Method for gradient deposition of wear-resistant coating on surface of aluminum alloy hub

Abstract

The invention discloses a method for gradient deposition of a wear-resistant coating on the surface of an aluminum alloy hub. The method specifically comprises the steps that S1, the aluminum alloy hub is pretreated; s2, roughening the surface of the aluminum alloy hub; s3, depositing a flexible layer on the surface of the aluminum alloy hub; s4, depositing a hard layer on the surface of the aluminum alloy hub; and S5, spraying a protective layer on the surface of the aluminum alloy hub. An AlCrNiCu flexible layer and an AlTiWN hard layer which are different in hardness are sequentially deposited on the surface of the aluminum alloy hub in a gradient mode through vacuum arc ion plating. Through gradient transition of hardness, the situation that the high-hardness AlTiWN hard layer is directly plated on the aluminum alloy hub, the hardness difference is large, and the internal stress is large, so that a plating layer cracks or is stripped is avoided. The AlTiWN hard layer is deposited on the AlCrNiCu flexible layer, the lattice matching degree of the AlTiWN hard layer is high, diffusion is good, the negative influence of ion plating metal liquid drops on the appearance of a plating layer can be effectively weakened, and therefore the high-quality wear-resisting plating layer is obtained.

Description

Technical Field

[0001] This invention relates to the field of functional coating technology, and in particular to a method for gradient deposition of a wear-resistant coating on the surface of an aluminum alloy wheel hub. Background Technology

[0002] The materials used in automotive wheels are gradually moving towards lightweight, high strength, and intelligent manufacturing. Aluminum alloys, with their advantages of light weight, rapid heat dissipation, high specific strength, high elasticity, and good shock absorption, have become the mainstream material for automotive wheels. For example, aluminum alloys such as 6061 and A356 are widely used as the main materials for aluminum alloy wheels in mid-to-high-end cars.

[0003] According to current manufacturing processes for aluminum alloy wheels, 6061 aluminum alloy is produced using a forging process, which results in wheels with higher strength and better performance. During forging, the aluminum alloy billet undergoes plastic deformation under pressure, making its internal structure more uniform, its grains finer, and its strength better. A356 aluminum alloy is produced using a low-pressure casting process, resulting in wheels with precise dimensions and a dense structure. Both forging and casting processes require subsequent CNC machining (precision numerical control) and surface treatment. Because aluminum alloy has low hardness and is easily worn, it is prone to scratches and corrosion in environments with high salt content, oil, rain, and sand. Therefore, aluminum alloy wheels require surface strengthening treatment. Surface strengthening treatment significantly improves surface hardness and wear resistance, prevents corrosion from dust, rain, and oil, prevents scratches from splashing sand, and also gives the wheels a uniform color, texture, and gloss, enhancing the overall aesthetics of the vehicle.

[0004] Existing surface treatment processes for aluminum alloy wheels mainly include electroplating and powder coating. Electroplating involves immersing the aluminum alloy wheel in an electroplating solution, where metal ions are deposited onto the wheel surface through electrolysis to form a metallic coating. This process generates significant pollution and is rarely used. Powder coating is currently the main surface treatment process for aluminum alloy wheels, offering advantages such as environmental friendliness, weather resistance, corrosion resistance, wear resistance, and stain resistance. However, because the powder coating used is an organic film-forming material, the coating has low hardness and limited wear resistance. Defects such as pinholes are prone to occur during thermosetting, and the adhesion to the aluminum alloy substrate is poor, posing a risk of peeling and discoloration. Protective layers using acrylic transparent powder or polyester transparent powder have poor wear resistance and protective properties.

[0005] Vacuum arc ion plating is a physical vapor deposition (PVD) coating technology that has been increasingly applied to the surface treatment of aluminum alloy wheels in recent years. The process primarily involves ionizing the cathode target metal material into a high-energy ion state. These metal ions are then accelerated by an electric field and bombard the wheel surface at high speed, depositing and penetrating to form a high-hardness alloy or ceramic coating. This type of coating is characterized by its bright color, density, high hardness, and strong adhesion. By controlling the coating time and rate, the coating thickness can be precisely controlled, avoiding unnecessary thickness deviations. While vacuum arc ion plating achieves a high-hardness coating, the significant difference in hardness between the coating and the substrate means that during micro-plastic deformation of the wheel, the coating is subjected to pressure, which can easily lead to warping, delamination, and even coating detachment. A typical technical problem is that when aluminum alloy wheel rims are coated with ordinary powder coating, severe scratches occur when the rim rubs against curbs. The coating has low hardness and poor wear resistance, but it doesn't peel off. When vacuum arc ion plating is used, severe scratches don't occur when the rim rubs against curbs, and the coating has high hardness and excellent wear resistance. However, if the scraping pressure is too great, the coating can peel off. Another technical problem is that although vacuum arc ion plating doesn't require a molten pool, it still produces a small amount of molten metal droplets. If these droplets deposit directly on the surface, they can easily cause surface defects, affecting the coating hardness. Summary of the Invention

