Abstract
Fatigue crack propagation of Ni-base superalloy718 casting was investigated at room temperature, using CT specimen of thickness of 6mm. A fracture observatin and section observation were carried out about the specimen. In addition, crystallographic orientation analysis by the EBSD measurement of polishing surface under the fracture was performed. As a result, at the domain of ΔK = 16-18MPa√m, crack propagation was diagonal and a fracture depended on the metal organization, at the domain of ΔK = 18-21 MPa√m, crack propagation was straight and the fracture surface was like ductility, and at the domain ΔK =21-30 MPa√m was the same as a low ΔK. At the domains of ΔK =16-18 and 21-30, fatigue crack propagation rate were slow. In the domain of ΔK=18-20, it was fast fatigue crack propagation rate and crystallographic orientation was near to (100).
