PHASE-EQUILIBRIA IN THE CR-NI-C SYSTEM AND THEIR USE FOR DEVELOPING PHYSICOCHEMICAL PRINCIPLES FOR DESIGN OF HARD ALLOYS BASED ON CHROMIUM CARBIDE

The Cr-Ni-C phase diagram at the melting point was plotted by a combin ation of procedures (metallography, x-ray, microprobe, differential th ermal analysis, Pirani-Alterthum method, etc.). A general feature of t his system is the existence of equilibria between the nickel-based pha se and all the other phases. The temperature of the quasibinary (Ni) (Cr7C3) eutectic was determined to be 1324 +/- 6 degrees C. Based on both the phase diagram of the Cr-Ni-C system and the bending strength and Rockwell hardness of the alloys, the optimal composition of the in itial carbide ingredient for production of hard alloys based on Cr3C2 with nickel-phosphorus binder was estimated as 13.0-13.3 at.%, substoi chiometric with respect to Cr3C2.