[0006] Currently, forming a ceramic hard coating on the surface of aluminum alloy wheels can significantly improve hardness, and high hardness exhibits excellent wear resistance. However, hard coatings have poor plasticity and are prone to brittle cracking under external pressure. Aluminum alloy wheels also exhibit micro-elastic deformation characteristics, which can easily cause the high-hardness coating to detach from the substrate. Therefore, wear resistance under high stress loads is affected. In view of this, this invention utilizes a gradient deposition method for wear-resistant coatings, sequentially depositing coatings of different hardnesses on the surface of the aluminum alloy wheel, thus buffering the hardness of the coating and avoiding the brittle cracking problem of the hard coating.

[0007] The technical solution of this invention is:

[0008] A method for gradient deposition of a wear-resistant coating on the surface of an aluminum alloy wheel hub mainly includes the following steps:

[0009] S1. Pre-treatment of aluminum alloy wheels: The surface burrs of the surface-finished aluminum alloy wheels are polished off, and the wheels are immersed in alcohol and ultrasonically cleaned to remove oil stains.

[0010] S2. Surface roughening of aluminum alloy wheel hubs: The cleaned aluminum alloy wheel hubs are uniformly roughened using a sandblasting machine.

[0011] S3. Deposition of a flexible layer on the surface of an aluminum alloy wheel hub: An AlCrNiCu flexible layer is deposited on the surface of the wheel hub using vacuum arc ion plating; the atomic ratio of the AlCrNiCu flexible layer is 35-40 at% Al, 1-3 at% Cr, 17-20 at% Ni, and 40-48 at% Cu; the Vickers hardness of the AlCrNiCu flexible layer is 4-6 times that of the aluminum alloy wheel hub.

[0012] S4. Deposition of a hard layer on the surface of the aluminum alloy wheel hub: An AlTiWN hard layer is deposited on the surface of the flexible layer of the wheel hub using vacuum arc ion plating; the atomic percentages of the AlTiWN hard layer are 25-28 at% Al, 12-16 at% Ti, 3-5 at% W, and 52-57 at% N; the Vickers hardness of the AlTiWN hard layer is 10-15 times that of the aluminum alloy wheel hub.

[0013] S5. Protective coating on aluminum alloy wheel hub surface: Polysilazane transparent coating is sprayed onto the hard layer surface of the wheel hub and baked to form a transparent protective layer.

[0014] Preferably, the polishing is done using #2000 sandpaper to remove burrs.

[0015] Preferably, the sandblasting machine uses 200-mesh alumina as the abrasive and sprays the abrasive at a high speed with a pressure of 4-10 bar to uniformly roughen the surface of the aluminum alloy wheel hub; the surface roughness Ra reaches 0.8-1.2 μm through the uniform surface roughening. Increasing the surface roughness through surface roughness can improve the adhesion of the flexible layer.

[0016] Preferably, in step S3, the cathode target Al is deposited by vacuum arc ion plating. (35-40) Cr (1-3) Ni (17-20) Cu (40-48) Inside the vacuum coating chamber, the high temperature generated by arc discharge causes the target material to rapidly evaporate and ionize into ions. Under the influence of an electric field, these ions deposit and permeate onto the surface of a rotating aluminum alloy hub, forming a flexible layer. This AlCrNiCu flexible layer possesses moderate hardness, achieved by depositing the cathode target material Al... (35-40) Cr (1-3) Ni (17-20) Cu (40-48) The proportions of each atom are controlled to make the Vickers hardness of the AlCrNiCu flexible layer 4 to 6 times that of the Vickers hardness of aluminum alloy wheel hub.

[0017] Preferably, the atomic composition of the AlCrNiCu flexible layer in step S3 is 37.26 at% Al, 1.36 at% Cr, 18.62 at% Ni, and 42.76 at% Cu. The Ni and Cu in AlCrNiCu are relatively soft and have good bonding strength with aluminum. This flexible layer, as a transition layer, possesses certain hardness, wear resistance, and flexibility, and adheres firmly to the surface of the aluminum alloy wheel hub.

