RU2730306C1 - Method of dry electrically polishing of part - Google Patents

Abstract

FIELD: electricity; technological processes.

SUBSTANCE: invention relates to the technology of electropolishing surfaces of parts from metals and alloys and can be used for processing surfaces of blades of turbomachines. Proposed method comprises immersion of metal part into electroconductive medium and supply of opposite sign of electric potential to part and electrically conductive medium. Electro conductive medium used is anionites made in form of fibers and impregnated with electrolyte solution, providing electrical conductivity of said fibers, ion removal of metal from surface of part with removal of microprotrusions and contact of entire polished surface of part with said fibers and fibers between each other. Fibers and part are brought into relative motion, electric potential is supplied to the part and fibers, which ensures ion removal of metal from the surface of the processed part and its electro-polishing in the medium of said fibers until the specified roughness of the polished part surface is obtained.

EFFECT: improved operating characteristics of the part.

6 cl, 1 dwg

Description

The invention relates to a technology for electropolishing the surface of parts made of metals and alloys and can be used for processing the surfaces of turbomachine blades to improve their performance.

With an increase in the surface roughness of critical metal parts operating under the influence of significant alternating loads, for example, shafts, gas turbine blades, etc., their performance characteristics sharply decrease. The quality of surface treatment of the airfoil of the blades significantly affects their strength characteristics, for example, an increase in the class of surface cleanliness contributes to an increase in the endurance limit and static strength of the blades (VF Makarov, EN Bychina, AO Chuyan. Mathematical modeling of the polishing process blades of gas turbine engines // Aviation and space engineering and technology. No. 8 (85), 2011, pp.11-14). The developed roughness of the surface of gas turbine blades leads to a deterioration in the gas-dynamic stability of a gas turbine engine (GTE), to an increase in aerodynamic losses, leading to a decrease in efficiency, to a loss of power, an increase in unit costs and to a decrease in the efficiency of an engine or a gas turbine plant.

At the same time, the production and repair of blades of gas turbine engines (GTE) and plants (GTU), due to high requirements for surface quality (Ra≤0.32 ... 0.16 microns), is characterized by significant labor intensity of their finishing. This causes problems in machining the surfaces of turbomachine parts. In this regard, the development of methods for obtaining high-quality surfaces of turbomachine parts is a very urgent task.

A known method of polishing the surface of a part with a petal circle, in which the parts (a turbine blade) report a reciprocating movement relative to the tool (AS USSR No. 1732604. IPC B24B 19/14. A method of polishing the feather of GTE blades with a petal circle. Publ. Bul. No. 1, 2014), in which polishing is performed with deformation of the flap wheel.

There is also known a method of processing that allows you to polish the curved edge of the blade of a gas turbine blades filled with a radial polishing wheel moving along the blade (RF Patent No. 2379170. IPC B24B 19/14. Method of processing blades of gas turbine engines. Publ. 2010).

However, mechanical action on the surface of the workpiece with a polishing tool in the known methods of polishing the workpiece surface leads to a deterioration in the quality parameters of the surface layer of materials. This circumstance leads to a decrease in the performance characteristics of the part, especially in cases of processing turbine blades with a thin nib.

The most promising methods of processing parts of complex shape, in particular the blades of turbomachines are electrochemical methods of surface polishing [Grilikhes S.Ya. Electrochemical and Chemical Polishing: Theory and Practice. Influence on the properties of metals. L., Mashinostroenie, 1987], with the greatest interest for the area under consideration are methods of electrolytic-plasma polishing (EPP) parts [for example, Patent GDR (DD) No. 238074 (A1), IPC C25F 3/16, publ. 06.08.1986].

There is also known a method of polishing metal surfaces, including anodic treatment in an electrolyte [Patent RB No. 1132, IPC C25F 3/16, publ. 1996, BI No. 3], as well as a method of electrochemical polishing [US Patent No. 5028304, IPC B23H 3/08, C25F 3/16, C25F 5/00, publ. 07/02/1991].

However, the known methods of electropolishing do not allow for a uniform surface treatment of a metal alloy part, especially parts of complex shape.

The closest technical solution chosen as a prototype is the dry electropolishing of a metal part, which consists in filling a working container made of an electrically conductive material with electrically conductive granules, fixing the part on a holder, immersing the part in electrically conductive granules filling the container, connecting the part to the anode, and the container to the cathode [WO2017186992 A1 - Method for smoothing and polishing metals via ion transport by means of free solid bodies, and solid bodies for carrying out said method. Publ. 2017.11.02]...

