Lazaryuk V. Design and investigation of free-tungsten hard alloys (Ti, Nb)C-Ni-Cr-Al

The free-tungsten hard alloys based on the complex carbide (Ti, Nb)C with nickel-chromium-aluminum binder have been designed and investigated. The chemical compositions and technological parameters of sintering were optimised. The alloying titanium carbide by niobium carbide decreases a solubility of the refractory base alloy in metal binder that suppresses the carbide grain growth. The limited solubility of chromium in the (Ti, Nb)C refractory base leads to a decrease of interaction between the metal binder and refractory phase. Increase of strength and high values of hardness and fracture toughness of the alloys are obtained at the expense of the structure refinement, a decrease of porosity and carbide grain size. The high temperature oxidation kinetic of (Ti, Nb)C-Ni-Cr-Al alloys was investigated on air at the temperature interval 1173-1392 К. Increase of Ni-Cr binder content from 10 to 24% (weight) raises the heat-resistance to 2-2,5 times. The phase's compositions, morphology, kinetic regularity and formation mechanism of the oxidised layers have been investigated.