Corrosion Performance of Oxide-Dispersion Strengthened Fe-Cr-Ni-Al Alloys in Coal Conversion Atmospheres

Profound interest has been shown in recent years in the development of oxide-dispersion-strengthened alloys for their exceptional creep resistance, high strength, and oxidation resistance at elevated temperatures. The mechanism of dispersion strengthening with suitable stable oxide particles offers the possibility of increasing the high-temperature strength of corrosion-resistant alloys without an associated loss in surface stability. In this study, iron-based alloys containing chromium, nickel, aluminum, and rare-earth oxides have been developed by mechanical alloying procedure. The presence of aluminum leads to alumina scales that exhibit superior corrosion resistance under oxidation and sulfidation conditions and in the presence of deposit materials. The presence of nickel and aluminum in the alloy leads to precipitation of Ni₃Al particles which enhance the mechanical properties of the alloy when compared with those of a ferritic alloy which contained no nickel. The austenitic structure of the present alloy should alleviate the ductile-brittle transition that is common in the ferritic alloys. Thermal aging of the alloys showed lack of porosity in the alloys, which is indicative of minimum notch sensitivity, an improvement over the materials currently available.