However, the known prototype method [WO2017186992] has low reliability and cannot be used for surface treatment of critical parts, such as blades of turbomachines, since there is a significant likelihood of "soldering" of granules to the surface to be treated and the resulting defects, leading to a decrease in performance processed parts.

The problem to be solved by the claimed invention is to improve the quality and reliability of processing metal parts, especially critical parts of complex shapes, such as blades of turbomachines.

The technical result of the invention is to improve the quality and reliability of the surface treatment of a metal part by increasing the uniformity of its surface processing, reducing the likelihood of defects and reducing its roughness.

The technical result is achieved due to the fact that in the method of dry electropolishing of a part, including immersing a metal part in an electrically conductive medium and supplying an opposite electric potential to the part and an electrically conductive medium, in contrast to the prototype, anion exchangers made in the form of fibers impregnated an electrolyte solution, which ensures the electrical conductivity of the said fibers and the ionic entrainment of metal from the surface of the part with the removal of microprotrusions from it, provide contact of the entire polished surface of the part with the said fibers and fibers with each other, set the fibers and the part in relative motion, supply the part and the fibers with an electric potential, providing ionic removal of metal from the surface of the workpiece and its electropolishing in the environment of the above fibers to obtain a given roughness of the polished surface of the workpiece.

In addition, the following additional methods of performing the method are possible: electropolishing is carried out by supplying a positive electric potential to the part, and a negative electric potential from 25 to 35 V to the said fibers, and the said fibers and the part are additionally carried out in a vibration motion with a frequency of 50-400 Hz, providing uniform washing by the mentioned fibers of the treated surface of the part; as said fibers of anion exchange resins, ion-exchange resins obtained on the basis of copolymerization of polystyrene or polyacrylate and divinylbenzene are used, and the cross-sectional dimensions of the fibers are selected from the range from 0.05 to 0.6 mm with their length from 4 mm to 45 mm, and the treatment with said fibers carried out in a pulsed mode with a change in polarity, with a pulse frequency range from 20 to 250 Hz, a pulse period from 4.3 to 72 μs, with a positive polarity current amplitude during a pulse from + 20 to 120 A and its duration 0.2 to 1 , 4 μs, with a current amplitude of negative polarity during a pulse from 25 to 40% of the used current amplitude of positive polarity, and its duration 0.1 to 0.6 μs, with a rectangular or trapezoidal shape of output current pulses and the duration of pauses between pulses from 4 to 70 μs.

a turbomachine made of alloy steel is used as a part, it is additionally driven into a reciprocating motion relative to its longitudinal axis, and one of the following aqueous solutions is used as electrolytes for impregnating said fibers from anion exchangers: or NH₄F, concentration from 6 to 24 g / l, or NaF, concentration from 4 to 18 g / l, or KF, concentration from 35 to 55 g / l, or NH mixture₄F and KF with NH content₄F - from 5 to 15 g / l and KF - from 30 to 50 g / l, or mixtures of NaF and KF with NaF content - from 3 to 14 g / l and KF - from 35 to 60 g / l, or NH mixture₄F and NaF with NH content₄F - from 4 to 12 g / l and KF - from 35 to 55 g / l, or NH mixtures₄F, NаF and KF with NH content₄F - from 3 to 9 g / l and KF - from 20 to 30 g / l, and NaF - from 10 to 25 g / l, or NH mixtures₄F and НF with NH content₄F - from 5 to 15 g / l and НF - from 3 to 5 g / l, or from 8 to 14% aqueous solution of NaNO_3,or in electrolytes with compositions, wt%: (NH₄)₂SO₄- five; Trilon B - 0.8, or containing sulfuric and orthophosphoric acids, block copolymer of ethylene and propylene oxides and sodium salt of sulfonated butyl oleate in the following ratio of components, wt%:

