RU2724734C1 - Method of electropolishing part - Google Patents

Abstract

FIELD: 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 for improving their operational characteristics. Proposed method comprises immersing the part in conducting medium and supplying opposite sign of electric potentials to the part and conducting medium through electrode introduced therein. Electroconductive medium used is a tape made of fibers of anion-impurities impregnated with electrolyte solution, which provides conductivity of the tape and ionic removal of metal from the part surface with removal of microprojections, using an electrode embracing the machined part surface with a gap, moving the tape in the gap, contacting the entire polished part surface with the tape and the tape with the electrode, electric potentials opposite to the sign are supplied to the part and to the electrode, which ensure ion breakdown of the metal from the surface of the part and its polishing when moving in the tape gap to obtain the specified roughness of the surface and rounding of the projections.EFFECT: higher quality and reliability of electropolishing.9 cl, 2 dwg

Description

The invention relates to the technology of electro-polishing the surface of parts made of metals and alloys and can be used to process the surfaces of the blades of turbomachines to improve their operational characteristics.

With increasing surface roughness of critical metal parts operating under the influence of significant alternating loads, such as shafts, gas turbine blades, etc., their operational characteristics are sharply reduced. The quality of the surface treatment of the blade feather significantly affects their strength characteristics, for example, an increase in the surface cleanliness class increases the endurance and static strength of the blades (V.F. Makarov, E.N. Bychina, A.O. Chuyan. Mathematical modeling of the polishing process blades of gas turbine engines // Aerospace Engineering and Technology. No. 8 (85), 2011, pp. 11-14). The developed surface roughness of the gas turbine blades leads to a deterioration in the gasdynamic 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 gas turbine installation.

At the same time, the production and repair of gas turbine engine blades (GTE) and installations (GTU), due to the high demands on surface quality (Ra≤0.32 ... 0.16 μm), is characterized by the considerable complexity of their finishing. This causes problems when machining surfaces of turbomachine parts. In this regard, the development of methods for producing high-quality surfaces of turbomachine parts is a very urgent task.

There is a method of polishing the surface of a part in a circle in which the parts (turbine blade) report reciprocating movement relative to the tool (AS USSR No. 1732604. IPC B24B 19/14. Method of polishing the pen of a GTE blade with a petal circle. Publ. Bull. No. 1 , 2014), in which polishing is performed with deformation of the blade circle.

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

However, the use of mechanical effects in known methods of polishing the surface of a part causes a deterioration in the quality parameters of the surface layer of materials, which leads to a decrease in its operational characteristics, especially in cases where parts such as turbine blades with a thin pen are processed.

The most promising methods for processing parts of complex shape, in particular turbomachine blades, are electrochemical methods of polishing surfaces [Griliches S.Ya. Electrochemical and chemical polishing: Theory and practice. Effect on the properties of metals. L., Mashinostroenie, 1987], while the methods of electrolyte-plasma polishing (EPP) of details [for example, Patent GDR (DD) No. 238074 (A1), IPC C25F 3/16, publ. 08/06/1986].

There is also a method of polishing metal surfaces, including anode processing 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 homogeneous surface treatment of parts made of metal alloy, especially parts of complex shape.

The closest technical solution selected as a prototype is a method polishing a metal part, which consists in filling with a conductive granule a working container made of electrically conductive material, 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 - 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 turbomachine blades, because there is a random interaction of the surface with granules, which leads to non-uniform surface treatment, leading to reduced performance of the processed parts.

The task to which the invention is directed is to improve the quality and reliability of processing metal parts, especially critical parts of complex shape, such as turbomachine blades, as well as the possibility of a given radius of rounding of the input and output edges of the blade feathers.

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

The technical result is achieved due to the fact that in the method of electropolishing a metal part, including immersing the part in a conductive medium and supplying an opposite sign of electric potential to the part and the conductive medium through an electrode introduced into said medium, in contrast to the prototype, a tape made as an electrically conductive medium is used from fibers of anion exchangers impregnated with an electrolyte solution providing the electrical conductivity of the said tape and ionic ablation of the metal from the surface of the part with the removal of microprotrusions, an electrode is used that covers the workpiece surface with a gap, the said tape is moved in the said gap, and the entire polished surface of the part is in contact tape and tapes with the said electrode, serves on the part and the said electrode the opposite in sign electrical potential, providing ionic ablation of metal from the surface of the workpiece and polishing it when moving in said gap of said tape until a predetermined roughness of the polished surface is obtained and the protrusions are rounded.

