WO2006038826A1 - Method for applying multilayer coatings to metal products - Google Patents

Abstract

The invention relates to metallurgy and mechanical engineering, namely to a method for increasing a service life, reliability and complete renovation of machine components by modifying the surface and applying protective, corrosion- and wear-resistant coatings. The combination of a high corrosion and wear resistance is obtainable by using multilayer coatings and by ion implantation of a surface and individual coating layers. The inventive method consists in covering parts with the corrosion and wear-resistant coating consisting of a plurality of layers, wherein each layer consists of one or several metals (titanium, zirconium, molybdenum, tungsten, nickel, silicium, iron, chromium and aluminium), solid solutions or implantation phases based thereon and wherein one or several layers are exposed to a ion implantation of high-energy non-metal ions in such a way that structural and composition modifications of a deposited layer are generated and increased performance properties are obtained. Said method makes it possible to apply a coating exhibiting a high corrosion and erosion resistance, thereby increasing the life service of parts, mainly of gas turbine compressor blades.

Description

 The method of applying a multilayer coating on metal products

Application area.

The invention relates to the field of metallurgy and mechanical engineering, in particular, to the development of methods for increasing the durability and reliability of machine parts by modifying the surface and applying coatings, in particular, to gas turbine blades, and, in particular, to compressor blades of aircraft engines.

State of the art

Aircraft and helicopters with gas turbine engines are often operated in conditions of significant dustiness of the air flow, as well as high humidity of the marine environment containing aggressive components. Operation and storage of engines in a tropical and marine atmosphere is accompanied by significant corrosion damage to the blades of stainless steels and nickel-based alloys. Air-abrasive erosion and corrosion are observed, pitting corrosion (PC) of aircraft engine parts, for example, compressor blades, is especially dangerous. The geometrical dimensions of the blades change, mechanical properties decrease and operational characteristics deteriorate, engine power decreases, fuel consumption increases, and the costs of engine maintenance and repair increase significantly. The use of dustproof devices and conservation methods to prevent such processes is not effective enough.

Worn blades are usually restored by polishing the edges of the profile and pen, or replaced with new ones. Blades with deep pitting pockets of corrosion are not repaired. Since the compressor blades are made of alloys based on titanium, nickel and high alloy steels, which are expensive and difficult to process, engine repair becomes very expensive.

Known methods for improving the resistance to corrosion and wear of parts of gas turbines and, in particular, aircraft engine blades.

So, in British patent Na 2226334, published 06/27/90, describes a method for producing a coating on a metal substrate, comprising applying the first layer of refractory transition metal IY-YI groups of the Periodic system elements and a second layer of nitrides, or oxides of these metals, with the exception of radioactive elements. The layers are applied by sputtering or ion deposition. The resulting coating increases the resistance of the substrate to corrosion and / or wear.

In British patents JV ° 2322382 and 2322383, published 26.08.98, a method for producing a multilayer coating, mainly on the details of gas turbines and aircraft engines, involves applying a layer rich in chromium, titanium and / or tantalum to the part, deposition on it of a layer of altominide platinum and a layer of aluminum oxide, and the application of an external barrier protective coating of ceramic. The method improves the resistance of parts to oxidation and corrosion.

There is also known a method (EP N ° 0 783 043, published July 9, 1997) for applying a multilayer coating to parts of aircraft engines and gas turbine components, including deposition of a corrosion-resistant metal layer on a product surface by plasma spraying or physical vapor deposition (PVD) , deposition on it of a ceramic layer having a columnar structure by physical evaporation and thermal barrier coating, in which erosion-resistant components such as silicon carbide and alumina are present The line. Yttrium stabilized rdirconium oxide is applied as a ceramic layer. The invention improves the resistance of the coating under thermal loads. In the patents of the Russian Federation closest to the proposed invention

Jvfe 2161661, published January 10, 2001, and Eurasian Patent No. 002682, published July 29, 2002, describe a method for applying a multilayer coating and increasing the durability of parts. These patents solve the problems of increasing wear resistance, in particular, erosion resistance in a gas-abrasive stream, while maintaining a sufficiently high level of mechanical, including fatigue properties of machine parts, in particular compressor blades of aircraft engines.

