RU2731705C1 - Method of electropolishing of metal part - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to electroplating and can be used for processing surfaces of blades of turbomachines for improving their operational characteristics. Method includes immersing a part into a conductive medium and feeding an opposite sign of the electric potential to the part and a conductive medium through an electrode introduced into said medium, wherein electropolishing is carried out in a medium of granules made from anion exchangers impregnated with electrolyte solution, providing electroconductivity of said granules, using an electrode enclosing the part surface to be treated with a gap, moving said granules through said gap to allow contact of the entire polished part surface with said granules and granules to each other, wherein ratio of granule size a and gap size b between electrode and part surface is selected not less than b = 10 a, and supplied to part and granules electric potential, which provides for polishing of processed part in medium of said granules to obtain specified roughness of surface.

EFFECT: higher quality and reliability of surface treatment of metal part due to increased homogeneity of its surface treatment, reduced probability of defects occurrence, reduced roughness and rounding of blade edges.

10 cl, 2 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 for gas turbine engines (GTE) and units (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 parts of turbomachines is a very urgent task.

A known method of polishing the surface of a part in a circle, in which the parts (turbine blade) communicate 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. Bull. 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, the use of mechanical action in the known methods for 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 of processing such parts as 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 electropolishing methods 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 method polishing 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 - | 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 chaotic interaction of the surface with granules, which leads to non-uniform surface treatment, leading to a decrease in the performance of the 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 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 airfoil.

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 treatment, reducing the likelihood of defects, reducing its roughness and rounding the blade airfoil edges.

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 electric potential to the part and the conductive medium through the electrode introduced into the medium, in contrast to the prototype, electropolishing is carried out in the medium of granules made of of anion exchangers impregnated with an electrolyte solution, which ensures the electrical conductivity of the said granules and ionic entrainment of metal from the surface of the part with the removal of microprotrusions from it, an electrode is used, covering the workpiece surface with a gap, moving said granules in the said gap, provide contact of the entire polished surface of the part with the said granules and of the granules between themselves, an electric potential is applied to the part and the granules, which ensures the ionic entrainment of metal from the surface of the workpiece and its polishing in the environment of the said granules to obtain a given roughness of the polished surface.

In addition, the following additional methods of performing the method are possible: ion-exchange resins obtained on the basis of copolymerization of either polystyrene or polyacrylate and divinylbenzene are used as anionites of the said granules, and the sizes of the granules a are chosen from the range a = (0.1 to 0.4 mm) at the size of the gap b between the external electrode and the surface of the part is not less than b = 10 a, and the said granules are additionally carried out in vibration motion; electropolishing with granules is carried out by feeding a positive electric potential to the part, and a negative electric potential from 12 to 35 V to the granules; electropolishing with granules is carried out in a pulsed mode with a change in polarity, with a pulse frequency range from 20 to 100 Hz, a pulse period from 50 μs to 10 μs, with a positive polarity current amplitude during a pulse of +50 A and their duration 0.4 to 0.8 μs, with a current amplitude of negative polarity during the pulse - 20 A, and their duration 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; a turbomachine blade made of alloy steel is used as a part, and one of the following aqueous solutions is used as electrolytes for impregnating said anion resin granules: 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, NaF 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

The turbomachine blade is additionally driven into reciprocating motion relative to its longitudinal axis, without touching the external electrode; Turbomachines made of titanium alloy are used as a part, and one of the following aqueous solutions is used as electrolytes for impregnating the said granules of 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 ; Turbomachines made of nickel alloy are used as a part, and one of the following aqueous solutions is used as electrolytes for impregnating said anionite granules: an aqueous solution of an ammonium fluoride salt with a concentration of 6-9.0 g / liter, or an aqueous solution of ammonium sulfate with a concentration 0.8 ... 3.4 or an aqueous solution 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. %:

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.

Figure 1 shows a schematic cross-sectional arrangement of a polished workpiece and an external electrode surrounding the workpiece. FIG. 2 shows a work piece in an external electrode. Figures 1 and 2 contain: 1 - workpiece holder; 2 - external electrode; 3 - granules impregnated with electrolyte; 4 - the gap between the electrode and the part; 5 - dividing partition. (arrows indicate the direction of movement of the granules).