In addition, the following additional methods are possible: the ion exchange resins obtained on the basis of the copolymerization of either polystyrene or polyacrylate and divinylbenzene are used as anion exchangers; the cross-sectional dimensions of the fibers are selected from a range from 0.05 to 0.6 mm with a length of 4 mm to 45 mm; tape processing is carried out by supplying a positive and a negative electric potential of 12 to 35 V to the tape; the tape and the part are additionally carried out in a vibratory movement with a frequency of 50-400 Hz, providing uniform interaction between the tape and the workpiece surface; tape processing is carried out in a pulsed mode with a polarity reversal, with a pulse frequency range of 20 to 250 Hz, a pulse period of 4.3 to 72 μs, with a positive polarity current amplitude during a pulse of + 20 to 120 A and its duration 0.2 up to 1.4 μs, with the amplitude of the current of negative polarity during the pulse from 25 to 40% of the used amplitude of the current of positive polarity, and its duration of 0.1 to 0.6 μs, with a rectangular or trapezoidal shape of the output current pulses and the duration of the pauses between pulses from 4 to 70 μs; as a part, a turbomachine blade made of alloy steel is used, and one of the following aqueous solutions is used as electrolytes for impregnation of the said tape: or NH₄F, a concentration of 6 to 24 g / l, or NaF, a concentration of 4 to 18 g / l, or KF a concentration of 35 to 55 g / l, or a mixture of NH₄F and KF in the NH content₄F - from 5 to 15 g / l and KF - from 30 to 50 g / l, or a mixture of NaF and KF with a NaF content of from 3 to 14 g / l and KF from 35 to 60 g / l, or a mixture of NH₄F and NaF at NH₄F - from 4 to 12 g / l and KF - from 35 to 55 g / l, or a mixture of NH₄F, NaF and KF in the 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 a mixture of NH₄F and HF at NH₄F - from 5 to 15 g / l and HF - from 3 to 5 g / l, or from 8 to 14% aqueous NaNO solution₃or in electrolyte compositions, wt.%: (NH₄)₂SO₄- five; Trilon B - 0.8, or containing sulfuric and phosphoric acid, a block copolymer of ethylene and propylene oxides and the sodium salt of sulfonated butyl oleate in the following ratio, wt.%:

Sulfuric acid - 10-30

Orthophosphoric acid - 40-80

Block copolymer of ethylene oxide and propylene - 0.05-1.1

Sodium salt of sulfonated butyl oleate - 0.01-0.05

Water - The rest;

the turbomachine blade is additionally driven in reciprocating motion relative to its longitudinal axis, without touching the external electrode; as a part, a turbomachine blade made of a titanium alloy is used, and one of the following aqueous solutions is used as electrolytes for impregnating the said tape: or an aqueous solution of a mixture of NH ₄ F   and KF with an NH ₄ F content of from 8 to 14 g / l and KF from 36 to 48 g / l, or an aqueous solution with a content of 30 - 50 g / l of KF · 2H ₂ O and 2 - 5 g / l of CrO ₃ ; the turbomachine blade additionally drives it in reciprocating motion relative to its longitudinal axis, without touching the external electrode; as a part, turbomachines made of a nickel alloy are used, and one of the following aqueous solutions is used as electrolytes for impregnating the tape: 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 phosphoric acid, a block copolymer of ethylene oxide and propylene and the 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 Sulfated Butyl Oleate Sodium Salt 0.01-0.05 Water Rest;

the turbomachine blade additionally causes it to reciprocate with respect to its longitudinal axis, without touching the external electrode.

The invention is illustrated by drawings. Figure 1 shows a schematic cross-sectional view of a polished part and an external electrode surrounding the part, in the gap between which there is a moving tape of anion exchange fibers. In FIG. 2 shows the workpiece in the outer electrode with a tape in the gap between the part and the outer electrode. Figures 1 and 2 contain: 1 - workpiece; 2 - external electrode; 3 - a tape of anion exchange fibers impregnated with an electrolyte; 4 - the gap between the electrode and the part; 5 - dividing wall. (arrows indicate the direction of movement of the tape).

