RU2568555C1 - Method of producing nanostructured conglomerated powdered material for coating by gas-dynamic and thermal spraying - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method includes dispersing nanostructured material into a liquid medium using ultrasound and drying the solution to obtain agglomerated nanostructured particles. As the liquid medium an alcohol solution is used and as the nanostructured material a material is used, which consists of 20-80 vol % titanium carbonitride powder with particle size of 40-60 nm and the rest is uncoated aluminium powder with particle size of 90-100 nm. The obtained agglomerated nanostructured particles undergo attritor treatment for 30 minutes at rotary speeds of 1400-2000 rpm.

EFFECT: easier adjustment of mattress pressure for a specified user, low coating porosity using the obtained powdered material.

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Description

The invention relates to powder metallurgy, mainly to the field of nanostructured materials, allowing them to be used when applying wear-corrosion-resistant nanostructured coatings by microplasma or supersonic cold gas-dynamic spraying.

Known powder composite material based on aluminum and the method for its preparation (RF patent No. 2175682 C1, C22C 21/02, C22 C1 / 04, publ. 10.11.2001). The composite material contains components in the following ratio, wt.%: Silicon 43.5-46; nickel 3.5-5.0; beryllium 0.01-0.05; alumina 1.5-3.0; aluminum - the rest, with a ratio of aluminum to silicon of 1.0-1.18. The method for producing the material includes the manufacture of a melt containing aluminum, silicon, nickel, sputtering, the addition of powdered silicon, while additionally beryllium and oxygen are added to it to produce the melt.

Known composite sealing material for plasma spraying based on aluminum (RF patent No. 2044097 C1, C22C 21/00, C23C 4/04, publ. 09/20/1995). As a sealing material for plasma spraying, it is proposed to use a mixture based on aluminum, which contains graphite, sodium silicate and talc in the following ratio, wt.%: Graphite 2-10; sodium silicate 8-12; talcum powder 25-35; aluminum is the rest. The composition is obtained in a known manner by mixing aluminum with talc (TRPV talc rubber powder according to GOST 19729-74), then graphite is mixed into this mixture, then an aqueous solution of sodium silicate with a density of 1250 - 1300 kg / m ^{3 is} added and the composite is mixed again to strength 0.20 0.23 MPa. The mixed composite is granulated, dried in a convective fluidized bed, and the dry granules are crushed and sieved by grain size.

The closest in technical essence to the claimed invention is a nanostructured material for thermal spraying (RF patent No. 2196846 C2, C23C 4/10, C23C 4/12, B05D 1/10, publ. 01.20.2003, application US 96/18467 from November 13, 1996), selected as a prototype. The known patent provides a method for producing nanoparticles of aggregated forms suitable for use according to the traditional technology of spraying nanostructured coatings. In one of the options for its preparation, the nanostructured feedstock contains spherical agglomerates obtained by gas condensation treatment. The method is a flexible process used for the synthesis of experimental quantities of nanostructured metal and ceramic powders. A characteristic feature of this process is its ability to form loosely agglomerated nanostructured powders that can be synthesized at relatively low temperatures. An evaporated source is used to create powder particles convectively transported to a cold substrate and collected on the latter. Immediately after preparation, the synthesized powders are first dispersed into a liquid medium using ultrasound and then spray dried or emitted as a high-speed beam from a nebulizer. The compositions used are WC / Co, Cr ₃ C ₂ / Ni, Fe ₃ Mo ₃ C / Pe, SiC _x N _y , etc.

The disadvantages of the known methods, including the prototype, are the high porosity of the agglomerated nanostructured particles, when sprayed which forms a highly adhesive functional coating, however, due to the high porosity (10-15%), the cohesive strength and corrosion resistance of the coating are significantly reduced. Practice shows that for working in extreme operating conditions, the starting powders and coatings based on them should have a porosity of not more than 3-5%, otherwise there will be either mechanical or corrosion formation and crack opening and destruction of the coatings.

The technical result is the creation of a nanostructured conglomerate powder material for coating by gas-dynamic and thermal spraying methods, which allows to obtain coatings with high mechanical characteristics and low porosity (up to 2%).

