V. S. Panov

Wetting of TiC-Wc system carbides with molten Ni3Al

In this work an investigation was made of the wettability of titanium and tungsten carbides and also of (Ti, W)C solid solutions by the molten intermetallic compound Ni/sub 3/Al, which has been used for some time as a binder for sintered carbides. The wetting process was investigated using the stationary variation of the sessile drop method in vacuum on a special induction unit with an Alundum tube enveloping a graphite fabric one, which serves as the heating body. The carbide-intermetallide contact zone was investigated by optical microscopy and micro-x-ray spectral analysis. The investigations conducted showed the possibility in principle of creation of compact TiC-WC pseudobinary system carbide-Ni/sub 3/Al intermetallide composites produced by liquid-phase sintering. Diagrams and table are included.

Preparation and study of some properties of NbC - WC and TaC - WC alloys

Conclusions1.The conditions of preparation of homogeneous solid solutions and alloys of the carbide systems NbC - WC and TaC - WC were investigated.2.Studies were made of the effects of composition on structure, lattice-constant variation, electrical resistivity, microhardness, the coefficient of thermal expansion, and the angle of contact of nickel for the systems TaC - WC and NbC - WC.3.The findings are entirely consistent with the type of composition vs property relationship characteristic of metallic binary alloys with limited solid-state solubility.4.It is demonstrated that, for solid solutions of WC in the cubic carbides TaC and NbC, raising the concentration of tungsten carbide is accompanied by an increase in hardness and electrical resistivity, and a decrease in the coefficient of thermal expansion and the angle of contact of nickel on solid solutions of the carbides.

The interaction of titanium carbide and carbonitride with nickelides

The study of the interaction of the constituents of composite materials is of great practical interest since it is for the purpose of improving existing and development of new compositions for various conditions of use. In recent years tungsten-free and lowtungsten composites [1-3], the development of which has been dictated by the necessity of economy in scarce tungsten, have become widely used.

Nature of the liquid phase forming during the sintering of R6M5 steel produced from machining waste

ConclusionsA thermogravimetric and electron microscopical investigation has been carried out into the nature and composition of the oxycarbide eutectic appearing at the grain boundaries of R6M5 steel at sintering temperatures below 1220°C. The need for two-stage sintering of R6M5 steel from machining waste as a means of obtaining nonporous blanks is explained. Optimum sintering conditions have been established, which are determined by the particle size of the powder and its oxygen content.

Effect of titanium carbide additions on the milling, pressing, and sintering of tungsten-molybdenum-vanadium steel powder

Conclusions1.A study was made of the milling of high-speed steel swarf with a titanium carbide addition and of the production of dense blanks from the resultant composite powders.2.It is shown that titanium carbide additions intensify the comminution of high-speed steel swarf and result in the formation of structures with evenly distributed fine (2.0–2.5 μ) carbide grains.3.The addition of titanium carbide raises the hardness of high-speed steel from 62 to 68 HRC.

Effects of niobium carbide additions upon the production and properties of sintered high-speed steel

Conclusions1.A study was made of the comminution to powder, in a rotary ball mill, of R18 high-speed steel swarf containing niobium carbide additions and of the subsequent processing of the resultant composite powders to dense blanks.2.Niobium carbide was found to intensify the swarf comminution process: In powder milled for 48 h, the presence of 5 vol.% NbC increased the yield of the −0.25-mm fraction from 46 to 81% and that of the finest (−0.04-mm) fraction from 35 to 45.5%. At the same time, the mean particle size decreased from 0.31 to 0.18 mm.3.A study was made of the pressing and sintering of the high-speed steel powder with niobium carbide additions. Strong compacts with a relative density of 70–73% were produced by pressing the powder, with a rubber addition, under a pressure of 8–10 tons/cm2.4.Sintering, in the absence of a liquid phase, for 60 min at 1250°C in very dry hydrogen was found to yield blanks with a relative density of more than 95%. The blanks were characterized by a fine-grained structure and a mean carbide grain size of 1.5–2μ.5.The addition of niobium carbide affected the size of the austenitic grain, reducing it from 18μ at 1 vol.% NbC to 7μ at 5 vol.% NbC.6.The introduction of niobium carbide raised the hardness of the sintered steel, from 59 HRC (without NbC) to 65 HRC at a NbC content of 5 vol.%.

Interaction of bronze with a solid lubricant in heating

In rubbing pairs for modern machines and mechanisms operating under extreme conditions materials which combine mechanical strength with good lubricating properties are used. Such requirements are answered most completely by metal-base powder composite materials with dichalcogenides of refractory metals of groups IV-VI of the periodic table, which have a low coefficient of friction in vacuum and inert gases in a broad temperature range and also under the action of radiation [I]. To a significant degree the properties of these materials depend upon the temperature of the start of interaction of the base with the dichalcogenide, which determines the sintering temperature of the material. It is known that under real conditions interaction develops at temperatures lower than the theoretical data given in the literature for dichalcogenides and is accompanied by the formation of compounds not possessing a lamellar structure in the majority of cases [2, 3].

Properties of R6M5 steel powders of various particle sizes and the structure of the steel in the sintered condition

ConclusionsAn investigation was carried out into the effect of particle size of powders produced by comminution of R6M5 high-speed steel waste (swarf) on their compressibility and sinterability. It is shown that with decreasing mean particle size the compressibility of such powders deteriorates, but their sinterability improves. The finer the steel powder, the lower is the sintering temperature necessary for the attainment of a given density. Varying the powder particles size brings about marked changes in the microstructure of the steel in the sintered condition. The liquid phase (ledeburitic eutectic) appearing during the sintering of steel powders of different particle sizes varies in form and distribution. With coarse powders (dm=100 μm) the eutectic is similar to that in cast steel, but with powders of small particle size (dm=22 μm) it is finer and evenly distributed throughout the structure in the form of thin lamellae.

Effect of conditions of preparation of metallic tungsten on the properties of T15K6 alloy

Conclusions1.A study was made of the single-stage reduction of WO3 to W in an industrial GSPI muffle furnace with a direct-flow feed of hydrogen into the furnace muffle.2.It is shown that, with hydrogen supplied by the direct-flow technique, it is possible to produce in a single stage, at unchanged furnace output, a homogeneous, fine-grained tungsten powder with an adsorption of more than 0.2 mg/g and a mean particle size of < 1μ.3.An investigation was carried out of the effect of sintering temperature on the properties of T15K6 alloy produced from tungsten powder prepared by the direct hydrogen flow technique.4.It is shown that, compared with a standard T15K6 alloy, an alloy of the same composition produced from tungsten powder prepared in a muffle furnace with a direct-flow hydrogen supply possesses a finer-grained WC phase structure and superior physicomechanical and cutting properties.

Atmospheric oxidation resistance of WC-NbC-Co alloys

Summary1.A study was made of the atmospheric oxidation of WC-NbC-Co alloys with varying niobium carbide contents at a constant cobalt content (25 vol.%) over the temperature range 500–800°C.2.It was demonstrated that the oxidation of WC-NbC-Co alloys obeys an approximately linear law, which is due to the high ratio of the volumes of the resulting oxides to the volume of the basis metal.3.It was established that an addition of niobium carbide to WC-Co alloys does not increase their oxidation resistance in air at 500–800°C.4.The phase composition of the oxide films forming on WC-NbC-Co alloys was determined and shown to remain practically unchanged when exposure time is increased and oxidation temperature is raised from 500–800°C.