The inventive method of electropolishing parts, in particular the surface of the pen blades in the manufacturing process or repair is carried out as follows.

Part 1 is fixed on the holder (Fig. 1 and Fig. 2) and placed in the external electrode 2 so that the electrode 2 and the workpiece 1 do not touch each other. In this case, a gap 4 is left between the electrode 2 and part 1, which ensures free movement of the tape 3 in it while ensuring simultaneous contact with the external electrode 2 and part 1. Part 1 with the external electrode 2 is placed in the working chamber of a polishing unit (not shown), insert the tape 3 into the gap 4 between the part 1 and the external electrode 2, ensuring a constant movement of the tape 3 in the gap 4 (Fig. 1) (for example, by rewinding it from one reel to another). At the same time, in the tape 3 the required level of electrolyte content is maintained. To intensify the process, the tape 3 can be additionally brought into vibrational motion. An electric potential is supplied to the workpiece 1 and the external electrode 2 and turn on the drive of the device for moving the tape 3 in the gap 4 between the workpiece 1 and the electrode 2 and polish the surface of the workpiece 1 until the specified surface roughness a is obtained; when processing the blade pen, the radius of curvature of the input and output edge of the pen. After processing, the finished part 1 is removed and put into a container for storage. In this case, depending on the configuration of the part 1, various versions of the external female electrode 2 can be used (in the form of a continuous curved plate, a plate with perforations, grids, etc.) and the gap value 4.

The electropolishing of part 1 (Fig. 1) is carried out by electrochemical processes (ionic ablation of the material of part 1) between part 1 and the external electrode 2 through tape 3 made of anion exchange fibers impregnated with an electrolyte solution that provides electrical conductivity of tape 3 and ionic metal ablation from the surface details 1 with removal of microprotrusions from it.

Set the outer covering electrode 2 around the part, ensure contact of the entire polished surface of the part 1 with the tape 3 and the tape 3 with the electrode 2, set the tape 3 in motion, moving it through vibration through the gap 4, ensuring that the tape 3 is cut off by the dividing wall 5, is fed to the part 1 and granules 3 the electric potential, providing ionic ablation of metal from the surface of the workpiece 1 and its polishing to obtain a given roughness of the polished surface. When processing a part 1 of the type of a turbomachine blade, part 1 is additionally brought into reciprocating motion relative to its longitudinal axis, without touching the external electrode 2.

As anion exchangers for tape 3, ion-exchange resins obtained based on the copolymerization of either polystyrene or polyacrylate and divinylbenzene are used. The cross-sectional dimensions of the fibers are selected from the range from 0.05 to 0.6 mm with a length of 4 mm to 45 mm.

The tape 3 is electropolished either by supplying a positive electric potential to the part 1, and a negative electric potential, from 12 to 35 V, to the external electrode 2, or in the pulsed mode with a polarity reversal, with a pulse frequency range from 20 to 100 Hz, a pulse period of 50 μs up to 10 μs, with a current amplitude of positive polarity during a pulse of +50 A and their duration 0.4 to 0.8 μs, with a current amplitude of a negative polarity during a pulse - 20 A, and their duration 0.2 to 0.4 μs , with a rectangular shape of the output current pulses and the duration of pauses between pulses from 49.6 μs to 9.2 μs.

When polishing a blade of a turbomachine (part 1) made of alloy steel, one of the following aqueous solutions is used as electrolytes for impregnating a tape 3 from anion exchangers: or NH₄F, a concentration of 6 to 24 g / l, or NaF, a concentration of 4 to 18 g / l, or KF a concentration of 35 to 55 g / l, or a mixture of NH₄F and KF in the NH content₄F - from 5 to 15 g / l and KF - from 30 to 50 g / l, or a mixture of NaF and KF with a NaF content of from 3 to 14 g / l and KF from 35 to 60 g / l, or a mixture of NH₄F and NaF at NH₄F - from 4 to 12 g / l and KF - from 35 to 55 g / l, or a mixture of NH₄F, NaF and KF in the 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 a mixture of NH₄F and HF at NH₄F - from 5 to 15 g / l and HF - from 3 to 5 g / l, or from 8 to 14% aqueous NaNO solution₃or in electrolyte compositions, wt.%: (NH₄)₂SO₄- five; Trilon B - 0.8, or containing sulfuric and phosphoric acid, a block copolymer of ethylene and propylene oxides and the sodium salt of sulfonated butyl oleate in the following ratio, wt.%:

