STABILITY OF CARBIDE PHASES IN NI-NB-CR-C ALLOYS

A thermodynamic calculation of the stability of phases in the nickel c orner of the Ni-Nb-Cr-C system is reported. With chromium content up t o 10 at.% the alloy phase composition remains unchanged: gamma-solid s olution + niobium carbide. With chromium content increased to 20 at.% the formation of Cr3C2 and CrC3 chromium carbides becomes possible. Th e temperature and concentration ranges in which these carbides can exi st were determined. It was found that Cr3C2 carbide is more stable at low temperatures (400-600-degrees-C), whereas Cr7C3 carbide is more st able at high temperatures (1200-1400-degrees-C).