A multi-layer corrosion-resistant coating on a magnesium alloy surface and a method for preparing the same

Abstract

The present application relates to the technical field of anticorrosion coating, and particularly relates to a multilayer anticorrosion coating on the surface of magnesium alloy and a preparation method thereof. The multilayer anticorrosion coating comprises a Zr layer and a Ta / ZrN multilayer structure layer; the Zr layer is deposited on the surface of a substrate; the Ta / ZrN multilayer structure layer comprises a Ta layer and a ZrN layer which are alternately deposited on the surface of the Zr layer; the thickness ratio of the Ta layer to the ZrN layer is 1:0.5-2. By depositing the Zr layer on the surface of the substrate and alternately depositing the Ta layer and the ZrN layer to form the Ta / ZrN multilayer structure layer, the internal stress of the nitride coating can be reduced, the bonding strength between the coating and the magnesium alloy substrate can be improved, the columnar crystal growth of the coating can be blocked, the coating structure can be densified, the wear resistance and the corrosion resistance of the magnesium alloy can be improved, and the problem that the defects formed in the existing magnetron sputtering thin film deposition process can reduce the corrosion resistance and the friction resistance of the thin film can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of anti-corrosion coatings, and in particular to a multi-layer anti-corrosion coating on the surface of a magnesium alloy and a preparation method thereof. Background Art

[0002] Modern manufacturing places great emphasis on clean energy, reusable resources, lightweighting, and structural integration. In this context, magnesium and its alloys have attracted great interest. Compared with other commonly used metal materials, magnesium alloys are lightweight, with a density of only 1.74g / cm 3 , which is about 2 / 3 of aluminum and 1 / 4 of steel. Its high machinability and damping capacity give magnesium alloys excellent working performance, making them an ideal choice for lightweight manufacturing. However, relative to the standard hydrogen electrode, the standard electrode potential of magnesium is -2.37V, which is lower than aluminum -1.663V and iron -0.440V. It is the most chemically active metal among all structural materials currently available and is prone to corrosion in environments such as humid air and oceans. In addition, magnesium alloys are relatively soft in texture, with a hardness of about 65HV and poor wear resistance. When used in a frictional environment, magnesium alloys often suffer from severe abrasive wear, which eventually leads to damage or even failure of the material. In short, the corrosion and wear problems of magnesium alloys have become the main factors restricting their promotion and application.

[0003] In recent years, surface treatment technology has developed rapidly, providing more options for the protection of magnesium alloys. The surface modification methods of magnesium alloys mainly include anodizing, micro-arc oxidation, chemical conversion film, electroplating, chemical plating, sol-gel method, physical vapor deposition, etc. Compared with traditional chemical methods such as electroplating, physical vapor deposition is carried out in a vacuum environment, and the magnesium alloy will not undergo oxidation reaction during the deposition process. In addition, this technology does not come into contact with aqueous solutions or other chemical solutions and will not corrode the surface of the magnesium alloy. Among them, among the PVD technologies with a higher degree of industrialization, magnetron sputtering has the characteristics of fast film formation speed, dense and uniform coating, high precision and good adhesion, and has been widely used in many industrial fields.

[0004] Due to its high chemical activity, magnesium is extremely sensitive to defects in its surface protective coating. Once a corrosive medium contacts the magnesium substrate, severe corrosion occurs, leading to coating failure. While coatings produced using magnetron sputtering offer high quality, they may still contain a small number of defects that extend throughout the coating thickness. Furthermore, when magnetron sputtering is used to produce a single-layer coating, a columnar structure often forms, and the coarse columnar grain boundaries can also serve as pathways for the corrosive medium. Therefore, only by eliminating these penetrating defects can the protective coating be fully utilized. Summary of the Invention

[0005] In order to solve the problem that defects formed in the existing magnetron sputtering film deposition process will reduce the corrosion resistance and friction resistance of the film, the purpose of the present invention is to provide a multi-layer anti-corrosion coating on the surface of a magnesium alloy and a preparation method thereof.

[0006] To achieve the above objectives, the technical solutions of the present invention are as follows.

[0007] A first aspect of the present invention provides a multilayer anti-corrosion coating on the surface of a magnesium alloy, wherein the multilayer anti-corrosion coating includes a Zr layer and a Ta / ZrN multilayer structural layer; the Zr layer is deposited on the surface of a substrate; the Ta / ZrN multilayer structural layer includes a Ta layer and a ZrN layer alternately deposited on the surface of the Zr layer; the thickness ratio of the Ta layer to the ZrN layer is 1:0.2~5.

[0008] Directly depositing a single ZrN layer on a magnesium alloy surface can easily lead to insufficient corrosion resistance due to penetrating defects in the coating. The present invention deposits a Zr layer on the substrate surface and alternately deposits ZrN and Ta layers on the Zr layer surface, effectively improving the corrosion resistance of the substrate. This is because alternating Ta layers within the ZrN layer inhibits the growth of columnar crystals in the coating, reduces penetrating defects in the coating, and densifies the coating structure. Furthermore, the magnetron sputtering process is more environmentally friendly than traditional electroplating processes, produces no environmentally harmful substances, and is therefore suitable for large-scale applications.