The experience of our developments in the field of powder materials [“High-speed mechanosynthesis using disintegrator plants to obtain nanostructured powder materials of a metal-ceramic system of wear-resistant class”, E. Y. Burkanova, BV Farmakovsky, “Materials Science Issues”, St. Petersburg, No. 1 (69), 2012], including with nanoscale elements, shows that an effective tool to significantly reduce porosity is the mechanical effect on the material by comprehensive compression (isostatic press Contents) or due to the dynamic shock impacts (processing disintegrators or attritor). Success in the implementation of the technological scheme is determined by the optimization of the main parameters of the hardening processing process: cup rotation speed and processing time.

The technical result is achieved due to the fact that in the method for producing a nanostructured conglomerated powder material for coating by gas-dynamic and gas-thermal spraying methods, including dispersing the nanostructured material into a liquid medium by means of ultrasound and drying the solution to obtain agglomerated nanostructured particles, additional attritor treatment is carried out in accordance with the invention agglomerated nanostructured particles for 30 minutes at speed x rotation of 1400-2000 rpm.

As a nanostructured material, titanium carbonitride is used in an amount of 20-80 vol.% And uncoated aluminum powder is used for the rest, and an alcohol solution is used as a liquid medium.

Titanium carbonitride is used in the form of particles with a size of 40-60 nm, and uncoated aluminum powder is used in the form of particles with a size of 90-100 nm, with the following particle size ratio titanium carbonitride / uncoated aluminum powder = 1.0 / (1.7-2.3 )

In the process of attritor processing at the stated speeds, dense spherical granules are formed with the formation of a strong bond between nanosized particles of titanium carbonitride and particles of aluminum powder. At attritor processing speeds of less than 1400 rpm, a sufficient amount of mechanical energy is not transferred to the material for the introduction of titanium carbonitride into aluminum powder particles and the formation of dense agglomerated granules does not occur. At processing speeds of more than 2000 rpm, significant heating and subsequent oxidation of the processed material occurs. Titanium carbonitride does not penetrate into the solid oxide film formed on the surface of aluminum powder particles, and, as a result, granules do not form. A 30-minute treatment is sufficient to form a nanostructured conglomerated powder material from the entire volume of the starting material loaded into the attritor. With a shorter processing time, not all agglomerated material passes into dense conglomerates, which leads to loss of material at the dispersion stage, and a longer processing noticeably increases the cost of the resulting material due to a marked increase in the energy intensity of the process.

When titanium carbonitride is added over 80%, a strong mechanical bond between the TiCN nanosized particles is not ensured, which leads to an increase in porosity of up to 10% and embrittlement of the sprayed coating. When adding less than 20%, the required hardness value of the sprayed coating is not achieved.

The equivalent diameter of nanocrystalline components should not exceed 100 nm. Otherwise, volumetric energy will prevail over the surface, which makes it impossible to form dense granules due to the high surface energy of the nanocrystalline components.

When changing the particle size ratio in the direction of decreasing the size of aluminum powder (in particular, with a ratio of 1.0: 1.6), a noticeable increase in the porosity of the granules is observed, due to the insufficient amount of material for incorporation of titanium carbonitride into it, which does not occur the formation of a mechanical bond between the components. When changing the particle size ratio in the direction of increasing the size of the aluminum powder (in particular, at a ratio of 1.0: 2.4), the formation is not of an agglomerated powder material, but of a homogeneous mass unsuitable for further sieving and spraying.

The practical implementation of the proposed technical solution was carried out according to the following developed scheme: processing of nanoscale TiCN in a PSB-4 ultrasonic bath with a power of 0.45 kW for 15-20 minutes in 92% solution of ethyl or isopropyl alcohol, dispersing into a suspension of nanosized aluminum powder - ALEX ™ material with using the installation of LDU-3 MPR with a power of 1 kW; drying the suspension in a muffle laboratory furnace type SNOL-1 to the complete removal of alcohol; high-energy attritorial processing of the powder for 30 minutes at a speed of rotation of the cups in the range of 1400-2000 rpm

The invention is illustrated by drawings, which depict:

in FIG. 1 - SEM image of a nanostructured conglomerated powder material;

in FIG. 2 - SEM image of a thin section of a nanostructured conglomerated powder material;

in FIG. 3 - SEM image of a transverse thin section of a coating obtained on the basis of a nanostructured conglomerated powder material.

