Study of Nanostructures in High-Chromium Oxide Dispersion-Strengthened Steels

The structure of two high-chromium (~14–15 at % Cr) oxide dispersion-strengthened steels was characterized using atom-probe tomography and transmission electron microscopy. One of the steels was manufactured using the conventional technology for preparing oxide dispersion-strengthened steels, with mechanical alloying of the matrix steel and yttrium oxide Y2O3 powder. Another steel was produced by mechanically alloying an oxidized powder of matrix steel with the intermetallic compound Fe3Y. It was shown that the average size of oxide inclusions in the examined steels ranged from 5 to 6 nm, with a number density from 1 × 1022 to 4 × 1023 m–3. The average size of clusters varied from 2 to 3 nm, with a number density ranging from 1 × 1023 to 3.2 × 1023 m–3. These clusters were predominantly enriched in Y and O. Steel produced with the addition of Fe3Y exibited a high number density of clusters (~3 × 1023 m–3) and a lower number density of oxides (~1 × 1022 m–3) compared to steels manufactured conventionally. It was also demonstrated that the high chromium concentration in the materials increased its presence in the matrix, thereby enhancing the corrosion resistance of the steels.