Method for improving film-substrate binding force between aluminum alloy and PVD coating

Abstract

The invention provides a method for improving the film-substrate binding force between an aluminum alloy and a PVD (Physical Vapor Deposition) coating. The method comprises the following steps that (1) an aluminum alloy matrix is sequentially subjected to sand blasting treatment, electrolytic polishing treatment, cleaning treatment and vacuum drying, and a pretreated matrix is obtained; (2) putting the pretreated substrate obtained in the step (1) into a PVD (Physical Vapor Deposition) furnace, and then sequentially carrying out glow cleaning and PVD coating treatment; the PVD coating treatment comprises the step of depositing a transition layer, a functional layer and a color layer on the surface of the pretreated substrate in sequence. According to the method provided by the invention, the problem that the hardness difference between the aluminum alloy matrix and the PVD coating is large is solved by combining the sand blasting treatment and the unique PVD coating treatment; and meanwhile, the roughness of the pretreated base body is controlled through electrolytic polishing, the film-base binding force between the PVD coating and the aluminum alloy base body is further improved, and meanwhile the corrosion resistance and the scratch resistance of the PVD coating are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal material treatment, and particularly relates to a method for improving the film-substrate adhesion between aluminum alloy and PVD coating. Background Art

[0002] Aluminum alloy has excellent comprehensive mechanical properties, such as high specific strength and high specific stiffness, and is widely used in many fields such as aerospace, rail transit, architectural decoration, and consumer electronics. However, aluminum alloy is soft and is prone to scratching, abrasion, etc. during use, affecting its appearance. Therefore, it is necessary to perform surface treatment on aluminum alloy to improve its surface hardness.

[0003] Currently, for the 3C consumer electronics industry, the main processes for surface treatment of Al alloy are anodic oxidation and micro-arc oxidation. Although the above processes can improve the surface hardness and corrosion resistance of Al alloy to a certain extent, there are the following problems: (1) The anodic oxidation / micro-arc oxidation process is complex and uses various chemicals, resulting in obvious environmental pollution, which does not conform to the concept of green and environmental protection development. (2) There are a large number of nanoscale pores on the surface of the anodic oxidation / micro-arc oxidation process, and it is necessary to perform sealing treatment on them during subsequent use, and the process flow is complex.

[0004] Physical vapor deposition process (PVD) is a green and environmentally friendly surface treatment technology. The ceramic coatings (nitride coatings of transition metals, carbide coatings, etc.) prepared by PVD have advantages such as high surface hardness, good chemical stability, high corrosion resistance, and good oxidation resistance, and are widely used in electronics, automobiles, household appliances, cutting tools, molds, etc. However, due to the low hardness of Al alloy, when directly depositing PVD coating on the surface of Al alloy, there are significant differences in the physical properties (large hardness difference) between the PVD ceramic coating and Al alloy, and the film-substrate adhesion of the PVD coating is poor, weakening the protective effect (scratch resistance, wear resistance, etc.) of the PVD film layer.

[0005] To alleviate the differences in physical properties (especially hardness values) between the ceramic coating and the Al substrate and improve the hardness of the aluminum alloy, heat treatment is often carried out on the Al alloy. The conventional heat treatment process is solution treatment + artificial aging treatment. For example, Patent CN110438421A discloses a strengthening method of "solution + PVD", where the solution treatment of the Al alloy is carried out in a PVD furnace. Although the above method can solve the problem of large hardness difference between the aluminum substrate and the PVD coating to a certain extent, it has problems such as high energy consumption, long operation time, and complex process. At the same time, there is also a method of preparing a transition layer on the surface of the aluminum substrate to improve the sudden change in hardness between the substrate and the PVD film. For example, Patent CN 218262757U discloses a process of chemically depositing different zinc, copper, nickel, and chromium metal layers layer by layer on the surface of the aluminum alloy. Although the above method can solve the problems of large hardness difference between the substrate and the PVD ceramic layer and the mismatch between hardness and scratch resistance requirements, there are still problems such as poor working environment and the treatment of metal plating solutions, and poor environmental protection.