[0009] In the present invention, the thickness ratio of the Ta layer to the ZrN layer affects the hardness, toughness, internal stress, corrosion resistance, etc. of the coating. The thickness ratio of the Ta layer to the ZrN layer is 1:0.2 to 5. For example, 1:0.2, 1:1, 1:2, 1:3, 1:4, 1:5, and any thickness within the above-listed numerical ranges are not listed here.

[0010] Preferably, the total thickness of the Ta / ZrN multilayer structure layer is 1 μm to 20 μm.

[0011] Preferably, the outermost layer of the Ta / ZrN multilayer structure is a ZrN layer.

[0012] The Zr layer is mainly used as a base layer. The present invention does not specifically limit the thickness ratio of the Ta layer to the Zr layer. The thickness of the Zr layer can be selected according to actual needs. For example, the thickness ratio of the Ta layer to the Zr layer is 1:0.76-2.5.

[0013] A second aspect of the present invention provides a method for preparing a multilayer anti-corrosion coating on a magnesium alloy surface, comprising the following steps:

[0014] A Zr layer is deposited on the surface of a substrate by a magnetron sputtering process; then ZrN layers and Ta layers are alternately deposited on the surface of the Zr layer to form a Ta / ZrN multilayer structure layer; the thickness ratio of the Ta layer to the ZrN layer is 1:0.2-5.

[0015] The present invention primarily uses magnetron sputtering technology to deposit a Zr layer on the substrate surface, and then alternately deposits ZrN and Ta layers on the Zr layer to form a Ta / ZrN multilayer coating. Compared to a single Ta layer, the multilayer anti-corrosion coating of the present invention exhibits higher hardness, wear resistance, and corrosion resistance. Compared to a single ZrN layer, the multilayer anti-corrosion coating of the present invention is denser and significantly reduces internal stress and brittleness.

[0016] Preferably, the total thickness of the Ta / ZrN multilayer structure is 1 μm to 20 μm; any value within this range is acceptable, such as 1 μm, 3 μm, 5 μm, 10 μm, 12 μm, 18 μm, 20 μm, and any thickness within the aforementioned ranges, which are not listed here. Preferably, the number of cycles of alternating Ta and ZrN layers is at least one, and the outermost layer of the Ta / ZrN multilayer structure is a ZrN layer.

[0017] ZrN coatings can improve the hardness, wear resistance, and corrosion resistance of magnesium alloy substrates. If the coating thickness is too thin, its wear and corrosion resistance will not meet the requirements of harsh operating conditions. To achieve the required performance, the ZrN coating thickness often needs to be increased. However, this often leads to increased internal stress in the coating and the coating tends to form coarse columnar crystals, which provide a penetrating channel for corrosive liquids and thus affect the coating's performance. If thicker ZrN coatings are deposited directly on the metal substrate, the high internal stress will also lead to poor bonding strength.

[0018] The present invention adopts the method of pre-depositing a Zr layer on the surface of the metal substrate and then alternately depositing a Ta layer and a ZrN layer. Compared with a ZrN coating of the same thickness, the bonding strength is improved, the internal stress of the coating is small, and the degree of microstructure refinement is high, which solves the problem in the prior art that the above-mentioned thickness and performance cannot be taken into account at the same time.

[0019] Preferably, the substrate is a magnesium alloy. The magnesium alloy described in the present invention is an existing magnesium alloy material, for example, AZ31B or other high-hardness magnesium alloys. The magnesium alloy described in the present invention is not limited to AZ31B and may also be other existing high-hardness magnesium alloys. Of course, the method of the present invention can also be applied to the corrosion protection of other metals and their alloys, for example, the substrate is an aluminum alloy or steel.

[0020] Preferably, the specific preparation method comprises the following steps:

[0021] A Zr target and a Ta target are placed at sputtering target positions respectively, and a substrate is placed on a sample stage; after evacuation, argon gas is introduced, a negative bias voltage is applied to the substrate, and the surface of the substrate is cleaned by glow sputtering; argon gas is introduced, the Zr target is magnetron sputtered, and a negative bias voltage is applied to the substrate to form ion bombardment to obtain a Zr layer; argon gas and nitrogen gas are introduced, the Zr target is magnetron sputtered, and a negative bias voltage is applied to the substrate to form ion bombardment to obtain a ZrN layer; argon gas is introduced, the Ta target is magnetron sputtered, and a negative bias voltage is applied to the substrate to form ion bombardment to obtain a Ta layer; the preparation steps of the ZrN layer and the Ta layer are repeated to form a Ta / ZrN multilayer structure layer on the surface of the Zr layer to obtain a multilayer anti-corrosion coating.