The method comprises ionic cleaning of the _surface, application of at least three-layer coating of one or a mixture of transition metals A- VT IV A of the Periodic Table of Elements, wherein the first layer is formed in a neutral gas atmosphere, the second - in a mixture of neutral and reaction gases, the third - precipitation in a mixture of neutral and reaction gases of nitrides, carbides, borides or mixtures thereof. One or more layers is subjected to ion implantation with argon, nitrogen or boron during the deposition process or after deposition.

The practical operation of various types of gas turbine engines with coatings obtained by the above methods showed that in some cases the corrosion resistance of the parts is insufficient and is one of the main reasons for rejecting compressor blades, reducing their durability and reliability. This is especially true when operating engines in tropical areas and the marine climate, where products are largely susceptible to pitting and general corrosion. The present invention is aimed at improving the corrosion and erosion resistance of parts, in particular gas turbine blades, including aircraft, power plants, gas pumping units and other equipment operating in corrosive conditions, including in humid marine and tropical conditions.

Disclosure of the invention.

Pitting (pitting corrosion) refers to local types of corrosion, in which the failure is concentrated at individual points on the surface of the part. This type of corrosion is caused by corrosive environments in which the ions CV, Br ^" , G, HS ^" , ClO ^"4 , CNS ^" are present, and the chlorine ion is the most aggressive. In a corrosive environment, a certain concentration of these anions should occur, and pitting corrosion (PC) develops in a certain temperature range.

Iron-based alloys are susceptible to PC in a wide range of media and interaction conditions. Nickel and titanium alloys are less prone to PC, however, under certain conditions, they can also undergo this type of corrosion, as well as general corrosion damage to the surface.

It is believed that in stainless steels, doping with nitrogen increases the resistance of the PC, while carbon, sulfur, phosphorus, as well as the presence of non-metallic inclusions sharply reduces the resistance of the PC. Non-metallic inclusions in general are one of the main reasons for the development of pittin corrosion in various alloys.

The cleanliness and surface quality have a great influence on PC resistance: the higher the surface treatment class, the less defects and impurities on the surface, the higher the PC resistance.

The technical result of the invention is a significant increase in corrosion resistance in various active media, especially, increase in the resistance to corrosion of machine parts and mechanisms, in particular, parts of aircraft, especially gas turbine compressor blades, while maintaining a high level of surface wear resistance.

The technical result is achieved in that the method of applying a multilayer coating on metal products includes several interrelated technological operations that are performed after the usual methods of manufacturing or repair of parts and standard surface cleaning: • ion cleaning and / or surface modification of the product,

• preliminary deposition on the product in an inert gas environment of at least one corrosion-resistant metal layer selected from the group consisting of molybdenum, niobium, tantalum, tungsten, chromium, titanium, zirconium, nickel, silicon or alloys based on them, the gradient of the content of elements increases from the surface of the product to the surface of the layer;

• applying a multilayer wear-resistant coating of at least three layers, consisting of: 1 layer, obtained by deposition in an inert gas medium of a metal or alloy layer selected from elements 1U-U1 of the groups of the periodic system of elements or alloys based on them; 2 layers obtained by precipitation in a mixture of inert and reaction gases of a solid solution of nitrogen, carbon or boron in the mentioned metals or alloys; deposition of 3 layers in the reaction gas medium of a nitride, carbide and / or boride layer of said metals, ion implantation of at least one layer with high-energy non-metallic ions; o deposition in an inert gas medium of at least one layer of the outer protective coating of a metal or alloy based on them, selected from the group consisting of molybdenum, niobium, tantalum, tungsten, chromium, titanium, zirconium, nickel and / or aluminum and / or corrosion-resistant enamel. This layer is designed to protect the surface of parts from corrosion during prolonged storage of engines. • When applying corrosion-resistant layers, it is necessary to ensure a composition gradient with increasing concentration of the corrosion-resistant element from the substrate to the surface of the layer.

