Preparation method of hydrogen-resistant oxidation film coating

Abstract

The invention provides a preparation method of a hydrogen-resistant oxidation film coating, which comprises the following steps: preparing a coating through thermal spraying, then carrying out laser remelting treatment on the prepared coating in a vacuum environment, vacuumizing the interior of a vacuum chamber, introducing argon as inert gas protection, controlling the pressure to be 0.01-1000Pa, the laser incident angle to be 0-44 degrees, the laser wavelength to be 1064nm and the laser power to be 3-6kW, and carrying out thermal spraying on the coating to obtain the hydrogen-resistant oxidation film coating. Laser spots are rectangular or circular, and the scanning speed is 2-5mm / s. According to the preparation method of the hydrogen-resistant oxidation film coating, after the thermal spraying MCrAlY coating is subjected to laser remelting in the vacuum inert environment, a layer of surface aluminum oxide is formed, so that a layer of continuous, compact and single aluminum oxide hydrogen-resistant oxidation film is formed in the subsequent high-temperature service of the coating; a ceramic oxide film generated in situ by the prepared hydrogen-resistant coating is not easy to crack and peel off, and has strong adhesion with a substrate alloy, so that the high-temperature service life of part of hydrogen-doped gas turbine parts in a hydrogen-doped service environment is effectively prolonged.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen permeation corrosion prevention technology, and specifically relates to a method for preparing a hydrogen permeation corrosion prevention film coating. Background Technology

[0002] Hydrogen-barrier coatings are a key technology for solving hydrogen-induced embrittlement and ensuring the safety of hydrogen energy storage and transportation. Especially in the field of hydrogen-blended gas turbines for new energy, changes in the operating environment of structural materials have brought new challenges to the high-temperature alloy materials and coating systems of gas turbines.

[0003] MCrAlY high-temperature oxidation resistant coatings possess high strength, good toughness, and high hardness, exhibiting excellent wear resistance and high-temperature oxidation resistance, making them widely used in aerospace, steel, shipbuilding, and petrochemical industries. Thermal spraying technology for coating preparation offers advantages such as fast deposition rates, high productivity, and wide applicability, enabling the production of high-quality, dense coatings with high bonding strength. In recent years, an improved supersonic flame spraying technology—Activated Combustion High-Voltage Gas Spraying (AC-HVAF)—has emerged, which can reduce the temperature of the supersonic flame, resulting in very low oxide content in the coating. The coating bonding strength can reach over 100 MPa, with high spraying efficiency. MCrAlY coatings prepared using this method have extremely low oxide content, very high interfacial bonding strength, and high coating deposition efficiency. Furthermore, after high-temperature oxidation, a continuous, single, and dense thermally grown oxide layer (TGO) with alumina as the main phase can form on the surface of the MCrAlY coating. However, as the high-temperature oxidation service progresses, the TGO in the coating needs further purification. The TGO growth rate curve is still relatively steep, the bonding force at the TGO / coating interface is not high, and the TGO protective layer of the coating is relatively easy to peel off.

[0004] Patent 202211500360.9 discloses a process for preparing a high-entropy composite oxide hydrogen-barrier coating using a sol-gel method. This method involves thorough calcination at a relatively low temperature followed by rapid cooling to achieve low-temperature synthesis of high-entropy ceramics. It is low-cost, simple to operate, and exhibits excellent hydrogen-barrier performance. However, the bonding between this type of coating and the substrate alloy is not only not a metallurgical bond, but also weaker than mechanical bonding, making it unsuitable for hydrogen-doped gas turbine applications.

[0005] The patent with publication number CN10699682A discloses a method for preparing cavitation-resistant coatings using a composite process of cold spraying and laser remelting. After laser treatment, the metal-ceramic coating is remelted to form a new microstructure, which greatly improves the coating's cavitation resistance. However, the cost of preparing the coating by cold spraying is very high, and laser remelting will also increase its preparation cost. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for preparing an oxygen-resistant oxide film coating, thereby solving the technical problems of low interfacial bonding strength between the MCrAlY coating and the alloy substrate, and easy cracking and peeling of the ceramic oxide film.

[0007] The present invention achieves the above-mentioned technical objectives through the following technical means.

[0008] A method for preparing an oxygen-resistant film coating includes the following steps:

[0009] Coatings are prepared by thermal spraying;

[0010] The prepared coating was subjected to laser remelting in a vacuum environment.

[0011] Furthermore, the vacuum environment is protected by an inert gas.

[0012] Furthermore, the pressure of the vacuum environment is 0.01~1000 Pa.

[0013] Furthermore, the inert gas is argon.

