RU2357019C2 - Method of electrolyte-plasma treatment of details - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to electrolytic-plasma refining of metallic products and can be used in turbomachinery during the treatment of operational and directing steam turbine blade, blades of gas-pumping devices and gas turbine compressors. Method includes immersion of details into electrolyte, forming around the treated surface of the details steam and gas envelope and discharge ignition between treated detail and electrolyte by means of feeding to the detail of electric potential, herewith detail is placed into inductor hollow, and steam and gas envelope is formed by detail induction heating.

EFFECT: providing of the ability of metal work treatment from more wide material range at increasing of operability of process, and also reduction of values of working potential between detail and electrolyte, necessary for holding of the treatment process.

35 cl, 3 tbl, 4 ex

Description

The invention relates to electrochemical (electrolyte-plasma) polishing of metal products, mainly from chromium-containing stainless steels, alloys, as well as titanium and titanium alloys, and can be used in turbomachinery in the processing of working and guide vanes of steam turbines, blades of gas pumping units and compressors of gas turbine engines, in order to ensure the necessary physical, mechanical and operational properties of turbomachine parts, as well as as a preparatory operation before ion-implantation modification of the surface of the part and the application of protective ion-plasma coatings.

The working blades of the compressor of a gas turbine engine (GTE) and a gas turbine installation (GGU), as well as steam turbines during operation, are subjected to significant dynamic and static loads, as well as corrosion and erosion destruction. Based on the performance requirements for the manufacture of gas turbine compressor blades, high-alloy chromium, chromomolybdenum (CrMo), chromomolybdenum-vanadium (CrMoV) and other medium and high alloy steels are used (for example, for steam turbine blades - steel grades 20X13 and 15X11MF, gas turbines - steel 20X13, EI 961). These steels are among the stainless steels with a Cr content of 11-14%, differing in the content of alloying elements: C, Mo, V. In addition, for the manufacture of compressor blades of gas turbines, titanium alloys are used, which are higher than technical titanium strength, including at high temperatures, while maintaining a sufficiently high ductility and corrosion resistance (for example, titanium alloys of the grades VT6, VT14, VT3-1, VT22, etc.).

However, turbine blades of these steels and alloys are highly sensitive to stress concentrators. Therefore, the defects formed in the manufacturing process of these parts are unacceptable, since they cause the occurrence of intense destruction processes. 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.

The most promising methods for processing 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 .: Engineering, 1987], while the most interesting for the field are electrolyte-plasma polishing (EPP) parts [for example, Patent GDR (DD) N 238074 (A1), cl. C25F 3/16, publ. 08/06/86, as well as Patent RB N 1132, cl. C25F 3/16, 1996, BI N 3].

A known method of polishing metal surfaces, including anode processing in an electrolyte [Patent RB N1132, class. C25F 3/16, 1996, BI N3], as well as a method for electrochemical polishing [US Patent N 5028304, class. B23H 3/08, C25F 3/16, C25F 5/00, publ. 07/02/91].

However, the known EPI methods have a significant energy intensity of the process, since they require the use of high electrical voltage (more than 100 V) when machining parts. In addition to the high energy intensity of the process and the occurrence of problems with the stability of the combined cycle gas turbine shell, these methods are limited only by the increased voltage range, while traditional methods of electric polishing take place at sufficiently low voltages, which in some cases allows to achieve a higher quality of part processing [for example, US patent No. 6165345, IPC C25F 5/00, publ. 12/26/2000]. The latter is due to the high activity of the processing process, which leads to significant unevenness in the processing of the part and does not allow to provide the necessary surface quality.

There is also a known method of cleaning the surface of an article, which consists in igniting a discharge between a workpiece and a liquid electrode, when a positive potential is applied to the workpiece, a gap between the electrodes (1.0-1.5) mm is established, the discharge current is maintained from 0.15 to 7 , 0 A at a discharge voltage U from 100 to 500 V, respectively (RF Patent N1441991, 06/07/93). A disadvantage of the known method of cleaning the surface of the product is that it allows you to process only the end face of the product, and only with a simple configuration in the form of a plane.

