RU2750784C1 - Method for obtaining powder composite material - Google Patents

Abstract

FIELD: powder metallurgy.

SUBSTANCE: invention relates to powder metallurgy, in particular to the production of powder composite materials with a binder based on iron and a hardener from refractory compounds. It can be used for the application of wear-resistant coatings and additive technologies. A reaction powder mixture is prepared from ferrotitanium, previously crushed to a fineness of not more than 56 microns, and soot with a fineness of not more than 0.2 microns, taken in a weight ratio of 92.5/7.5. It is mechanically activated in a planetary mill at a drum rotation speed of 755-960 rpm and a centrifugal acceleration of 40-65 g for 10-15 minutes. Then, the synthesis is carried out in the thermal explosion mode.

EFFECT: production of a composite material of a given phase composition, providing an increase in wear resistance.

3 cl, 5 dwg, 2 tbl, 3 ex

Description

The invention relates to powder metallurgy, in particular to the production of powder composite materials with a binder based on iron and a hardener from refractory compounds, in particular, titanium carbide. The invention makes it possible to obtain powders with the structure of a metal-matrix composite of a given phase composition (titanium carbide - an iron-based binder), which can be used for applying wear-resistant coatings and for additive technologies.

A known method of producing a composite material based on titanium carbide from RF patent 2095193, publ. 10.11.1997 [1].

The invention relates to powder metallurgy and makes it possible to obtain a composite material based on titanium carbide with high abrasive characteristics and can be used for applying a protective coating to metal surfaces. The essence of the invention: a mixture of powders of initial components containing titanium, chromium, carbon is prepared, taken in the amount necessary to obtain the target material containing chromium carbide and titanium carbide at their molar ratio of 1: 1-10, the mixture is placed in a reactor, synthesis is carried out in combustion mode by local ignition of the mixture under a pressure of 0.005-0.05 MPa, after extraction, the target material is subjected to grinding and fractionation, while an additional 15-35 wt. % of nickel powder, and after mixing, the mixture can be briquetted in the form of granules or tablets.

The disadvantage of this invention is the complexity and multistage procedure for obtaining a metal matrix composite suitable for applying a wear-resistant coating and for additive technologies.

A known method of manufacturing blanks from composite materials from RF patent 2285583, publ. 20.10.2006 [2].

A method of manufacturing blanks from composite materials includes mixing steel powders fractions of no more than 93 microns and a refractory compound of a fraction of not more than 40 microns in a ratio of 9: 1-7: 3 by weight and grinding to a fraction of not more than 40 microns. The charge is placed in gas-permeable shells, sealed, and hydrostatic pressing is carried out at 300-1000 MPa. The resulting blanks are sintered in vacuum at a residual pressure with a stepwise heating mode and a controlled speed between individual steps and annealed in a stepwise mode from the sintering temperature. The technical result is an increase in density, uniformity and strength.

The disadvantage of the known invention is that to obtain the final product, a mixture with a ready-made industrial powder of titanium carbide is used with the addition of steel powder, which does not make it possible to obtain a homogeneous intragranular metal-matrix structure of the composite. Also, to obtain a functional end product, it is necessary to use several stages of energy-intensive / labor-intensive operations.

A known method of producing a powder composition based on titanium carbosilicide from RF patent 2460706, publ. 09/10/2012 [3].

A method for producing a powder composition based on titanium carbosilicide includes obtaining a powder mixture consisting of titanium, silicon carbide and graphite taken in a molar ratio of 3: 1.25: 0.75, mechanosynthesis in a planetary evacuated mill at a drum rotation frequency of 320 rpm, in intermittent mode, cold pressing, heat treatment in a vacuum furnace at a temperature of 1350 ° C for 3 hours and subsequent grinding of the obtained sample in a planetary mill using titanium tooling to obtain a powder of the required size. The technical result of the invention is to obtain a powder composition with a high content of titanium carbosilicide without undesirable impurities.

The disadvantage of the known invention is that expensive titanium powder is used as a starting component in a large volume to obtain the final product. Also, the process of synthesis of a composite powder material is carried out in a time-consuming and energy-consuming vacuum sintering mode.

A known method of producing a high-temperature powder composite material based on silicon carbides and titanium from RF patent 2638866, publ. 12/18/2017 [4].

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

The disadvantages are the same as in the RF patent 2460706, that is, the method uses a large amount of expensive titanium powder and the synthesis process is carried out in a time-consuming and energy-consuming vacuum sintering mode.