A multilayer coating is applied to products made of steel (alloys based on iron) or alloys based on nickel, titanium. Parts, in particular, are compressor blades or disks, parts of aircraft engines, gas pumping and power plants.

To obtain the required thickness, the number of layers of a multilayer coating can be from 5 to 300, mainly from 5 to 30. In this case, the layers of wear-resistant coating are repeatedly alternated, and the corrosion-resistant component of the coating can contain from 1 to 150 layers, mainly 1-5 layers.

To increase the corrosion and erosion resistance, at least one coating layer is subjected to ion implantation with high-energy metallic and / or non-metallic ions. In some cases, after ion implantation, a corrosion-resistant coating is heat treated. When applying the layers, argon, neon, helium, or mixtures thereof are used as neutral gases.

To ensure a more uniform and continuous coating, after applying the outer protective coating, if necessary, conduct its heat treatment. Heat treatment may also be necessary to ensure the effects of implantation at greater depths.

In order to redistribute stresses and improve mechanical properties, a product with a multilayer coating is subjected to hardening treatment with microspheres, hydro shot blasting, or pneumatic shot blasting.

The present invention assumes that the surface of the part to be coated is modified. After the standard cleaning and washing procedure, the surface of the part is processed in a vacuum-plasma unit, equipped with a source of high-energy ions, or in a separate installation equipped with a system of ion implantation and purification. The purpose of this modification is the activation and cleaning of the surface from impurities, the creation of conditions for coating with high adhesion, the reduction of local internal stresses and the ionic alloying of the surface layers with elements with high corrosion and / or erosion resistance. Such treatment in comparison with abrasive-liquid preparation, polishing or chemical preparation of the surface increases the cleanliness and quality of the surface, improves the adhesion of the coating to the surface of metals.

Then one or more layers of a corrosion-resistant metal or alloy are applied with a high content of elements such as nickel, chromium, silicon, molybdenum, tantalum, niobium, tungsten, titanium, zirconium, so that a continuous layer of a corrosion-resistant alloy is created, not subject to pitting and general corrosion in working environments. The application of such a layer should provide a gradient change in the composition of the corrosion-resistant element. At least one deposited layer is treated with a high-energy source of metal ions and / or argon ions or another neutral gas to increase the corrosion resistance of the deposited layer by changing the concentration or mixing of the components and reducing the number of defects in the layer. After ion treatment, in some cases, additional heat treatment is necessary to ensure diffusion and ion post-implantation processes, leading the structure to equilibrium or recrystallization of the surface layer. Such heat treatment can be carried out directly in the installation chamber through the use of a specially installed source of thermal energy.

Since all processes can be carried out in one installation, the corrosion-resistant coating has a clean surface and is a good basis for applying a multilayer wear-resistant coating. To increase the density and continuity of this layer, implantation of high-energy ions of neutral gases is used.

Then, if necessary, ion cleaning is carried out, after which a wear-resistant coating is applied. The composition of at least one layer of wear-resistant coatings are additionally alloyed with elements with high corrosion resistance: chromium, molybdenum, tungsten, niobium, tantalum.

The last stage of the coating formation process is the deposition of at least one layer, which should provide increased corrosion resistance of the layers from the interstitial phases (yashridny, boride, carbide, or other interstitial phases). This stage can be carried out in an additional installation, such as enameling. When applying a narcotic layer of a coating containing molybdenum, nickel, chromium, tungsten, niobium, tantalum and / or alloys of these elements and / or aluminum and / or corrosion-resistant enamel, in some cases, additional heat treatment at elevated temperature is required to ensure a more uniform and continuous coverage.

Therefore, the corrosion-resistant and wear-resistant coating according to this invention may include the following main stages of formation;

1. Preparation of the surface of the part using ion etching, treatment in chemical solutions of salts or ACIDS AND / OR ION CLEANING. Surface modification by implantation of corrosion-resistant metals or inert gases to increase adhesion and increase the corrosion resistance of the surface of the part. Then the application of a corrosion-resistant layer consisting of metals and / or alloys based on chromium, nickel, molybdenum, tungsten, tantalum, niobium, titanium, zirconium, silicon, aluminum.