[0018] Preferably, the process control of vacuum arc ion plating in step S3 is as follows: first, the coating chamber is evacuated to 10... - 3 Pa, then argon gas is introduced until the vacuum degree is 10. -1 Pa; Arc needle contact arc discharge, arc current of 10-15A, target ionization; rotating aluminum alloy hub heated to 200-300℃, bias voltage of -50V to -100V applied, ionized metal particles accelerated bombard the surface of aluminum alloy hub, depositing to form a flexible layer; by controlling the deposition time, the thickness of the flexible layer reaches 20-30μm.

[0019] Preferably, the atomic composition of the AlTiWN hard layer in step S4 is 27.55 at% Al, 14.42 at% Ti, 3.35 at% W, and 54.68 at% N. The AlTiWN hard layer exhibits excellent hardness and wear resistance, and bonds well with the transitional AlCrNiCu flexible layer. Using Al, Ti, and W cathode targets, the targets are ionized into high-energy ion states in a nitrogen atmosphere, and deposited onto the surface of the flexible layer to form the AlTiWN hard layer. This hard layer is well-compatible with the flexible layer, forming a unified whole, and possesses high hardness, wear resistance, and corrosion resistance.

[0020] Preferably, the process control of vacuum arc ion plating in step S4 is as follows: the aluminum alloy wheel hub with the deposited flexible layer is transferred into the coating chamber, and a vacuum is drawn to 10... -3 Pa, then argon gas is introduced until the vacuum degree is 10. -2 Pa, then nitrogen gas is introduced to maintain a vacuum of 5-10 Pa; under nitrogen atmosphere, arc discharge is performed using an arc needle contact method, with Al target arc current of 20-25 A, Ti target arc current of 10-12 A, and W target arc current of 3-5 A. The evaporation rate of each target material is controlled by adjusting the power supply of each target; the rotating aluminum alloy hub is heated to 300-400℃, and a bias voltage of -100V to -200V is applied, ionized metal particles are accelerated to bombard the surface of the aluminum alloy hub, and a hard layer is deposited on the flexible layer; the thickness of the hard layer is made to 15-20 μm by controlling the deposition time.

[0021] By sequentially depositing a flexible layer and a hard layer on the surface of the aluminum alloy wheel hub, the transitional flexible layer increases the adhesion to the aluminum alloy wheel hub, and the AlTiWN hard layer bonds well with the transitional AlCrNiCu flexible layer. On the other hand, the AlCrNiCu flexible layer has a certain degree of flexibility compared to the AlTiWN hard layer. Through the gradient transition, the high-hardness AlTiWN hard layer is avoided from being directly plated on the aluminum alloy wheel hub, where the large hardness difference and high internal stress can lead to coating cracking or peeling.

[0022] During vacuum arc ion plating, metal droplets are inevitably generated. These droplets deposit on the surface, causing surface roughness and even internal defects. Conventionally, during the ionization of Al, Ti, and W targets in a nitrogen atmosphere, a small number of fine metal droplets are generated. Direct deposition of these droplets on the aluminum alloy wheel surface easily leads to surface roughness and coating defects. By depositing an AlTiWN hard layer on an AlCrNiCu flexible layer, which has a high degree of lattice matching and good diffusion, the negative impact of metal droplets on the coating appearance can be effectively mitigated.

[0023] Preferably, the polysilazane transparent coating is sprayed to a thickness of 10–15 μm, left to stand for 10–15 minutes, and then heat-cured in a curing chamber at 130–150°C for 1–2 hours to form a transparent protective layer. The polysilazane transparent coating, through heat curing, forms a ceramic coating with excellent transparency, hydrophobicity, oleophobicity, high hardness, and wear and scratch resistance, matching the hard layer. In particular, its excellent hydrophobicity and oleophobicity give the wheel hub an anti-fouling effect, effectively preventing oil, dust, dirt, and rainwater from adhering to the wheel hub during use, ensuring a clean surface over a long period.

[0024] In the field of aluminum alloy wheel surface treatment, technicians hope to improve the wear resistance and corrosion resistance of the wheel by increasing the hardness of the coating. Vacuum arc ion plating can form a high-hardness coating with excellent adhesion on the surface of aluminum alloy wheels, and the interface of the high-hardness ion plating layer can diffuse deep into the wheel, effectively improving the film adhesion performance. However, the hardness of the high-hardness ion plating layer differs from that of the aluminum alloy wheel by tens of times. When the aluminum alloy wheel exhibits micro-elastic deformation under load, the excessive hardness difference causes the hard coating to crack and peel off when the wheel is subjected to slight deformation under pressure. This invention uses a gradient deposition method to first deposit a relatively low-hardness flexible layer on the surface of the aluminum alloy wheel, and then further deposit a high-hardness hard layer. Through the transition of coatings with different hardnesses, the peeling off of the high-hardness coating when the aluminum alloy wheel undergoes slight deformation is avoided.

