Effect of niobium on nitrogen solubility in high chromium steel

The interaction parameters of alloying elements on nitrogen in liquid Fe-Cr alloys containing niobium have been determined. The equilibrium nitrogen solubility in the liquid iron alloy was measured by metal-gas equilibrium technique under 0.04 to 1.0atm of nitrogen atmosphere at 1 823 to 1 923K. Nitrogen solubility in Fe-Cr-Nb melts obeyed Sieverts' law for all compositions studied in present study. The results obtained are summarized as follows; (1) The solubility of nitrogen markedly increased with increasing chromium and niobium. The interaction parameters in liquid iron alloys containing 10-18% of Cr and 0.2-2% of Nb are obtained. (2) The solubility of nitrogen was lower at a higher temperature in Fe-Cr melts in this study. (3) Test results indicated that it is not likely to form niobium nitride in Fe-Cr-Nb-N alloys and it was confirmed by EDS.