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

The workpiece 1 is fixed on the holder (Fig. 1 and Fig. 2) and is placed in the external electrode 2 so that the electrode 2 and the workpiece 1 do not touch each other. At the same time, a gap 4 is left between electrode 2 and part 1, which ensures free movement of granules in it 3. (In the particular case, the value b of the gap 4 between the external electrode 2 and the surface of part 1 can be at least b = 10 a, where a is the dimensions granules selected from the range a = (0.1 to 0.4 mm)). Part 1 with an external electrode 2 is placed in a working container, the container is filled with granules 3 (Fig. 1) and the granules 3 are moved through a gap 4 between part 1 and an external electrode 2 (for example, a screw conveyor). To intensify the process, the granules 3 can be additionally held in vibration. An electric potential is applied to the workpiece 1 and the external electrode 2 and the drive of the device for feeding the granules 3 into the gap 4 between the workpiece 1 and the electrode 2 is switched on and the surface of the workpiece 1 is polished until the specified surface roughness is obtained and, when processing the blade blade, the radius of curvature of the input and the trailing edges of the pen. After finishing the processing, the finished part 1 is taken out and put into a container for storage. In this case, depending on the configuration of part 1, you can use various options for the external female electrode 2 (in the form of a solid curved plate, a plate with perforations, a grid, etc.) and the size of the gap 4.

Electropolishing of part 1 (Fig. 1) is carried out in the medium of granules 3, made of anion exchangers impregnated with an electrolyte solution, providing electrical conductivity of granules 3 and ionic entrainment of metal from the surface of part 1 with the removal of microprotrusions from it. An external covering electrode 2 is installed around the part, ensure contact of the entire polished surface of part 1 with granules 3 and granules 3 with each other, set the granules in motion, moving them with vibration through the gap 4, ensuring the flow of spent granules 3 is cut off by the partition 5, fed to the part 1 and granules 3 electric potential, providing ionic carryover of metal from the surface of the workpiece 1 and its polishing in the medium of granules 3 to obtain a given roughness of the polished surface. When processing part 1 of the turbomachine blade type, part 1 is additionally driven into reciprocating motion relative to its longitudinal axis, without touching the outer electrode 2.

As anion exchangers for granules 3, ion-exchange resins obtained on the basis of copolymerization of either polystyrene or polyacrylate and divinylbenzene are used. The sizes of granules 3 are selected from the range from 0.1 to 0.4 mm. When processing part 1, granules 3 are additionally carried out in vibration motion.

Electropolishing with granules 3 is carried out either by applying a positive electric potential to part 1 and a negative electric potential to granules 3, ranging from 12 to 35 V, or in a pulsed mode with a change in polarity, 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 1) made of alloy steel, one of the following aqueous solutions is used as electrolytes for impregnating granules 6 of 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 turbomachine blade made of a titanium alloy, one of the following aqueous solutions is used as electrolytes for impregnating said anionite granules: 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 turbomachine blade made of a nickel alloy, one of the following aqueous solutions is used as electrolytes for impregnating the said anionite granules: 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, 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 polishing process is carried out until a predetermined value of the surface roughness of the blades is obtained.

The movement of granules 3 through the gap 4 and their vibration allow to ensure uniform processing of the entire surface of part 1 and thereby increase the quality and uniformity of its surface properties, and in addition, when processing parts such as a blade feather, to provide a finishing dimensional processing of the input and output edges of the blade. The forced movement of the granules 3 through the gap 4 does not allow the granules to adhere to the treated surface of the part 1 and form, as a result of said adhesion, point defects.

When implementing the method, the following processes occur. When the granules 3 move in the gap 4, they collide with the treated surface of the part 1. In this case, collisions between the granules 3 also occur in the entire volume of the gap 4, thus creating uniform conditions for the flow of electrical processes for the entire volume of granules 3 located there. In this case, the electrical processes between the part (anode) and the granules (cathode) occur due to the contact of the mass of electrically conductive granules 3 with each other and with the external electrode 2 (cathode) in contact with the granules 3, which is under negative potential, which is under negative potential. When granules collide with microprotrusions on the treated surface of part 1, ionic entrainment of mass from microprotrusions occurs, as a result of which the surface is leveled, its roughness decreases and the surface is polished.

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 (N.R.) was considered a result in which no polishing effect was observed on the polished surface, and when machining parts such as a blade blade, the edges of the part were not rounded. In the absence of 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.

Granules made of anionites and impregnated with an electrolyte solution with dimensions from 0.1 to 0.4 mm (0.05 mm (N.R.), 0.1 mm (U.R.), 0.2 mm (U.R. .), 0.4 mm (U.R.), 0.6 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 used in the proposed invention of anion exchangers 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 MP 68 ”, 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 granules with a frequency of 50 ... 400 Hz was used: 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 up 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 change: electropolishing with granules was carried out by feeding a positive electric potential to the part and a negative electric potential from 25 to 35 V to the granules: 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.

Applied electrolytes for impregnation of granules 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 granules 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 polishing 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.)

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

Processing conditions for the proposed method.