Upon a detailed examination of FIG. 1 it is clearly seen that the nanocrystalline components of the conglomerated powder material have strong mechanical interstitial bonds. So, the nanoscale components of the cubic shape, which according to the X-ray microanalysis are identified as TiCN, are tightly connected to the nanoscale particles of a spherical shape, which are identified as ALEX ™. When considering FIG. 2, strong bonds between nanoscale components of various morphology are also noticeable. A CEM image of the cross section of the coating is shown in FIG. 3. The coating is dense, non-porous, it also inherits a nanostructured state with a uniform distribution of components, which gives an ungraded hardness in the longitudinal and transverse directions.

Example 1

To dispersed in a 92% solution of ethyl alcohol nanoscale TiCN powder was added nanosized material alextm in an amount of 80% vol. (calculated on dry components), with a ratio between particle sizes TICN / ALEX ™ = 1.0 / 1.7. ALEX ™ nanosized material was dispersed into an alcohol suspension using an LDU-3 MPR unit with a power of 1 kW for 20 minutes. The suspension was dried in a muffle laboratory electric furnace of the SNOL-1 type until the alcohol was completely removed. The dry powder composition was subjected to attritor treatment for 30 minutes, and the speed of rotation of the cups was in the range of 1400-2000 rpm After processing, the powder material was dispersed with the allocation of fractions for spraying 20-40 microns.

Coatings were sprayed from the proposed nanostructured conglomerated powder material with dimensions from 20 to 40 microns using a Dimet-3 type HGDN apparatus. The composition of the sprayed material, determined on a Bruker D8 Advance X-ray diffractometer, in wt.%:

Al 88.3;

Al ₂ O ₃ - 8.3;

TiCN - 3.4.

The thickness of the coatings formed by this method is 50-500 microns, which provides the required performance characteristics. The porosity of this kind of coatings, measured using a computerized image analysis of the cross section on a LeicaDM-2500 microscope, was 0.3%. The results of microhardness studies performed at the NanoScan-3D universal research complex showed that the coatings have a microhardness of 10.31 GPa.

Example 2

To dispersed in a 92% solution of isopropyl alcohol nano-sized powder TiCN was added nano-sized material ALEX ™ in an amount of 20% vol. (calculated on dry components), with a ratio between particle sizes TiCN / ALEX ™ = 1.0 / 2.3. ALEX ™ nanosized material was dispersed into an alcohol suspension using an LDU-3 MPR unit with a power of 1 kW for 15 minutes. The suspension was dried in a muffle laboratory electric furnace of the SNOL-1 type until the alcohol was completely removed. The dry powder composition was subjected to attritor treatment for 30 minutes, and the speed of rotation of the cups was in the range of 1400-2000 rpm After processing, the powder material was dispersed with the allocation of fractions for spraying 20-40 microns.

Coatings were sprayed from the proposed nanostructured conglomerated powder material with dimensions from 20 to 40 μm using a microplasma spraying machine of the UGNP 2/2250 type. The composition of the sprayed material, determined on a Bruker D8 Advance X-ray diffractometer, in wt.%:

Al - 64.4;

Al ₂ O ₃ - 6.4;

TiCN - 29.2.

Slight heating of the sprayed material due to the short-term stay of the powder in the plasma jet provides partial penetration of the powder, which contributes to the preservation of the nanostructure in the sprayed conglomerate. The thickness of the coatings formed in this way is 50-500 microns, which provides the required performance characteristics.

Studies of the microhardness and porosity of the coatings were measured by the methods described in example 1, and amounted to 14.24 GPa and 1.3%, respectively. Adhesion studies were conducted by shear testing. The research results are shown in the table.

The application of the proposed method for producing nanostructured conglomerated powder material for coating by gas-dynamic and gas-thermal spraying methods allows to reduce the porosity of the coatings in comparison with the prototype and to ensure their high strength characteristics.

Claims (1)

A method of producing a nanostructured conglomerated powder material for coating by gas-dynamic and gas-thermal spraying, comprising dispersing a nanostructured material into a liquid medium by means of ultrasound and drying the solution to obtain agglomerated nanostructured particles, characterized in that an alcohol solution is used as a liquid medium and a nanostructured material is used material consisting of 20-80 vol.% titanium carbonitride powder with a size of 40-60 nm and the rest is epokryty aluminum powder with a particle size of 90-100 nm, with the following ratio of said powder particle sizes:
titanium carbonitride powder / uncoated aluminum powder = 1.0 / (1.7-2.3),
in this case, an attritor treatment of agglomerated nanostructured particles is carried out for 30 minutes at rotation speeds of 1400-2000 rpm.

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