[0006] Therefore, it is necessary to develop a new process plan for depositing PVD ceramic coatings on the surface of aluminum alloys. Summary of the Invention

[0007] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a method for improving the film-substrate adhesion between aluminum alloy and PVD coating. The method improves the surface hardness of the aluminum alloy through sandblasting treatment, and at the same time controls the deposition process time and the alternating deposition of metal / ceramic layers during the PVD coating process to solve the problem of large hardness difference between the aluminum alloy and the PVD coating, improve the film-substrate adhesion, and improve the corrosion resistance and scratch resistance of the coating.

[0008] To achieve the purpose of this invention, the following technical solutions are adopted:

[0009] The present invention provides a method for improving the film-substrate adhesion between aluminum alloy and PVD coating, and the method includes the following steps:

[0010] (1) The aluminum alloy substrate is successively subjected to sandblasting treatment, electrolytic polishing treatment, cleaning treatment, and vacuum drying to obtain a pretreated substrate;

[0011] (2) The pretreated substrate obtained in step (1) is placed in a PVD furnace, and then glow cleaning and PVD coating treatment are carried out successively;

[0012] The PVD coating treatment includes successively depositing a transition layer, a functional layer, and a color layer on the surface of the pretreated substrate.

[0013] In the present invention, the surface hardness of the aluminum alloy substrate is improved by sandblasting treatment. Meanwhile, during the PVD coating treatment stage, the alternating deposition of metal / ceramic layers is achieved by controlling the deposition process, solving the problem of a large difference in hardness between the aluminum alloy substrate and the PVD coating. In addition, the present invention controls the roughness of the pretreated substrate by electrolytic polishing, further improving the film-substrate adhesion between the PVD coating and the aluminum alloy substrate, while enhancing its corrosion resistance and scratch resistance. In summary, through the synergistic effect of sandblasting treatment, electrolytic polishing and PVD coating treatment, the present invention further improves the film-substrate adhesion between the aluminum alloy and the PVD coating.

[0014] As a preferred technical solution of the present invention, the abrasive used in the sandblasting treatment in step (1) includes any one or a combination of at least two of emery, glass beads, white fused alumina, garnet sand or quartz sand. Typical but non-limiting combinations include: a combination of emery, white fused alumina and quartz sand, a combination of glass beads and garnet sand, or a combination of emery, glass beads, white fused alumina, garnet sand and quartz sand.

[0015] Preferably, the mesh number of the abrasive used in the sandblasting treatment in step (1) is 200-600 mesh. For example, it can be 200 mesh, 300 mesh, 400 mesh, 500 mesh or 600 mesh, etc., but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0016] Preferably, the time of the sandblasting treatment in step (1) is 20-40 min. For example, it can be 20 min, 25 min, 30 min, 35 min or 40 min, etc., but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0017] Preferably, the pressure of the sandblasting treatment in step (1) is 3-5 bar. For example, it can be 3 bar, 3.5 bar, 4 bar, 4.5 bar or 5 bar, etc., but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0018] The present invention improves the hardness of the aluminum alloy by sandblasting treatment. The reason is that during the sandblasting process, the sand grains ejected at high speed will impact the surface of the aluminum alloy, causing micro-deformation on its surface, thereby generating compressive stress on the surface of the aluminum alloy and improving the surface hardness of the aluminum alloy; thus reducing the hardness difference between the aluminum alloy and the PVD coating and achieving the purpose of improving the film-substrate adhesion.

[0019] As a preferred technical solution of the present invention, a cleaning treatment is further included before the electrolytic polishing treatment in step (1).

[0020] Preferably, the electrolyte used in the electrolytic polishing treatment in step (1) includes concentrated phosphoric acid and ethanol.

[0021] Preferably, the concentration of the concentrated phosphoric acid is 80-90 wt%, for example, it can be 80 wt%, 82 wt%, 84 wt%, 86 wt%, 88 wt% or 90 wt%, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0022] Preferably, the concentration of the ethanol is ≥99 wt%, for example, it can be 99 wt%, 99.1 wt%, 99.2 wt%, 99.3 wt%, 99.4 wt% or 99.5 wt%, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0023] Preferably, the volume ratio of the concentrated phosphoric acid to the ethanol is 1:1-2, for example, it can be 1:1, 1:1.2, 1:1.4, 1:1.6, 1:1.8 or 1:2, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0024] Preferably, the voltage of the electrolytic polishing treatment in step (1) is 10-20 V, for example, it can be 10 V, 12 V, 14 V, 16 V, 18 V or 20 V, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0025] Preferably, the time of the electrolytic polishing treatment in step (1) is 5-10 min, for example, it can be 5 min, 6 min, 7 min, 8 min, 9 min or 10 min, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0026] Preferably, the cleaning treatment in step (1) includes ultrasonic cleaning.