Closest to the claimed technical solution is a method of cleaning the surface of the product, comprising igniting a discharge between the workpiece and the electrolyte by applying positive potential to the product, the product being placed at a distance of 0-2 mm from the surface of the electrolyte, and the discharge current between the product and the electrolyte is maintained within 0.1-7.0 A at a discharge voltage of 500-20 V [RF Patent No. 2111284, IPC C23G 5/00, published. 1998.05.20]. Although this method allows processing parts at lower costumes, it cannot be used to process parts having a complex configuration, for example, parts such as turbomachine blades. This is due to the fact that the known method provides for a uniform gap between the surface of the electrolyte and the part, which is impossible for non-planar parts.

The task to be solved by the claimed invention is aimed at providing the possibility of processing metal products from a wider range of materials, including chromium and chromium-nickel alloys and steels, as well as titanium and its alloys, zirconium and its alloys, while increasing the flexibility of the process due to separate creation of a vapor-gas shell and a plasma discharge in it, as well as lowering the values of the working potentials between the part and the electrolyte necessary for the processing process.

The technical result is achieved by the fact that in the method of electrolyte-plasma processing of a part, including immersing the part in an electrolyte, forming a vapor-gas shell around the workpiece surface and igniting a discharge between the workpiece and the electrolyte by applying an electric potential to the part, unlike the prototype, the part is placed in a cavity inductor, and the vapor-gas shell is formed by induction heating of the part, while, as an option, the vapor-gas shell is first formed, and then fed to the part electric potential, while the potential can be either positive or negative.

The technical result is also achieved by the fact that in the method of electrolyte-plasma processing of a part, stainless steel and alloys, in particular chromium and chromium-nickel alloys and steels, are used as the part material, and the treatment is carried out by polishing until the roughness is not lower than R _a = 0.08 ... 0 , 12 microns, and as a part, as an option, a turbomachine blade is used, and processing of the blade, in particular only the blade blade, is carried out at an operating voltage of 18 ... 490 V.

The technical result is also achieved by the fact that in the method of electrolyte-plasma processing of a part, the following is used as the electrolyte: 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 of components, 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 - Else

or aqueous solutions of salts of inorganic acids of ammonium and alkali metals, or salts of lower carboxylic acids, or solutions of free acids, or electrolyte: containing an ammonium salt of inorganic acid, ammonium salts of lower carboxylic acids and organic or inorganic substances forming complex compounds with alloy metals; or electrolyte composition, wt.%:

(NH ₄ ) ₂ SO ₄ - 5

Trilon B - 0.8;

or electrolyte composition, wt.%:

(NH ₄ ) ₃ PO ₄ - 5

H ₃ PO ₄ - 0.5

Tartrate K - 0.5

or use aqueous solutions of sodium salts, and, as an option, as an aqueous solution of sodium salts use a 3-22% solution of sodium hydrogencarbonate; or use aqueous solutions of ammonium chloride, sodium chloride; or use aqueous solutions of ammonium salts, and, as an option, ammonium citric acid one-, two-, or trisubstituted, or mixtures thereof in the following ratio of components, wt.%:

Ammonium citric acid one-, or two-, or trisubstituted, or mixtures thereof - 2-18

Water - Else

or aqueous solutions of salts with a pH value of 4 ... 9.

The technical result is also achieved by the fact that in the method of electrolyte-plasma processing of the part, titanium and titanium alloys, zirconium and zirconium alloys are used as the part material, and the part is polished until the roughness is not lower than R _a = 0.08 ... 0.12 μm moreover, the blade of a turbomachine is used as a part, and the processing of the blade, in particular only the blade blade, is carried out at an operating voltage of 18 ... 520 V, and aqueous electrolyte solutions, which include salts of borofluorides, are used as the electrolyte homogeneous, silicofluoride, hexafluorotitanic or hydrofluoric acids.