Sulfuric acid - 10-30

Ortho-phosphoric acid - 40-80

Block copolymer of ethylene and propylene oxides - 0.05-1.1

Sodium salt of sulfonated butyl oleate - 0.01-0.05

Water - Rest;

a turbomachine blade made of titanium alloy is used as a part, it is additionally driven into reciprocating motion relative to its longitudinal axis, and one of the following aqueous solutions is used as electrolytes for impregnating said fibers from anion exchangers: or an aqueous solution of a mixture of NH ₄ F   and KF with NH ₄ F content - from 8 to 14 g / l and KF - from 36 to 48 g / l, or an aqueous solution containing 30 - 50 g / l KF 2H ₂ O and 2 - 5 g / l CrO ₃ ; as a part, a turbomachine blade made of nickel alloy is used, it is additionally driven into reciprocating motion relative to its longitudinal axis, and one of the following aqueous solutions is used as electrolytes for impregnating said fibers from anion exchangers: an aqueous solution of ammonium fluoride salt with a concentration of 6 - 9.0 g / liter, or an aqueous solution of ammonium sulfate with a concentration of 0.8 ... 3.4 or an aqueous solution containing sulfuric and orthophosphoric acids, a block copolymer of ethylene and propylene oxides and sodium salt of sulfonated butyl oleate in the following ratio of components, wt. %:

Sulphuric acid 10-30 Orthophosphoric acid 40-80 Block copolymer of ethylene and propylene oxides 0.05-1.1 Sulfonated butyl oleate sodium salt 0.01-0.05 Water Rest

The essence of the invention is illustrated by drawings. The figure (Fig.) Shows a schematic arrangement of the electropolished part in the environment of electrically conductive fibers. The figure contains: 1 - holder; 2 - workpiece to be processed; 3 - metal rod-electrode; 4 — anion-resin fibers impregnated with electrolyte. (arcuate arrows indicate the direction of rotation of the part; straight arrows are the reciprocating movement of the part, relative to the anionite fibers; ω is the angular velocity of rotation of the part.)

The inventive method for dry electropolishing of a part, in particular the surface of a blade airfoil during its manufacture or refurbishment, is carried out as follows.

Part 2 is fixed on the holder 1 (Fig.) And placed in a working container filled with electrically conductive anionite fibers 4. An electric potential is applied to the workpiece 2 and the metal rods-electrodes 3 and the drive for rotation of the workpiece 2 is switched on and the surface of the workpiece 2 is electropolished until the specified roughness is obtained, after which the finished workpiece 2 is removed and put into a container for storage. In this case, depending on the configuration of part 2, it is possible to rotate the part either in reciprocating motion, or simultaneously or sequentially in rotation and reciprocation.

Electropolishing of part 2 is carried out in an environment of fibers 4 made of anion exchangers impregnated with an electrolyte solution, which ensures the electrical conductivity of fibers 4 and ionic entrainment of metal from the surface of part 2 with the removal of microprotrusions from it. During processing, the entire polished surface of part 2 is in contact with fibers 4 and fibers 4 with each other, part 2 is set in rotational motion, an electric potential is applied to part 2 and fibers 4, which provides ionic removal of metal from the surface of the workpiece 2 and its electropolishing in the medium of fibers 4 to obtain the specified roughness of the polished surface.

As anion exchangers for fibers 4, ion-exchange resins are used, obtained on the basis of copolymerization of either polystyrene or polyacrylate and divinylbenzene. The cross-sectional dimensions of the fibers 4 are selected from the range from 0.05 to 0.6 mm with a length from 4 mm to 45 mm. When processing part 2, it is additionally carried out in vibration movement.

Electropolishing with fibers 4 is carried out either by applying a positive electric potential to part 2 and a negative electric potential to fibers 4, ranging from 25 to 35 V, or in a pulse mode with a polarity change, with a pulse frequency range from 20 to 100 Hz, a pulse period from 50 μs to 10 μs, with a current amplitude of positive polarity during a pulse of +50 A and their duration of 0.4 to 0.8 μs, with a current amplitude of negative polarity during a pulse of 20 A, and their duration of 0.2 to 0.4 μs, with a rectangular shape of the output current pulses and the pause duration between pulses from 49.6 μs to 9.2 μs.

