REGULARITIES OF CONTACT INTERACTION OF TITANIUM CARBIDE WITH NI AND NI–MO MELTS

Abstract

Regularities of dissolution, phase formation, and  structure formation, which are implemented in conditions of the contact interaction of titanium carbide of various compositions with Ni and  Ni–(5÷25 %)Mo melts are investigated. It is established for the first time that the dissolution of carbide TiCx in nickel-based melts is incongruent: carbon preferentially transfers into the melt at x ≥ 0,9 and  titanium at x ≤ 0,8.  The limiting stage of dissolution is atomic diffusion of metal in the liquid phase. Regularities of the formation of Ti1–nMonCx carbide (C-phase)—the main contact interaction product in the TiC/Ni–Mo system—are revealed. It is established that  the C-phase in conditions of the relative excess of the Ni–Mo melt is formed preferentially by the dissolution–isolation mechanism, while in its lack (in impregnation conditions of a carbide massif)—by the dissolution–precipitation mechanism. The composition of autonomous isola- tion of the C-phase depending on the experimental conditions (1450 °C, 0,5–25 h) varies in limits from  Ti0,4Mo0,6C0,7 (а = 4,27  Å) to Ti0,7Mo0,3C0,6 (а = 4,29  Å). The composition at the unsteady dissolution stage is determined by the molybdenum concentration in the melt and  at the steady dissolution stage—by the ratio of titanium and  molybdenum concentrations in the melt.