[0014] Furthermore, the process parameters for laser remelting are as follows: laser incident angle 0~44°, laser wavelength 1064nm, laser power 3~6kW, laser spot is rectangular or circular, and scanning speed 2~5mm / s; the laser is one of fiber laser, semiconductor laser, or CO2 laser.

[0015] Furthermore, the prepared coating is an MCrAlY coating with a thickness of 200~500μm and a composition of NiCoCrAlHfYSi type or NiCoCrAlYTa type.

[0016] Furthermore, the coating is prepared by supersonic flame thermal spraying, wherein: air pressure is 0.7~0.8MPa, air flow rate is 300L / min; propane fuel pressure is 0.65~0.80MPa, propane fuel flow rate is 450L / min; powder feeding gas N2 pressure is 0.1MPa, powder feeding gas N2 flow rate is 60 L / min; spraying distance is 250~400mm; powder feeding rate is 50~200g / min; spray gun moving speed is 10~20mm / s; and the number of spraying passes is 10~20.

[0017] Furthermore, before thermal spraying, the surface of the target workpiece is pretreated, including sandblasting roughening treatment.

[0018] Furthermore, in the sandblasting roughening process, the sandblasting abrasive is brown corundum with a particle size of 100 mesh, and the sandblasting pressure is 0.6~0.8MPa.

[0019] Furthermore, after sandblasting and roughening, the target workpiece is ultrasonically cleaned using a mixture of acetone and anhydrous ethanol, and then dried.

[0020] The beneficial effects of this invention are as follows:

[0021] (1) The present invention provides a method for preparing a hydrogen-resistant hydrogen film coating. After laser remelting the thermally sprayed MCrAlY coating in a vacuum inert environment, a layer of surface alumina is formed, so that the coating forms a continuous, dense and single alumina hydrogen-resistant film during subsequent high-temperature service. The ceramic oxide film generated in situ by the prepared hydrogen-resistant coating is not easy to crack and peel off, and has strong adhesion to the base alloy, thereby effectively improving the high-temperature service life of some hydrogen-doped gas turbine components under hydrogen-doped service environment.

[0022] (2) The present invention can improve the microstructure of MCrAlY coating, significantly reduce metastable phases and homogenize the second phase structure; the coating / high temperature alloy interface changes from mechanical interlocking to metallurgical bonding; the TGO formed in the MCrAlY coating after high temperature service is mainly alumina with very low content of other oxides, and can significantly reduce the growth rate of TGO. Attached Figure Description

[0023] Figure 1 This is an elemental surface distribution diagram after vacuum laser remelting in Example 1;

[0024] Figure 2 This is an elemental surface distribution diagram after vacuum laser remelting in Example 2;

[0025] Figure 3 A comparison of the cross-sectional morphology of the coatings after high-temperature oxidation at 1050℃ for 200h in each test case;

[0026] Figure 4 A comparison of the surface morphology of the coatings after high-temperature oxidation at 1050℃ for 200h in each test case;

[0027] Figure 5 SEM image of the coating after conventional laser remelting in Comparative Example 3;

[0028] Figure 6 The image shows the SEM image of the coating after conventional laser remelting and subsequent exposure to 1050℃ for 200 hours, as shown in Comparative Example 3. Detailed Implementation

[0029] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0030] The method for preparing a hydrogen-resistant film coating of the present invention includes the following steps:

[0031] Step 1, Preprocessing

[0032] Step 1.1: The target high-temperature alloy workpiece is roughened by sandblasting, wherein the sandblasting abrasive is brown corundum with a particle size of 100 mesh, and the sandblasting pressure of the sandblasting machine is 0.6~0.8MPa;

[0033] Step 1.2: After sandblasting and roughening, ultrasonic cleaning is performed using a mixture of acetone and anhydrous ethanol.

[0034] Step 1.3: After cleaning, dry the target workpiece.

[0035] Step 2, thermal spraying

[0036] A preliminary MCrAlY coating with a thickness of 200–500 μm was prepared on the surface of the pretreated target workpiece using a supersonic flame thermal spraying method.

[0037] 1) The MCrAlY coating composition adopts NiCoCrAlHfYSi type or NiCoCrAlYTa type;

[0038] 2) The parameters for supersonic flame thermal spraying are as follows: air pressure 0.7~0.8MPa, air flow rate 300L / min; propane fuel pressure 0.65~0.80MPa, propane fuel flow rate 450L / min; powder feeding gas N2 pressure 0.1MPa, powder feeding gas N2 flow rate 60 L / min; spraying distance 250~400mm; powder feeding rate 50~200g / min; spray gun moving speed 10~20mm / s; number of spraying passes 10~20 passes.

