China Foundry (Feb 2008)
Double oxide film defects in Ni-based super-alloy castings
Abstract
A new class of defects has been recently discovered, which are regarded as double oxide film defects. In this study, a number of Ni-based vacuum-cast test bars were investigated. The fractures in the broken test bars were observed by Scanning Electron Microscopy (SEM). Energy Dispersive Spectroscopy (EDS), as well as Wavelength Dispersive Spectroscopy (WDS) were used to characterize the chemical elements of the fracture's surface. Observation by SEM revealed the presence of inclusions identified as films that appeared to have initiated the growth of carbides. This study has added to the evidence that oxide film defects do exist in Ni-based super-alloy in certain vacuum casting conditions. It provides a reference for researchers' further study on the defects, and provides a possible direction for researchers to improve casting technology so as to remove these defects.
