RU2710761C1 - Method of applying an erosion-resistant coating onto the surface of a steel blade of a steam turbine - Google Patents

Method of applying an erosion-resistant coating onto the surface of a steel blade of a steam turbine Download PDF

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RU2710761C1
RU2710761C1 RU2018147540A RU2018147540A RU2710761C1 RU 2710761 C1 RU2710761 C1 RU 2710761C1 RU 2018147540 A RU2018147540 A RU 2018147540A RU 2018147540 A RU2018147540 A RU 2018147540A RU 2710761 C1 RU2710761 C1 RU 2710761C1
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Russia
Prior art keywords
chromium
surface
blade
microlayers
coating
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RU2018147540A
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Russian (ru)
Inventor
Геннадий Викторович Качалин
Алексей Феликсович Медников
Константин Сергеевич Медведев
Александр Борисович Тхабисимов
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Акционерное общество "Дальневосточная генерирующая компания"
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Priority to RU2018147540A priority Critical patent/RU2710761C1/en
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    • CCHEMISTRY; METALLURGY
    • C23COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23CCOATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/02Pretreatment of the material to be coated
    • CCHEMISTRY; METALLURGY
    • C23COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23CCOATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/06Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
    • CCHEMISTRY; METALLURGY
    • C23COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23CCOATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C14/00Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
    • C23C14/22Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
    • C23C14/34Sputtering
    • C23C14/35Sputtering by application of a magnetic field, e.g. magnetron sputtering

Abstract

FIELD: machine building.SUBSTANCE: invention relates to power engineering and can be used for protection against erosion wear of steel working blades of wet-steam stages of turbines exposed to high-speed drop-impact action in corrosion-active media at increased fatigue loads. Method for application of coating on surface of turbine blade includes electrolytic-plasma polishing of blade surface, its arrangement in vacuum chamber, in which magnetron with target of chromium is installed, heating of vacuum chamber and pumping of air from it, cleaning and etching of blade surface with ions of inert gas, periodic supply of reaction gas into vacuum chamber and formation on said surface of even number of alternating chromium microlayers and chromium compound, wherein hydrocarbon gas is used as reaction gas, microlayers of chromium compound are formed in form of chromium carbide with thickness of 1.4±0.6 mcm, chromium micro-layers with thickness of 0.45±0.15 mcm, with total number of micro layers in range from 6 to 10 and controlling flow of hydrocarbon gas from condition of total concentration of carbon atoms in coating 3.25±0.25 at. %.EFFECT: technical result consists in increasing the service life of the applied erosion-resistant coating by increasing its corrosion resistance and fatigue strength.1 cl, 3 tbl

Description

Technical field

The invention relates to the field of power engineering and can be used to protect against erosion wear of steel blades of wet-steam turbine stages subjected to high-speed drop impact in corrosive environments with increased fatigue loads.

State of the art

A known method of protecting turbine blades (patent RU No. 2585580, publ. 05.27.2016, IPC С23С 14/48), including preparing the surface of the blades for coating using electrolyte-plasma polishing, applying the first coating layer of an alloy based on nickel, applying to the first layer of the second layer of an alloy based on aluminum and heat treatment of the blades with a coating [RU 2585580, publ. 05/27/2016].

The disadvantage of this technical solution is the narrow scope due to the low efficiency of this method for protecting the blades of large turbines.

The closest in technical essence to the present invention is a method of coating [patent RU 2660502, publ. 07/06/2018], including plasma electrolyte polishing of the blade surface, its placement in a vacuum chamber, in which magnetrons with chromium targets are installed, heating the vacuum chamber and pumping air out of it, cleaning and etching the surface of the blade with inert gas ions, periodic feeding into the vacuum the reaction gas chamber and the formation on the indicated surface of an even number of successively alternating chromium microlayers and chromium microlayers. This method is selected as a prototype.