[0025] The present invention discloses a method for gradient deposition of a wear-resistant coating on the surface of an aluminum alloy wheel hub. Compared with the prior art, the advantages of this method are as follows:

[0026] 1. By using vacuum arc ion plating, a flexible layer and a hard layer are sequentially and gradually deposited on the surface of the aluminum alloy wheel hub. This gradient transition avoids the direct deposition of high-hardness coatings on the aluminum alloy wheel hub surface, which can cause micro-deformation and peeling of the coating due to excessive hardness differences and high internal stress.

[0027] 2. A flexible layer and a hard layer are sequentially deposited on the surface of the aluminum alloy wheel hub through vacuum arc ion plating. The transition of the flexible layer increases the bonding force with the aluminum alloy wheel hub.

[0028] 3. By selecting a suitable target material, AlTiWN and AlCrNiCu have a high degree of lattice matching, resulting in good diffusion when the AlTiWN hard layer is deposited on the AlCrNiCu flexible layer. This effectively mitigates the negative impact of molten metal droplets on the coating appearance. The protective layer is a ceramic coating formed by the thermosetting of polysilazane, which has good transparency, hydrophobicity, oleophobicity, high hardness, and wear and scratch resistance, matching the hard layer.

[0029] 4. The equipment used in the method of this invention is a single piece of equipment. The equipment technology is mature, and the thickness and uniformity of the coating can be precisely controlled through process control. It is easy to operate and the production environment is green and emission-free. Attached Figure Description

[0030] Figure 1 This is a simplified process flow diagram of a gradient deposition wear-resistant coating on the surface of an aluminum alloy wheel hub according to the present invention. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to specific examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1

[0033] S1. Pre-treatment of aluminum alloy wheels: The aluminum alloy wheels of A356 aluminum low-pressure casting precision machined are polished with #2000 sandpaper to remove burrs, and then immersed in alcohol and ultrasonically cleaned to remove oil stains.

[0034] S2. Surface roughening of aluminum alloy wheel hub: The cleaned aluminum alloy wheel hub is uniformly roughened using a sandblasting machine. 200-mesh aluminum oxide is used as the abrasive, and the abrasive is blasted at a high speed with a pressure of 5 bar (spray angle of 60°) to uniformly roughen the surface of the aluminum alloy wheel hub. The sandblasting time is 2 minutes. The roughness Ra after uniform roughening reaches 0.8 to 1.0 μm.

[0035] S3. Deposition of a flexible layer on the surface of aluminum alloy wheel hubs: Vacuum arc ion plating is used, with AlCrNiCu as the cathode target material, and the atomic percentages are 37.26 at% Al, 1.36 at% Cr, 18.62 at% Ni, and 42.76 at% Cu. The coating chamber is first evacuated to 10... -3 Pa, then argon gas is introduced until the vacuum degree is 10. -1 Pa; plug the mounting holes of the aluminum alloy wheel hub, heat to 300℃, rotate uniformly at 20 rpm, and apply a bias voltage of -100V; use arc needle contact arc discharge with an arc current of 15A to ionize the target material; the ionized metal particles accelerate and bombard the surface of the aluminum alloy wheel hub, depositing to form a flexible layer; deposit for 22 minutes to achieve a flexible layer thickness of 25μm;

[0036] S4. Deposition of a hard layer on the surface of the aluminum alloy wheel hub: Vacuum arc ion plating is used, with Al, Ti, and W targets as cathode materials. The aluminum alloy wheel hub with the flexible layer deposited is transferred into the coating chamber, and a vacuum of 10 is applied. -3 Pa, then argon gas is introduced until the vacuum degree is 10. -2 The vacuum level was maintained at 5 Pa by introducing nitrogen gas. The aluminum alloy hub was heated to 400℃ and a bias voltage of -150V was applied. It was rotated uniformly at a speed of 20 rpm. Arc discharge was performed in a nitrogen atmosphere using a needle-type contact method. The evaporation rate of each target material was controlled by adjusting the power supply of each target. The arc current of Al target was 23A, the arc current of Ti target was 10A, and the arc current of W target was 4A. The target material was ionized into a high-energy ion state in a nitrogen atmosphere and deposited onto the surface of the flexible layer to form an AlTiWN hard layer. The deposition time was 32 min, resulting in a hard layer thickness of 20 μm. The atomic percentages of the AlTiWN hard layer were 27.55 at% Al, 14.42 at% Ti, 3.35 at% W, and 54.68 at% N.

