results showed that the surface strain of the coating becomes smaller than that of the substrate when delamination occurs from the interface of the substrate. Two parameters of critical strain of e c and e f, which correspond respectively for the static test and the cyclic test, are introduced to evaluate the existence of delamination according to the e- σ s and e-N curve. It is considered possible to evaluate the occurrence of delamination in cyclic tests using the static critical strain of e c, instead of e f.