The prototype method provides for the preliminary nitriding of the surface of the protected blades. The nitrided surface has high hardness, which allows it to withstand droplet impact for a long time, which determines the increased erosion resistance of the coating due to damping of stresses arising in the microlayers of the coating from droplet impact. However, when the product is operated in a corrosive working medium, the nitrided surface of the blade is quickly damaged after drop-impact and fatigue failure of the microlayers of the coating applied to it, which leads to low rates of the prototype coating in terms of corrosion resistance.

Disclosure of the invention

The technical task of the invention is to increase the corrosion resistance and fatigue strength of the applied coating while maintaining its high erosion resistance.

The technical result of the invention is to increase the resource applied by the present method to an erosion-resistant coating by increasing its corrosion resistance and fatigue strength.

The subject of the invention is a method for coating a surface of a turbine blade, including electrolyte-plasma polishing of the surface of the blade, its placement in a vacuum chamber in which magnetrons with targets from chromium are installed, heating the vacuum chamber and pumping air out of it, cleaning and etching the surface of the blade with inert ions gas, the periodic supply of reaction gas to the vacuum chamber and the formation on the indicated surface of an even number of successively alternating chromium microlayers and chromium compounds, from characterized in that hydrocarbon gas is used as a reaction gas, while forming chromium microlayers in the form of chromium carbide with a thickness of 1.4 ± 0.6 microns, chromium microlayers with a thickness of 0.45 ± 0.15 microns, the total number of microlayers in the range from 6 to 10 and regulate the flow of hydrocarbon gas from the condition of the total concentration of carbon atoms in the coating of 3.25 ± 0.25 at. %

The formation on the surface of the blade of a protective coating of an even number of successively alternating plastic microlayers of chromium and chromium carbide, harder than the microlayers of chromium nitride (used in the prototype method), provides high hardness of the coating without performing the preliminary nitriding of the blade surface provided by the prototype, which reduces its corrosion durability.

The invention has a development, which consists in the fact that electrolyte-plasma polishing of the surface of the blade is carried out in 9.5 ± 2.5% aqueous solution of ammonium sulfate while maintaining its slightly alkaline reaction and a temperature of 80 ± 10 ° C with a voltage on the blade of 315 ± 15 V .

The implementation of the invention in view of its development

A coating on the surface of the blade is formed in a vacuum chamber in which a magnetron with a chromium target is mounted.

Before placing in a vacuum chamber, electrolyte-plasma polishing of the blade is carried out, which reduces the roughness of its surface and, thereby, improves adhesion to the coating. To do this, the blade is immersed in an electrolyte - a solution of ammonium sulfate, which is heated to form a vapor-gas shell around the blade, and a positive constant voltage is applied to the blade.

After polishing, the blade is placed on the carousel in a vacuum chamber in which a magnetron with a target of chromium is installed. Then the vacuum chamber is heated, air is pumped out of it, the surface of the blade is cleaned and etched with inert gas ions (argon), completing the preparation for coating. Surface nitriding performed according to the prototype before coating formation is not performed.

Reactive hydrocarbon gas (e.g., methane or propane) is periodically fed into the chamber. During coating formation, the blade, rotating on the carousel, cyclically passes in front of the magnetron. In this case, in the absence of hydrocarbon gas in the chamber, a chromium microlayer is formed on the surface of the blade, and in the presence of hydrocarbon gas in the chamber, a chromium microlayer. In the process of multiple passage of the blade in front of the magnetron with periodic supply of reaction hydrocarbon gas, a multilayer coating is formed on the surface of the blade from alternating chromium microlayers and chromium carbide microlayers.

The coating is formed of several pairs of microlayers (from 3 to 5 pairs), each of which is a chromium microlayer and a chromium carbide microlayer deposited on top of it. The first on the surface of the blades is a metal chromium microlayer, which has high adhesion and porosity, which is necessary for the strength of the coating as a whole, its corrosion resistance. The second is a hard and wear resistant chromium carbide microlayer. Subsequent microlayers - alternating plastic chromium microlayers and solid chromium carbide microlayers resist the propagation of cracks formed in solid microlayers into the lower plastic microlayers. The last layer is a hard and wear-resistant chromium carbide microlayer.