[0022] Preferably, the specific method of cleaning the substrate surface by glow sputtering is as follows:

[0023] Evacuate to a vacuum degree of less than 5×10 -3 After Pa, argon gas is introduced, the vacuum degree is controlled at 0.1Pa~0.4Pa, and a bias voltage of -200V~-600V is applied to the substrate to make the gas glow discharge, and the substrate surface is glow sputtered and cleaned by argon ions; the glow sputtering cleaning time is 10min~60min.

[0024] Preferably, the method of depositing the Zr layer is as follows:

[0025] Argon gas is introduced, the vacuum degree is controlled at 0.1 Pa to 0.4 Pa, and a bias voltage of 0V to -100V is applied to the substrate to form ion bombardment to obtain a Zr layer.

[0026] The method for depositing the Ta layer is as follows:

[0027] Argon gas is introduced, the vacuum degree is controlled at 0.1Pa to 0.4Pa, and a bias voltage of 0V to -100V is applied to the substrate to form ion bombardment to obtain a Ta layer.

[0028] The method for depositing the ZrN layer is as follows:

[0029] Argon and nitrogen are introduced at a flow ratio of 1 to 5:1, the vacuum degree is controlled at 0.1 Pa to 0.4 Pa, and a bias voltage of 0 V to -100 V is applied to the substrate to form ion bombardment to obtain a ZrN layer.

[0030] During the ZrN deposition process, excessively high nitrogen flow rates can easily lead to target poisoning, affecting the deposition rate. Furthermore, exceeding the nitrogen required for the reaction results in waste. Excessively low nitrogen flow rates prevent sufficient ZrN formation, resulting in the equivalent of depositing pure metallic Zr. Therefore, the present invention employs an argon to nitrogen flow ratio of 1:0.5 to 10.

[0031] Beneficial effects of the present invention:

[0032] 1. The present invention deposits a Zr layer on the surface of the substrate and alternately deposits a ZrN layer and a Ta layer on the surface of the Zr layer to form a Ta / ZrN multilayer structure layer. This can reduce the internal stress of the nitride coating, improve the bonding strength between the coating and the magnesium alloy substrate, block the growth of columnar crystals in the coating, densify the coating structure, effectively provide good protection for the substrate, reduce the difficulty of stripping the coating, and help improve the wear resistance and corrosion resistance of the magnesium alloy. This solves the problem that defects formed in the existing magnetron sputtering thin film deposition process will reduce the corrosion resistance and friction resistance of the film.

[0033] 2. The present invention can adjust the hardness, toughness, internal stress and corrosion resistance of the multi-layer anti-corrosion coating by changing the thickness ratio of the Ta layer and the ZrN layer.

[0034] 3. The present invention adopts magnetron sputtering technology, which is greener and more environmentally friendly than traditional electroplating technology, does not produce environmentally harmful substances, and is conducive to large-scale application. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A schematic structural diagram of a multi-layer anti-corrosion coating on a magnesium alloy surface provided in one embodiment of the present invention.

[0036] Figure 2 This is a cross-sectional SEM image of the multilayer anti-corrosion coating on the surface of the magnesium alloy in Example 1.

[0037] Figure 3 This is the cross-sectional SEM image of the single-layer Ta coating on the surface of the magnesium alloy in Comparative Example 2.

[0038] Figure 4 The potentiodynamic polarization curves of the magnesium alloy and the multi-layer anti-corrosion coating on the magnesium alloy in Example 1 in a 3.5 wt% NaCl solution are shown in FIG. Wherein, Ecorr represents the corrosion potential; jcorr represents the corrosion current density.

[0039] Figure 5 SEM images of the multilayer anti-corrosion coating on the magnesium alloy surface in Example 1 before and after 24 hours of acidic salt spray exposure. (a) is the secondary electron morphology before corrosion; (b) is the secondary electron morphology after corrosion; (c) is the backscattered electron morphology before corrosion; and (d) is the backscattered electron morphology after corrosion.

[0040] Figure 6 SEM images of the single-layer Ta coating on the magnesium alloy in Comparative Example 2 before and after 24 hours of acidic salt spray exposure. (a) is the secondary electron morphology before corrosion; (b) is the secondary electron morphology after corrosion; (c) is the backscattered electron morphology before corrosion; and (d) is the backscattered electron morphology after corrosion.

[0041] Figure 7The following are SEM images of the different coatings on the magnesium alloy surfaces after 24 hours of acidic salt spray exposure in Examples 1 to 4 and Comparative Examples 1 to 2. (a) is a backscattered electron morphology image of the coating in Comparative Example 2; (b) is a backscattered electron morphology image of the coating in Comparative Example 1; (c) is a backscattered electron morphology image of the coating in Example 2; (d) is a backscattered electron morphology image of the coating in Example 3; (e) is a backscattered electron morphology image of the coating in Example 4; and (f) is a backscattered electron morphology image of the coating in Example 1. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0043] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0044] The technical solution of the present invention is further described below through specific embodiments.

