Multilayer coating for high-stress metal pieces

Abstract

A multilayer coating (100) for a metal piece (10), particularly for turbomachinery parts, more specifically for turbomachinery impellers, comprising: a first layer (20) applied to at least a portion of the metal piece (10) having a hydrogen diffusion coefficient of less than 10⁻⁷ m² / sec even under stress (the hydrogen diffusion coefficient is measured by a hydrogen permeation test); and a second layer (30) applied on top of the first layer (20) and exposed to a hydrogen-containing process fluid. The second layer (30) comprises an oxide selected from aluminum oxide (Al₂O₃), titanium dioxide (TiO₂), and silicon dioxide (SiO₂). The first layer (20) and the second layer (30) can be applied according to various deposition process techniques at temperatures below 500°C.

Description

[Technical Field]

[0001] The subject matter disclosed herein is multilayer coatings for metal pieces in turbomachinery components, more specifically in turbomachinery impellers, and methods for preventing hydrogen diffusion in metal pieces in turbomachinery components, more specifically in turbomachinery impellers. [Background technology]

[0002] Turbomachinery components used in hydrogen (=H2) processing, particularly rotating parts, are typically made from materials that readily become brittle when in direct contact with hydrogen. In fact, hydrogen is a small molecule that can even split into atomic hydrogen atoms. These hydrogen atoms can enter (i.e., diffuse) into small cavities in the metal structure, settle there, and increase the risk of crack formation within the material.

[0003] To prevent corrosion of metal pieces and / or to improve their resistance, protective coatings can be applied to the surface of metal pieces. However, conventional coatings have drawbacks when applied to rotating parts, especially impellers, as the complex shapes of the parts make the coating process particularly difficult. Furthermore, substrates of high-speed rotating parts, especially high-strength steel, cannot be coated at high temperatures (i.e., temperatures above 500°C) to avoid affecting the metal microstructure of the substrate. Moreover, the high rotational speed of impellers during operation causes high strain on the metal pieces, stretching them. Consequently, incomplete coating and / or cracks in the coating (which may not resist the stretching of the metal pieces) can expose parts of the metal surface to hydrogen, thus allowing hydrogen to diffuse into the metal pieces.

[0004] Therefore, to handle hydrogen-containing fluids (ultimately fluids containing 100% hydrogen), it is desirable to have an efficient hydrogen diffusion barrier, especially one that is deposited at temperatures below 500°C (so as not to affect the micromorphology of the metal piece) and that is resistant to stress and strain during operation to prevent the metal piece from becoming brittle, especially in the case of high strain caused by the centrifugal speed of rotating parts. [Overview of the project]

[0005] In one embodiment, the subject disclosed herein is a multilayer coating for metal pieces, particularly turbomachinery parts, more specifically turbomachinery impellers, which is applied to at least a portion of the metal piece and even when subjected to stress. -7 m 2 The present invention relates to a multilayer coating comprising a first layer having a hydrogen diffusion coefficient of less than 1 / second (the hydrogen diffusion coefficient is measured by a hydrogen permeation test), and a second layer applied on top of the first layer and exposed to a hydrogen-containing process fluid. The second layer comprises an oxide selected from aluminum oxide (Al2O3), titanium dioxide (TiO2), and silicon dioxide (SiO2). The first and second layers are applied at a temperature of less than 500°C.

[0006] In another embodiment, the subject disclosed herein is a method for preventing hydrogen diffusion in metal pieces, particularly turbomachinery components, more specifically in turbomachinery impellers, a. A step of applying a first layer onto at least a portion of a metal piece using a technique selected from spraying, physical vapor deposition (PVD), and chemical vapor deposition (CVD), wherein the first layer is made of a first material that is low permeability to hydrogen. b. A step of applying a second layer on a first layer, wherein the second layer is made of a second material that is oxidation-resistant and / or corrosion-resistant and / or erosion-resistant, The application of process "a" and process "b" are carried out at temperatures below 500°C. [Brief explanation of the drawing]

[0007] Many of the disclosed embodiments of the present invention and their associated advantages will be better understood by referring to the following embodiments for carrying out the invention, and a more complete understanding will be easily obtained, as they will be better understood when considered in relation to the accompanying drawings. [Figure 1] A simplified diagram of an embodiment of an innovative multilayer coating for metal pieces is shown. [Figure 2] A flowchart of an innovative method for preventing hydrogen diffusion in metal pieces is shown. [Figure 3] Figure 1 shows an embodiment of an impeller that may include an innovative multilayer coating. [Modes for carrying out the invention]

