Yu. V. Levinskii

Production of titanium carbide powder from titanium swarf

ConclusionsIt is demonstrated that titanium carbide powder can be obtained from titanium swarf. The following optimum parameters of carbidization in a vacuum corresponding to 0.013 Pa have been established: 1.5-h holding at a temperature of 1873°K; 0.5-h holding at 2273°K; 0.5-h comminution in a vibratory mill; and 0.5-h holding at 2273°K, The amount of oxygen in the titanium carbide powder produced was found to be less than that in the powder currently manufactured in the Soviet hard-metal industry.

Modulus of elasticity of some refractory compounds

ConclusionsMeasurements were made of the moduli of elasticity of nonporous refractory compounds prepared by the method of diffusion impregnation. The following values were obtained: 49,300±2000 kg/mm2 for NbN, 58,700±2000 kg/mm2 for TaN, 58,000±2000 kg/mm2 for NbC, 65,000±2000 kg/mm2 for NbB2, 70,000±2000 kg/mm2 for TaB2, 68,500±2000 kg/mm2 for Mo2B5, and 79,000±2000 kg/mm2 for W2B5.

Reduction of R6M5 high-speed steel powder

ConclusionsOn the basis of a thermodynamic calculation of the reduction of iron., chromium, and vandanium oxides and of experimental data, the following optimum reduction annealing conditions were chosen for R6M5 powder from swarf: temperature 900–950°C, vacuum corresponding to 1.3–0.13 Pa, and holding time 2 h. In this powder about 25% of all oxygen was found to be present in the difficult-to-reduce chromium and vanadium oxides and 75% in iron oxides. An expression is proposed for calculating the amount of carbon that should be added to the powder.

Influence of gases on the sintering of porous solids VI. Sintering of solids containing several dissolved gases

Conclusions1.An examination is made of the behavior of a porous solid containing several dissolved gases. Equations describing the kinetics of pore size variation in various specific cases are proposed and analyzed.2.It is shown that, with reactive gases, high total gas pressures may be generated in the pores of a solid even when these gases have only a small solubility in the solid.3.To lower the gas pressure in the pores of a metal, it is necessary either to decrease the amount of gas dissolved in the metal or introduce alloying additions with which the gas will combine to form thermodynamically stable solid compounds.

A MECHANISM HINDERING BOUNDARY SLIDING IN POROUS POLYCRYSTALLINE SOLIDS

In [I, 2] Geguzin proposes a new mechanism of spontaneous activated sintering of porous solids involving relative diffusional sliding of particles. In the same articles the author draws attention to the fact that the process of diffusional boundary sliding, which leads to very rapid shrinkage, may be hindered by the need for particles to adjust themselves to one another in shape by volume diffusion.

Spontaneous combustion and pyrophoric properties of some powder materials

Conclusions1.The effect of spontaneous ignition was observed and the flash points were determined for metallic powders of titanium, zirconium, and hafnium in a nitrogen medium.2.It has been established that, although the amount of the diluent in mechanical mixtures with metallic titanium, zirconium, and hafnium powders does not influence the flash point of the latter, it still reduces the pyroeffect in spontaneous ignition.3.The moisture and granularity of powdered zirconium considerably affect its flash point in a nitrogen medium. Zirconium powder must be dried befor it is subjected to heat treatment.4.The pyrophoric properties of titanium, zirconium, molybdenum, and tungsten powders in pure form as well as in mixtures with carbon black or boron were investigated, and the temperatures at which the pyroeffect arises in these powders in inert media or in vacuum were determined.

Preparing hard-alloy mixtures in a magnetic induction rotor

The parameters have been optimized in welding titanium carbide powder for the preparation of TiC-Ni-Mo and WC-Co hard-alloy mixtures. The equipment enables one to accelerate the processing of the TiC-Ni-Mo hard-alloy mixtures to give a processing time of 1 hour subject to a given composition and average particle size of 0.8 μm. The major properties of specimens made from the mixtures are no worse than those of industrial analogs made by standard methods and in certain cases are better than them.

Preparation of titanium oxide powder of prescribed composition

A mathematical model is suggested for the process of titanium chip impregnation with oxygen. The model is based on the assumption that it is possible to ignore the effect of a thin surface oxide film on oxygen impregnation of α-Ti solid solution. The process of producing TiO powder with a particle size of less than 100 µm has been optimized for the minimum expenditure of energy.

Titanium carbide-based carbide steels made of chips of titanium alloys

Properties and microstructure of carbide steels produced on the basis of titanium carbide are studied. Powdered TiC was obtained from chip wastes of the titanium alloys VT1-0, VT20, VT3-1, VT25, VT5-1, and OT4-1 in three ways: nitridingcarbidizing, double carbidizing, and oxidizing-carbidizing. It has been determined that presence of nitrogen deteriorates the properties of carbide steels. The high values of strength and hardness obtained by oxidizing-carbidizing and double carbidizing of VT5-1 alloy chips testify to the advisability of using such chips for producing carbide steels.

Volumetric deformation of Al-4.4% Cu and Al-4.4% Cu-0.5% Mg compacts during sintering

ConclusionsFormation of intermetallics with heating of compacts is accompanied by an exothermic effect as a result of which the temeprature for eutectic melting of a specimen (548°C) is achieved sooner than in the surrounding volume. The magnitude of the corresponding temperature drop depends on copper content and it is 5°C for Al-4.4% Cu, and for Al-50% Cu it is 23°C. Introduction of 0.5% magnesium into Al-4.4% Cu alloy reduced the temperature for melt formation as a result of appearance of a more readily melting ternary eutectic.Growth of Al-Cu and Al-Cu-Mg compacts during sintering in the solid solution region of the composition diagram is caused by diffusion impregnation. With sintering in the liquid-solid region of the diagram apart from diffusion impregnation compact growth is affected by spreading of melt over the surface and grain boundaries of aluminum particles whose relative contribution to the overall compact growth is about 30%. Compacts of Al-4.4% Cu-0.5% Mg increase to a greater extent than for Al-4.4% Cu, which is caused by an increase in their liquid phase content.