[0037] S5. Protective coating on aluminum alloy wheel hub surface: Spray polysilazane transparent coating on the hard layer surface of the wheel hub with a coating thickness of 15μm, let it stand for 15min, and then send it into the curing box for heat curing at 150℃ for 1h to form a transparent protective layer.

[0038] Example 2

[0039] S1. Pre-treatment of aluminum alloy wheel hub: The 6061 aluminum forged and precision machined aluminum alloy wheel hub is deburred by #2000 sandpaper, and then immersed in alcohol and ultrasonically cleaned to remove oil stains.

[0040] S2. Surface roughening of aluminum alloy wheel hub: The cleaned aluminum alloy wheel hub is uniformly roughened using a sandblasting machine. 200-mesh aluminum oxide is used as the abrasive, and the abrasive is blasted at a high speed with a pressure of 5 bar (spray angle of 60°) to uniformly roughen the surface of the aluminum alloy wheel hub. The sandblasting time is 3 minutes. The roughness Ra after uniform roughening reaches 1.0 to 1.2 μm.

[0041] S3. Deposition of a flexible layer on the surface of aluminum alloy wheel hubs: Vacuum arc ion plating is used, with AlCrNiCu as the cathode target material, and the atomic percentages are 37.26 at% Al, 2.77 at% Cr, 18.62 at% Ni, and 41.35 at% Cu. The coating chamber is first evacuated to 10... -3 Pa, then argon gas is introduced until the vacuum degree is 10. -1 Pa; plug the mounting holes of the aluminum alloy wheel hub, heat to 300℃, rotate uniformly at 20 rpm, and apply a bias voltage of -100V; use arc needle contact arc discharge with an arc current of 15A to ionize the target material; the ionized metal particles accelerate and bombard the surface of the aluminum alloy wheel hub to deposit and form a flexible layer; deposit for 20 minutes to make the thickness of the flexible layer reach 25μm;

[0042] S4. Deposition of a hard layer on the surface of the aluminum alloy wheel hub: Vacuum arc ion plating is used, with Al, Ti, and W targets as cathode materials. The aluminum alloy wheel hub with the flexible layer deposited is transferred into the coating chamber, and a vacuum of 10 is applied. -3 Pa, then argon gas is introduced until the vacuum degree is 10. -2 The vacuum level was maintained at 10 Pa by introducing nitrogen gas. The aluminum alloy hub was heated to 400℃ and a bias voltage of -150V was applied. It was rotated uniformly at a speed of 20 rpm. Arc discharge was performed in a nitrogen atmosphere using a needle-type contact method. The evaporation rate of each target material was controlled by adjusting the power supply of each target. The arc current of Al target was 20A, the arc current of Ti target was 12A, and the arc current of W target was 5A. The target material was ionized into a high-energy ion state in a nitrogen atmosphere and deposited onto the surface of the flexible layer to form an AlTiWN hard layer. The deposition time was 35 min, resulting in a hard layer thickness of 20 μm. The atomic percentages of the AlTiWN hard layer were 25.33 at% Al, 15.16 at% Ti, 4.03 at% W, and 55.48 at% N.

[0043] S5. Protective coating on aluminum alloy wheel hub surface: Spray polysilazane transparent coating on the hard layer surface of the wheel hub with a coating thickness of 15μm, let it stand for 15min, and then send it into the curing box for heat curing at 150℃ for 1h to form a transparent protective layer.

[0044] Comparative Example 1

[0045] S1. Pre-treatment of aluminum alloy wheels: The aluminum alloy wheels of A356 aluminum low-pressure casting precision machined are polished with #2000 sandpaper to remove burrs, and then immersed in alcohol and ultrasonically cleaned to remove oil stains.

[0046] S2. Surface roughening of aluminum alloy wheel hub: The cleaned aluminum alloy wheel hub is uniformly roughened using a sandblasting machine. 200-mesh aluminum oxide is used as the abrasive, and the abrasive is blasted at a high speed with a pressure of 5 bar (spray angle of 60°) to uniformly roughen the surface of the aluminum alloy wheel hub. The sandblasting time is 2 minutes. The roughness Ra after uniform roughening reaches 0.8 to 1.0 μm.