[0008] In one embodiment, the subject matter disclosed herein relates to a hydrogen diffusion barrier provided on a metal piece subjected to high stress, such as an impeller of a turbomachinery rotating at a high rotational speed. The hydrogen diffusion barrier is made of a two-layer coating, where the first coating is applied directly onto the metal impeller and prevents most of the hydrogen diffusion by its ability to follow the deformation of the metal substrate without showing cracks, even when subjected to stress, i.e., during and / or after the operation of the impeller. The second layer is applied on top of the first layer and comprises an oxide selected from aluminum oxide (Al2O3), titanium dioxide (TiO2), and silicon dioxide (SiO2). The second layer may still have a very low hydrogen diffusion coefficient when uninterrupted (i.e., without cracks), but also has low resistance to strain and therefore often undergoes cracks that affect the overall hydrogen diffusion coefficient. The second layer also prevents corrosion and / or oxidation and / or erosion of the substrate of the metal piece. Therefore, the synergistic cooperation between the first and second layers generates an innovative hydrogen diffusion barrier that is more efficient at preventing hydrogen diffusion than is known at the current level of technology.

[0009] In another embodiment, the subject disclosed herein is a method for providing a hydrogen diffusion barrier on a metal impeller, even when subjected to stress, i.e., during and / or after the operation of the impeller, by applying a first protective layer on the metal impeller to prevent hydrogen diffusion, and by applying a second protective layer on the first protective layer to prevent corrosion and / or oxidation and / or erosion of the first protective layer. The application of the first and second layers is carried out at a temperature of less than 500°C, and as a result, the (micro and / or macro) shape of the metal impeller is not altered.

[0010] Next, we will refer in detail to embodiments of the present disclosure illustrated in the drawings. The embodiments and drawings are provided for illustrative purposes of the present disclosure and should not be construed as limiting the present disclosure. It will be apparent to those skilled in the art that various modifications and variations can be made to the present disclosure without departing from the scope or spirit of the present disclosure. In the following description, similar reference numerals are used to illustrate the embodiments in the drawings to indicate elements that perform the same or similar functions. Furthermore, for clarity of the illustration, some reference numerals may not be repeated in all drawings.

[0011] Figure 1 shows an exemplary multilayer coating 100. The multilayer coating 100 is configured to be applied to a metal piece 10, in particular to a turbomachinery component, more specifically to a turbomachinery impeller.

[0012] The multilayer coating 100 is particularly advantageous for protecting metal pieces 10 when handling hydrogen-containing fluids. In fact, as will become apparent below, the multilayer coating 100 is particularly advantageous for protecting high-stress components of turbomachinery from hydrogen diffusion and maintaining hydrogen diffusion protection properties against oxidation and / or corrosion and / or erosion.

[0013] Turbomechanical impellers are typically exposed to temperatures up to 250°C due to the temperature of the working fluid (i.e., the fluid handled by the turbomechanical impeller) and are subjected to high strain due to the high rotational speed of the turbomechanical impeller (i.e., the material of the turbomechanical impeller is subjected to stretching due to the centrifugal force caused by the rotational speed).

[0014] According to the example shown in Figure 1, the coating 100 comprises two layers 20 and 30, the first layer 20 being applied to at least a portion of the metal piece 10, preferably the entire surface of the metal piece 10, and the second layer 30 being applied to the first layer 20, preferably the entire surface of the first layer 20. In order to form an efficient hydrogen diffusion barrier, the first layer 20 is configured to be effective even when stress is applied. -7 m 2 The second layer 30 has a hydrogen diffusion coefficient of less than 10 / second, and the second layer 30 may contain an oxide selected from aluminum oxide (Al2O3), titanium dioxide (TiO2), and silicon dioxide (SiO2), and as a result the overall hydrogen diffusion coefficient of the coating 100 (i.e., through both the first and second layers) is 10 -9 m 2 It is less than per second.

[0015] It should be noted that the hydrogen diffusion coefficient is advantageously measured by hydrogen permeation tests, particularly in accordance with ASTM G148-97 (2018). In particular, the hydrogen diffusion coefficient can be obtained from the Arrhenius equation. D(T) = D0 e - [E / R × T] Here -D(T): Diffusion coefficient [m2 / sec], -D0: Diffusion coefficient [m² / sec] when the temperature is infinite. -E: Activation energy for diffusion [joules / moles] -R: Universal gas constant (8.314 [joules / moles]) * Kelvin).