The technical objective of the present invention is to develop a method for producing a powder composite material with the structure of a metal-matrix composite of a given phase composition: titanium carbide - an iron-based binder. Received by the proposed method, the powder composite material can be used for the application of wear-resistant coatings and use in additive technologies.

Also, an additional technical result of the invention is that the use of the method makes it possible to reduce material costs by an order of magnitude due to the use as an initial component of cheap cast ferrotitanium - a product of large-scale ferroalloy metallurgy instead of expensive titanium powder.

The specified technical result is achieved by the fact that a method for producing a powder composite material is applied, including the preparation of a reaction powder mixture by grinding ferrotitanium and mixing the initial components with its subsequent mechanical activation, pressing a workpiece, carrying out synthesis, while preparing a reaction powder mixture from pre-ground to a fineness of no more 56 microns of ferrotitanium and carbon black - soot with a fineness of not more than 0.2 microns, taken in a weight ratio of 92.5 / 7.5, while its subsequent mechanical activation is carried out in a planetary mill at a drum rotation speed of 755-960 rpm, which corresponds to a centrifugal acceleration of 40-65 g for 10-15 minutes, and the synthesis is carried out in a thermal explosion mode.

Pre-ground ferrotitanium powder for preparing a reaction mixture with carbon black is obtained as follows: first, cast ferrotitanium is crushed to a fraction of <315 μm; then, the obtained coarse ferrotitanium powder is milled in a planetary mill in air for 5 minutes at a drum rotation speed of 480 rpm, which corresponds to 16 g.

The workpiece is pressed from the activated reaction powder mixture to a residual porosity of 40-45%, it is placed in a sealed reactor filled with argon at atmospheric pressure, then the reactor is placed in a furnace preheated to 800 ° C. After heating the powder compact to the autoignition temperature, an exothermic reaction of titanium carbide synthesis takes place in the thermal explosion mode with the formation of a synthesis product in the form of a metal matrix composite.

Disclosure of the invention.

A method has been developed for producing a powder composite material of the system - titanium carbide with a binder based on iron using a synthesis reaction in a powder mixture of ferrotitanium and carbon (soot).

The chemical composition of ferrotitanium FTi35C5 used in the invention (according to the supplier's certificate) is presented in Table 1. According to the results of X-ray diffraction analysis (Fig. 1), the initial ferrotitanium contains two phases: Ti (Fe _0.875 Al _0.125 ) ₂ - a solid solution of aluminum in the intermetallic TiF ₂ and Ti _5.21 Fe _0.02 Si _2.7 - solid solution of iron in titanium silicide Ti ₅ Si ₃ . The phase based on the intermetallic compound is the main one (84 wt%), and the content of the phase based on the silicide is 16%. The microstructure and morphology of press crushed ferrotitanium are shown in FIG. 2.

The method makes it possible to obtain powders with the structure of a metal-matrix composite of a given phase composition (titanium carbide - an iron-based binder), which can be used for applying wear-resistant coatings and in additive technologies. At the same time, the proposed method provides the synthesis of target phases in an optimal ratio, at which the content of the solid carbide phase, dispersion, morphology and uniformity of the distribution of carbide particles over the volume of the metal bond gives a manifold increase in wear resistance. High abrasive wear resistance is ensured by the fact that hard carbide inclusions prevent the abrasive grain from wearing out the intercarbide layers of the metal bond.

The method of obtaining a powder composite material is based on the synthesis of pre-mechanically activated reaction powder mixtures in a thermal explosion mode.

At the same time, a charge is prepared from a mixture of pre-crushed cast ferrotitanium with a fineness of not more than 56 microns and carbon black - soot with a fineness of not more than 0.2 microns. The selected dispersion of the milled ferrotitanium powder (less than 56 microns) was determined based on the efficiency of technological processes for milling ferrotitanium and mechanoactivation of the reaction mixture. To obtain a powder of ferrotitanium finer than 56 μm, a longer grinding process is required, and the use of larger fractions (more than 56 μm) can complicate the synthesis process in a mechanically activated mixture and lead to incomplete transformations and contamination of the synthesis products with reagents. Mechanical activation of crushed ferrotitanium is carried out in a planetary mill in air for 5 minutes at a drum rotation speed of 480 rpm, which corresponds to 16 g. This grinding time is sufficient for a 98% yield of the fraction less than 56 microns. Grinding of a single charge of ferrotitanium powder lasting more than 5 minutes leads to additional wear of the equipment, to additional labor and energy costs. The morphology of the coarse powder particles obtained by crushing under pressure and subjected to subsequent grinding is shown in FIG. 2b.