[0047] S3. Deposition of a hard layer on the surface of the aluminum alloy wheel hub: Vacuum arc ion plating is used, with Al, Ti, and W targets as cathode materials. The aluminum alloy wheel hub is transferred into the coating chamber, and a vacuum of 10 is applied. -3 Pa, then argon gas is introduced until the vacuum degree is 10. -2 Pa, then nitrogen gas is introduced to maintain a vacuum of 5 Pa; the aluminum alloy hub is heated to 400℃, a bias voltage of -150V is applied, and it is rotated uniformly at a speed of 20 rpm; arc discharge is performed in a nitrogen atmosphere using an arc needle contact method, and the evaporation rate of each target material is controlled by adjusting the power supply of each target. The arc current of Al target is 23A, the arc current of Ti target is 10A, and the arc current of W target is 4A; the target material is ionized into a high-energy ion state in a nitrogen atmosphere and deposited and penetrated onto the surface of the aluminum alloy hub. The deposition time is 32 min, and the atomic percentages of the AlTiWN hard layer are 27.55 at% Al, 14.42 at% Ti, 3.35 at% W, and 54.68 at% N;

[0048] S4. Protective coating on aluminum alloy wheel hub surface: Spray polysilazane transparent coating on the hard layer surface of the wheel hub with a coating thickness of 15μm, let it stand for 15min, and then send it into the curing box for heat curing at 150℃ for 1h to form a transparent protective layer.

[0049] Under the same conditions as in Example 1, no pre-ion-plated flexible layer was used.

[0050] Comparative Example 2

[0051] S1. Pre-treatment of aluminum alloy wheel hub: The 6061 aluminum forged and precision machined aluminum alloy wheel hub is deburred by #2000 sandpaper, and then immersed in alcohol and ultrasonically cleaned to remove oil stains.

[0052] S2. Surface roughening of aluminum alloy wheel hub: The cleaned aluminum alloy wheel hub is uniformly roughened using a sandblasting machine. 200-mesh aluminum oxide is used as the abrasive, and the abrasive is blasted at a high speed with a pressure of 5 bar (spray angle of 60°) to uniformly roughen the surface of the aluminum alloy wheel hub. The sandblasting time is 3 minutes. The roughness Ra after uniform roughening reaches 1.0 to 1.2 μm.

[0053] S3. Deposition of a flexible layer on the surface of aluminum alloy wheel hubs: Vacuum arc ion plating is used, with AlCrNiCu as the cathode target material, and the atomic percentages are 37.26 at% Al, 2.77 at% Cr, 18.62 at% Ni, and 41.35 at% Cu. The coating chamber is first evacuated to 10... -3 Pa, then argon gas is introduced until the vacuum degree is 10. -1 Pa; plug the mounting holes of the aluminum alloy wheel hub, heat to 300℃, rotate uniformly at 20 rpm, and apply a bias voltage of -100V; use arc needle contact arc discharge with an arc current of 15A to ionize the target material; the ionized metal particles accelerate and bombard the surface of the aluminum alloy wheel hub to deposit and form a flexible layer; deposit for 20 minutes to make the thickness of the flexible layer reach 25μm;

[0054] S4. Deposition of a hard layer on the surface of the aluminum alloy wheel hub: Vacuum arc ion plating is used, with Al, Ti, and W targets as cathode materials. The aluminum alloy wheel hub with the flexible layer deposited is transferred into the coating chamber, and a vacuum of 10 is applied. -3 Pa, then argon gas is introduced until the vacuum degree is 10. -2 The vacuum level was maintained at 10 Pa by introducing nitrogen gas. The aluminum alloy hub was heated to 400℃ and a bias voltage of -150V was applied. It was rotated uniformly at a speed of 20 rpm. Arc discharge was performed in a nitrogen atmosphere using a needle-type contact method. The evaporation rate of each target material was controlled by adjusting the power supply of each target. The arc current of Al target was 35A, the arc current of Ti target was 5A, and the arc current of W target was 3A. The target material was ionized into a high-energy ion state in a nitrogen atmosphere and deposited onto the surface of the flexible layer to form an AlTiWN hard layer. The deposition time was 35 min, and the thickness of the hard layer reached 20 μm. The atomic percentages of the AlTiWN hard layer were 32.45 at% Al, 10.22 at% Ti, 2.14 at% W, and 55.19 at% N.

