RU2694935C1 - Method of series electrolytic-plasma polishing of blisk blades of turbomachines and working capacity for its implementation - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to electrolytic-plasma polishing of articles from alloyed steels, high-melting and titanium alloys and can be used in turbomachinery construction during processing of blisk blades compressors of gas turbine engines to ensure the required operational properties of parts of turbomachines. Method includes dipping of treated blisk blades in electrolyte, which is in container, formation around processed surface of blades blisk steam-gas shell and ignition of discharge between treated surface of blisk blades and electrolyte. Container for electrolyte is a reservoir made from electrically insulating material with electrodes arranged in container reservoir pockets. Successively after finishing of the current blade polishing, the next blisk blade is lowered into the container and processing is performed till finishing of all blisk blades polishing. Working container is configured to be arranged in inter-blade space near the treated blade and providing coverage of the entire treated surface of the blisk blade.

EFFECT: higher quality of blisk blade processing.

6 cl, 5 dwg, 3 ex

Description

The invention relates to electrolytic-plasma polishing of products from alloyed steels, refractory and titanium alloys, and can be used in turbo-machine engineering in the processing of blisks of gas turbine engine compressors, to provide the necessary operational properties of parts of turbomachines.

Working blades of gas turbine engines and installations during operation are exposed to significant dynamic and static loads. On the basis of the requirements for operational properties, for the manufacture of gas turbine blades, alloy steels and titanium alloys are used, which have a sufficiently high strength, including at high temperatures, while maintaining plasticity.

However, turbine blades are highly sensitive to stress concentrators. Therefore, defects resulting from the manufacturing process of these parts are unacceptable, since they cause the occurrence of intensive processes of destruction. This causes problems when machining surfaces of parts of turbomachines. In this regard, the development of methods for obtaining high-quality surfaces of parts of turbomachines is a very urgent task.

The most promising methods for machining turbomachine blades are electrochemical methods for polishing surfaces [Griliches S.Ya. Electrochemical and chemical polishing: Theory and practice. Effect on the properties of metals. L., Mashinostroenie, 1987.], while the most interesting for this area are the methods of electrolytic-plasma polishing (EPP) of parts [for example, GDR Patent (DD) No. 238074 (A1), IPC C25F 3/16, publ. 08.08.86., As well as Patent of the Republic of Belarus No. 1132, IPC C25F 3/16, 1996, BI No. 3].

A known method of polishing metal surfaces, including anodic treatment in the electrolyte [Patent RB No. 1132, IPC C25F 3/16, 1996, BI No. 3], as well as a method of electrochemical polishing [US Patent No. 5028304, IPC V23H 3/08, C25F 3 / 16, C25F 5/00, publ. 07/02/91.]

Known methods of electrochemical polishing do not allow for high-quality polishing of the surface of the blades of the blisks of turbomachines.

There is also known a method of electrolytic-plasma polishing of parts [RF Patent №2373306, IPC C25F 3/16. Method of multi-stage electrolytic-plasma polishing of products from titanium and titanium alloys. Bul No.32, 2009], which includes immersing a part in an electrolyte containing an oxidizing agent, a fluorine-containing compound and water, forming a vapor-gas sheath around the surface being treated and igniting a discharge between the part being processed and the electrolyte by supplying an electric potential to the part being processed.

However, the known method [Patent of the Russian Federation No. 2373306, IPC C25F 3/16] is a multistage process, which on the one hand leads to an increase in the complexity of the part machining process, a reduction in the quality and reliability of the machining process due to the need to provide more process parameters and their ratios, increase its complexity.

The closest to the claimed technical solution is the method of electrolytic-plasma polishing of turbine blades [RF Patent №2552203, IPC C25F 3/16. The method of polishing parts made of titanium alloys. Bul No.16, 2015], which involves immersing a part in an electrolyte, forming a vapor-gas envelope around the surface to be treated and igniting a discharge between the part being processed and the electrolyte by applying an electric potential to the part being processed.

However, the prototype method cannot be used to polish the GTE compressors' blisks, since electrolyte-plasma processing of products with a significant surface area produces an excessive amount of heat, which makes the process unstable and leads to the appearance of defects on the surface of the blades. In addition, the processing of large products, which include gas compressor compressor bliski, requires a significant amount of electricity and when implementing the polishing process in these conditions, the efficiency is sharply reduced. processing. Known devices (AS USSR №1039251, IPC C25F 7/00, 04.01.81, RF patent №2009212, IPC C21D 1/44, 03.15.94), containing a bath for the electrolyte, the working electrode and the electrolyte circulation system, including pump with a pipe for supplying electrolyte, a window with a pipe for returning electrolyte.

