Development of L12-ordered Ni3(Al,Ti)-strengthened alumina-forming austenitic stainless steel alloys

The stability of coherent L12-ordered Ni3(Al,Ti) intermetallic precipitates was studied in Fe–14Cr–32Ni–3Nb–(3–4)Al–(1–3)Ti (wt.%) based alumina-forming austenitic stainless alloys. Computational thermodynamics predicted the formation of multi-intermetallic phases, including L12 and β-NiAl (B2), in an austenite matrix below ∼900 °C. Microstructure characterization revealed a significant stabilization of the L12 phase by Zr addition, with the amount of L12 increasing with increasing Ti addition. However, the Ti addition also degraded the oxidation resistance. Further additions of C and B successfully improved both creep and oxidation properties.