[0016] The applicant has studied that various combinations of the first layer 20 and the second layer 30 having the above-mentioned characteristics form an efficient hydrogen diffusion barrier for the metal piece 10 to be protected.

[0017] Furthermore, the applicant has studied a multilayer coating 100 that can apply the first layer 20 and the second layer 30 at a temperature below 500 °C so that the metal piece 10 is not affected by geometric deformation and / or the microstructure of the metal piece 10 is not affected.

[0018] Advantageously, the first layer 20 has a thickness greater than 25 μm, particularly in the range of 25 - 150 μm, preferably in the range of 50 - 100 μm.

[0019] According to the first example, the first layer 20 can include an aluminum-based material, i.e., a material having a composition of at least 50% aluminum. According to the second example, the first layer 20 can include chromium nitride. According to the third example, the first layer 20 may include tungsten carbide, particularly tungsten carbide added with cobalt or cobalt chromium. However, many other embodiments are possible without departing from the scope of the present disclosure.

[0020] Furthermore, as will be described in more detail below, the first layer 20 and the second layer 30 can be applied onto the metal piece 10 according to various deposition process techniques, for example, depending on the shape of the metal piece 10 and / or the material of the first layer 20 and / or the material of the second layer 30.

[0021] As already explained, the multilayer coating 100 may be exposed to a hydrogen-containing process fluid, and in particular, the second layer 30 is configured to be exposed to a hydrogen-containing fluid. Advantageously, the second layer 30 is a non-porous material, for example, a material exhibiting a porosity value of less than 0.05%, ultimately equal to 0%, according to mercury porosimetry or cross-sectional image analysis. In either case, it should be noted that the second layer 30 may present defects, particularly structural defects, especially when subjected to high stress during operation. However, typically, structural defects result in localized damage that increases the hydrogen diffusion coefficient but does not impair the overall functionality of the layer. More advantageously, the second layer has a thickness greater than 3 μm, particularly in the range of 3 to 25 μm, preferably in the range of 5 to 15 μm.

[0022] It should be noted that the aforementioned properties of the second layer 30, particularly its low (ultimately zero) porosity and thickness, make the second layer 30 particularly suitable for avoiding oxidation and / or corrosion and / or erosion of the first layer 20 (if necessary).

[0023] In another aspect, the subject matter disclosed herein relates to turbomachine components including the multilayer coatings described above, particularly to turbomachine impellers, and more specifically to metal turbomachine impellers (see the exemplary impeller shown in Figure 3).

[0024] Multilayer coatings cover at least a portion of a turbomachinery component, preferably the entire surface of the turbomachinery component, to prevent hydrogen diffusion within the turbomachinery component, and thus advantageously prevent embrittlement of the turbomachinery component caused by hydrogen diffusion within the material, especially when the component will be exposed to a hydrogen-containing fluid, particularly when the turbomachinery impeller is configured to handle (i.e., compress or expand) a hydrogen-containing fluid (ultimately a 100% hydrogen-containing fluid).

[0025] According to another aspect, the subject matter disclosed herein relates to an innovative method 200 for preventing hydrogen diffusion in metal pieces, particularly turbo machine parts, more specifically turbo machine impellers. Generally, the innovative method 200 includes the following steps "a" and "b": a. A step 210 of applying a first layer on at least a part of the metal piece using a technique selected from spraying, dipping, physical vapor deposition (=PVD), and chemical vapor deposition (=CVD), wherein the first layer is made of a first material that is poorly permeable to hydrogen even when stressed, the step 210 of applying the first layer; b. A step 220 of applying a second layer on the first layer, wherein the second layer is made of a second material that is oxidation resistant and / or corrosion resistant and / or erosion resistant, the step 220 of applying the second layer, and includes The application 210 of step "a" and the application 220 of step "b" are carried out at a temperature below 500 °C.

[0026] As already explained, the first layer is made of a material having a hydrogen diffusion coefficient of less than 10 -7 m 2 / s, thus resulting in a layer that is poorly permeable to hydrogen. In particular, the innovative method aims to prevent embrittlement of the metal piece caused by hydrogen diffusion in the material when the metal piece is to be exposed to a fluid containing hydrogen, particularly when the metal piece is a turbo machine impeller configured to process (i.e., compress or expand) a fluid containing hydrogen (ultimately a fluid containing 100% hydrogen).

[0027] According to step "a" of the innovative method 200, the first layer can be applied to at least a part of the metal piece, preferably the entire surface of the metal piece, according to various deposition process techniques.

