High temperature fatigue deformation behaviors of thermally sprayed steel measured with electronic speckle pattern interferometry method

High temperature fatigue (R=0) damage and deformation behaviors of SUS304 steel thermally sprayed with Al2O3/NiCr coating were investigated using an electronic speckle pattern interferometry (ESPI) method. Surface cracks and delamination occurred after 1×105 cycles test when σmax was 202 MPa at 873 K. The lengths and number of cracks and delamination largely decreased when σmax or temperature decreased to 115 MPa or 573 K, respectively. Strain values along cracks measured with the ESPI method were much larger than other areas due to crack opening under the tensile load. The positions of strain concentration zones on strain distribution figures by ESPI method were well corresponded to those of cracks on sprayed coatings. Strain values decreased largely where local delamination occurred.