Effect of tungsten nanoparticles on sintering of the Sn-Cu-Co-W powder material

The effect of tungsten nanoparticles on the kinetics of sintering of the Sn-Cu-Co-W powder material used as a binder in diamond tools was studied. The W16,5 grade tungsten powder was mechanically activated in the AGO-2U planetary centrifugal mill for 60 minutes at the carrier rotation frequencies of 800 RPM. The mixture of tungsten, tin, copper, and cobalt powders was compacted by static pressing in press dies and then sintered in vacuum at the temperature of 820°C. The morphology and sizes of powder particles, as well as the structure of the sintered samples, were studied by the methods of scanning electronic microscopy. It has been demonstrated that tungsten nanoparticles have a noticeable effect on the process of dissolution-reprecipitation of cobalt in liquid-phase sintering.

STUDY OF THERMOMECHANICAL PROPERTIES OF UHMWPE

The paper presents comparative studies of the thermomechanical properties of ultra-high molecular weight polyethylene (UHMWPE) and its composite containing 0.5% coke-graphite powder (CGP). It was found that explosive pressing with a pressure of 0.25-0.6 GPa provides high heat resistance of UHMWPE and the investigated composite (154-156 ° C). The heat resistance of the composite decreases to 143-145 ° C, but it is higher than that of a similar material after static pressing (128 ° C).

Electro-mechanical model of indicator polymer fiber-optic PEL-coating for diagnosing mechanical effects.

A mathematical model of the functioning of the indicator polymer piezoelectroluminescent (PEL) coating for diagnosing external mechanical effects - quasi-static pressing of rigid ball particles has been developed. The algorithm of numerical processing of informative intensity of light flux at the output from optical fiber built into indicator coating of optical fiber PEL-sensor is presented. A numerical analysis for the case of single mechanical effect revealed the regularities of influence of the values of the sensor spiral pitch on the informative parts of the resulting spectra of light flux intensity and pressure distribution along the length of the sensor spiral. Informative characteristic points of pressure spectra plots were revealed; these are points of maxima, abscissa and values of which make it possible to find the desired values of radius and pressing force of a rigid ball particle.

STUDY OF THE INFLUENCE OF ALUMINUM DISPERSION ON THERMAL EXPANSION OF HIGHLY FILLED FLUOROPLASTIC COMPOSITE MATERIALS

The effect of dispersion and concentration of aluminum particles and sintering on the thermal expansion of fluoroplastic-aluminum composite materials has been investigated. Composite materials were obtained by static pressing of powder mixtures of fluoroplastic with 50 and 70% aluminum, followed by sintering. It was found that a decrease in the size of aluminum particles increases thermal expansion and decreases the density of CMs, but does not affect heat resistance. It was found that an increase in the aluminum concentration leads to a decrease in the thermal expansion of CM.

STUDY OF THE INFLUENCE OF METAL DISPERSITY ON THERMAL EXPANSION OF FLUOROPLAST-ALUMINUM COMPOSITE MATERIALS

The effect of dispersion and concentration of aluminum particles and sintering on the thermal expansion of fluoroplastic-aluminum composite materials has been investigated. Composite materials were obtained by static pressing of powder mixtures, followed by sintering. It was found that a decrease in the size of aluminum particles does not affect heat resistance, but increases thermal expansion and decreases the density of CM. Found that an increase in the aluminum concentration leads to a decrease in the thermal expansion of CMs before sintering and an increase after sintering.

Determining the influence exerted by the static conditions of final squeezing on the compaction process of iron-based powder materials

This paper reports a study into the process of re-compaction of powder briquettes in the conditions of static pressing at a pressure of 800 MPa. The technological parameters of the pressing process have been analyzed, which make it possible to improve the compaction of powder briquettes based on iron. Such parameters are the outer greasing, which reduces friction between a green compact and the walls of the press tool matrix, and the firing, which removes the deformation strengthening of the green compacts and increases their plasticity. The green compacts’ sealing mechanism involved in the final squeezing process has been established, which is associated with the grinding of pre-compressed particles due to the strain in the contact areas. The increase in the stressed state of green compacts following the final squeezing was confirmed by the results of studying the residual micro-strains. The change in the stressed state of iron green compacts has been confirmed by the study into the structurally sensitive characteristics, which include the materials’ magnetic and electrical properties. Determining the magnetic characteristics has shown that final squeezing leads to an increase in coercive force, which can be explained by both the increase in the stressed state and the grinding of grains. Investigating the impact exerted by the annealing environment on the value of magnetic characteristics has demonstrated that annealing in hydrogen is more effective in terms of improving magnetic properties than annealing in a vacuum. This is due to the refining of grain boundaries through the processes of reduction of oxide films. The study of the mechanical characteristics of green compact materials based on iron powder has established that final squeezing leads to an increase in the hardness and strength of materials depending on the conditions of deformation. A significant improvement in the green compacts’ strength (820‒824 MPa) is due to both a decrease in porosity by 8‒10 % and an increase in the contact area as a result of plastic deformation after the annealing

Study of structure formation in aluminum filled polytetrafluoroethylene after explosive compression

The features of the structure formation in polytetrafluoroethylene filled with 10 and 30% (vol.) aluminum after static and explosive pressing have been studied. It was revealed that after static pressing during sintering, interphase separation occured, which is confirmed by the formation of structures of the «closed buds» type. After explosive pressing with sintering, fibrils between polytetrafluoroethylene and aluminum and a polymer layer covering metal particles were found, and there was no interfacial separation that indicates the formation of a strong adhesive bond and is confirmed by the formation of aluminum fluoride.

STUDY OF THE STRUCTURE OF HIGHLY FILLED FLUOROPLAST-ALUMINUM COMPOSITES

Structure formation in fluoroplastic-aluminum composites obtained by static and explosive pressing has been investigated. The concentration of dispersed aluminum was 50 and 70% vol. In fluoroplastic-aluminum composites, after static pressing, spalling of metal particles, formed during the preparation of a microsection, was found, which indicates low adhesion of the polymer and metal. The production of fluoroplastic-aluminum composites using explosive pressing leads to the formation of a monolithic material with a high adhesive interaction of the components and the formation of a metal frame.

RESEARCH OF FEATURE OF STRUCTURE FORMATION IN PTFE-ALUMINUM COMPOSITE MATERIALS DURING SINTERING

The structure formation in fluoroplastic-aluminum composite materials during sintering after static pressing was studied. The concentration of dispersed aluminum was 30% vol.. After sintering, interfacial separation was observed in the fluoroplastic-aluminum composite materials, which is formed during crystallization due to shrinkage, which indicates a low adhesion of the filler to the polymer. Sintering of composite materials in a closed volume leads to the formation of a material with a lower porosity than when sintering in a free volume.