Nitriding of chromium in nitrogen gas at high temperatures

Abstract

Parabolic rate constants of the reaction of chromium with nitrogen gas under oxygen-free conditions have been determined over a range of temperature (1000–1250°C) and nitrogen pressure (0.265–101.33 kPa). The growth rate of the subnitride was measured by a thermogravimetric technique using a single specimen. Wagner's oxidation theory is used to calculate the self-diffusivity and intrinsic diffusivity of nitrogen in the subnitride from a theoretical analysis of the parabolic rate constant. The calculated diffusivities varied with the composition of the subnitride, having minimum values at intermediate compositions of the nonstoichiometric chromium nitride “Cr₂N.”