The thickness of the microlayer coating set the duration of the magnetron (or the number of cycles of rotation of the carousel) in the presence or absence of hydrocarbon gas in the chamber).

The deposition of a micro layer of chromium (in the absence of a hydrocarbon gas in the chamber) is performed for the time necessary to obtain a micro layer of a thickness of 0.45 ± 0.15 μm. The deposition of a microlayer of chromium carbide (when a hydrocarbon gas is fed into the chamber) is performed for the time required to obtain a microlayer with a thickness of 1.4 ± 0.6 μm. The total concentration of carbon atoms in the coating, equal to 3.25 ± 0.25 at. %, provide by adjusting the flow rate of the reaction hydrocarbon gas supplied to the vacuum chamber. (The tolerances given for the specified thickness of the microlayers and the concentration of carbon atoms take into account the technological error and inertia of the described process of applying a multilayer coating). According to the claimed method, the total number of coating microlayers lies in the range of even numbers from 6 to 10.

To determine the total number of microlayers, the best in erosion resistance, comparative tests of samples were carried out, the results of which are presented in table 1.

Figure 00000001

As can be seen from table 1, the coating applied by the present method, with an even number of layers in the range from 6 to 10, is not inferior to the prototype in terms of erosion resistance (according to its description, the relative erosion resistance on the same steel grade is 4.2).

To compare erosion and corrosion resistance, as well as the fatigue strength of the coating applied by the proposed method, with the corresponding characteristics of the coating applied by the prototype method, comparative tests were carried out, the results of which for samples made of blade steel grade 20X13 are shown in table 2.

Samples of group (I) correspond to the prototype. Samples of groups (II-IV) are samples No. 2, 3, 4 according to table 1. Group (I) was a control. The resistance of samples of other groups was determined in relation to the fatigue strength, erosion and corrosion resistance of samples of group (I). Erosion tests were carried out at the Erosion-M hydraulic shock stand. Pitting corrosion resistance tests were carried out using an IPC-Pro MF electronic potentiostat and an open three-electrode thermostated cell using anodic polarization method to determine the potential and pitting resistance bases in an aqueous medium, such as circulating water chloride contaminated. Fatigue studies in pure bending with rotation based on 10 7 cycles were carried out on a KU-1 unit.

Figure 00000002

From the table. 2 it follows that the samples coated by the proposed method have increased 3.0 ÷ 3.6 times the resistance to pitting corrosion and increased by 10% fatigue strength. However, they retain high erosion resistance of the prototype.

Comparative tests of 12X13 blade steel samples showed similar advantages over the prototype.

As can be seen from the foregoing, the method of applying a protective coating, characterized by the claimed combination of features, provides an increase in the corrosion and fatigue resistance of the applied coating while maintaining its high erosion resistance and, thereby, prolongs the life of the protected turbine blades operating in a corrosive environment.

The main parameters of the electrolyte-plasma polishing regime (voltage, temperature and acid pH of the solution) affect the roughness of the surface to be protected. According to the development of the proposed method, electrolyte-plasma polishing is carried out, maintaining the following mode: temperature 80 ± 10 ° C, voltage 315 ± 15V, the concentration of the solution is 9.5 ± 2.5%. At the same time, during the polishing process, a slightly alkaline reaction (pH> 7) of the electrolyte is controlled and maintained (for example, by adding sodium hydroxide NaOH).

This mode of electrolyte-plasma polishing (its parameters are given taking into account technological tolerances), increases the adhesion of blade steels to the applied coating, and as a result, further improves its fatigue characteristics.

To compare the erosion and corrosion resistance, as well as the fatigue strength of the coating applied by the proposed method, taking into account its development and the corresponding characteristics of the coating applied by the prototype method, comparative tests of blade steel samples were carried out.