Sulfuric acid - 10-30

Orthophosphoric acid - 40-80

Block copolymer of ethylene oxide and propylene - 0.05-1.1

Sodium salt of sulfonated butyl oleate - 0.01-0.05

Water - The rest.

When polishing a blade of a turbomachine made of a titanium alloy, one of the following aqueous solutions is used as electrolytes for impregnating a tape 3 from anion exchangers: or an aqueous solution of a mixture of NH ₄ F   and KF with an NH ₄ F content of from 8 to 14 g / l and KF from 36 to 48 g / l, or an aqueous solution with a content of 30 - 50 g / l of KF · 2H ₂ O and 2 - 5 g / l of CrO ₃ .

When polishing a blade of a turbomachine made of a nickel alloy, one of the following aqueous solutions is used as electrolytes for impregnating a tape 3 of 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 phosphoric acid, a block copolymer of ethylene oxide and propylene and the 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 Sulfated Butyl Oleate Sodium Salt 0.01-0.05 Water Rest

The polishing process is carried out to obtain a given value of the surface roughness of the part 1.

The movement of the tape 3 through the gap 4 and its vibration make it possible to ensure uniform processing of the entire surface of the part 1 and thereby increase the quality and uniformity of the properties of its surface, and in addition, when processing parts such as feather blades, to provide final dimensional processing of the input and output edges of the blade. The forced movement of the tape 3 through the gap 4 allows for uniform contact, and therefore the surface treatment of the part 1, while the use of granules, as is the case in the prototype [WO2017186992], leads to the formation of point defects caused by the adhesion of granules to the treated surface of the part 1 .

When implementing the method, the following processes occur. When the tape 3 moves in the gap 4, it simultaneously contacts the workpiece surface 1 and the external electrode 2, creating uniform flow conditions when polishing part 1 of electrochemical processes. In this case, the electrochemical processes (ionic ablation of the material from the treated surface) between the part (anode) and the tape 3 (cathode) occur due to the contact of the anionite fibers of the tape 3 with the external electrode 2 (cathode) located at a negative potential. In the collision of the tape 3 with microprotrusions on the treated surface of the part 1, ionic ablation of the mass from the microprotrusions occurs, as a result of which the surface is leveled, its roughness is reduced and the surface is polished.

The following studies were also conducted on polishing parts (turbomachine blades) of alloy steels, nickel and titanium alloys. An unsatisfactory result (N.R.) was considered the result in which the polishing effect was not observed on the polished surface, and when machining parts such as a feather blade, the edges of the part did not round. In the absence of defects on the surface of the part, the result was considered satisfactory (U.R.)

In all cases, the following modes of processing parts were universal.

Tape made of anion exchange fibers with dimensions

- fiber cross-section (0.03 mm (N.R.), 0.05 mm (U.R.), 0.1 mm (U.R.), 0.2 mm (U.R.), 0 , 4 mm (U.R.), 0.6 mm (U.R.), 0.8 mm (N.R.));

- fiber length from 4 mm to 45 mm (3 mm (N.R.), 5 mm (U.R.), 10 mm (U.R.), 25 mm (U.R.), 45 mm (U .R.), 60 mm (N.R.));

The anion exchangers used are ion-exchange resins based on the copolymerization of either polystyrene or polyacrylate and divinylbenzene. The brands of synthetic resin-based anion exchangers used in the present invention are: Anion exchanger 17-8СС, Anion exchanger Purolite A520E, Lewatit S 6328 A (based on styrene-divinylbenzene copolymer), “Lewatit M500”, “Lewatit MonoPlus MK 51”, “Lewatit MonoPo 68 MP ”, Purolite C150E, Purolite A-860 (macroporous strongly basic acrylate-based anion exchange resin), anion exchange resin sulfonated styrene-divinylbenzene anion exchange resin. The listed anion exchangers, impregnated with the above electrolyte compositions, showed a positive result when polishing blades of alloy steels.