The closest to the technical essence is selected as a prototype capacity for electrolytic-plasma polishing (RF patent №2268326, IPC C21D 1/44, 03.15.94), made of non-conductive material and containing in the internal working volume at least one electrode connected to the cathode.

However, this device [RF patent №2268326, IPC C21D 1/44, 03.15.94] cannot be applied to the treatment of bliski blades having large dimensions, since excessive amounts of heat are generated when processing products with a significant surface area, which makes the process unstable and leads to defects on the surface of the blades. In addition, the processing of large products, which include gas compressor compressor bliski, requires a significant amount of electricity and when implementing the polishing process in these conditions, the efficiency is sharply reduced. processing.

The challenge to which the invention is directed, is to improve the quality and reliability of the process of polishing bliskov GTE compressor of titanium alloys.

The task is solved due to the fact that in the method of sequential electrolytic-plasma polishing of blisks of turbomachines, including immersion of the treated blisks in the electrolyte in the working capacity, forming a vapor-gas membrane around the surface of the blades and the ignition of the discharge between the surface of the blisks and electrolyte by supplying the electric potential and polishing of the blades of the blades to the processed blisk to obtain a given roughness and x surfaces characterized in that as a working capacity for an electrolyte, a working capacity is used, with walls made of dielectric material located inside these walls of electrodes, open from the inside of the walls of the working capacity, dimensions and shape of the working capacity providing coverage with the working gap of the whole surface to be treated blades blades and the possibility of placing the working capacity in the interscapular space about at least one of the processed blades, is lowered into the said working capacity, at least one bliske blade to be processed, ensure that the entire polished surface of the bliska blade is in contact with the electrolyte, serves on the blisk positive, and a negative electric potential is applied to the electrolyte through the electrode in the walls of the working capacity to obtain a given bliske blade surface roughness, then remove the processed blade from the mentioned working capacity, lower the next blade of the bliska into the working container and repeat the indicated cycle until the complete processing of all blades of the bl ska.

It is possible to use the following additional methods of the method: use an additional electrolyte tank connected to the working capacity and forming a single system of communicating vessels, providing loading and discharge of electrolyte from the working capacity, and electrolyte is circulated between the working capacity and the additional capacity during the polishing of blis blades. providing the set temperature and electrolyte composition; as used Blisk turbine blisks of a titanium alloy and the electrolyte is an aqueous solution of a mixture of NH ₄ F and KF at a content of NH ₄ F - from 5 to 15 g / l and KF - from 30 to 50 g / l; as a blisch use blisk turbine made of alloyed steel, and as the electrolyte use an aqueous solution of hydroxylamine hydrochloric acid and sodium fluoride with the following content of components, g / l: hydroxylamine hydrochloric acid NH ₂ OH × HCl - from 22 to 30, sodium fluoride NaF - from 7 up to 15; as a blisk, use a blisk of a refractory alloy turbine, and as an electrolyte use an aqueous solution of hydroxylamine hydrochloric acid and sodium fluoride with the following content of components, g / l: hydroxylamine hydrochloric acid NH ₂ OH × HCl - from 30 to 38, sodium fluoride NaF - from 12 before 18.

The technical result is also achieved due to the fact that the working capacity for the sequential electrolytic-plasma polishing of bliske blades is made of a dielectric material and containing at least one electrode connected to the cathode in the internal working volume, unlike the prototype, the working capacity is made of dimensions and shape providing coverage with a working gap of the entire surface of the bliske blade and the possibility of placing the working capacity in the interscapular space of the blade to be processed As well as equipped, connected to it into a single system of communicating vessels through pipelines with a pump with additional capacity, providing draining of the working capacity, pouring into the working capacity and electrolyte circulation during polishing, as well as provided with a seal in the inlet neck, providing sealing of the working capacity when pressing it to the bliska when placed in the working capacity of the processed blades bliska. The walls of the working container have pockets open into the internal cavity of the working container, inside of which are placed electrodes that do not protrude beyond the dimensions of the wall of the working container.

The essence of the proposed method, the possibility of its implementation and use are illustrated by the examples presented below.