[0045] In the following examples, the experimental methods and detection methods are conventional methods unless otherwise specified; the reagents and materials are commercially available unless otherwise specified.

[0046] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0047] Magnesium alloy surface coatings are prone to easy detachment and poor corrosion resistance, resulting in poor protection of the magnesium alloy substrate. Therefore, improving the adhesion between the coating and the metal substrate and reducing penetrating defects in the coating are the basis for improving the corrosion resistance of magnesium alloy surface coatings.

[0048] To address the aforementioned issues, an embodiment of the present invention provides a magnesium alloy Ta / ZrN multilayer corrosion-resistant coating. The multilayer corrosion-resistant coating comprises a Zr layer and a Ta / ZrN multilayer structure; the Zr layer is deposited on the surface of a substrate; the Ta / ZrN multilayer structure comprises ZrN layers and Ta layers alternately deposited on the surface of the Zr layer; and the thickness ratio of the Ta layer to the ZrN layer is 1:0.2-5. The total thickness of the Ta / ZrN multilayer structure is 1-20 μm. The Ta / ZrN multilayer structure can inhibit columnar crystal growth and alleviate residual stress in the coating. The corrosion-resistant coating exhibits good bonding with the magnesium alloy substrate.

[0049] A method for preparing a multi-layer anti-corrosion coating on a magnesium alloy surface of the present invention comprises the following steps:

[0050] (1) Place the metal Ta, Zr targets and magnesium alloy on the sputtering target position and sample stage in the vacuum chamber of the magnetron sputtering equipment respectively.

[0051] (2) Evacuate the vacuum chamber of the magnetron sputtering equipment until the vacuum degree is lower than 5×10 -3 Then, argon gas is introduced into the vacuum chamber of the magnetron sputtering equipment, the vacuum degree is controlled at about 0.2 Pa, and a bias voltage of -200V to -600V is applied to the substrate. The sample surface is bombarded and cleaned by argon ions, and the glow cleaning time is 10 to 60 minutes.

[0052] (3) Argon gas is introduced into the vacuum chamber of the magnetron sputtering equipment to control the vacuum range to 0.1~0.4Pa, and a bias voltage of 0V~-100V is applied to the substrate to magnetron sputter the Zr target to obtain a Zr base layer.

[0053] (4) Argon and nitrogen are introduced into the vacuum chamber of the magnetron sputtering equipment. The flow ratio of argon and nitrogen is 1 to 5:1. The vacuum range is controlled to be 0.1 to 0.4 Pa. A bias voltage of 0 V to -100 V is applied to the substrate to sputter the Zr target to obtain a ZrN layer.

[0054] (5) Argon gas is introduced into the vacuum chamber of the magnetron sputtering equipment to control the vacuum range to 0.1~0.4Pa, and a bias voltage of 0V~-100V is applied to the substrate to magnetron sputter the Ta target to obtain a Ta layer.

[0055] (6) Repeat steps (4) and (5) to form a Ta / ZrN multilayer structure layer on the surface of the Zr layer to obtain a multilayer anti-corrosion coating.

[0056] The preparation method of the Ta / ZrN multilayer coating provided by the present invention is to prepare the Ta / ZrN multilayer coating by magnetron sputtering, which can reduce the internal stress of the nitride coating, improve the bonding strength between the coating and the magnesium alloy substrate, inhibit the growth of columnar crystals in the coating, densify the coating structure, effectively provide good protection for the substrate, reduce the difficulty of stripping the coating, and help improve the wear resistance and corrosion resistance of the magnesium alloy. The preparation method of the Ta / ZrN multilayer corrosion-resistant coating provided by the present invention can adjust the hardness, toughness, internal stress and corrosion resistance of the coating by changing the thickness ratio of the Ta layer and the ZrN layer. The preparation method of the ablation-resistant Ta / ZrN multilayer coating provided by the present invention is more environmentally friendly than traditional electroplating chromium and does not produce environmentally harmful substances.

[0057] The present invention is described in detail below with reference to the accompanying drawings and embodiments, but the present invention is not limited to the following embodiments. Example

[0058] A method for preparing a multi-layer anti-corrosion coating on a magnesium alloy surface, such as Figure 1 As shown, the following steps are included:

[0059] 1) Using AZ31B as the substrate, the AZ31B substrate is ground, polished, cleaned, and dried, and then fixed on a rotatable workpiece holder in a vacuum chamber.

[0060] 2) Evacuate the vacuum chamber of the magnetron sputtering equipment to ≤4×10 -3 Pa, argon gas was introduced into the vacuum chamber of the magnetron sputtering equipment to make the gas pressure 0.2 Pa, and a -500V bias was applied to the substrate, and the substrate surface was cleaned by glow plasma sputtering for 30 minutes.

[0061] 3) Argon gas was introduced into the vacuum chamber of the magnetron sputtering equipment to a pressure of 0.2 Pa, a Zr target was sputtered at a power of 2000 W, and a bias voltage of -60 V was applied to the substrate to deposit a Zr layer with a thickness of 500 nm.

