Electrophysical properties of niobium carbide single crystals

Conclusions An investigation was carried out into the temperature dependence of the electrical resistivity, thermal conductivity, and coefficient of thermo-emf of single-crystal niobium carbide. It is shown that the electrical resistivity of single-crystal niobium carbide, a material of high purity and perfect structure, is higher than that of polycrystalline materials.Translated from Poroshkovaya Metallurgiya, No. 10(238), pp. 59–62, October, 1982.     

Structure and some properties of niobium carbide single crystals

Conclusions High-purity niobium carbide single crystals of different compositions within the range of homogeneity of the carbide were grown by crystallization from a melt. X-ray diffraction studies and metallographic examinations revealed that the single crystals obtained contained both perfect regions and regions distorted by thermal stresses and composition heterogeneities. As a result of x-ray diffraction studies, the presence of substructures of the first and second orders in the single crystals was established. Maximum disorientation was found to attain 0.2–0.5° for blocks of the first order and to be about 0.05° for blocks of the second order. The density of dislocations in the niobium single carbides was on the order of 10⁵ cm^–2. Within the limits of niobium carbide compositions investigated no differences in mechanical properties (microhardness and resistance to cracking) were detected. It was established that in single crystals of compositions NbC_0.78-NbC_0.82 room-temperature deformation took place over the {111} 110 system. The room-temperature fracture of the single crystals was mainly brittle in character.Translated from Poroshkovaya Metallurgiya, No. 12(228), pp. 81–86, December, 1981.     

Composition dependence of the abrasive properties of fused niobium carbide powder

Conclusions A study was made of the abrasive characteristics of fused niobium carbide phases. The effects of carbon content variation upon the properties of the carbide phases were determined. Of the materials investigated, the carbide phase NbC_0.82 shows greatest promise for the manufacture of abrasive tools.Translated from Poroshkovaya Metallurgiya, No. 1 (145), pp. 90–93, January, 1975.     

Effect of niobium carbide on the properties of tungsten-free hard alloys

Conclusions A study was made of the effects of alloying with niobium carbide of the carbide phase of a TiC-Ni-Mo hard alloy (in amounts equal to 2,5,10, and 25 mole% relative to the TiC content) upon the physicomechanical properties of the alloy. It is shown that raising the amount of NbC in the alloy increases its transverse rupture strength (to 132 kg/mm²) and impact strength, leaving its hardness virtually unchanged (91 HRA); the improvement in properties is attributable to a slight increase in the ductility of the grains of the hard phase — a complex TiC-NbC carbide.Translated from Poroshkovaya Metallurgiya, No. 9 (129), pp. 83–86, September, 1973.     

Solubility of niobium carbide and niobium carbonitride in alloyed austenite and ferrite

The available data on the solubility of niobium carbide and niobium carbonitride in plain carbon and alloyed austenite has been analyzedvia dilute solution thermodynamics with a view to establishing a consistent set of interaction parameters for predicting austenite + niobium carbonitride equilibria. The computation algorithm includes the prediction of phase mass fractions as a function of alloy composition and temperature between 900° and 1300 °C (tie lines). Analogous ferrite equilibria are included.     

Properties and structure of niobium carbide heating elements

Conclusions In operation at 1900°C in a carbon-free atmosphere at a residual pressure of 10^–2-2· 10^–3 Pa a heating element of composition NbC + Nb₂C + Nb experiences a steady loss of carbon at a rate of 0.5–1 m/h from its surface, with the formation of a metallic phase. Heating elements of this composition may be recommended for service in vacuum resistance furnaces at temperatures of up to 1900°C, where they can be expected to have a useful life of the order of 1000 h. Niobium monocarbide heating elements operating at 2100–2500°C in a carbon-containing atmosphere under a pressure of 10^–2-2·10^–3 Pa experience no change in phase composition or shape and only minor changes in structure, and possess good thermal fatigue resistance. They can thus be employed in vacuum electric furnaces under these conditions. Long experience (more than two years) with the operation of a laboratory vacuum electric furnace with a niobium carbide heating element in the temperature range 1000–1500°C has demonstrated that the use of niobium carbide heating elements widens scope for new electro-thermal equipment.Translated from Poroshkovaya Metallurgiya, No. 3(231), pp. 92–97, March, 1982.