2. Treatment of the applied corrosion-resistant layer with high-energy ions of neutral gases or metal ions.

3. If necessary, additional ionic surface cleaning and heat treatment. 4. Application of a multilayer wear-resistant coating consisting of metal layers and layers of interstitial phases, including ion implantation with neutral gases or reaction gases.

5. Ionic cleaning of the surface, consisting of the phases of implementation.

6. Ion implantation of one or more coating layers. 7. Application of an external corrosion-resistant layer consisting of molybdenum, niobium, tantalum, tungsten, chromium, titanium, nickel, zirconium, aluminum, alloys based on them and / or enamel.

8. Ion implantation by neutral gases of the coating surface.

9. If necessary, additional heat treatment of materials or parts with coatings.

10. If necessary, vibration damping, shot peening or shot-peening hardening of the surface to redistribute stresses and increase the mechanical characteristics of the part or product.

Embodiments of the invention.

High wear and corrosion resistance is ensured by deposition of layers of nickel, chromium or other refractory metals or alloys with a high content of these elements in an inert gas on the metal substrate after cleaning and ion treatment. Then a multilayer coating is applied from alternating interstitial phases, solid solutions and metal layers resulting from the deposition of metals in a reaction or neutral gas medium, and then an additional layer in an inert gas medium. The method is as follows.

Before coating, the surface of the substrate is cleaned with a source mounted in the coating chamber of the installation, or with an ion source in a separate installation. Coating was carried out in a facility equipped with an ion implantation source, equipped with high-precision optical pyrometers and dosed supply systems of neutral and reaction gases into the ion-plasma deposition chamber and into a source of high-energy ions, as well as control devices and a computer monitoring system for process parameters. Samples or blades of aircraft engine compressors and gas pumping units made of stainless nickel-chromium steels, or from titanium or nickel-based alloys of the type (Inconel 718), after standard cleaning and washing operations, were first treated with argon ions to clean the surface of the blades from solid, liquid or absorbed gas impurities. Then, additional cleaning was carried out with a high-energy ion source, which ensures the complete removal of impurities from the surface of the parts.

Then, a corrosion-resistant layer was applied to the surface either from a refractory corrosion-resistant metal, for example, chromium, molybdenum, tantalum, niobium, silicon, tungsten, or a mixture of these metals, or an alloy based on nickel or based on refractory metals with a high content of corrosion-resistant elements. To determine the effectiveness of various combinations of corrosion-resistant layers and wear-resistant layers, cathodes were made of various metals and alloys, in particular the following:

• Chrome brand Xl (98% Cg)

• Alloy low-80% Nϊ-20% Cg • Alloy BX2 (0.2% TiD2% V. 0.3-1.0% Y, the rest is chrome)

• Alloy BX4 (32% Ni, 0.2% Ti, 0.3% V, 1.5% W, the rest is chrome)

• Molybdenum grade MT (0.5% Ti)

• Molybdenum grade BM2 (0.2% Ti, 0.3-0.4% Zr,)

• Niobium alloy grade BH4 (1.5% Zr, 9.6% Mo, 0.03% La, 0.3% C, the rest is niobium) • Tungsten grade TCB (0.2% Ta, 0.1% C)

• Alloy of titanium-zirconium (33% Zr, 67% Ti)

• Zirconium grade E 125

• Titanium grade VT 1-00

• BT8 titanium alloy • BTЗ titanium alloy = 1

• Aluminum

• Alloy XH50BMTUB (33% Cr, 4.8% Mo, 4.8% W, 0.8% Nb, 0.8% Al, the rest is nickel) o Inconel 718 (19% Cg, 3% Mo, 5% Nb, 18 % Fe, Ni-ost.) About Rene R41 (19% Cr, ll% Co, 10% Mo, 3% Ti, l, 5% AI, Ni-ost). • Udimet U 700 (20Cr, 14% Co, 5% Mo, 3% Ti, 1, 5% A1. 0.05% B. Ni -ost)