[0062] 4) Argon and nitrogen were introduced into the vacuum chamber of the magnetron sputtering equipment with an Ar:N2 flow ratio of 2:1 and a gas pressure of 0.2 Pa. The Zr target was sputtered at a power of 2000 W and a -60 V bias was applied to the substrate to deposit a ZrN layer with a thickness of 500 nm.

[0063] 5) Argon gas was introduced into the vacuum chamber of the magnetron sputtering equipment to a pressure of 0.2 Pa, and a Ta target was sputtered at a power of 2000 W. A bias voltage of -60 V was applied to the substrate to deposit a Ta layer with a thickness of 500 nm.

[0064] 6) Alternately repeating steps 4) and 5), wherein the outermost layer is a ZrN layer, to obtain a TaZrN multilayer corrosion-resistant coating with a total thickness of 3 μm. The thickness ratio of the Ta layer to the ZrN layer in the Ta / ZrN multilayer corrosion-resistant coating is 1:1. Example

[0065] A method for preparing a multi-layer anti-corrosion coating on a magnesium alloy surface comprises the following steps:

[0066] 1) Using AZ31B as the substrate, the AZ31B substrate is ground, polished, cleaned, and dried, and then fixed on a rotatable workpiece holder in a vacuum chamber.

[0067] 2) Evacuate the vacuum chamber of the magnetron sputtering equipment to ≤4×10 -3 Pa, argon gas was introduced into the vacuum chamber of the magnetron sputtering equipment to make the gas pressure 0.2 Pa, and a -500V bias was applied to the substrate, and the substrate surface was cleaned by glow plasma sputtering for 30 minutes.

[0068] 3) Argon gas was introduced into the vacuum chamber of the magnetron sputtering equipment to a pressure of 0.2 Pa, a Zr target was sputtered at a power of 2000 W, and a bias voltage of -60 V was applied to the substrate to deposit a Zr layer with a thickness of 500 nm.

[0069] 4) Argon and nitrogen were introduced into the vacuum chamber of the magnetron sputtering equipment with an Ar:N2 flow ratio of 2:1 and a gas pressure of 0.2 Pa. The Zr target was sputtered at a power of 2000 W and a -60 V bias was applied to the substrate to deposit a ZrN layer with a thickness of 450 nm.

[0070] 5) Argon gas was introduced into the vacuum chamber of the magnetron sputtering equipment to a pressure of 0.2 Pa. The Ta target was sputtered at a power of 2000 W. A bias voltage of -60 V was applied to the substrate to deposit a Ta layer with a thickness of 650 nm.

[0071] 6) Alternately repeating steps 4) and 5), wherein the outermost layer is a ZrN layer, to obtain a Ta / ZrN multilayer corrosion-resistant coating with a total thickness of 3 μm. The thickness ratio of the Ta layer to the ZrN layer in the Ta / ZrN multilayer corrosion-resistant coating is 13:8. Example

[0072] A method for preparing a multi-layer anti-corrosion coating on a magnesium alloy surface comprises the following steps:

[0073] 1) Using AZ31B as the substrate, the AZ31B substrate is ground, polished, cleaned, and dried, and then fixed on a rotatable workpiece holder in a vacuum chamber.

[0074] 2) Evacuate the vacuum chamber of the magnetron sputtering equipment to ≤4×10 -3Pa, argon gas was introduced into the vacuum chamber of the magnetron sputtering equipment to make the gas pressure 0.2 Pa, and a -500V bias was applied to the substrate, and the substrate surface was cleaned by glow plasma sputtering for 30 minutes.

[0075] 3) Argon gas was introduced into the vacuum chamber of the magnetron sputtering equipment to a pressure of 0.2 Pa, a Zr target was sputtered at a power of 2000 W, and a bias voltage of -60 V was applied to the substrate to deposit a Zr layer with a thickness of 500 nm.

[0076] 4) Argon and nitrogen were introduced into the vacuum chamber of the magnetron sputtering equipment with an Ar:N2 flow ratio of 2:1 and a gas pressure of 0.2 Pa. The Zr target was sputtered at a power of 2000 W and a -60 V bias was applied to the substrate to deposit a ZrN layer with a thickness of 700 nm.

[0077] 5) Argon gas was introduced into the vacuum chamber of the magnetron sputtering equipment to a pressure of 0.2 Pa, and a Ta target was sputtered at a power of 2000 W. A bias voltage of -60 V was applied to the substrate to deposit a Ta layer with a thickness of 200 nm.

[0078] 6) Alternately repeating steps 4) and 5), wherein the outermost layer is a ZrN layer, to obtain a Ta / ZrN multilayer corrosion-resistant coating with a total thickness of 3 μm. The thickness ratio of the Ta layer to the ZrN layer in the Ta / ZrN multilayer corrosion-resistant coating is 2:7. Example

[0079] A method for preparing a multi-layer anti-corrosion coating on a magnesium alloy surface comprises the following steps:

[0080] 1) Pure magnesium is used as a substrate. The magnesium substrate is ground, polished, cleaned, dried, and then fixed on a rotatable workpiece holder in a vacuum chamber.

