Corrosion Resistance of Fe-Cr-Si Alloy Powders Prepared by Mechanical Alloying

Powders with nanometric crystallites of two ternary alloys Fe0.90Cr0.05Si0.05 and Fe0.85Cr0.10Si0.05 were prepared by mechanical alloying (MA) in a planetary high-energy ball mill at various milling times followed by annealing in a vacuum at 900 K to induce an oxygen-induced surface segregation of Cr and Si atoms. The prepared powders were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The obtained results show that all prepared powders crystallize in the body-centered cubic structure and are composed of micrometric particles, which are polycrystalline and consist of many nanometric crystallites. The mean size of the particles as well as the crystallites decreases progressively with milling time. In order to study the anti-corrosion properties of the obtained materials, the powders were exposed to atmospheric gases at 870 K. After each oxidation step, the formation of iron oxides was investigated using 57Fe transmission Mossbauer spectroscopy (TMS). It was found that the powders of Fe0.90Cr0.05Si0.05 and Fe0.85Cr0.10Si0.05 obtained after 10 and 20 h of MA are extremely resistant to oxidation. This result can be connected with the fact that XPS measurements reveal a high concentration of Cr and Si atoms on the surface of powder particles.