The test results are shown in table 3.

Figure 00000003

Group (I) included samples No. 2, 3, 4 of table 1, i.e. samples with coatings deposited on non-nitrided surfaces according to the claimed method without taking into account its development (with electrolyte-plasma polishing in a mode known, for example, from the description of patent RU 2585580). Samples of group (II) had coatings deposited according to the claimed method with conducting electrolyte-plasma polishing in the mode according to an additional paragraph of the patent formula.

From the table. 3 it follows that the development of the proposed method further increases the resistance to pitting corrosion and the fatigue strength of the coating while maintaining its erosion resistance.

Claims (2)

1. The method of coating the surface of a turbine blade, including electrolytic plasma polishing of the surface of the blade, its placement in a vacuum chamber in which a magnetron with a chromium target is installed, heating the vacuum chamber and pumping air out of it, cleaning and etching the surface of the blade with inert gas ions , periodically supplying the reaction gas to the vacuum chamber and forming on the indicated surface an even number of successively alternating chromium microlayers and a chromium compound, characterized in that carbon is used hydrogen gas as a reaction gas; in this case, chromium microlayers are formed in the form of chromium carbide with a thickness of 1.4 ± 0.6 microns, chromium microlayers with a thickness of 0.45 ± 0.15 microns with a total number of microlayers in the range from 6 to 10 and are regulated the flow of hydrocarbon gas from the condition of the total concentration of carbon atoms in the coating of 3.25 ± 0.25 at.%.
2. The method according to p. 1, characterized in that the electrolyte-plasma polishing of the surface of the blade is carried out in 9.5 ± 2.5% aqueous solution of ammonium sulfate with the maintenance of its slightly alkaline reaction and a temperature of 80 ± 10 ° C with a voltage on the blade of 315 ± 15 V.
RU2018147540A 2018-12-29 2018-12-29 Method of applying an erosion-resistant coating onto the surface of a steel blade of a steam turbine RU2710761C1 (en)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090106207A1 (en) * 2007-10-18 2009-04-23 Fast Search And Transfer Asa Method for restricting access to search results and a search engine supporting the method
US7758968B2 (en) * 2003-12-11 2010-07-20 Siemens Aktiengesellschaft Component with thermal barrier coating and erosion-resistant layer
EP2677063A1 (en) * 2012-06-20 2013-12-25 General Electric Company Erosion and corrosion resistant coatings for exhaust gas recirculation-based gas turbines
RU2585580C1 (en) * 2015-03-03 2016-05-27 Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Уфимский государственный авиационный технический университет" Method for protection against erosion and salt corrosion of blades of turbo machines from alloyed steels
RU2660502C1 (en) * 2017-11-28 2018-07-06 федеральное государственное бюджетное образовательное учреждение высшего образования "Национальный исследовательский университет "МЭИ" (ФГБОУ ВО "НИУ "МЭИ") Method for applying a coating to the surface of a steel product

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7758968B2 (en) * 2003-12-11 2010-07-20 Siemens Aktiengesellschaft Component with thermal barrier coating and erosion-resistant layer
US20090106207A1 (en) * 2007-10-18 2009-04-23 Fast Search And Transfer Asa Method for restricting access to search results and a search engine supporting the method
EP2677063A1 (en) * 2012-06-20 2013-12-25 General Electric Company Erosion and corrosion resistant coatings for exhaust gas recirculation-based gas turbines
RU2585580C1 (en) * 2015-03-03 2016-05-27 Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Уфимский государственный авиационный технический университет" Method for protection against erosion and salt corrosion of blades of turbo machines from alloyed steels
RU2660502C1 (en) * 2017-11-28 2018-07-06 федеральное государственное бюджетное образовательное учреждение высшего образования "Национальный исследовательский университет "МЭИ" (ФГБОУ ВО "НИУ "МЭИ") Method for applying a coating to the surface of a steel product

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