[0081] 2) Evacuate the vacuum chamber of the magnetron sputtering equipment to ≤4×10 -3 Pa, argon gas was introduced into the vacuum chamber of the magnetron sputtering equipment to make the gas pressure 0.2 Pa, and a -500V bias was applied to the substrate, and the substrate surface was cleaned by glow plasma sputtering for 30 minutes.

[0082] 3) Argon gas was introduced into the vacuum chamber of the magnetron sputtering equipment to a pressure of 0.2 Pa, a Zr target was sputtered at a power of 2000 W, and a bias voltage of -60 V was applied to the substrate to deposit a Zr layer with a thickness of 500 nm.

[0083] 4) Argon and nitrogen were introduced into the vacuum chamber of the magnetron sputtering equipment with an Ar:N2 flow ratio of 5:1 and a gas pressure of 0.2 Pa. The Zr target was sputtered at a power of 2000 W and a -60 V bias was applied to the substrate to deposit a ZrN layer with a thickness of 500 nm.

[0084] 5) Argon gas was introduced into the vacuum chamber of the magnetron sputtering equipment to a pressure of 0.2 Pa, and a Ta target was sputtered at a power of 2000 W. A bias voltage of -60 V was applied to the substrate to deposit a Ta layer with a thickness of 500 nm.

[0085] 6) Alternately repeating steps 4) and 5), wherein the outermost layer is a ZrN layer, to obtain a Ta / ZrN multilayer corrosion-resistant coating with a total thickness of 3 μm. The thickness ratio of the Ta to ZrN layers in the Ta / ZrN multilayer corrosion-resistant coating is 1:1.

[0086] Comparative Example 1

[0087] The method for preparing a single-layer ZrN coating on the surface of a magnesium alloy, compared with Example 1, is to deposit a ZrN layer of the same thickness only on the surface of the substrate. The specific preparation method includes the following steps:

[0088] 1) Using AZ31B as the substrate, the AZ31B substrate is ground, polished, cleaned, and dried, and then fixed on a rotatable workpiece holder in a vacuum chamber.

[0089] 2) Evacuate the vacuum chamber of the magnetron sputtering equipment to ≤4×10 -3 Pa, argon gas was introduced into the vacuum chamber of the magnetron sputtering equipment to make the gas pressure 0.2 Pa, and a -500V bias was applied to the substrate, and the substrate surface was cleaned by glow plasma sputtering for 30 minutes.

[0090] 3) Argon gas was introduced into the vacuum chamber of the magnetron sputtering equipment to a pressure of 0.2 Pa, a Zr target was sputtered at a power of 2000 W, and a bias voltage of -60 V was applied to the substrate to deposit a Zr layer with a thickness of 500 nm.

[0091] 4) Argon and nitrogen were introduced into the vacuum chamber of the magnetron sputtering equipment with an Ar:N2 flow ratio of 2:1 and a gas pressure of 0.2 Pa. The Zr target was sputtered at a power of 2000 W and a -60 V bias was applied to the substrate to deposit a single-layer ZrN coating with a total thickness of 3 μm.

[0092] Comparative Example 2

[0093] The method for preparing a single-layer Ta coating on the surface of a magnesium alloy, compared with Example 1, is to deposit a Ta layer of the same thickness only on the surface of the substrate. The specific preparation method includes the following steps:

[0094] 1) Using AZ31B as the substrate, the AZ31B substrate is ground, polished, cleaned, and dried, and then fixed on a rotatable workpiece holder in a vacuum chamber.

[0095] 2) Evacuate the vacuum chamber of the magnetron sputtering equipment to ≤4×10 -3After 1.5 Å, argon gas was introduced into the vacuum chamber of the magnetron sputtering equipment to make the gas pressure 0.2 Pa, and a -500 V bias was applied to the substrate, and the substrate surface was cleaned by glow sputtering for 30 min.

[0096] 3) Argon gas was introduced into the vacuum chamber of the magnetron sputtering equipment to a pressure of 0.2 Pa, a Zr target was sputtered at a power of 2000 W, and a bias voltage of -60 V was applied to the substrate to deposit a Zr layer with a thickness of 500 nm.

[0097] 4) Argon gas was introduced into the vacuum chamber of the magnetron sputtering equipment to a pressure of 0.2 Pa, a Ta target was sputtered at a power of 2000 W, and a bias voltage of -60 V was applied to the substrate to deposit a single-layer Ta coating with a total thickness of 3 μm.

[0098] Table 1 Comparison of conditions

[0099]

[0100] Test 1: SEM analysis.

