PNNL

Abstract

The transport paths of O during intergranular oxidation in binary Ni-Cr were investigated. To isolate this corrosion scenario, a CO/CO2 gas mixture the oxygen potential was kept under the Ni/NiO equilibrium. A combination of electron microscopy and atom probe tomography (APT) was used to study the nanometer-scale details of the passivation and penetrative intergranular oxidation processes at high-energy grain boundaries. Oxygen transport towards the terminating oxidation front is elucidated with dedicated usage of oxygen tracer exchange experiments. Secondary ion mass spectroscopy and APT support classical theories of internal oxidation, revealing preferred transport paths at the oxide/alloy interface with sub-nanometer resolution.