During processing, the vibrational movement of the part with a frequency of 50 ... 400 Hz was used: 40 Hz (N.R.), 50 Hz (U.R.), 100 Hz (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 an amplitude of 1.0 up to 6.0 mm (0.5 mm - N.R., 1.0 mm - U.R., 2.0 mm - 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.).

In 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 (U.R.), 120Hz (N.R.)

- 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 (U.R.), 5 μs (N.R.);

- the amplitude of the current of positive polarity during the pulse +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 (U.R.), 10.0 μs (N.R.);

- when the amplitude of the current of negative polarity during the pulse is 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 (U.R.), 0.4 μs (U.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 changing polarity: electro polishing was performed by supplying a positive electric potential to the part, and a negative electric potential from 12 to 35 V to the tape (external electrode): 8 V (N.R.), 12 V (U.R.), 20 V ( U.R.), 30 V (U.R.), 35 V (U.R.), 45 V (N.R.),

The first group: alloy steel parts.

Parts (samples and blades) of alloy steels EP718-ID, VZh105-ID, EP718-PD, VZh105-PD were subjected to processing.

Processing conditions for the proposed method.

Used electrolytes for impregnation of a tape made of anion exchangers:

1) NH ₄ F, concentration from 6 to 24 g / l (going beyond NH ₄ F concentrations 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 with a concentration of 35 to 55 g / l, (going beyond the concentration range of 35 to 55 g / l gives a negative result);

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

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

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

7) NH mixtures₄F, NaF and KF in the NH content₄F - from 3 to 9 g / l (going beyond NH concentrations₄F - 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) mixtures of NH ₄ F   and НF with the content of NH ₄ F - 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 (yield limits of HF concentrations from 3 to 5 g / l, gives a negative result),

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

The second group: parts (samples and blades) made of titanium alloys VT9, VT-1, VT3-1, VT8. The blades were treated with a tape of anion exchange fibers impregnated with an electrolyte of an aqueous solution of a mixture of NH ₄ F   and KF with an NH ₄ F content of from 8 to 14 g / l and KF from 36 to 48 g / l and polished at a current density of 1.2 to 1.8 A / cm ² until the smallest possible surface roughness was achieved.

Processing conditions for the proposed method.

The composition of the electrolyte: an aqueous solution of a mixture of NH ₄ F   and KF when the content of NH ₄ F (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.)

Third group: parts (samples and blades) made of nickel alloys of grades ZhS6U, ZhS32. The blades were treated with a tape of anion exchange resin impregnated with electrolyte and polished at a current density of 1.5 to 2.1 A / cm ² to achieve the smallest possible surface roughness.

Processing conditions for the proposed method.

Tape saturated with an electrolyte of the composition: 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 polishing method [WO2017186992] when processing parts of complex shape from alloy steels, nickel and titanium alloys by the proposed method, the formation of defects in the form of unpolished surface sections was practically not observed, while when processing by the known polishing method [WO2017186992] defects were formed in the form of local unprocessed areas and point defects (as a result of sticking and soldering of granules). On average, when processing by the prototype method [WO2017186992], about 14% was observed that a defect occurs in the number of all machined parts (alloy steels - 17%, nickel alloys - 12%, titanium alloys - 14%).

Thus, the proposed method for electropolishing a part made it possible to achieve the technical result set in the invention — improving the quality and reliability of processing the surface of a metal part by increasing the uniformity of processing of its surface, reducing the likelihood of defects, reducing its roughness and rounding the edges of the feather blade.