[0101] Figure 1 A schematic structural diagram of a multi-layer anti-corrosion coating on a magnesium alloy surface provided in one embodiment of the present invention. Figure 2 The cross-sectional SEM image of the multi-layer anti-corrosion coating on the surface of the magnesium alloy in Example 1. Figure 2 It can be seen that the light-colored layer corresponds to Ta and the dark-colored layer corresponds to ZrN. It can be seen that the ZrN layer and the Ta layer grow alternately in the coating.

[0102] Figure 3 The cross-sectional SEM image of the single-layer Ta coating on the surface of the magnesium alloy in Comparative Example 2. Figure 3 It can be seen that there are a large number of columnar crystals in the coating.

[0103] The above analysis demonstrates that Example 1 of the present invention utilizes magnetron sputtering technology to produce a multilayer corrosion-resistant coating on a magnesium alloy surface with excellent corrosion resistance. Compared to the single-layer Ta coating of Comparative Example 2, the alternating Ta / ZrN multilayer corrosion-resistant coating of Example 1 avoids the columnar crystal structure typically formed when magnetron sputtering is used to prepare a single-layer coating, thereby preventing the formation of corrosive medium channels created by coarse columnar grain boundaries. Compared to a single-layer ZrN coating, the Ta / ZrN multilayer corrosion-resistant coating of Example 1 of the present invention exhibits a denser coating structure, thereby increasing the coating's hardness and significantly reducing internal stress and brittleness.

[0104] This proves that the method of Example 1 of the present invention can improve the hardness, wear resistance and corrosion resistance of the Ta / ZrN multilayer corrosion-resistant coating.

[0105] Test 2: Corrosion resistance analysis.

[0106] Figure 4 The potentiodynamic polarization curves of the magnesium alloy and the multi-layer anti-corrosion coating on the magnesium alloy in Example 1 in a 3.5 wt% NaCl solution are shown in FIG. Wherein, Ecorr represents the corrosion potential; jcorr represents the corrosion current density.

[0107] from Figure 4 It can be seen that the corrosion current density of the multilayer anti-corrosion coating on the surface of the magnesium alloy in Example 1 is significantly reduced and the corrosion potential is significantly increased. This shows that compared with the magnesium alloy, the corrosion resistance of the multilayer anti-corrosion coating on the surface of the magnesium alloy in Example 1 is indeed improved.

[0108] Figure 5 SEM images of the multilayer anti-corrosion coating on the magnesium alloy surface in Example 1 before and after 24 hours of acidic salt spray exposure. (a) is the secondary electron morphology before corrosion; (b) is the secondary electron morphology after corrosion; (c) is the backscattered electron morphology before corrosion; and (d) is the backscattered electron morphology after corrosion.

[0109] Depend on Figure 5 It can be seen that the multi-layer anti-corrosion coating on the surface of the magnesium alloy in Example 1 does not expose the magnesium alloy substrate after being corroded by acidic salt spray for 24 hours.

[0110] Figure 6 SEM images of the single-layer Ta coating on the magnesium alloy in Comparative Example 2 before and after 24 hours of acidic salt spray exposure. (a) is the secondary electron morphology before corrosion; (b) is the secondary electron morphology after corrosion; (c) is the backscattered electron morphology before corrosion; and (d) is the backscattered electron morphology after corrosion.

[0111] Depend on Figure 6 It can be seen that the magnesium alloy substrate is exposed after the single-layer Ta coating on the surface of the magnesium alloy in Comparative Example 2 is corroded by acidic salt spray for 24 hours.

[0112] Through the above data analysis, it can be seen that the multi-layer anti-corrosion coating on the surface of the magnesium alloy in Example 1 of the present invention can effectively suppress defects in the coating, prevent the generation of corrosion cavities and cracks, protect the base magnesium alloy from corrosion during the acidic salt spray process, and improve the overall corrosion resistance of the magnesium alloy.

[0113] Test 3: Effect of different thickness ratios of Ta layer and ZrN layer on coating performance.

[0114] The hardness and corrosion resistance of the Ta / ZrN multilayer corrosion-resistant coatings prepared in Examples 1 to 4, the single-layer ZrN coating prepared in Comparative Example 1, and the single-layer Ta coating prepared in Comparative Example 2 were analyzed. The results are shown in Tables 2 and Figure 7 shown.

[0115] Table 2 Influence of different thickness ratios of Ta layer and ZrN layer on coating performance

[0116]

[0117] The analysis results in Table 2 show that the hardness of the prepared coating gradually increases with the increase of the thickness of the ZrN layer, and the corrosion resistance also varies with the change of the thickness ratio of the ZrN layer and the Ta layer.

[0118] Figure 7 The SEM images of the magnesium alloy surfaces with different coatings in Example 1 to Example 4 and Comparative Example 1 to Comparative Example 2 after 24 hours of acid salt spray are shown in the following figures. In the figures, (a) is the backscattered electron morphology image of the coating in Comparative Example 2; (b) is the backscattered electron morphology image of the coating in Comparative Example 1; (c) is the backscattered electron morphology image of the coating in Example 2; (d) is the backscattered electron morphology image of the coating in Example 3; (e) is the backscattered electron morphology image of the coating in Example 4; and (f) is the backscattered electron morphology image of the coating in Example 1.