These components are taken in a weight ratio of 92.5 / 7.5, respectively (i.e., for 92.5 weight parts of crushed activated ferrotitanium powder, 7.5 weight parts of carbon black are needed). This ratio of these components is selected based on the complete consumption of titanium from ferrotitanium powder for the reaction with soot to form titanium carbide.

The mixing of the powders is preliminarily carried out in a standard mixer with an offset axis of rotation (of the "drunken barrel" type) for 4 hours. Then the charge before synthesis in the thermal explosion mode is subjected to mechanical activation in a high-energy planetary mill. The use of the proposed method allows one to reduce material costs by an order of magnitude due to the use of ferrotitanium instead of expensive titanium powder. The use of additional mechanical activation of the reaction mixtures guarantees the complete completion of the low-temperature solid-phase reaction of titanium carbide synthesis in the reaction mixture of ferrotitanium with soot with the formation of a metal-matrix composite strengthened by a submicron carbide phase. This structure of the composite powder improves the mechanical properties of coatings and bulk materials obtained using the synthesized powder.

Additional mechanical activation of the reaction powder mixture is carried out during the stated time in a planetary mill at drum rotation speeds corresponding to a centrifugal acceleration of 40-65 g. The declared parameters of the technological modes of the method are selected experimentally.

Modes of additional mechanical activation (MA) of the reaction powder mixture and the phase composition of the final synthesis products are presented in Table 2. For practical use, modes are recommended that ensure the minimum residual content of the reagent (ferrotitanium) at an average intensity that does not cause overheating of the powder charge. Overheating can lead to powder sticking to balls and drum walls or mechanosynthesis with "poisoning" of the reaction surface with a thin layer of carbide, which prevents subsequent synthesis in the thermal explosion mode.

The residual porosity of the workpiece equal to 40-45% is necessary for the successful synthesis in the thermal explosion mode, which is carried out in a sealed reactor filled with argon at atmospheric pressure. In this case, the reactor is placed in an oven preheated to 800 ° C. When the reactor was kept at this temperature in the furnace, the walls of the reactor were heated and the compact from the reaction mixture placed inside the reactor was heated to the temperature of initiation of the exothermic synthesis reaction.

Table 1

Chemical composition, % Ti Al Si C P S Cu V Mo Zr Sn 32.45 9.75 4.65 0.18 0.035 0.029 0.85 0.88 0.35 0.15 0.02

table 2

No. MA mode Content in synthesis products,% TiC α-Fe Ti (Fe _0.875 Al _0.125 ) ₂ one 40g, 5 min 10.4 52.0 37.6 2 40g, 10 mins 33.2 60.6 6.2 3 40g, 15 min 40.4 52.2 7.4 four 64.2g, 10min 36.2 63.8 -

The invention is illustrated in figures 1-5.

FIG. 1 shows an X-ray diffraction pattern of the used FTi35S5 ferrotitanium powder.

FIG. 2 shows the microstructure (a) and the morphology of particles of cast ferrotitanium FTi35S5 after crushing under a press (b).

FIG. 3 shows the fractional composition of ferrotitanium powder grinding time in a planetary mill at a "soft" mode (480 rev / min, M _w / M _n = 10). Grinding time (minutes): a-0 (initial); b-1 min; c-2 min; g-3 min.

FIG. 4 shows the morphology (a) and microstructure (b) of the synthesized powder of the TiC-Fe composite obtained by thermal explosion of a mechanically activated (64.2 g, 10 min) reaction powder mixture "ferrotitanium - soot".

FIG. 5 shows the X-ray diffraction pattern of the synthesized powder of the TiC-Fe composite obtained by the thermal explosion of a mechanically activated (40 g, 10 min) reaction powder mixture "ferrotitanium - soot".

Examples of specific implementation.

Example 1.

Ingots of ferrotitanium FTi35S5 as delivered at the factory are subjected to preliminary mechanical crushing on a press at a pressure of about 4.9 MPa. The crushing products were sieved through sieves with a mesh size of 315 and 56 μm. Then the fraction with a fineness of 56-315 microns is additionally subjected to grinding in a planetary mill with a drum rotation speed of 480 rpm. with a ratio of balls and ferrotitanium powder of 5: 1 for 5 minutes. Grinding is carried out in air without filling the grinding drums with inert gas. Ground ferrotitanium powder is sieved through a 56 µm sieve. In this case, the percentage yield of the target fraction not exceeding 56 μm is 98 mass. % of the initial download.

