RU2638866C1 - Method of producing high temperature powder composite material based on silicon carbides and titanium - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to the production of a composite material based on silicon carbides and titanium, comprising the preparation of a powder mixture consisting of titanium, silicon carbide, and graphite, and mechanically activation of the powder mixture. The powder mixture contains 66 wt % Ti, 17 wt % SiC and 17 wt % C. The mechanical activation of the powder mixture is carried out in a planetary mill at a drum rotation frequency of 240-320 rpm in the irregular mode for 180 min, and then the plasma-spark sintering of the mechanically activated powder mixture is carried out in a vacuum at 1350-1450°C, a pressure of 15-30 MPa, an exposure of 5-8 min, followed by gradual cooling for 1 h.

EFFECT: regulation of the phase content in the composite material is provided.

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Description

The invention relates to the production of high-temperature composite materials operating under conditions of increased loads and temperatures, can find application in powder metallurgy, in the chemical, energy, oil and gas industries.

It is known to obtain titanium carbosilicide by solid-phase synthesis under vacuum and with an excess of silicon component. At the intermediate stages of synthesis, an excess of elemental silicon is removed from the material by evaporation (Preparation of Ti ₃ SiC ₂ / P.V. Istomin, A.V. Nadutkin, Yu.I. Ryabkov, B.A. Goldin // Inorganic Materials, 2006, Volume 42 , No. 3. S. 292-297).

The disadvantage of this method is the difficulty in controlling the content of impurity phases due to the introduction of an excess of the silicon component in the initial charge, as well as the need for subsequent grinding, pressing and sintering, or hot pressing operations to obtain products.

A known method of producing a composite material in which a powder mixture consisting of titanium, silicon carbide, carbon or compounds containing them with the addition of 3-7 wt. % of nanosized alumina is subjected to mechanosynthesis in a vacuum mill, followed by cold and hot pressing at 5-15 MPa (RF patent No. 2410197, IPC B22F 3/14, 2011).

The disadvantages are the difficulty of regulating the content of impurity phases and the high energy consumption in obtaining the material.

The closest technical solution is a method of obtaining a powder composition, comprising preparing a powder mixture consisting of titanium, silicon carbide and graphite, taken in a molar ratio of 3: 1.25: 0.75, mechanosynthesis of the powder mixture in a planetary mill at a drum rotation speed of 320 rpm / min in intermittent mode using titanium grinding media, cold pressing, heat treatment in vacuum at 1350 ° C for 3 hours to obtain a sintered intermediate, grinding the sintered intermediate in a planetary mill using m of titanium snap (RF patent No. 2460706, IPC C04B 35/565, 2012).

The disadvantage of this method is the difficulty of controlling the phase content due to the introduction of aluminum oxide into the initial charge and the complexity of the process.

The objective of the invention is to obtain a powder composition with the ability to control the phase content and simplify the process.

The technical result is achieved by the fact that in the method for producing a high-temperature powder composite material based on titanium and silicon carbides, comprising preparing a powder mixture consisting of titanium, silicon carbide and graphite, taken in a ratio of 66 wt. % Ti, 17 wt. % SiC, 17 wt. % С, mechanical activation of the powder mixture in a planetary mill at a drum rotation frequency of 240-320 rpm in intermittent mode for 180 minutes, plasma-spark sintering in vacuum is carried out at a temperature of 1350-1450 ° C, a pressure of 15-30 MPa and an exposure time of 5 -8 min followed by gradual cooling for 1 hour.

Preparation of a powder mixture includes the following operations: weighing the components of the mixture on an analytical balance, based on their predetermined proportions, the process of mechanical activation of the mixture, including dry grinding, homogenization and solid-phase mutual reactions of the components of the mixture in evacuated cuvettes of a planetary mill.

The mechanical activation of the powder mixture in a high-energy planetary mill allows us to obtain the ultimate degree of grinding crystallites, which after processing are in a highly nonequilibrium state, which increases the reactivity of the components of the powder mixture, providing a decrease in the temperature and duration of high-temperature heating during subsequent processes of formation of the powder composite material.

The prepared mechanically activated powder mixture is subjected to plasma-spark sintering (SIS) to obtain a powder composition with a given particle size and phase content of silicon carbide and titanium carbide. IPR is based on passing high-power electric current pulses through the processed material with the simultaneous application of pressure. High density energy is concentrated at the sites of formation of contact isthmuses between the particles of the powder mixture, which ensures uniformity of the sintered composite material.

IPR allows you to synthesize a powder composition with a grain size of 1-10 μm and an adjustable percentage (60-80%) of the titanium carbide phase and achieve a higher density in the range of 4.5-4.8 g / cm ³ compared with hot pressing.

The resulting material will have a higher complex of physico-mechanical properties, for example, increased wear resistance, as well as resistance to aggressive environments and elevated temperatures.

A method of obtaining a composite material based on silicon carbides and titanium is as follows (example).

For the preparation (mechanical activation) of the initial mixture, titanium powders with a particle size of 100-300 μm, silicon carbide with a particle size of 10-100 μm, graphite with a particle size of 1-10 μm are taken. The initial mixture of powders of titanium, silicon carbide, graphite (in a ratio of 66 wt.% Ti, 17 wt.% SiC, 17 wt.% C) is placed in a cuvette of a planetary mill together with grinding balls in the ratio (powder mixture: grinding balls) 1: 15, vacuum to a residual pressure of less than 10 Pa. For the process of mechanical activation use the planetary mill "Sand". Mechanical activation is carried out at a rotational speed of a mill drum of 280 rpm in intermittent mode for 180 minutes. These parameters provide the supply to the particles of the mixture of energy necessary to activate the formation of new phases.

Then, the process of plasma-spark sintering of the powder mixture in a graphite mold is carried out: a load of 15 MPa is applied, the powder mixture is heated by passing a pulsed direct current in vacuum at a heating rate of 80 deg./min, at a temperature of 1350 ° C, an exposure time of 8 minutes is made. Then carry out gradual cooling for 1 hour.

X-ray phase analysis of the obtained material confirms the adjustable phase content: 60-80 wt. % TiC and 20-40 wt. % SiC.

Thus, the present invention allows to obtain a high-temperature powder composite material based on silicon carbide and titanium with the ability to control the phase content and simplify the process.

Claims (1)

A method of obtaining a composite material based on silicon carbides and titanium, comprising preparing a powder mixture consisting of titanium, silicon carbide and graphite, and mechanically activating a powder mixture, characterized in that the powder mixture contains 66 wt. % Ti, 17 wt. % SiC and 17 wt. % C, while the mechanical activation of the powder mixture is carried out in a planetary mill at a drum rotation frequency of 240-320 rpm in an intermittent mode for 180 minutes, and then plasma-spark sintering of the mechanically activated powder mixture in vacuum at 1350-1450 ° C, pressure 15-30 MPa, holding for 5-8 minutes, followed by gradual cooling for 1 h.