Production of a Ni-TiN composite powder by nitridation of titanium nickelide

Experimental data on the study of nitriding the powdered NiTi intermetallic compound formed in the course of reduction of calcium hydride are given. A theoretical analysis showed that this process occurs in the external mode with the decomposition of titanium nickelide NiTi through a Ni3 Ti intermediate phase into titanium nickelide and a Ni(Ti) solid solution of titanium in nickel. It was found that, at t = 1000–1200°C, nitridation should be terminated by the formation of the following equilibrium phase: TiN1.0 titanium nitride of stoichiometric composition and nickel containing practically no titanium. A model of the nitridation process is proposed which provides the qualitative description of the growth of forming TiN and Ni phases and evaluation of the time of total disappearance of titanium nickelide for NiTi powder particles of a specific size.