When polishing a turbomachine blade (part 2) made of alloy steel, the blade 2 is additionally driven into reciprocating motion relative to its longitudinal axis. One of the following aqueous solutions is used as electrolytes for impregnating fibers from anion exchangers: or NH₄F, concentration from 6 to 24 g / l, or NaF, concentration from 4 to 18 g / l, or KF, concentration from 35 to 55 g / l, or NH mixture₄F and KF with NH content₄F - from 5 to 15 g / l and KF - from 30 to 50 g / l, or mixtures of NaF and KF with NaF content - from 3 to 14 g / l and KF - from 35 to 60 g / l, or NH mixture₄F and NaF with NH content₄F - from 4 to 12 g / l and KF - from 35 to 55 g / l, or NH mixtures₄F, NаF and KF with NH content₄F - from 3 to 9 g / l and KF - from 20 to 30 g / l, and NaF - from 10 to 25 g / l, or NH mixtures₄F and НF with NH content₄F - from 5 to 15 g / l and НF - from 3 to 5 g / l, or from 8 to 14% aqueous solution of NaNO_3,or in electrolytes with compositions, wt%: (NH₄)₂SO₄- five; Trilon B - 0.8, or containing sulfuric and orthophosphoric acids, block copolymer of ethylene and propylene oxides and sodium salt of sulfonated butyl oleate in the following ratio of components, wt%:

Sulfuric acid - 10-30

Ortho-phosphoric acid - 40-80

Block copolymer of ethylene and propylene oxides - 0.05-1.1

Sodium salt of sulfonated butyl oleate - 0.01-0.05

Water is the rest.

When polishing a blade of a turbomachine made of a titanium alloy, it is additionally driven into reciprocating motion relative to its longitudinal axis, and one of the following aqueous solutions is used as electrolytes for impregnating the said granules of anionites: or an aqueous solution of a mixture of NH ₄ F   and KF with NH ₄ F content - from 8 to 14 g / l and KF - from 36 to 48 g / l, or an aqueous solution containing 30 - 50 g / l KF 2H ₂ O and 2 - 5 g / l CrO ₃ .

When polishing a blade of a turbomachine made of a nickel alloy, it is additionally driven into a reciprocating motion relative to its longitudinal axis, and one of the following aqueous solutions is used as electrolytes for impregnating said fibers from anion exchangers: an aqueous solution of ammonium fluoride salt with a concentration of 6-9.0 g / liter, or an aqueous solution of ammonium sulfate with a concentration of 0.8 ... 3.4 or an aqueous solution containing sulfuric and orthophosphoric acids, a block copolymer of ethylene and propylene oxides and sodium salt of sulfonated butyl oleate in the following ratio, wt. %:

Sulphuric acid 10-30 Orthophosphoric acid 40-80 Block copolymer of ethylene and propylene oxides 0.05-1.1 Sulfonated butyl oleate sodium salt 0.01-0.05 Water Rest

The polishing process is carried out until a predetermined value of the surface roughness of the blades is obtained.

Reciprocating movements of part 2 relative to fibers 4 and their vibration make it possible to ensure uniform processing of the entire surface of part 2 and thereby improve the quality and uniformity of its surface properties. In addition, the significant value (length) of the anionite fibers, in contrast to the granules used in the prototype, sharply reduces the likelihood of fibers sticking to the treated surface, due to the adhesion of the fibers to each other and, in addition, the adhesion between the fibers provides better electrical conductivity of the working medium. which, in turn, contributes to an increase in the productivity of the process and an intensification of the ion entrainment process.

When implementing the method, the following processes occur. During the reciprocating movement of the fibers, they collide with the treated surface of the part 2. In this case, collisions between the fibers 4 also occur in the entire volume of the working container (not shown), thus creating uniform conditions for the flow of electrical processes for the entire volume of fibers 4. In this case, electrical processes between part 2 (anode) and fibers (cathode) occur due to the contact of the mass of electrically conductive fibers with each other and with a negative potential of the working container and / or electrodes 3 (cathodes) introduced into the mass of fibers, which are at a negative potential ... When fibers 4 collide with microprotrusions on the treated surface of part 2, ionic carryover of mass from microprotrusions occurs, as a result of which the surface is leveled, its roughness decreases and the surface is electropolished.

The following studies were also carried out on the polishing of parts (blades of turbomachines) made of alloy steels, nickel and titanium alloys. An unsatisfactory result (NR) was considered a result in which, as a result of adhesion of fibers, point defects appeared on the polished surface and the polishing effect was not observed. In the absence of point or other defects on the surface of the part, the result was recognized as satisfactory (U.R.)

In all cases, the following modes of processing parts turned out to be universal.

Fibers made of anionites and impregnated with an electrolyte solution with dimensions:

- cross-section: (0.03 mm (N.R.), 0.05 mm (U.R.), 0.2 mm (U.R.), 0.6 mm (U.R.), 0 , 8 mm (N.R.));

- length: (2 mm (N.R.), 4 mm (U.R.), 8 mm (U.R.), 16 mm (U.R.), 25 mm (U.R.), 35 mm (U.R.), 45 mm (U.R.), 55 mm (N.R.))