The essence of the proposed method, the possibility of its implementation and use are illustrated by examples, the characteristics of which are presented in tables 1-3.

The inventive method of electrochemical polishing of metal products is as follows. The metal product to be processed is immersed in a bath with an aqueous electrolyte solution, placed in the inductor cavity, the component is induction heated until a vapor-gas shell is formed around the component, positive voltage is applied to the product, and negative (anode treatment) is applied to the product or negative voltage is applied to the product, and to the electrolyte - positive (cathodic treatment), as a result of which a discharge occurs between the workpiece and the electrolyte. As a bath, a container made of a material resistant to electrolyte is used. Processing is carried out in an electrolyte medium while maintaining a vapor-gas shell around a part.

When implementing the method, the following processes occur. Under the influence of induction currents, the surface of the part is heated and a vapor-gas shell forms around it. Excessive heat arising from the induction heating of the part and, in part, of the electrolyte is removed through the cooling system, while maintaining the desired process temperature. Under the action of electric voltage (electric potential between the part and the electrolyte), a discharge arises in the vapor-gas shell, which is an ionized electrolytic plasma, which ensures the flow of intensive chemical and electrochemical reactions between the treated part and the medium of the gas-vapor shell.

When a positive potential is applied to the part, during the course of these reactions, the surface of the part is anodized with the chemical etching of the formed oxide. Moreover, with anodic polarization, the vapor-gas layer consists of electrolyte vapors, anions, and gaseous oxygen. Since etching occurs mainly on microroughnesses, where a thin oxide layer is formed, and anodizing processes continue, as a result of the combined action of these factors, the roughness of the treated surface decreases and, as a result, polishing of the latter occurs.

In the case of cathodic polarization, the vapor-gas shell around the part consists of electrolyte vapors, cations, and hydrogen gas, therefore, along with the chemical interaction of cations with the material of the surface layer of the part, micro spark discharges occur in the gas-vapor shell, which leads to electroerosive and cavitation effects on the treated surface.

Example 1. The processed metal plates made of stainless steel 12X18P10T were immersed in a bath with an aqueous solution of electrolyte and, placed in the cavity of the inductor, induction heating was performed until a vapor-gas shell was formed around the part, then a positive voltage was applied to the plates, and a negative voltage was applied to the plates. Parts were machined in an electrolyte based on an aqueous solution of sodium hydrogencarbonate (baking soda). The electrolyte was circulated cooled (the average process temperature was maintained at 45-60 ° C). Processing samples were plate sizes of 50 × 20 × 2 mm Table 1 shows the test results of samples of stainless chromium-nickel steel, carried out according to the first embodiment.

Table 1 No. Material Concentration, wt.% Potential difference, V The initial height of the microroughness, R _a , microns Microroughness height after processing, R _a , microns one 2 3 four 5 6 one 12X18R10T 5 fifteen 0,120 0,120 2 10 fifteen 0,110 3 fifteen fifteen 0,120 four twenty fifteen 0,110 5 12X18R10T 5 eighteen 0,120 0,045 6 10 eighteen 0,050 7 fifteen eighteen 0,030 8 twenty eighteen 0,025 9 12X18R10T 5 one hundred 0.12 0,030 10 10 one hundred 0.015 eleven fifteen one hundred 0,020 12 twenty one hundred 0,025 13 12X18R10T 5 200 0.12 0,025 fourteen 10 200 0,030 fifteen fifteen 200 0.015 16 twenty 200 0,020 17 12X18R10T 5 300 0.12 0,025 eighteen 10 300 0,025 19 fifteen 300 0,030 twenty twenty 300 0,035 21 12X18R10T 5 400 0.12 0,030 22 10 400 0,035 23 fifteen 400 0,035 24 twenty 400 0,035 one 2 3 four 5 6 21 12X18R10T 5 490 0.12 0,035 22 10 490 0,045 23 fifteen 490 0,035 24 twenty 490 0,055 25 12X18R10T 5 510 0.12 0,085 26 10 510 0,095 27 fifteen 510 0,095 28 twenty 510 0,100