[0055] S5. Protective coating on aluminum alloy wheel hub surface: Spray polysilazane transparent coating on the hard layer surface of the wheel hub with a coating thickness of 15μm, let it stand for 15min, and then send it into the curing box for heat curing at 150℃ for 1h to form a transparent protective layer.

[0056] By adjusting the process, the hardness of the hard layer is significantly reduced.

[0057] Example of effect

[0058] 1. Microhardness test

[0059] The initial hardness, hardness of the deposited flexible layer, and hardness of the deposited hard layer of the aluminum alloy wheel hub were tested using microhardness testing. A diamond pyramid indenter with a 130° indenter was used, with a pressure load of 0.3 kgf and a loading and holding time of 10 s. The Vickers hardness (HV) test results are shown in Table 1. The surface roughness Ra of the wheel hub after the hard layer was deposited was also measured and is shown in Table 1.

[0060] Table 1:

[0061]

[0062] 2. Test the surface wear resistance of the wheel hub after the hard coating is deposited.

[0063] Referring to the test conditions of the copper accelerated acetic acid salt spray test (CASS) in GB / T 10125-2021 (Artificial Atmosphere Corrosion Test - Salt Spray Test), the salt spray resistance of the wheel hub was tested to evaluate the surface wear resistance of the wheel hub after the hard coating was deposited. Furthermore, the wheel hub was loaded, causing a shape change exceeding 10% of its original dimensions, and the CASS salt spray resistance after hard coating deformation was tested. The degree of coating corrosion was recorded after 480 hours. The results are shown in Table 2.

[0064] To further investigate the wear resistance of the hard layer after copper-accelerated acetic acid salt spray corrosion, high-hardness silicon nitride was used as the abrasive. A force of 50 N was applied, and the hard layer, after 480 hours of corrosion, was polished for 10 minutes at a speed of 300 r / min. The peeling and detachment of the coating were observed. The results are shown in Table 2.

[0065] Table 2:

[0066]

[0067]

[0068] 3. Test the scratch-scraping grade of the deposited hard layer.

[0069] The adhesion strength of the hard coating was tested using the scratch test. Referring to GB / T 9286-2021 (Cross-cut test for paints and varnishes to evaluate the adhesion strength of coatings), a special cross-cut knife was used to make a grid-like cut on the coating surface until it penetrated the coating to the substrate surface. Standard adhesive tape was then applied and quickly peeled off, and the peeling of the coating at the cut edges was observed to assess the adhesion level. Level 0: No peeling at the cut edges; Level 1: Peeling area ≤ 5%; Level 2: Peeling area 5%-15%; Level 3: Peeling area 15%-35%; Level 4: Peeling area 35%-65%; Level 5: Peeling area > 65%. The test results are shown in Table 3.

[0070] At the same time, the surface was tapped with a pointed hammer to observe the damage to the hard layer. The test results are shown in Table 3.

[0071] Table 3:

[0072] Test metrics Evaluation of adhesion grade of deposited hard layer Surface phenomena after tapping of deposited hard layers Example 1 Level 1 Minor scratches appeared, but no peeling. Example 2 Level 1 Minor scratches appeared, but no peeling. Comparative Example 1 Level 3 Micro-scratches and peeling appeared. Comparative Example 2 Level 2 Micro-marks and cracks appear

[0073] The test results of the various effect examples above show that the present invention, by gradient deposition of coatings with different hardness, enables the surface of aluminum alloy wheels to have high hardness and high wear resistance. While maintaining high hardness, the coating has strong adhesion and will not fall off due to external impact or wheel deformation. The wear-resistant coating on the wheel surface has significant anti-extrusion performance and is fully adapted to the micro-elasticity characteristics of aluminum alloy wheels.

