Abstract
In this study, we examine those properties of freestanding CoNiCrAlY thin film detached chemically from the coated substrate. Tensile tests are conducted using the small testing device, which was developed by us, inserted into a vacuum chamber of a scanning electron microscope (SEM). Based on SEM continuous observation during tensile loading of the thin film, the deformation and fracture mechanisms of freestanding CoNiCrAlY are discussed. It was found that CoNiCrAlY thin film has a typical brittle-ductile transition; it indicates brittle deformation and fracture at testing temperature lower than 700[K]. In the testing temperature higher than that, the CoNiCrAlY thin film elongates and is fractured with a high ductility. The reason for this transition was considered from SEM observations to be brought by mobility such as splat boundary sliding occurred during tensile loading. SEM also showed that a large inelastic deformation observed at the high-temperature is caused by the damage factors of both the micro cracking formed at splat boundary and the crack opening. Those factors leads to ductile fracture in CoNiCrAlY thin film exposed at the high temperature.
