Characteristics of Precipitation in an As-cast Nb- and V-containing High Nitrogen CrMn Austenitic Steel

The phase diagram of an Nb- and V-containing 18Mn18Cr0. 5N steel was investigated using thermodynamic calculation. The compositions and characteristics of precipitates were investigated by scanning electron microscopy, energy dispersive spectrometry, X-ray diffraction, and differential scanning calorimetry. Under equilibrium conditions, MX precipitates at 1350 °C. MX is a substitutional solid solution of Nb4 N3.38, and its composition (at. %) is approximately: Nb 40, N 40, V 8, and Fe, Cr, and Mn balance. The precipitates, with shapes including irregular bulk, rod, and ellipsoid, are primarily distributed at grain boundaries and triple junctions, and their size is approximately 5–10 μm. Finally, the microalloying of high nitrogen CrMn austenite steels, control of precipitate size, and the effect of precipitate on hot forming were discussed.