Electrically conductive porous granules impregnated with an electrolyte of the composition 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 polishing method [WO2017186992], when processing parts of complex shapes made of alloy steels, nickel and titanium alloys according to the proposed method, the formation of defects in the form of unpolished surface areas was practically not observed, while during processing by the known polishing method [WO2017186992] the formation of defects in the form of local untreated areas and point defects (as a result of adhesion and soldering of granules) took place. On average, when processing according to the prototype method [WO2017186992], about 14% of the occurrence of a defect was observed from the number of all processed parts (alloyed steels - 17%, nickel alloys - 12%, titanium alloys - 14%).

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

Claims (12)

1. A method for electropolishing a metal part, including immersing a part in a conductive medium and supplying an opposite electric potential to the part and a conductive medium through an electrode introduced into the medium, characterized in that electropolishing is carried out in an environment of granules made of anion resins impregnated with an electrolyte solution, providing electrical conductivity of said granules and ionic entrainment of metal from the surface of the part with the removal of microprotrusions, while using an electrode covering the workpiece surface with a gap, moving said granules through said gap to ensure contact of the entire polished surface of the part with said granules and granules with each other, and the ratio the size of the granules a and the size of the gap b between the electrode and the surface of the workpiece are chosen at least b = 10 a, and an electric potential is applied to the workpiece and granules, which provides ionic removal of metal from the surface of the workpiece and its polishing e of the above-mentioned granules to obtain a given roughness of the polished surface. 2. A method according to claim 1, characterized in that ion-exchange resins obtained on the basis of copolymerization of either polystyrene or polyacrylate and divinylbenzene are used as the anionites of said granules, and the size of the granules is selected from the range of 0.1-0.4 mm,moreover the said granules are additionally set in vibration motion. 3. A method according to claim 1, characterized in that electropolishing with granules is carried out either by supplying a positive electric potential to the part and a negative electric potential from 12 to 35 V to the granules, or in a pulsed mode with a polarity reversal, with a pulse frequency range of 20 to 100 Hz , pulse period from 50 μs to 10 μs, with a current amplitude of positive polarity during a pulse of +50 A and their duration from 0.4 to 0.8 μs, with a current amplitude of negative polarity during a pulse of -20 A and their duration from 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. 4. A method according to claim 2, characterized in that electropolishing with granules is carried out either by supplying a positive electric potential to the part and a negative electric potential from 12 to 35 V to the granules, or in a pulsed mode with a polarity reversal at a pulse frequency range of 20 to 100 Hz, pulse period from 50 μs to 10 μs, with a current amplitude of positive polarity during a pulse of +50 A and their duration from 0.4 to 0.8 μs, with a current amplitude of negative polarity during a pulse - 20 A and their duration from 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. 5. The method according to any one of claims. 1-4, characterized in that a turbomachine blade made of alloy steel is used as a part, and one of the following aqueous solutions is used as an electrolyte for impregnating said anion resin granules: NH ₄ F 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 a mixture of NH ₄ F and KF with an NH ₄ F content of 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 mixtures of NH ₄ F and NaF with NH ₄ F content from 4 to 12 g / l and NaF from 35 to 55 g / l, or mixtures of NH ₄ F, NaF and KF with NH ₄ F content from 3 to 9 g / l, KF from 20 to 30 g / l and NaF from 10 to 25 g / l, or mixtures of NH ₄ F and НF with NH ₄ F content 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 electrolyte compositions, wt%: (NH ₄ ) ₂ SO ₄ 5, Trilon B 0.8, or in an aqueous solution containing sulfuric and orthophosphoric acids, block copolymer of ethylene and propylene oxides and sodium salt with ultrafiltered butyl oleate at 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 6. The method according to claim 5, characterized in that the turbomachine blade is additionally driven into reciprocating motion relative to its longitudinal axis without touching the external electrode. 7. A method according to any one of claims. 1-4, characterized in that a turbomachine blade made of a titanium alloy is used as a part, and one of the following aqueous solutions is used as an electrolyte for impregnating said anionite granules: 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 . 8. The method according to claim 7, characterized in that the turbomachine blade is additionally driven into reciprocating motion relative to its longitudinal axis without touching the external electrode. 9. The method according to any one of claims. 1-4, 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 an electrolyte for impregnating said anionite granules: an aqueous solution of an 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 orthophosphoric acids, a block copolymer of ethylene and propylene oxides 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 sodium salt of sulfonated butyl oleate 0.01-0.05 water rest 10. The method according to claim. 9, characterized in that the turbomachine blade is additionally driven into reciprocating motion relative to its longitudinal axis without touching the external electrode.

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