To obtain the reaction mixture, the obtained ground ferrotitanium powder with a fineness of less than 56 μm is mixed with a powder of technical carbon (soot) grade P-803 (fineness <0.2 μm), which was previously dried in a vacuum at 600 ° C for 1 h; the specified components in a weight ratio of 92.5 / 7.5 (i.e., for 92.5 g of crushed activated ferrotitanium powder, 7.5 g of soot is needed). The mixing of ferrotitanium powder and carbon black is carried out in a mixer with an offset axis of rotation of the “drunken barrel” type for 4 hours.

The resulting reaction powder mixture is additionally subjected to mechanical activation for 10 minutes in a planetary mill at a drum rotation speed of 754.7 rpm, which corresponds to a centrifugal acceleration of 40 g. The drums were preliminarily purged with argon for 5 minutes at an argon flow rate of 4 l / min and left at an excess pressure of 1 atm. The ratio of the mass of the balls to the mass of the powder mixture in the drums is 20/1. After mechanical activation, the outer surface of the drums was cooled in running cold water for 5 minutes to prevent ignition of the treated mixtures when the drums were opened.

The mechanically activated reaction mixture was molded in the form of cylindrical blanks with a diameter of 20 mm with a residual porosity of 40-45%, then placed in a cylindrical shell of titanium foil 100 μm thick and 21 mm in diameter. for the synthesis.

Synthesis using a compacted workpiece from a reaction powder mixture was carried out in the thermal explosion mode. For this purpose, the workpiece was placed in a sealed reactor filled with argon at atmospheric pressure. The reactor was placed in an oven preheated to 800 ° C. When the reactor was kept in the furnace, the preform placed inside the reactor was heated from the reaction mixture by radiation from the walls of the reactor to the temperature of initiation of the synthesis reaction with an abrupt increase in the preform temperature. After the completion of the exothermic reaction, the preform temperature was gradually decreased to the furnace temperature, after which the reactor was removed from the furnace and cooled in air. During the entire time from placing the reactor in the furnace until it is completely cooled in air to prevent oxidation, the reactor was blown through with an argon flow at a rate of 2 L / min.

The phase composition of the synthesis product according to example 1 corresponds to number 2 of table 2.

Example 2.

Carried out analogously to example 1 to mechanical activation of the reaction mixture. The difference from example 1 is that the specified reaction powder mixture is additionally subjected to mechanical activation for 15 minutes in a planetary mill. This is followed by a sequence of technological operations similar to example 1.

The phase composition of the synthesis product according to example 2 corresponds to number 3 of table 2.

Example 3.

Carried out analogously to example 1 to mechanical activation of the reaction mixture. The difference from example 1 is that the specified reaction powder mixture is additionally subjected to mechanical activation in a planetary mill at a drum rotation speed of 960 rpm, which corresponds to a centrifugal acceleration of 64.2 g for 10 minutes. This is followed by a sequence of technological operations similar to example 1.

The phase composition of the synthesis product according to example 3 corresponds to number 4 of table 2.

Claims (6)

1. A method of producing a powder composite material with the structure of a metal-matrix composite of the phase composition titanium carbide - an iron-based binder, including the preparation of a reaction powder mixture followed by its mechanical activation, pressing a workpiece and carrying out synthesis, characterized in that a reaction powder mixture is prepared from pre-crushed ferrotitanium with dispersion <56 microns and carbon black - soot with a dispersion of not more than 0.2 microns, taken in a weight ratio of 92.5 / 7.5, while its subsequent mechanical activation is carried out in a planetary mill at a drum rotation speed of 755-960 rpm, which corresponds to a centrifugal acceleration of 40-65 g, for 10-15 minutes, and the synthesis is carried out in a thermal explosion mode. 2. The method according to claim 1, characterized in that the ferrotitanium powder with a fineness of less than 56 microns is obtained as follows: - first, cast ferrotitanium, which is a product of large-scale production of ferroalloys, is crushed under a press, followed by sieve screening of the 56-315 micron fraction. - then the obtained fraction 56-315 μm is milled in a planetary ball mill in air for 5 minutes at a drum rotation speed of 480 rpm, which corresponds to 16 g. 3. The method according to claim 1, characterized in that the pressing of the workpiece from the mechanically activated reaction mixture is carried out to a residual porosity of 40-45%. 4. The method according to claim 1, characterized in that the synthesis is carried out in a thermal explosion mode in a sealed reactor filled with argon at atmospheric pressure, while the reactor is placed in a furnace preheated to 800 ° C.

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