The invention is illustrated in the following diagram. FIG. 1-5 shows the process of electrolytic-plasma polishing of the bliske blade and the design of the working capacity. FIG. 1 shows a fragment of a bliska with one processed bliske spatula; FIG. 2 - with two processed blisk blades. FIG. 3 is a cross-sectional view of the bliske blade being processed; FIG. 4 is a cross section of the blade being processed and the working container with electrodes located inside the wall of the working container; FIG. 5 is a longitudinal section of the blade with a working capacity. Figures 1-5 contain: 1 - blisk; 2 - bliske scapula; 3 - processed (current) blade blisk; 4 - working capacity; 5 - seal on the neck of the working capacity: 6 - electrolyte; 7 - pockets; 8 - electrode; 9 - inlet and outlet pipes of the working capacity; 10 - vapor-gas envelope. (The arrows indicate the direction of movement of the electrolyte).

The process of sequential polishing is as follows (Fig. 1-5). Blisk 1 is fixed on the holder with the horizontal position of its longitudinal axis (not shown), one or several lower blades 3 of the bliska being processed one is dipped into the working container 4 (Fig. 1 and Fig. 2). In this case, the working container 4 is pressed through the seals 5 on its neck and sealed its volume. Electrolyte 6 is pumped into the working tank 4 with the treated blade 3 through pipelines with the help of a pump from an additional tank and circulates it (not shown). Circulation of the electrolyte 6 from the additional capacity to the working capacity 4 and vice versa ensures the maintenance of the desired process temperature and the stability of the electrolyte composition (Fig. 4).

An electric potential is supplied to the blisk 1 from the anode and to the electrodes 8 from the cathode. As a result of the electrical potential being applied, a vapor-gas sheath 10 is formed around the surface of the bliske blade blades, a discharge is triggered between the surface of the blade 3 of the bliska blade 3 and electrolyte 6 and the surface of the blade 3 is processed electrolytic-plasma polishing (Fig. 4 and Fig. 5). As the capacity for the electrolyte use of the working capacity 4, made of insulating material located in the pockets 7, in the walls of the working chamber 4 of the electrodes 8 (Fig. 4). The working tank 4 is located in the interscapular space near the blade 3 being processed of the blisk 1. (If necessary, a larger number of blades can be treated in the same way (Fig. 2)). The processing of the blade 3 is carried out to obtain a given surface roughness.

When a sufficient potential is applied to blisk 1 and electrode 8, a vapor-gas envelope 10 is formed around the blade 3, a discharge occurs between the item being processed and the electrolyte, and the blade surface is polished by the electrolyte-plasma method. The process of electrolytic-plasma polishing is carried out at an electric potential of from 250 V to 320 V, and the electrolyte used is: an aqueous solution of a mixture of NH ₄ F and KF when the content of NH ₄ F is from 5 to 15 g / l and KF is from 30 to 50 g / l, when processing bliska from titanium and titanium alloys; aqueous solution of hydroxylamine hydrochloric acid and sodium fluoride with the following content of components, g / l: hydroxylamine hydrochloric acid NH ₂ OH × HCl - from 22 to 30, sodium fluoride NaF - from 7 to 15, when processing a blis of alloyed steel; aqueous solution of hydroxylamine hydrochloric acid and sodium fluoride with the following content of components, g / l: hydroxylamine hydrochloric acid NH ₂ OH × HCl - from 30 to 38, sodium fluoride NaF - from 12 to 18, when processing blis of refractory alloys.

After the treatment of the blade 3, the electrolyte 6 is removed from the working tank 4, the treated blade 3 is removed from the working tank 4 and the next blade bliska 1 is lowered into the work tank and the indicated treatment cycle is repeated until all blades are processed completely.

Polishing is carried out at a temperature of from 70 ° C to 96 ° C. Polishing, depending on the parameters of the part, can be conducted at a current of 0.2 A / cm ² to 0.7 A / cm ² for at least 1.5 minutes. The polished blade of the turbomachine must have a roughness of the original surface of not more than Ra 0.80 microns. The treatment is carried out in an electrolyte medium while maintaining around the part of the vapor-gas membrane.

When implementing the method, the following processes occur. Under the action of flowing currents, the surface of the part heats up and a vapor-gas shell is formed around it. Excessive heat that occurs when the part and electrolyte are heated is discharged through the cooling system when electrolyte is circulated from the additional container to the case. The volume of additional capacity must significantly exceed the volume of the elastic cover and ensure the stability of the temperature regime and the composition of the electrolyte. Under the action of electrical voltage (electrical potential between the part and the electrolyte) in the vapor-gas envelope there is a discharge, which is an ionized electrolytic plasma, ensuring the flow of intensive chemical and electrochemical reactions between the workpiece and the vapor-gas envelope medium.

