Effect of Process Control Agent on Microstructures and High-Temperature Oxidation Behavior of a Nickel-Based ODS Alloy

Two nickel-based oxide-dispersion-strengthened (ODS) alloys supplemented with different amounts of process control agent (PCA) were prepared. The microstructures including grains and nanometric oxides and the subsequent oxidation behavior of these ODS alloys were investigated. It was found that the distribution of nanometric oxides in the nickel-based ODS alloy is uniform and the grains are refined by adding a proper amount of PCA in the mechanical milling, while the blocking effect on the diffusion of active elements Y, Al and Ti among powders takes place with an excessive amount of PCA, resulting in the precipitation of large-size oxides in local areas of the alloy. After oxidation in air at 1000 degrees C for 200 h, the oxide scales on the surface of both nickel-based ODS alloys are composed of Cr2O3. As Y-rich oxide particles are precipitated in the matrix, the thickness of the oxide scale is significantly reduced compared with non-ODS alloys. However, due to the influence of grain boundaries on the diffusion of elements, the oxide scale on the surface of an alloy with finer grain size is thicker. The oxidation resistance of ODS alloys strongly depends on the exact manufacturing process.