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Claims (11)

1. A method of electropolishing a part, comprising immersing the part in a conductive medium and supplying electrical potentials opposite in sign to the part and the conductive medium through an electrode introduced into said medium, characterized in that a tape made of anion exchange resin fibers impregnated with an electrolyte is used as an electrically conductive medium providing electrical conductivity of the aforementioned tape and ionic ablation of the metal from the surface of the part with the removal of microprotrusions, using an electrode covering the workpiece surface with a gap, moving the said tape in the said gap, providing contact of the entire polished surface of the part with the said tape and the tape with the said electrode, electrical potentials opposite in sign are supplied to the part and to the said electrode, which ensure ionic ablation of the metal from the surface of the workpiece and its polishing when moving in the said gap of the said tape until it is given roughness of the polished surface and rounding of the protrusions. 2. The method according to p. 1, characterized in that the ion exchange resins obtained on the basis of copolymerization of either polystyrene or polyacrylate and divinylbenzene are used as the anion exchangers of the tape fibers, the fiber cross-sectional sizes being selected from a range from 0.05 to 0.6 mm when their length is from 4 mm to 45 mm, and the processing of the said tape is carried out by supplying a positive and a negative electric potential of 12 to 35 V to the tape, moreover, the said tape and the item are additionally carried out in a vibrational frequency of 50-400 Hz, providing uniform interaction between said tape and the workpiece surface. 3. The method according to p. 1, characterized in that the ion exchange resins obtained on the basis of copolymerization of either polystyrene or polyacrylate and divinylbenzene are used as the anion exchangers of the tape fibers, the fiber cross-sectional sizes being selected from a range from 0.05 to 0.6 mm when their length is from 4 mm to 45 mm, and the processing of the mentioned tape is carried out in a pulsed mode with a polarity change, with a pulse frequency range of 20 to 250 Hz, a pulse period of 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 trapezoidal shape of the output current pulses and the duration of pauses between pulses from 4 to 70 μs. 4. The method according to any one of paragraphs. 1-3, characterized in that the blade part of a turbomachine made of alloy steel is used as a part, and one of the following aqueous solutions is used as electrolytes for impregnation of said tape: or NH₄F, a concentration of 6 to 24 g / l, or NaF, a concentration of 4 to 18 g / l, or KF a concentration of 35 to 55 g / l, or a mixture of NH₄F and KF at NH₄F - from 5 to 15 g / l and KF - from 30 to 50 g / l, or a mixture of NaF and KF with a content of NaF - from 3 to 14 g / l and KF - from 35 to 60 g / l, or a mixture of NH₄F and NaF at NH₄F - from 4 to 12 g / l and KF - from 35 to 55 g / l, or a mixture of NH₄F, NaF and KF in the 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 a mixture of NH₄F and HF at NH₄F - from 5 to 15 g / l and HF - from 3 to 5 g / l, or from 8 to 14% aqueous NaNO solution₃or in electrolyte compositions, wt.%: (NH₄)₂SO₄ - five; Trilon B - 0.8, or containing sulfuric and phosphoric acid, a block copolymer of ethylene oxide and propylene and the 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 Sulfated Butyl Oleate Sodium Salt 0.01-0.05 Water rest 5. The method according to p. 4, characterized in that the blade of the turbomachine additionally bring it into reciprocating motion relative to its longitudinal axis, without touching the external electrode. 6. The method according to any one of paragraphs. 1-3, characterized in that as a part, turbomachines made of titanium alloy are used, and one of the following aqueous solutions is used as electrolytes for impregnating the said tape: or an aqueous solution of a mixture of NH ₄ F and KF with an NH ₄ F content of 8 to 14 g / l and KF - from 36 to 48 g / l, or an aqueous solution with a content of 30 - 50 g / l KF · 2H ₂ O and 2 - 5 g / l CrO ₃ . 7. The method according to p. 6, characterized in that the blade of the turbomachine additionally bring it into reciprocating motion relative to its longitudinal axis, without touching the external electrode. 8. The method according to any one of paragraphs. 1-3, characterized in that a turbomachine blade made of nickel alloy is used as a part, and one of the following aqueous solutions is used as electrolytes for impregnating said tape: an aqueous solution of ammonium fluoride salt with a concentration of 6 - 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 phosphoric acid, a block copolymer of ethylene oxide and propylene and the 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 Sulfated Butyl Oleate Sodium Salt 0.01-0.05 Water rest 9. The method according to p. 8, characterized in that the blade of the turbomachine additionally bring it into reciprocating motion relative to its longitudinal axis, without touching the external electrode.

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