Example 2. The processed blade of a turbomachine made of chrome steel grade 20X13, immersed in a bath with an aqueous solution of an electrolyte in the cavity of the inductor, produced induction heating until a vapor-gas shell was formed around the part, and then a positive voltage was applied to the part, and negative to the electrolyte. Parts were machined in an electrolyte based on an aqueous solution of ammonium sulfate with a concentration of 0.8 ... 3.4%. Circulating cooling of the electrolyte was carried out (the average process temperature was maintained at 50 ° ... 65 ° C). Table 2 shows the results of processing the surface of the feather blades.

table 2 No. Material Concentration, wt.% Potential difference, V The initial height of the microroughness, R _a , microns Microroughness height after processing, R _a , microns one 2 3 four 5 6 one 20X13 0.7 fifteen 0.12 0.12 2 0.7 eighteen 0.11 3 0.7 one hundred 0.12 four 0.7 200 0.12 5 0.7 300 0.10 6 0.7 400 0.11 7 0.7 490 0.10 8 0.7 500 0.10 one 2 3 four 5 6 9 20X13 0.8 fifteen 0.12 0.11 10 0.8 eighteen 0.06 eleven 0.8 one hundred 0.05 12 0.8 200 0.05 13 0.8 300 0.04 fourteen 0.8 400 0,03 fifteen 0.8 490 0.06 16 0.8 500 0.10 17 20X13 2.5 fifteen 0.12 0.09 eighteen 2.5 eighteen 0,07 19 2.5 one hundred 0.05 twenty 2.5 200 0,03 21 2.5 300 0,03 22 2.5 400 0.06 23 2.5 490 0,07 24 2.5 500 0.11 21 20X13 3.4 fifteen 0.12 0.12 22 3.4 eighteen 0,07 23 3.4 one hundred 0.05 24 3.4 200 0.02 21 3.4 300 0.02 21 3.4 400 0.04 22 3.4 490 0.06 23 3.4 500 0.09 21 20X13 3.6 fifteen 0.12 0.10 22 3.6 eighteen 0,07 23 3.6 one hundred 0.06 24 3.6 200 0.04 21 3.6 300 0.02 21 3.6 400 0.05 22 3.6 490 0.06 23 3.6 500 0.09

In addition, anodic processing of steels of grades 15X11MF, EI 961, P-718 (showing similar results shown in tables 1 and 2) in electrolytes of the compositions, wt.%:

1. (NH ₄ ) ₂ SO ₄ - 5; Trilon B - 0.8.

2. 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 of components, 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.

3. Aqueous solutions of salts of inorganic acids of ammonium and alkali metals or salts of lower carboxylic acids, as well as solutions of free acids.

4. An electrolyte containing an ammonium salt of an inorganic acid, ammonium salts of lower carboxylic acids and organic or inorganic substances forming complex compounds with alloy metals.

5. Aqueous solutions of sodium salts (3-22% solution of acidic sodium carbonate).

6. Aqueous solutions of ammonium chloride, sodium chloride.

7. Aqueous solutions of ammonium salts (ammonium citric acid one- or two- or trisubstituted, or mixtures thereof in the following ratio of components, wt.%:

Ammonium citric acid one-, or two-, or trisubstituted, or mixtures thereof - 2-18

Water - Else).

Example 3. The treatment was subjected to samples of stainless steel 12X18H10T and steel EI-961 with dimensions 50 × 20 × 2 mm coated with ion-plasma coatings (titanium nitride), a thickness of 8-11 μm, in order to remove the latter from the surface of the parts. The coating removal process was carried out in a 5% aqueous solution of ammonium sulfate, at an average temperature of 60-70 ° C. The samples were immersed in a bath with an aqueous electrolyte solution, placed in the inductor cavity, induction heating was performed until a vapor-gas shell was formed around the part, and then a negative voltage was applied to the part, and a positive voltage was applied to the electrolyte. The complete removal of the coating was approximately 16 minutes.