The used anion exchangers are ion exchange resins obtained on the basis of copolymerization of either polystyrene or polyacrylate and divinylbenzene. Grades of anion exchangers used in the present invention based on synthetic resins: Anionite 17-8ChS, Anionite Purolite A520E, Lewatit S 6328 A (based on styrene-divinylbenzene copolymer), "Lewatit M500", "Lewatit MonoPlus MK 51", "Lewatit MonoPlus MK 51" ”, Purolite C150E, Purolite A-860 (macroporous strong base anion exchange resin based on acrylates), sulfonated styrene-divinylbenzene copolymer anionite. The listed anion exchangers, impregnated with the above electrolyte compositions, showed a positive result when polishing alloy steel blades.

During processing, the vibration movement of fibers was used relative to the surface of the part with a frequency of 50 ... 400 Hz: 40 Hz (N.R.), 50 Hz (U.R.), 100Hz (U.R.), 150 Hz (U. .R.), 250 Hz (U.R.), 300 Hz (U.R.), 350 Hz (U.R.), 400 Hz (U.R.), 450 Hz (N.R.) and amplitude 1.0 to 6.0 mm (0.5 mm - N.R., 1.0 mm - U.R., 2.0mm - U.R., 3.0 mm - U.R., 4 , 0 mm - U.R., 5.0 mm - U.R., 6.0 mm - U.R., 7.0 mm - N.R.).

Pulse mode with polarity reversal:

- pulse frequency range from 20 to 100 Hz: 15Hz (N.R.), 20Hz (U.R.), 40Hz (U.R.), 60Hz (U.R.), 80Hz (U.R.), 100Hz (N.O.), 120Hz (N.O.)

- pulse period from 50 μs to 10 μs: 60 μs (N.R.), 50 μs (U.R.), 40 μs (U.R.), 30 μs (U.R.), 20 μs ( U.R.), 10 μs (W.R.), 5 μs (N.R.);

- current amplitude of positive polarity during a pulse of +50 A and their duration 0.4 μs to 0.8 μs: 0.2 μs (N.R.), 0.4 μs (U.R.), 0.6 μs (U.R.), 0.8 μs (W.R.), 10.0 μs (N.R.);

- with a current amplitude of negative polarity during the pulse - 20 A, and their duration is 0.2 μs to 0.4 μs, 0.1 μs (N.R.), 0.2 μs (U.R.), 0, 3 μs (W.R.), 0.4 μs (W.R.), 0.5 μs (N.R.);

- with a rectangular shape of the output current pulses (U.R.),

- and the duration of pauses between pulses from 49.6 μs to 9.2 μs - (U.R.) out of range - (N.R.).

In the mode without polarity reversal: electropolishing with fibers was carried out by applying a positive electric potential to the part and a negative electric potential from 25 to 35 V to the fibers: 22 V (N.R.), 25 V (U.R.), 28 V (U.R. .), 30 V (U.R.), 35 V (U.R.), 40 V (N.R.),

The first group: alloy steel parts.

Parts (samples and blades) made of EP718-ID, VZh105-ID, EP718-PD, VZh105-PD alloy steels were processed.

Processing conditions for the proposed method.

Electrolytes used for impregnating fibers made of anion exchangers:

1) NH ₄ F, with a concentration of 6 to 24 g / l (going beyond the concentration of NH ₄ F from 6 to 24 g / l gives a negative result);

2) NaF, concentration from 4 to 18 g / l, (going beyond the concentration range from 4 to 18 g / l, gives a negative result);

3) KF concentration from 35 to 55 g / l, (going beyond the concentration range from 35 to 55 g / l, gives a negative result);

4) NH ₄ F mixtures   and KF with NH ₄ F content - from 5 to 15 g / l (going beyond the concentration of NH ₄ F - from 5 to 15 g / l, gives a negative result) and KF - from 30 to 50 g / l (going beyond the concentrations of KF - from 30 to 50 g / l, gives a negative result),

5) mixtures of NaF   and KF with NaF content - from 3 to 14 g / l (going beyond the concentration of NaF - from 3 to 14 g / l, gives a negative result), and KF - from 35 to 60 g / l (going beyond the concentration of KF - from 35 to 60 g / l, gives a negative result),

