EPMA and TEM characterization of intergranular tellurium corrosion of Ni-16Mo-7Cr-4Fe superalloy

The corrosion behavior of a Ni-16Mo-7Cr-4Fe alloy was investigated in a tellurium (Te) vapor atmosphere at 800 °C. Te was identified via electron probe microanalysis at the grain boundary regions of the corroded alloy. The morphology, chemical composition, and crystalline structure of those areas were characterized in a transmission electron microscope. Chromium tellurides were observed at both grain boundaries and intergranular carbide-matrix interfaces. Based on the results, the mechanism of intergranular Te corrosion and its possible correlation with intergranular cracking is discussed.