The coatings were applied as follows: the cathodes of the corresponding metal or alloy and samples or parts were installed in the chamber, then, after ion cleaning, a corrosion-resistant layer was applied, which, in some cases, was subjected to ion implantation and, if necessary, heat treatment. After that, a wear-resistant multilayer coating was applied with implantation of argon ions, carbon nitrogen, boron, and then a corrosion-resistant outer layer. In some cases, additional heating was carried out in the chamber after applying the outer layer to create a more dense and defect-free layer on the wear-resistant phases of implantation, as well as additional implantation.

If the planned version of the coating allowed, then all the processes were carried out in one chamber, in other cases 2 plants were used with cathode replacement and changing the processing modes.

In alternative embodiments, the described deposition steps of refractory metals, nickel, titanium, zirconium or alloys based thereon can be repeated. The alternation of different layers in the coating is provided by alternately heating the cathodes in an atmosphere of argon or another neutral gas, or by simultaneously activating various cathodes.

In preferred embodiments, each or some of the coating layers at different stages of its application is exposed to a high-energy flow of argon ions, or nitrogen, or carbon, or boron by changing the atmosphere in the ion source and / or in the installation chamber.

Table 1 gives examples of studied coatings indicating the order and thickness of the layers, as well as the composition of the samples of materials used in the coating in accordance with this invention.

Примечания:Examples of coatings from various materials are given in table. one Table 1.

Notes:

• Metal layers (metals or alloys) are applied in an inert atmosphere;

• Layers of solid solutions are applied in a mixture of inert and reaction gases, • Layers of the interstitial phases are applied in an atmosphere with a high content of reaction gases, the composition of chemical compounds is represented by the formula in parentheses and the corresponding element (N, C, B)

• x2-50 -number of layers- [] are applied in the indicated order to the required coating thickness, • * ionic cleaning before applying the layer;

• ** ion implantation with N, Ar ₇ C, B, Ar atoms.

• layers of solid solutions are proved by symbols of metals and a dissolved element,

• KS — the outer layer of corrosion-resistant enamel

Corrosion tests.

Samples without coatings and with a multilayer coating according to the claimed method were subjected to corrosion tests by the following methods.

1. The standard method according to ASTM G48-76 (method * 1) in 1O ⁰ ZoFeCl ₃ at a temperature of 25 ⁰ C for 72 hours, while the corrosion rate is calculated by the formula

Vfc = 2000Δm / S, where VIc is the corrosion rate g / m ² .chac (/ m ² h), Δt is the total weight loss of the samples (5 samples), S is the total surface area of the samples.

The average number of pits (n / S 1 / cm ² ) per unit surface area was also determined.

2.. A method for modeling the operation of blades in a tropical climate. The blades were heated at 420 degrees in the chamber for 1 hour. Then the blades were cooled in a 3% solution of sodium chloride, kept in a humid chamber for 23 hours, and the cycle was repeated 10 times. The purpose of these tests was to simulate the work shoulder blades in tropical marine climate. Assessment of corrosion resistance was carried out by visual inspection of the blades after each cycle and by counting the number of pits on the surface of the blades after corrosion tests (Np-pit). The test results showed that the resistance of samples without coatings is much lower than the resistance of blades with a coating according to this application (see table 2)

3. Corrosion tests were also carried out on the blades of aircraft engine compressors in a climate chamber at a temperature of 35 ° C in pairs of 3% sodium chloride solution for 20 days to assess corrosion damage on pitting corrosion on the blades (simulating parking corrosion), data were averaged over 12 blades and are given below:

1. Uncoated blades - more than 180 ggings on the feather,

2. Blades with a serial coating of titanium nitride - 150 pits,

3. Blades with a multilayer coating with implantation according to the patent of the Russian Federation JMb 2161661-20 pits. 4. Blades with a corrosion-resistant and wear-resistant coating according to this application - 0 pits.

