ev UDC 621.762The paper studies the densification kinetics in hot pressing of mixtures with equimass content (50 : 50) of Cr 3 C 2 and TiN without a binder at 1350, 1470, and 1800°C under 16.2, 21.6, and 35.7 MPa, a mixture of Cr 3 C 2 -50 wt.% TiN with 5 wt.% of the Ni-Cr binder at 1300, 1350, and 1370°C under 5 and 10 MPa, and a mixture of Cr 3 C 2 -50 wt.% TiN with 20 wt.% of the Ni-Cr binder at 1180, 1220 MPa with isothermal holding for up to 25 min. The behavior of materials in hot pressing is analyzed using the viscous flow theory for porous body. It is shown that the compaction of an alloy without a binder and with the Ni-Cr binder in hot pressing is described by a generalized equation of volume viscous flow of a porous body. It is controlled by non-linear creep with an effective activation energy of 3.2 eV in materials without a binder and by a viscous flow in alloys with a metal binder. The structure and mechanical properties of the materials obtained are studied.The wear resistance of composite and metal ceramics can be improved by combining refractory phases with nonisomorphic crystal structure and different physical and mechanical properties. Based on this, we have investigated cermets based on the Cr 3 C 2 -TiN system [1]. Sintering of samples with different contents of titanium nitride in various protective media (hydrogen, nitrogen, vacuum) does not ensure the density close to that of a compact material.This study is focused on hot pressing of powder mixtures containing equimass contents of chromium carbide and titanium nitride without and with the Ni-Cr metal binder.The starting materials were chromium carbide (Cr 3 C 2 ) and titanium nitride (TiN) powders (Donetsk Chemical Reagent Plant) and nickel and chromium powders in amounts needed to produce a nichrome metal binder (Ni + 20 wt.% Cr) of 5 to 20 wt.% in the composite. The samples were hot pressed in graphite molds heated by induction current from a VChI-2/100 high-frequency generator using a P-125 press. As the sample is densified, its weight does not practically change and its cross section remains constant, the current relative density was determined using the change in height, final density, and height of the sample. The current values of height were continuously recorded from an indicator.The densification kinetics of a powder mixture with equimass content (50 : 50) of Cr 3 C 2 and TiN without a binder was studied at 1350, 1470, and 1800°C at constant pressure of 16.2, 21.6, and 35.7 MPa. Temperatures of 1300, 1350, and 1370°C were selected for mixtures containing 5 wt.% of a metal binder and 1180, 1220, and 1270°C at 5 and 10 MPa for mixtures with 20 wt.% of a metal binder. Figures 1 to 3 summarize the data on densification kinetics. The densification rate of the samples regularly decreases, the rate of decrease increasing with temperature and pressure of isothermal holding. The data on densification kinetics also indicate that composites without a metal binder are compacted to practically nonporous state at much lower temperatures and ...

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621.762We have analyzed the process of structure formation during pressing of copper-tungsten composites. We have established the effect of the amount of the rigid phase (tungsten alloy) in the mix on the pattern of structure formation and the properties (Young's modulus and bending strength) of unsintered articles made from heterogeneous powder material based on copper. We have experimentally established that despite the substantially higher porosity and high volume fraction of the rigid phase, specimens of composition Cu − 50% W alloy have higher green strength and higher modulus of elasticity. Analysis of the true stress − true strain curves of the porous cold-pressed articles compared with the results of microstructural studies allowed us to determine the effect of the structure formation pattern on the strength properties of articles made from copper-based powder material containing tungsten alloy. By studying the structural features of the porous articles, we determined the mechanism for creation of interparticle contact which determines the strength characteristics of unsintered compacts of heterogeneous composition based on a plastic matrix with different amounts of the rigid phase.