Behavior of synchronous reduction and nitridation of iron/vanadium oxides with NH3–H2 mixtures

Abstract

Ferrovanadium nitride, which comprises V and N, is an important alloy additive for the production of high-strength low-alloy steel. As an efficient reducing agent and nitrogen source, ammonia gas is widely used in the preparation of metal nitrides. In this study, ferrovanadium nitride alloy powder is prepared by reducing and nitriding VO2/Fe2O3 in NH3–H2 gas mixtures with different nitriding potentials. Thermodynamic analysis indicate that the reduction and nitridation of VO2 and Fe2O3 is feasible. VO2 is converted into VN, whereas Fe and Fe4N can be formed depend on the reaction conditions. Lower temperatures and higher nitriding potentials are beneficial to the formation of Fe4N. Based on Rietveld refinement analysis, the formation of Fe4N and the atomic occupancy of V and N in vanadium oxynitride, which is associated with the temperature, reaction time, and nitriding potential, is determined. A ferrovanadium nitride alloy powder with an O content of 0.26 wt.% is prepared by reducing and nitriding VO2/Fe2O3 at 900 °C for 1 h at a nitriding potential of 4.4 × 10−3 Pa−0.5.

Keywords

• Reduction
• Nitridation
• Phase transformation
• Ferrovanadium nitride
• Ammonia gas