Kinetics and contact interaction mechanism of titanium carbonitride with the Ni–Mo melt

Abstract

Kinetic features and the contact interaction mechanism of hot-pressed (residual porosity <3%) of titanium carbonitride samples of various compositions with the Ni–25% Mo melt (t = 1400–1500°C, τ = 0.1–25 h) are investigated by electron-probe microanalysis. It is established that the dissolution rate of the interstitial refractory phase (IRP) in the Ni–Mo melt lowers in a series TiC–TiC_0.7N_0.3–TiC_0.5N_0.5, while the degree of process incongruence rises. The composition of intermediate interaction products varies correspondingly. The peculiarities of formation of the most important phase component of the TiCN cermets—K-phase of the Ti_1–nMo_nC_x composition—are revealed. It is proven by the local mass spectrometry method that the K-phase has a carbide nature. It is also established that it is formed only if the initial titanium carbonitride TiC_1–xN_x is sufficiently enriched with carbon (x ≤ 0.5). It is stated that the K-phase is an actual basis of all cermets with the Ni–Mo binder. Its bulk concentration in alloys exceeds the content of the nominal alloy base by a factor of several times. The chemical substantiation of the selection of titanium carbonitride of the TiC_0.5N_0.5 composition as an optimal “precursor” of the K-phase, which is formed during liquid-phase sintering of TiCN cermets, is given originally.