[0028] As already explained, the first layer can be applied by spraying the first material onto the surface of a metal piece ("spray deposition"), or by immersing the metal piece in a bath coating ("dip coating" or "immersion coating"), or by typically evaporating the first material in a vacuum and depositing it onto the surface of the metal piece ("physical vapor deposition" or "PVD"), or by depositing the first material onto the surface of a metal piece by a chemical reaction in a gas ("chemical vapor deposition" or "CVD"), or by depositing the first material onto the surface of a metal piece by a chemical reaction in a gas using electrical energy to generate a plasma useful for supplying energy for the chemical reaction ("plasma-assisted chemical vapor deposition" or "PACVD").

[0029] It should be noted that chemical vapor deposition can be performed at both high and low temperatures. Advantageously, the first layer is applied using low-temperature chemical vapor deposition, particularly at temperatures in the range of 0 to 350°C.

[0030] Advantageously, the second layer is applied using chemical deposition in vapor (e.g., "plasma-assisted chemical deposition" or "PACVD," or "plasma chemical deposition" or "PECVD," or "inductive plasma chemical deposition" or "IPECVD") which uses electrical energy to generate a plasma useful for supplying energy for carrying out chemical reactions. In other words, the second layer is applied using one of these low-temperature chemical deposition methods, in particular to avoid damaging (especially burning) the first layer already applied on the metal piece.

[0031] According to a preferred embodiment, low-temperature chemical deposition is carried out at a temperature in the range of 0 to 350°C. According to a preferred embodiment, low-temperature chemical deposition is carried out at a pressure in the range of 0 to 1 bar.

Claims

1. A multilayer coating (100) for metal pieces (10), particularly for turbomachinery parts, more specifically for turbomachinery impellers, wherein the coating (100) is - A first layer (20) applied to at least a portion of the metal piece (10), which even when subjected to stress, 10 －７ I understand ２ Having a hydrogen diffusion coefficient of less than / second, the hydrogen diffusion coefficient is measured by a hydrogen permeation test, the first layer (20) and - A second layer (30) applied on the first layer (20), the second layer (30) comprising an oxide selected from aluminum oxide (Al2O3), titanium dioxide (TiO2), and silicon dioxide (SiO2), The second layer (30) is configured to be exposed to a process fluid containing hydrogen, The first layer (20) and the second layer (30) are multilayer coatings (100) applied at a temperature of less than 500°C.

2. The multilayer coating (100) according to claim 1, wherein the second layer (30) is configured to avoid oxidation.

3. The multilayer coating (100) according to claim 1, wherein the second layer (30) is configured to avoid corrosion.

4. The multilayer coating (100) according to claim 1, wherein the second layer (30) is configured to avoid erosion.

5. The multilayer coating (100) according to claim 1, wherein the second layer (30) has a thickness in the range of 3 to 15 μm.

6. The multilayer coating (100) according to claim 1, wherein the first layer (20) comprises an aluminum-based material.

7. The first layer (20) comprises chromium nitride, the multilayer coating (100) according to claim 1.

8. The multilayer coating (100) according to claim 1, wherein the first layer (20) comprises tungsten carbide, particularly tungsten carbide to which cobalt or cobalt-chromium has been added.

9. A method (200) for preventing hydrogen diffusion in metal pieces, particularly turbomachinery parts, more specifically in turbomachinery impellers, wherein the method (200) is: a. Step (210) of applying a first layer onto at least a portion of the metal piece using a technique selected from spraying, dipping, physical vapor deposition (PVD), and chemical vapor deposition (CVD), wherein the first layer is made of a first material that is low permeable to hydrogen even when under stress, b. Step (220) of applying a second layer onto the first layer, wherein the second layer is made of a second material that is oxidation-resistant and / or corrosion-resistant and / or erosion-resistant, Method (200) in which the application of step "a" (210) and the application of step "b" (220) are carried out at a temperature of less than 500°C.

10. The method according to claim 9 (200), wherein the second layer is applied using chemical vapor deposition (CVD).

11. The method according to claim 10 (200), wherein the second layer is applied using low-temperature chemical deposition, particularly plasma-assisted chemical deposition (PACVD), plasma chemical deposition (PECVD), or induction plasma chemical deposition (IPECCVD), at a temperature in the range of 0 to 350°C.

12. A turbomachinery component comprising a multilayer coating as described in claim 1, more particularly a turbomachinery impeller (300), wherein the multilayer coating covers at least a portion of the turbomachinery component.

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