When applying a positive potential to the blade, during the course of these reactions, anodizing of the surface of the part occurs with simultaneous chemical etching of the formed oxide. Moreover, in the case of anodic polarization, the vapor-gas layer consists of electrolyte vapors, anions, and gaseous oxygen. Since the etching occurs mainly on microroughness, where a thin oxide layer is formed, and the anodizing processes continue, as a result of the combined action of these factors, the roughness of the surface being treated decreases and, as a result, the polishing of the latter. After polishing the bliske blade, it is washed, pumping water into the case, instead of the electrolyte removed. Then remove the elastic cover and put it on the next blade to be processed and repeat this cycle until polishing of all the blades is completed.

Example 1. Processing was subjected to blades blisk compressor GTE of titanium alloys grades VT6, VT8, VT8M. The bliske treated blades were polished successively with an electrically insulating cover made of polymer. The bliske spatula to be treated was immersed in a bath with an aqueous electrolyte solution and a positive voltage was applied to the bliske and a negative voltage was applied to the electrolyte. An electrical potential of 250 V, 300 V, 320 V was applied to the workpiece. The parts were processed in an electrolyte medium based on an aqueous solution of a mixture of NH ₄ F and KF with an NH ₄ F content of 11 g / l and KF of 36 g / l.

Example 2. Processing was subjected to blades blisk compressor GTE from bliske alloyed steel grades 20X13 and 15X11MF, 20X13, EY 961 ;. The bliske treated blades were polished successively with an electrically insulating cover made of polymer. The bliske spatula to be treated was immersed in a bath with an aqueous electrolyte solution and a positive voltage was applied to the bliske and a negative voltage was applied to the electrolyte. An electric potential of 300 V, 320 V was applied to the workpiece. The parts were processed in an electrolyte medium based on an aqueous solution of hydroxylamine hydrochloric acid and sodium fluoride with the following content of components, g / l: hydroxylamine hydrochloric acid NH ₂ OH × HCl - 28 g / l. sodium fluoride NaF - 9 g / l ..

Example 3. Processing was subjected to blades blisk compressor GTE from bliska alloyed steel grades 20X13 and 15X11MF, 20X13, EY 961 ;. The bliske treated blades were polished successively with an electrically insulating cover made of polymer. The bliske spatula to be treated was immersed in a bath with an aqueous electrolyte solution and a positive voltage was applied to the bliske and a negative voltage was applied to the electrolyte. Electric potential, 300 V, 320 V was applied to the workpiece. Details were processed in an electrolyte medium based on an aqueous solution of hydroxylamine hydrochloric acid and sodium fluoride with the following content of components, g / l: hydroxylamine hydrochloric acid NH ₂ OH × HCl - from 32, sodium fluoride NaF - 14 g / l.

During processing, circulation cooling of the electrolyte was performed (the average process temperature was maintained in the range of 70 ° ... 96 ° C). The processing time of each blade was 2 minutes. The initial roughness of the treated surface was Ra 0.18 μm, after polishing Ra 0.03-0.02 μm.

To assess the performance properties of parts processed by the proposed method, the following tests were carried out. Samples of titanium alloys of grades VT6, VT8, VT8M, VT1-0, from alloyed steels of grades 20X13 and 15X11MF, 20X13, He 961, from alloys based on nickel EP741NP, ZhS6U, ZhS32 were subjected to processing according to the methods of prototypes (RF patent № 2552203), according to the conditions and processing modes described in the prototype method, and according to the variants of the proposed method. (For an unsatisfactory result (NR), a result was taken at which no polishing of the titanium part occurred, for a satisfactory result (RR), when a polishing effect was observed)

Prototype method showed unsatisfactory results.

The processing scheme of the bliske blades in the prototype method: immersion of the bliske in electrolit - (NR).

The modes of processing samples for the proposed method.

Bliska blade processing scheme: polishing of the blisk blades by placing the processed blisk blade in a working container with electrodes - (RR); Blisk immersion entirely in the tank with electrolyte - N.R.

Electric potential: 240 V - NR, 250 V - U.R., 270 V - U.R., 290 V - U.R., 300 V - U.R., 320 V - U.R. , 340 V - N.P.