[0119] The backscattered electron morphology images of the coating surfaces after 24 hours of acid salt spray show that, as shown in Figure 7 (a) of FIG. 1, the single-layer Ta coating is almost entirely corroded to the substrate within 24 hours, showing poor corrosion resistance. As shown in Figure 7 (b) of FIG. 1, the single-layer ZrN layer can improve the hardness of the coating, but a large number of columnar crystals allow the corrosion medium to corrode to the substrate, showing poor corrosion resistance.

[0120] Figure 7 As shown in (c) to (f) of FIG. 1, the Ta / ZrN multilayer coating surface has only a few pitting holes, the corrosion resistance is improved, and the number of pitting holes changes with the change of the thickness ratio of the different Ta layer and ZrN layer.

[0121] The above analysis shows that, compared with Comparative Example 1 and Comparative Example 2, the method of the embodiments of the present application can effectively adjust the hardness, toughness, internal stress and corrosion resistance of the coating by changing the thickness ratio of the Ta layer and the ZrN layer.

[0122] The above is only a preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A multi-layer anti-corrosion coating on the surface of a magnesium alloy, characterized in that: The multi-layer anti-corrosion coating comprises a Zr layer and a Ta / ZrN multi-layer structure layer; The Zr layer is deposited on the surface of the substrate; the substrate is a magnesium alloy; The Ta / ZrN multilayer structure layer includes ZrN layers and Ta layers alternately deposited on the surface of the Zr layer; the thickness ratio of the Ta layer to the ZrN layer is 1:0.2-5; The total thickness of the Ta / ZrN multilayer structure layer is 1 μm to 20 μm; The outermost layer of the Ta / ZrN multilayer structure is a ZrN layer.

2. A method for preparing a multi-layer anti-corrosion coating on a magnesium alloy surface as claimed in claim 1, characterized in that: The following steps are involved: A Zr layer is deposited on the substrate surface using a magnetron sputtering process; Then, ZrN layers and Ta layers are alternately deposited on the surface of the Zr layer to form a Ta / ZrN multilayer structure layer; The substrate is a magnesium alloy; The thickness ratio of the Ta layer to the ZrN layer is 1:0.2-5.

3. The method for preparing a multi-layer anti-corrosion coating on a magnesium alloy surface according to claim 2, characterized in that: The specific preparation method comprises the following steps: Place the Zr target and the Ta target at the sputtering target position respectively, and place the substrate on the sample stage; after evacuating the vacuum, introduce argon gas, apply a negative bias voltage to the substrate, and clean the substrate surface by glow sputtering; Argon gas is introduced to magnetron sputter a Zr target, and a negative bias voltage is applied to the substrate to form ion bombardment to obtain a Zr layer; Argon and nitrogen are introduced to magnetron sputter a Zr target, and a negative bias is applied to the substrate to form ion bombardment to obtain a ZrN layer; Argon gas is introduced to magnetron sputter a Ta target, and a negative bias voltage is applied to the substrate to form ion bombardment to obtain a Ta layer; Repeat the preparation steps of the ZrN layer and the Ta layer to form a Ta / ZrN multilayer structure layer on the surface of the Zr layer to obtain a multilayer anti-corrosion coating.

4. The method for preparing a multi-layer anti-corrosion coating on a magnesium alloy surface according to claim 3, characterized in that: The specific method of cleaning the substrate surface by glow sputtering is as follows: Evacuate to a vacuum degree of less than 5×10 -3 After Pa, argon gas is introduced, the vacuum degree is controlled at 0.1Pa~0.4Pa, and a bias voltage of -200V~-600V is applied to the substrate to make the gas glow discharge, and the substrate surface is glow sputtered and cleaned by argon ions; the glow sputtering cleaning time is 10min~60min.

5. The method for preparing a multi-layer anti-corrosion coating on a magnesium alloy surface according to claim 3, characterized in that: The method for depositing the Zr layer is as follows: Argon gas is introduced, the vacuum degree is controlled at 0.1Pa to 0.4Pa, and a bias voltage of 0V to -100V is applied to the substrate to form ion bombardment to obtain a Zr layer; The method for depositing the Ta layer is as follows: Argon gas is introduced, the vacuum degree is controlled at 0.1Pa to 0.4Pa, and a bias voltage of 0V to -100V is applied to the substrate to form ion bombardment to obtain a Ta layer; The method for depositing the ZrN layer is as follows: Argon and nitrogen are introduced at a flow ratio of 1 to 5:1, the vacuum degree is controlled at 0.1 Pa to 0.4 Pa, and a bias voltage of 0 V to -100 V is applied to the substrate to form ion bombardment to obtain a ZrN layer.

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