[0039] Step 3, Vacuum laser remelting

[0040] The target workpiece is placed in a vacuum environment, and the MCrAlY coating prepared on its surface is subjected to heat treatment by laser remelting, wherein:

[0041] 1) After the vacuum chamber containing the target workpiece is evacuated, an inert gas (argon is specifically used in this embodiment) is introduced to maintain the pressure inside the chamber at 0.01~1000Pa.

[0042] 2) The laser type can be fiber laser, semiconductor laser, or CO2 laser. The incident angle between the laser and the workpiece surface is 0~44°, the laser wavelength is 1064nm, the laser power is 3~6kW, the laser spot is rectangular or circular, and the scanning speed is 2~5mm / s.

[0043] This invention modifies the structure of the MCrAlY coating through the aforementioned vacuum laser remelting process, thereby further enhancing its performance. Specifically, vacuum laser remelting purifies the TGO in the MCrAlY coating after high-temperature service, resulting in a smooth and stable TGO growth rate curve. The bonding at the TGO / coating interface becomes a metallurgical bond, significantly improving the adhesion of the TGO protective layer. Consequently, the ceramic oxide film formed in situ by the prepared hydrogen-barrier coating is less prone to cracking and peeling in the face of hydrogen-induced corrosion during high-temperature service, and exhibits stronger adhesion to the substrate alloy.

[0044] To verify the performance of the above technical solution, the following test example is given:

[0045] Example 1

[0046] 1. Pretreatment: Brown fused alumina particle size: 100 mesh, sandblasting pressure: 0.6~0.8MPa;

[0047] 2. Thermal spraying: Air pressure 0.7MPa, air flow rate 300L / min; propane fuel pressure 0.65MPa, propane fuel flow rate 450L / min; N2 powder feeding gas pressure 0.1MPa, N2 powder feeding gas flow rate 60L / min; spraying distance 250mm; powder feeding rate 100g / min; spray gun moving speed 10mm / s; number of spray passes 20. The coating chemical composition is Ni22Co17Cr12Al0.5Hf0.5Y0.4Si, and the powder particle size distribution is 5~63μm.

[0048] 3. Vacuum laser remelting: The pressure inside the vacuum chamber is 1000Pa, the laser is incident perpendicularly (the incident angle is 0), the laser wavelength is 1064nm, the laser power is 3kW, the laser spot is a rectangle with a size of 2mm×5mm, and the laser scanning speed is 5mm / s.

[0049] The surface distribution of the prepared coating elements is as follows Figure 1 As shown, after vacuum laser remelting, an aluminum oxide film with a thickness of 1~2μm is formed on the surface of the MCrAlY coating.

[0050] Example 2

[0051] 1. Pretreatment: Brown fused alumina particle size: 100 mesh, sandblasting pressure: 0.6~0.8MPa;

[0052] 2. Thermal spraying: Air pressure 0.7MPa, air flow rate 300L / min; propane fuel pressure 0.65MPa, propane fuel flow rate 450L / min; N2 powder feeding gas pressure 0.1MPa, N2 powder feeding gas flow rate 60L / min; spraying distance 250mm; powder feeding rate 200g / min; spray gun moving speed 10mm / s; number of spray passes 20. The coating chemical composition is Ni23Co20Cr8.5Al0.6Y4.0Ta, and the powder particle size distribution is 5~37μm.

[0053] 3. Vacuum laser remelting: vacuum chamber pressure 100Pa, laser incident angle 44°, laser wavelength 1064nm, laser power 5kW, laser spot size 2mm×5mm rectangle, laser scanning speed 3mm / s.

[0054] The surface distribution of the prepared coating elements is as follows Figure 2 As shown, after vacuum laser remelting, an aluminum oxide film of about 1 μm thickness is formed on the surface of the MCrAlY coating.

[0055] Meanwhile, the following test cases "without vacuum laser remelting treatment" are provided for horizontal comparison:

[0056] Comparative Example 1:

[0057] Based on Example 1, the vacuum laser remelting process step is removed.

[0058] Comparative Example 2:

[0059] Based on Example 2, the vacuum laser remelting process step is removed.

[0060] The coating morphologies of the four test examples after high-temperature oxidation at 1050℃ in air for 200 hours are as follows: Figure 3 and Figure 4 As shown, where:

[0061] Figure 3 For the comparison of the cross-sectional morphology of the coating, (a) is Comparative Example 1, (b) is Example 1, (c) is Comparative Example 2, and (d) is Example 2. It can be seen from the figures that after vacuum laser remelting treatment of the present invention, the alumina film formed by the MCrAlY coating is thinner and has better bonding with the coating. No cracks were observed to form and spinel formation was also basically not observed.