Example 4. Processing was subjected to samples of titanium alloys of grades VT-1, VT-5, VT6, VT14, VT3-1, VT22. The processed samples were immersed in a bath with an aqueous solution of electrolyte and, placed in the cavity of the inductor, induction heating was performed until a vapor-gas shell was formed around the part, and then a positive voltage was applied to the part, and a negative voltage was applied to the electrolyte. Parts were machined in an electrolyte based on an aqueous solution, which included salts of hydrofluoric, silicofluoric, hexafluorotitanic or hydrofluoric acids (NH ₄ BF ₄ ; Na ₂ SiF ₆ ). During processing, as in previous cases, the electrolyte was circulated cooled (the average process temperature was maintained in the range of 50 ° ... 65 ° C). Table 3 shows the results of processing the surface of the feather blades (for example, titanium alloy VT6).

Table 3 No. Material Concentration, wt.% Potential difference, V The initial height of the microroughness, R _a , microns Microroughness height after processing, R _a , microns l 2 3 four 5 6 one VT6 0.7 fifteen 0.12 0.12 2 0.7 eighteen 0.12 3 0.7 one hundred 0.11 four 0.7 200 0.12 5 0.7 300 0.10 6 0.7 400 0.12 7 0.7 520 0.11 8 0.7 540 0.10 9 VT6 0.8 fifteen 0.12 0.12 10 0.8 eighteen 0,07 eleven 0.8 one hundred 0.05 12 0.8 200 0.06 13 0.8 300 0.02 fourteen 0.8 400 0,03 fifteen 0.8 520 0,07 16 0.8 540 0.11 17 VT6 2.5 fifteen 0.12 0.11 eighteen 2.5 eighteen 0.08 19 2.5 one hundred 0.06 twenty 2.5 200 0.02 21 2.5 300 0.04 22 2.5 400 0.05 23 2.5 200 0.05 24 2.5 540 0.10 21 VT6 3.4 fifteen 0.12 0.10 22 3.4 eighteen 0.08 23 3.4 one hundred 0.04 24 3.4 200 0,03 21 3.4 300 0.04 21 3.4 400 0.04 22 3.4 520 0.05 23 3.4 540 0.10 21 VT6 3.6 fifteen 0.12 0.11 22 3.6 eighteen 0.08 23 3.6 one hundred 0.06 24 3.6 200 0,03 21 3.6 300 0.02 21 3.6 400 0.02 22 3.6 520 0.08 23 3.6 540 0.10

Claims (35)