[0074] Furthermore, it should be understood that although the embodiments have been described in detail, the specific process parameters vary depending on the vacuum arc ion plating equipment. Those skilled in the art will understand that the process parameters can be adjusted to achieve the technical objectives without departing from the inventive concept and spirit. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for gradient deposition of a wear-resistant coating on the surface of an aluminum alloy wheel hub, characterized in that, The main steps include: S1. Pre-treatment of aluminum alloy wheels: The surface burrs of the surface-finished aluminum alloy wheels are polished off, and the wheels are immersed in alcohol and ultrasonically cleaned to remove oil stains. S2. Surface roughening of aluminum alloy wheel hubs: The cleaned aluminum alloy wheel hubs are uniformly roughened using a sandblasting machine. S3. Deposition of a flexible layer on the surface of an aluminum alloy wheel hub: An AlCrNiCu flexible layer is deposited on the surface of the wheel hub using vacuum arc ion plating; the atomic ratio of the AlCrNiCu flexible layer is 35-40 at% Al, 1-3 at% Cr, 17-20 at% Ni, and 40-48 at% Cu; the Vickers hardness of the AlCrNiCu flexible layer is 4-6 times that of the aluminum alloy wheel hub. S4. Deposition of a hard layer on the surface of the aluminum alloy wheel hub: An AlTiWN hard layer is deposited on the surface of the flexible layer of the wheel hub using vacuum arc ion plating; the atomic percentages of the AlTiWN hard layer are 25-28 at% Al, 12-16 at% Ti, 3-5 at% W, and 52-57 at% N; the Vickers hardness of the AlTiWN hard layer is 10-15 times that of the aluminum alloy wheel hub. S5. Protective coating on aluminum alloy wheel hub surface: Polysilazane transparent coating is sprayed onto the hard layer surface of the wheel hub and baked to form a transparent protective layer.

2. The method for gradient deposition of a wear-resistant coating on the surface of an aluminum alloy wheel hub according to claim 1, characterized in that, The sanding process uses #2000 sandpaper to remove burrs.

3. The method for gradient deposition of a wear-resistant coating on the surface of an aluminum alloy wheel hub according to claim 1, characterized in that, The sandblasting machine uses 200-mesh alumina as the abrasive and sprays the abrasive at a high speed with a pressure of 4-10 bar to uniformly roughen the surface of the aluminum alloy wheel hub; the uniform surface roughening treatment makes the surface roughness Ra reach 0.8-1.2 μm.

4. The method for gradient deposition of a wear-resistant coating on the surface of an aluminum alloy wheel hub according to claim 1, characterized in that, The atomic percentages of the AlCrNiCu flexible layer in step S3 are 37.26 at% Al, 1.36 at% Cr, 18.62 at% Ni, and 42.76 at% Cu.

5. The method for gradient deposition of a wear-resistant coating on the surface of an aluminum alloy wheel hub according to claim 1, characterized in that, The process control for vacuum arc ion plating in step S3 is as follows: first, the coating chamber is evacuated to 10... -3 Pa, then argon gas is introduced until the vacuum degree is 10. -1 Pa; Arc needle contact arc discharge, arc current is 10-15A, target material ionization; rotating aluminum alloy hub is heated to 200-300℃, bias voltage is applied from -50V to -100V, ionized metal particles accelerate to bombard the surface of aluminum alloy hub, deposit to form a flexible layer.

6. The method for gradient deposition of a wear-resistant coating on the surface of an aluminum alloy wheel hub according to claim 1, characterized in that, The thickness of the flexible layer is 20–30 μm.

7. The method for gradient deposition of a wear-resistant coating on the surface of an aluminum alloy wheel hub according to claim 1, characterized in that, The atomic percentages of the AlTiWN hard layer in step S4 are 27.55 at% Al, 14.42 at% Ti, 3.35 at% W, and 54.68 at% N.

8. The method for gradient deposition of a wear-resistant coating on the surface of an aluminum alloy wheel hub according to claim 1, characterized in that, The process control for vacuum arc ion plating in step S4 is as follows: the aluminum alloy wheel hub with the deposited flexible layer is transferred into the coating chamber, and a vacuum is drawn to 10... -3 Pa, then argon gas is introduced until the vacuum degree is 10. -2 Pa, then nitrogen gas is introduced to maintain a vacuum of 5-10 Pa; in the nitrogen atmosphere, arc discharge is performed using the arc needle contact method, with Al target arc current of 20-25 A, Ti target arc current of 10-12 A, and W target arc current of 3-5 A. The evaporation rate of each target material is controlled by adjusting the power supply of each target; the rotating aluminum alloy hub is heated to 300-400℃, and a bias voltage of -100V to -200V is applied. Ionized metal particles are accelerated to bombard the surface of the aluminum alloy hub, depositing a hard layer on the flexible layer.

9. The method for gradient deposition of a wear-resistant coating on the surface of an aluminum alloy wheel hub according to claim 1, characterized in that, The thickness of the hard layer is 15–20 μm.

10. The method for gradient deposition of a wear-resistant coating on the surface of an aluminum alloy wheel hub according to claim 1, characterized in that, The polysilazane transparent coating is sprayed to a thickness of 10-15 μm, left to stand for 10-15 minutes, and then placed in a curing chamber for heat curing at 130-150℃ for 1-2 hours to form a transparent protective layer.

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