6) NH ₄ F mixtures   and NaF with NH ₄ F content - from 4 to 12 g / l (going beyond the concentration of NH ₄ F - from 4 to 12 g / l, gives a negative result) and KF - from 35 to 55 g / l (going beyond the concentrations of KF - from 35 to 55 g / l, gives a negative result),

7) NH mixtures₄F, NаF and KF with NH content₄F - from 3 to 9 g / l (going beyond the concentration of NH₄F - from 3 to 9 g / l, gives a negative result), and KF - from 20 to 30 g / l, (going beyond the concentration of KF - from 20 to 30 g / l, gives a negative result), and NaF - from 10 to 25 g / l (going beyond the concentration of NaF - from 10 to 25 g / l, gives a negative result),

8) NH ₄ F mixtures   and НF with NH ₄ F content - from 5 to 15 g / l (going beyond the concentration of NH ₄ F - from 5 to 15 g / l, gives a negative result), and НF - from 3 to 5 g / l (going beyond HF concentration range from 3 to 5 g / l, gives a negative result),

9) from 8 to 14% aqueous solution of NaNO ₃ (going beyond the concentration of NaNO ₃ from 8 to 14%, gives a negative result).

The second group: parts (samples and blades) made of titanium alloys of VT9, VT-1, VT3-1, VT8 grades. The blisk was immersed in a container with electrically conductive porous fibers impregnated with an electrolyte of the composition an aqueous solution of a mixture of NH ₄ F   and KF with NH ₄ F content - from 8 to 14 g / l and KF - from 36 to 48 g / l and electropolishing was carried out at a current density of 1.2 to 1.8 A / cm ² until the minimum possible surface roughness was achieved.

Processing conditions for the proposed method.

Electrolyte composition: aqueous solution of NH ₄ F mixture   and KF with NH ₄ F content (6 g / L - N.R., 8 g / L - U.R., 10 g / L - U.R., 12 g / L - U.R., 14 g / l - U.R., more than 14 g / l - N.R.) and KF (32 g / l - N.R., 36 g / l - U.R., 42 g / l - U.R. , 45 g / l - U.R., 48 g / l - U.R., 52 g / l - N.R.)

parts (samples and blades)

The third group: parts (samples and blades) from nickel alloys of grades ZhS6U, ZhS32. The blisk was immersed in a container with electrically conductive porous fibers impregnated with electrolyte and electropolished at a current density of 1.5 to 2.1 A / cm ² until the minimum possible surface roughness was reached.

Processing conditions for the proposed method.

Electrically conductive porous fibers impregnated with an electrolyte composition of an aqueous solution of ammonium fluoride salt with a concentration of 6 - 9.0 g / liter (5.0 g / liter (N.R.), 6.0 g / liter (U.R.), 7, 0 g / liter (U.R.), 8.0 g / liter (U.R.), 10.0 g / liter (U.R.), 12.0 g / liter (N.R.)) and at a current density of 1.5 to 2.1 A / cm ² (1.3 A / cm ² (N.R.), 1.5 A / cm ² (U.R.), 1.6 A / cm ² (U.R.), 1.9 A / cm ² (U.R.), 2.1 A / cm ² (U.R.), 2.3 A / cm ² (N.R.)) ...

Compared with the known method of dry electropolishing [WO2017186992] when processing parts of complex shape made of alloy steels, nickel and titanium alloys according to the proposed method, the formation of point defects was not observed, while when processing according to the known method of polishing [WO2017186992] the formation of point defects as a result adhesion and soldering of granules was observed on average in 85% of the amount of all processed parts (alloyed steels - 81%, nickel alloys - 84%, titanium alloys - 91%). The proposed method made it possible to almost completely eliminate the appearance of point defects resulting from adhesion of fibers.

Thus, the proposed method of dry electropolishing of parts made it possible to achieve the technical result set in the invention - to improve the quality and reliability of the surface treatment of a metal part by increasing the uniformity of its surface treatment, reducing the likelihood of defects and reducing its roughness.

...

