Mechanochemical synthesis of high-temperature metal-matrix composites, dispersion-hardened by titanium carbides

The results of XRD structural studies of the evolution of the phase composition and structure of high-temperature metal-ceramic composites obtained in situ by mechanochemical synthesis in reaction mixtures (Ti–C)–хМe (Me = Ti, Ni, Mo; х = 50–70 wt. %) have been given. When processing the initial powders in a planetary ball mill with an energy intensity of 7.0 W/g, mechanically stimulated reactions are realized with the formation of metal-ceramic composites within 8–20 min. In all of the considered compositions, except for Me = 70 wt. % Ti, a liquid-phase combustion mechanism is realized with the formation of a metal-matrix amorphous-crystalline structure of supersaturated solid solutions, which are dispersion-hardened by titanium carbides. In the (Ti–C)–70 wt. % Ti mixture, solid-phase interaction is realized with the formation of a supersaturated solid solution αTi(C) with its subsequent decomposition with the precipitation of TiC0.47. The initiation stage duration tign for Me = Ti is approximately 2–4 min. The formation of a low-temperature Ni–Ti eutectic in the (Ti–C)–50Ni composition helps to reduce the duration of the reaction ignition tign to 1 minute and to increase the synthesis rate of TiC0.78–0.83 inclusions. Increasing the concentration to 70 wt. % Ni leads to an increase in tign to 4 min. A decrease in the adiabatic temperature promotes the formation of carbon-depleted carbide TiC0.64–0.78. The use of refractory molybdenum as a matrix metal increases tign and is in the range of approximately 4–8 minutes. In compositions (Ti–C)–xMe (Me = Ti, Ni), the mechanosynthesized TiC content reaches approximately 40 ± 3 wt. % at x = 50 % and approximately 27 ± 1 wt. % at x = 70 %. In compositions (Ti–C)–xMo with x = 50 and 60 wt. %, a NaCl-type (Mo, Ti)C carbide forms in quantity of 69 wt. %. The obtained results demonstrate the promising prospects for mechanochemical in situ synthesis of dispersion-strengthened composites based on refractory metals for materials with enhanced heat resistance and high-temperature stability.