[0062] Figure 4For the comparison of coating surface morphology, Figures (a), (b), and (c) are comparative example 1, and Figures (d), (e), and (f) are comparative example 2. It can be clearly seen from the figures that a large number of spinels are formed on the surface of the MCrAlY coating that has not undergone vacuum laser remelting, which destroys the continuity and uniformity of the alumina film and has a negative effect on the high-temperature hydrogen barrier of the hydrogen-doped gas turbine metal parts.

[0063] In addition, the following test cases of "laser remelting under normal atmospheric pressure" are provided for comparative analysis:

[0064] Comparative Example 3:

[0065] Based on Example 1, the vacuum laser remelting process is replaced with a laser remelting process under conventional air pressure, wherein the laser setting parameters are the same as in Example 1.

[0066] Test results are as follows Figure 5 and Figure 6 As shown, where Figure 5 The image shows the coating after conventional laser remelting. Figure 6 The coating shown is the result of high-temperature oxidation at 0.50℃ in air for 200 hours in Comparative Example 3.

[0067] Depend on Figure 5 It can be seen that the microstructure of the MCrAlY coating has changed significantly, and the phase structure of the coating is significantly different from that of Comparative Example 1 and Example 1. Among them, a 5-10 μm thick thermally grown oxide film is formed on the surface of the MCrAlY coating. This may be due to the high energy storage of the metal substructure of the coating prepared by HVAF. After high-energy laser input, the oxide on the coating surface grows rapidly. The bottom of the thermally grown oxide film of the coating is 0.5 μm of alumina, and the rest is a spinel structure, which leads to a decrease in the mechanical properties of the oxide film on the coating surface and its hydrogen diffusion resistance performance (compared to Example 1).

[0068] Depend on Figure 6 It can be seen that: using only laser remelting under conventional conditions, the growth rate of the thermally grown oxide layer on the coating surface is relatively low after high-temperature oxidation service, which has certain benefits for the coating system, but the total thickness of the thermally grown oxide can still reach 5~10μm; secondly, spinel still exists on the upper part of the thermally grown oxide, which destroys the continuity and uniformity of the alumina film, and will inevitably have a negative effect on its continued hydrogen diffusion resistance during high-temperature service; in addition, the thermally grown oxide / coating interface has cracks, which has an adverse effect on the mechanical stability of the coating system.

[0069] This invention is not limited to the above-described embodiments. Any obvious improvements, substitutions, or modifications that can be made by those skilled in the art without departing from the essence of this invention are within the scope of protection of this invention.

Claims

1. A method for preparing an oxygen-resistant film coating, characterized in that: Includes the following steps: Coatings are prepared by thermal spraying; The prepared coating was subjected to laser remelting in a vacuum environment.

2. The method for preparing an oxygen-resistant film coating according to claim 1, characterized in that: The vacuum environment is protected by an inert gas.

3. The method for preparing an oxygen-resistant film coating according to claim 2, characterized in that: The pressure of the vacuum environment is 0.01~1000Pa.

4. The method for preparing an oxygen-resistant film coating according to claim 2, characterized in that: The inert gas is argon.

5. The method for preparing an oxygen-resistant film coating according to claim 1, characterized in that: The laser remelting parameters are set as follows: laser incident angle 0~44°, laser wavelength 1064nm, laser power 3~6kW, laser spot is rectangular or circular, and scanning speed 2~5mm / s; the laser is one of fiber laser, semiconductor laser, or CO2 laser.

6. The method for preparing an oxygen-resistant film coating according to claim 1, characterized in that: The prepared coating is an MCrAlY coating with a thickness of 200~500μm and a composition of NiCoCrAlHfYSi type or NiCoCrAlYTa type.

7. The method for preparing an oxygen-resistant film coating according to claim 1, characterized in that: The coating was prepared by supersonic flame thermal spraying, with the following parameters: air pressure 0.7~0.8MPa, air flow rate 300L / min; propane fuel pressure 0.65~0.80MPa, propane fuel flow rate 450L / min; powder feeding gas N2 pressure 0.1MPa, powder feeding gas N2 flow rate 60 L / min; spraying distance 250~400mm; powder feeding rate 50~200g / min; spray gun moving speed 10~20mm / s; and 10~20 spray passes.

8. The method for preparing an oxygen-resistant film coating according to claim 1, characterized in that: Before thermal spraying, the surface of the target workpiece is pretreated, including sandblasting roughening.

9. The method for preparing an oxygen-resistant film coating according to claim 8, characterized in that: In the aforementioned sandblasting roughening treatment, the sandblasting abrasive is brown corundum with a particle size of 100 mesh, and the sandblasting pressure is 0.6~0.8MPa.

10. The method for preparing an oxygen-resistant film coating according to claim 8, characterized in that: After sandblasting and roughening, the target workpiece is ultrasonically cleaned with a mixture of acetone and anhydrous ethanol, and then dried.

Images