High Temperature Fatigue Deformation Behavior of Ceramics Thermally Sprayed SUS304 Steel Measured with an ESPI System
Mitsuo KIDO, Rongguang WANG, Syouzou NAKAMURA, Mutsumi TAKEDA, Masahiro YAMAZAKI and Tarou TOKUDA
Abstract:In this paper, the surface strain of an Al2O3/Ni-Cr atmospheric plasma thermally sprayed SUS304 steel specimen during the fatigue test (max=173MPa, R=0, 873K) was measured with an electronic speckle pattern interferometry (ESPI) system. The relationship between surface strain and crack initiation / delamination behavior was discussed. The strain value obtained from the ESPI system was confirmed to be almost the same as that obtained from a strain gauge on an un-sprayed specimen when tensile stress was loaded at 293K. Thermal expansion deformation and stress deformation at high temperatures were easily measured with the ESPI system. The presence of cracks and delamination on a sprayed coating can be detected in situ and the strain concentration or disappearing can be detected without damage. The sprayed specimen surface strain was almost the same as the un-sprayed specimen at 873K, which indicates that deformation of the sprayed coating is always associated with substrate surface deformation at high temperature. The maximum surface strain was lower after 1~105 cycles fatigue than after 2 cycles fatigue. Surface cracks occurred but stopped at the inner Ni-Cr layer after 2 fatigue cycles at 873K. Many surface cracks and delaminations along the interface between the Ni-Cr layer and substrate were confirmed after 1~105 fatigue cycles. Key Words:Alumina ceramics, Thermally spraying coating, Electronic Speckle Pattern Interferometry (ESPI), Fatigue, Strain, Deformation