Wear resistance tests The wear resistance of various options of proposed coatings was determined after erosion resistance tests on real blades of aircraft engine compressors in an experimental setup at a flow rate of 120-150 m / s, an abrasive flow rate of 50 g / min, an angle of attack of 8-90 ° - the resistance is determined by a change in the mass of the blades (in mg) in the air-abrasive flow of rotating blades without coatings and with coverings (* 2) - and the magnitude of the change in the chord of the blade in the upper section (in microns) (* 2A). The results of corrosion tests and the wear resistance of some coating options are presented in Table 2. Table 2. Corrosion resistance and wear resistance of materials with various coatings.

Erosion tests were carried out on an experimental installation in an air-abrasive flow with rotating samples in comparison with uncoated samples or blades, or various versions of the same steel grades with coatings between each other.

The fatigue tests of blades with preferred coatings and blades without coatings showed that the fatigue strength of the blades after coating is practically unchanged, remains at a high level and provides the necessary reliability of the part. The test conditions of the blades for fatigue strength corresponded to real parameters during the operation of aircraft engines.

Claims

 Claim. 1. The method of applying a multilayer coating on metal products, including ion cleaning and / or surface modification of the product by implantation of inert gas or metal ions: molybdenum, tungsten, titanium, zirconium, nickel, cobalt, silicon, aluminum, tantalum, niobium, chromium; deposition on the modified surface of the part of a corrosion-resistant layer of one of the aforementioned metals or an alloy based on it, and the gradient of the concentration of the element should increase from the surface of the part to the outer surface; - applying a multilayer at least three-layer wear-resistant coating by successive deposition in an inert gas medium of a metal layer selected from one or more elements of IVA ..- VI A groups of the Periodic system, or alloys based on them; deposition in a mixture of inert and reaction gases of a layer of a solid solution of nitrogen, carbon or boron in said metals or alloys; sedimentation in the medium of reactive gases of a layer of interstitial phases — nitride or carbide, and / or boride of said metals; ion implantation of at least one layer with high-energy non-metallic ions; - at least one layer of an external corrosion-resistant protective coating of a metal selected from the group consisting of molybdenum, niobium, tantalum, tungsten, chromium, titanium, zirconium, nickel or alloys based on them is deposited on a wear-resistant coating in an inert gas environment and / or aluminum and / or enamel. • 2. The method according to claim 1, characterized in that the multilayer coating is applied to products made of steel, or alloys based on titanium or nickel. 3. The method according to p. 1, characterized in that the products that are coated> are blades or other parts of aircraft engines, gas pumping and power plants. 4. The method according to p. 1, characterized in that the number of layers of the multilayer coating can be from 5 to 300, mainly from 5 to 30. 5. The method according to p. 1, characterized in that the corrosion-resistant coating contains from 1 to 6 layers. b. The method according to claim 5, characterized in that the ratio of the thicknesses of the coating layers in microns is in the following proportion: (l-5) :( l-5) :( 2-10) :( 3-15) :( l: 5 ) :( 3:15), i.e. the layers alternate in an approximate ratio l: 1: 2: 3: 1: 3, where 1-metal layers, 2-CJIΌSh. solid solutions, 3-layers of phases of implementation. 7. The method according to p. 5, characterized in that to obtain the required thickness, the applied coating layers are repeatedly alternated, 8. The method according to p. 1, characterized in that at least one layer of a corrosion-resistant coating is subjected to ion implantation with high-energy metallic and / or non-metallic ions. 9. The method according to p. 7, characterized in that the heat treatment is carried out corrosion-resistant coating and / or ion cleaning. 10. The method according to any one of paragraphs 7, 8, characterized in that the applied corrosion-resistant coating is subjected to additional ion cleaning. 11. The method according to p. 1, characterized in that as neutral gases use argon, neon, helium or mixtures thereof. 12. The method according to p. 1, characterized in that after applying the outer protective coating, carry out its heat treatment. 13. The method according to p. 1, characterized in that the product is coated with a multilayer lokrgshem subjected to hardening treatment with microspheres, hydroblasting or pneumatic shot blasting.