Effects of oxygen and nitrogen on the rate of nitrogen dissolution in iron-chromium and iron-vanadium alloys

The rate constant of nitrogen dissolution in a Fe-20mass%Cr has been measured as a function of oxygen content by N-14-N-15 isotope exchange reaction at 1 973 K. Adsorption coefficient of oxygen on a Fe-20mass%Cr at 1 973 K has been determined to be 100 in terms of [mass%] from present results. This value is smaller than that on pure iron (0 mass% Cr), 144, which was determined by our previous work. Moreover, dependence of the rate constant of nitrogen dissolution in Fe-Cr and Fe-V alloys on nitrogen partial pressure has been measured by the same technique in order to investigate the adsorption effect of nitrogen itself. Adsorption coefficient of nitrogen calculated from present results is much smaller than that of oxygen and it is confirmed that nitrogen is not so surface active as oxygen in molten Fe-Cr and Fe-V alloys. However, it is observed that the value of adsorption coefficient increases from 0.0509 to 0.156 in terms of root P-N2 by addition of chromium up to 60 mass% Cr at 1 873 K. Addition of vanadium is more effective for increasing the adsorption coefficient and the value for Fe-6.2mass%V at 1 973 K is 6 times larger than that for pure iron.