1. A method of electrolyte-plasma treatment of a part, comprising immersing the part in an electrolyte, forming a gas-vapor shell around the workpiece surface and igniting a discharge between the workpiece and the electrolyte by applying an electric potential to the part, characterized in that the part immersed in the electrolyte is placed in the inductor cavity, and the vapor-gas shell around the part is formed by induction heating. 2. The method according to claim 1, characterized in that the vapor-gas shell is first formed, and then an electric potential is supplied to the part. 3. The method according to claim 1, characterized in that the part serves a positive potential. 4. The method according to claim 2, characterized in that the component serves a positive potential. 5. The method according to claim 1, characterized in that a negative potential is supplied to the part. 6. The method according to claim 2, characterized in that a negative potential is supplied to the part. 7. The method according to claim 3, characterized in that stainless steel and alloys are used as the material of the part, and the treatment is carried out by polishing until the roughness is not lower than R _a = 0.08-0.12 μm. 8. The method according to claim 4, characterized in that stainless steel and alloys are used as the material of the part, and the treatment is carried out by polishing until the roughness is not lower than R _a = 0.08-0.12 μm. 9. The method according to claim 5, characterized in that stainless steel and alloys are used as the material of the part, and the treatment is carried out by polishing until a roughness of at least R _a = 0.08-0.12 μm is provided. 10. The method according to claim 6, characterized in that stainless steel and alloys are used as the material of the part, and the treatment is carried out by polishing until the roughness is not lower than R _a = 0.08-0.12 μm. 11. The method according to any one of claims 1 to 6, characterized in that the blade of the turbomachine is used as a part. 12. The method according to any one of claims 7 to 10, characterized in that chromium and chromium-nickel steels and alloys are used as stainless steel and alloy, and a turbomachine blade is used as a part. 13. The method according to p. 12, characterized in that the blades are processed at an operating voltage of 18-490 V. 14. The method according to p. 12, characterized in that they process only the feather of the scapula. 15. The method according to item 13, wherein the electrolyte is an aqueous solution of ammonium sulfate with a concentration of 0.8-3.4%. 16. The method according to item 13, wherein the electrolyte is 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 oxide and propylene 0.05-1.1 sulfonated butyl oleate sodium 0.01-0.05 water rest 17. The method according to item 13, wherein the electrolyte is an aqueous solution of inorganic salts of ammonium and alkali metals or salts of lower carboxylic acids, as well as solutions of free acids. 18. The method according to item 13, wherein the electrolyte is an electrolyte containing an ammonium salt of an inorganic acid, ammonium salts of lower carboxylic acids and organic or inorganic substances forming complex compounds with the alloy metals. 19. The method according to p. 18, characterized in that they use an electrolyte composition, wt.%:
(NH ₄ ) ₂ SO ₄ 5 Trilon B 0.8 20. The method according to p. 18, characterized in that use the electrolyte composition, wt.%:
(NH ₄ ) ₃ PO ₄ 5 H ₃ RO ₄ 0.5 potassium tartrate 0.5 21. The method according to item 13, wherein the electrolyte is an aqueous solution of sodium salt. 22. The method according to item 21, characterized in that as an aqueous solution of sodium salt using 3-22% solution of sodium hydrogencarbonate. 23. The method according to item 13, wherein the electrolyte is an aqueous solution of ammonium chloride, sodium chloride. 24. The method according to item 13, wherein the electrolyte is an aqueous solution of ammonium salt. 25. The method according to paragraph 24, wherein the ammonium salt is ammonium citric acid one- or two- or trisubstituted, or a mixture thereof in the following ratio of components, wt.%: Ammonium citric acid one-, or two- or three-substituted, or a mixture of 2-18; water the rest. 26. The method according to claim 1, characterized in that as the electrolyte use an aqueous solution of salts with a pH value of 4-9. 27. The method according to claim 3, characterized in that the material of the part is titanium and a titanium alloy, zirconium and zirconium alloy, and the part is polished until a roughness of at least R _a = 0.08-0.12 μm is provided. 28. The method according to claim 4, characterized in that the material of the part is titanium and a titanium alloy, zirconium and zirconium alloy, and the part is polished until a roughness of at least R _a = 0.08-0.12 μm is provided. 29. The method according to claim 5, characterized in that the material of the part is titanium and a titanium alloy, zirconium and zirconium alloy, and the part is polished until a roughness of at least R _a = 0.08-0.12 μm is provided. 30. The method according to claim 6, characterized in that the material of the part is titanium and a titanium alloy, zirconium and zirconium alloy, and the treatment is carried out by polishing until a roughness of at least R _a = 0.08-0.12 μm is provided. 31. The method according to any one of paragraphs.27-30, characterized in that the blade of a turbomachine is used as a part. 32. The method according to p, characterized in that the processing of the blades is carried out at an operating voltage of 18-520 V. 33. The method according to p, characterized in that they process only the feather of the scapula. 34. The method according to p, characterized in that as the electrolyte use an aqueous solution of salts with a pH value of 4-9. 35. The method according to p, characterized in that the electrolyte is an aqueous electrolyte solution, which includes salts of hydrofluoric, silicofluoric, hexafluorotitanic or hydrofluoric acids.