Electrolyte:

The electrolyte used is: an aqueous solution of a mixture of NH ₄ F and KF when the content of NH ₄ F is from 5 to 15 g / l and KF is from 30 to 50 g / l, when processing a blisk of titanium and titanium alloys; aqueous solution of hydroxylamine hydrochloric acid and sodium fluoride with the following content of components, g / l: hydroxylamine hydrochloric acid NH ₂ OH × HCl - from 22 to 30, sodium fluoride NaF - from 7 to 15, when processing blis from alloyed steel (steel grades 20X13 and 15X11MF , 20X13, YO 961)); aqueous solution of hydroxylamine hydrochloric acid and sodium fluoride with the following content of components, g / l: hydroxylamine hydrochloric acid NH ₂ OH × HCl - from 30 to 38, sodium fluoride NaF - from 12 to 18, when processing a blisk from refractory alloys (nickel-based alloy EP741NP ).

Electrolyte temperature: from 70 ° С to 96 ° С.

The magnitude of the electric current: from 0.2 A / cm ² to 0.7 A / cm ² .

Time: 1.5-10 minutes.

The roughness of the original polished surface is not more than Ra 0.80 microns.

Thus, studies have shown that the use of the proposed method of polishing blades bliska of titanium and titanium alloys, alloyed steels and refractory alloys can improve, as compared with the prototype, the quality of their processing. The average roughness of the polished surface when processing by the proposed method amounted to Ra 0.04 ... 0.02 μm.

Claims (6)

1. A method of sequential electrolytic-plasma polishing of blisks for turbomachines, including immersion of the treated blisks in the electrolyte in the working capacity, forming a vapor-gas membrane around the surface of the blades and blasting of the discharge between the surface of the blisks and electrolyte by supplying electric potential to the bliske and polishing bliske blades to obtain a given surface roughness, characterized in that A working electrolyte tank uses a working tank with walls made of dielectric material located inside these walls of electrodes, open from the inside of the walls of the working tank, dimensions and shape of the working capacity, providing coverage with the working gap of the entire surface of the bliska blade and the possibility of placing the working tank in the interscapular space around at least one blade to be processed, lower at least one blade to be processed into said working capacity , ensure contact of the entire polished surface of the bliska blade with the electrolyte, serves on the blis positive and electrolyte through the electrode in the walls of the working capacity - negative electric potential and treat until a given surface roughness of the bliske blade is obtained, then remove the treated blade from the said working capacity, The next bliske blade is lowered into the working container and the indicated cycle is repeated until all bliske blades are completely processed. 2. The method according to p. 1, characterized in that use additional capacity with electrolyte connected to the working capacity and forming a single system of communicating vessels, providing loading and draining of the electrolyte from the working capacity, and in the process of polishing blisk blades conduct electrolyte circulation between the working capacity and additional capacity, providing the set temperature and electrolyte composition. 3. The method according to p. 1 or 2, characterized in that carry out the polishing of the bliska turbine of a titanium alloy, and as the electrolyte use an aqueous solution of a mixture of NH ₄ F and KF when the content of NH ₄ F is from 5 to 15 g / l and KF from 30 to 50 g / l. 4. The method according to p. 1 or 2, characterized in that they carry out polishing of the bliska of a turbine made of alloyed steel, and as an electrolyte use an aqueous solution of hydroxylamine hydrochloric acid and sodium fluoride with the following content of components, g / l: hydroxylamine hydrochloric acid NH ₂ OH × HCl from 22 to 30, sodium fluoride NaF from 7 to 15. 5. The method according to p. 1 or 2, characterized in that carry out the polishing of the bliska of the turbine from refractory alloys, and as the electrolyte using an aqueous solution of hydroxylamine hydrochloric acid and sodium fluoride with the following content of components, g / l: hydroxylamine hydrochloric acid NH ₂ OH × HCl from 30 to 38, sodium fluoride NaF from 12 to 18. 6. Working capacity for sequential electrolytic-plasma polishing of blisks' blades, made of dielectric material and containing at least one electrode connected to the cathode in the internal working volume, characterized in that it is connected to it in a single system of communicating vessels through pipelines pump additional capacity, providing drainage from the working capacity, pouring into the working capacity and electrolyte circulation during the polishing process, and sealing in the inlet neck, ensuring m sealing the working capacity while pressing it to the bliska when placed in the working capacity of the bliska blade being processed, while the working capacitance is made in dimensions and shape, providing coverage with the working gap of the entire surface of the bliska blade and placing the working capacity in the interscapular space of the blade being processed, and The working container has pockets open into the internal cavity of the working container, inside of which are placed electrodes that do not protrude beyond the dimensions of the wall of the working container.

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