Claims (8)

1. A method of dry electropolishing of a part, including immersing a metal part in an electrically conductive medium and supplying an opposite electric potential to the part and an electrically conductive medium, characterized in that anion exchangers made in the form of fibers impregnated with an electrolyte solution providing the electrical conductivity of the said fibers, ionic entrainment of metal from the surface of the part with the removal of microprotrusions and contact of the entire polished surface of the part with the mentioned fibers and fibers with each other, set the fibers and the part in relative motion, supply an electric potential to the part and fibers, providing ion entrainment of metal from the surface of the workpiece and its electropolishing in the environment of the mentioned fibers to obtain a given roughness of the polished surface of the part. 2. The method according to claim 1, characterized in that electropolishing is carried out by supplying a positive electric potential to the part, and a negative electric potential from 25 to 35 V to said fibers, and the said fibers and the part are additionally carried out in a vibration motion with a frequency of 50-400 Hz, providing uniform washing the workpiece surface with said fibers. 3. The method according to claim 1, characterized in that as said fibers of the anion exchangers, ion-exchange resins obtained on the basis of copolymerization of polystyrene or polyacrylate and divinylbenzene are used, and the cross-sectional dimensions of the fibers are selected from the range from 0.05 to 0.6 mm with their length from 4 mm to 45 mm, and processing with the mentioned fibers is carried out in a pulsed mode with a change in polarity, with a pulse frequency range from 20 to 250 Hz, a pulse period from 4.3 to 72 μs, with a current amplitude of positive polarity during a pulse from + 20 to 120 A and its duration 0.2 to 1.4 μs, with a current amplitude of negative polarity during a pulse from 25 to 40% of the used current amplitude of positive polarity, and its duration 0.1 to 0.6 μs, with a rectangular or the trapezoidal shape of the output current pulses and the pause duration between pulses from 4 to 70 μs. 4. A method according to any one of claims. 1-3, characterized in that a turbomachine blade made of alloy steel is used as a part, the blade is additionally driven into reciprocating motion relative to its longitudinal axis, and one of the following aqueous solutions is used as an electrolyte for impregnating said fibers from anion exchangers: NH₄F with a concentration of 6 to 24 g / l, or NaF with a concentration of 4 to 18 g / l, or KF with a concentration of 35 to 55 g / l, or NH mixtures₄F and KF with NH content₄F from 5 to 15 g / l and KF from 30 to 50 g / l, or mixtures of NaF and KF with NaF content from 3 to 14 g / l and KF from 35 to 60 g / l, or NH mixture₄F and NaF with NH content₄F from 4 to 12 g / l and KF from 35 to 55 g / l, or NH mixtures₄F, NаF and KF with NH content₄F from 3 to 9 g / l and KF from 20 to 30 g / l, and NaF from 10 to 25 g / l, or NH mixtures₄F and НF with NH content₄F from 5 to 15 g / l and HF from 3 to 5 g / l, or from 8 to 14% aqueous solution of NaNO_3,or in an electrolyte composition, wt%: (NH₄)₂SO₄5, Trilon B 0.8, or containing sulfuric and orthophosphoric acid, block copolymer of ethylene and propylene oxides and sodium salt of sulfonated butyl oleate in the following ratio of components, wt%: sulphuric acid 10-30 orthophosphoric acid 40-80 block copolymer of ethylene and propylene oxides 0.05-1.1 sodium salt of sulfonated butyl oleate 0.01-0.05 water rest 5. The method according to any one of claims. 1-3, characterized in that a turbomachine blade made of a titanium alloy is used as a part, the blade is additionally driven into reciprocating motion relative to its longitudinal axis, and one of the following aqueous solutions is used as an electrolyte for impregnating said fibers from anion exchangers: aqueous solution of a mixture of NH ₄ F   and KF with NH ₄ F content from 8 to 14 g / l and KF from 36 to 48 g / l or an aqueous solution containing 30 to 50 g / l KF · 2H ₂ O and 2 - 5 g / l CrO ₃ . 6. The method according to any one of claims. 1-3, characterized in that a turbomachine blade made of a nickel alloy is used as a part, the blade is additionally driven into reciprocating motion relative to its longitudinal axis, and one of the following aqueous solutions is used as an electrolyte for impregnating said fibers from anion exchangers: an aqueous solution of ammonium fluoride with a concentration of 6.0-9.0 g / l, or an aqueous solution of ammonium sulfate with a concentration of 0.8-3.4 g / l, or an aqueous solution containing sulfuric and orthophosphoric acids, a block copolymer of ethylene oxides and propylene and sodium salt of sulfonated butyl oleate, with the following ratio of components, wt. %: sulphuric acid 10-30 orthophosphoric acid 40-80 block copolymer of ethylene and propylene oxides 0.05-1.1 sodium salt of sulfonated butyl oleate 0.01-0.05 water rest

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