Review of Thermodynamic Properties of the Cr-N System

Existing thermodynamic data for the Cr-N system were analyzed. High-temperature heat contents measured by Sato were reevaluated, and the heat capacity of Cr₂N was determined to be 15.05+6.58×10⁻³ T (°K) and that of CrN 11.10+ 1.58×10³ T . Using these heat capacities and an estimated ΔS°_{298, f} of 20×1 cal/°K-g atom N for the formation of the nitrides, second- and third-law calculations for all available vapor-pressure data were made. The two calculations agreed very well for the data of Mills. The heats of formation of Cr₂N and CrN are -31.8×1.0 and -28.4×1.5 kcal/mol, respectively. A partial phase diagram of the Cr-N system is presented.