[0027] Preferably, the temperature of the vacuum drying in step (1) is 70-90 °C, for example, it can be 70 °C, 74 °C, 78 °C, 82 °C, 86 °C or 90 °C, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0028] Preferably, the time of the vacuum drying in step (1) is 50-70 min, for example, it can be 50 min, 54 min, 58 min, 62 min, 66 min or 70 min, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0029] Preferably, the roughness of the pretreated substrate in step (1) is 0.01-0.2 μm, for example, it can be 0.01 μm, 0.05 μm, 0.1 μm, 0.15 μm or 0.2 μm, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0030] It should be noted that the cleaning processes before and after the electrolytic polishing treatment of the present invention are both ultrasonic treatments to remove impurities such as grease on the surface of the aluminum alloy. The cleaning steps are as follows: The aluminum alloy is sequentially placed in a degreasing tank, an alkali cleaning tank, a neutralizing tank, and a pure water tank for ultrasonic cleaning; the treatment time of the aluminum alloy substrate in each cleaning tank is 3 to 5 minutes, for example, it can be 3 minutes, 3.4 minutes, 3.8 minutes, 4.2 minutes, 4.6 minutes, or 5 minutes, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0031] As a preferred technical solution of the present invention, the voltage of the glow cleaning in step (2) is 600 - 800V, for example, it can be 600V, 640V, 680V, 720V, 760V, or 800V, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0032] Preferably, the duty cycle of the glow cleaning in step (2) is 45 - 55%, for example, it can be 45%, 47%, 49%, 51%, 53%, or 55%, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0033] Preferably, the temperature of the glow cleaning in step (2) < 80°C, for example, it can be 78°C, 75°C, 70°C, 65°C, 60°C, 55°C, or 50°C, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0034] Preferably, the time of the glow cleaning in step (2) is 20 - 40 minutes, for example, it can be 20 minutes, 25 minutes, 30 minutes, 35 minutes, or 40 minutes, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0035] In the present invention, the arc - starting gas used in the glow cleaning is Ar with a purity of 99.99%, and its purpose is to remove the oxide layer on the surface of the aluminum alloy and activate the surface of the substrate. Among them, the temperature of the glow cleaning < 80°C. If the temperature is too high, it will cause the surface hardness of the aluminum alloy to decrease after sandblasting, thereby affecting the film - substrate bonding force.

[0036] As a preferred technical solution of the present invention, the temperature in the PVD furnace during the PVD coating treatment in step (2) is 50 - 80°C, for example, it can be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0037] In the present invention, the PVD coating treatment is a low-temperature sputtering treatment, which promotes the nucleation of the film layer during sputtering, reduces the stress and microcracks of the film layer, and simultaneously refines the grain size of the film layer. If the temperature is too high, it will cause a decrease in the hardness of the aluminum alloy and affect the film-substrate bonding force. If the temperature is too low, the diffusion ability of the film material during the coating process will be weak, resulting in an increase in defects in the film material and affecting the denseness of the film.

[0038] As a preferred technical solution of the present invention, the film layer thickness of the transition layer is 1-1.5 μm. For example, it can be 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm or 1.5 μm, etc., but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0039] Preferably, the target used during the deposition of the transition layer includes an alloy target of any one or at least two elements among Cr, Ti or Zr. Typical but non-limiting combinations include: Cr target, Ti target, Zr target, CrTi target, CrZr target, TiZr target or CrTiZr target.

[0040] In the present invention, the transition layer is a metal layer, and its function is to relieve the physical property differences between the substrate and the ceramic layer and release the stress during the deposition process. If the thickness of the transition layer is too thick, it will cause an extension of the coating process time and affect the coating efficiency. On the contrary, if the thickness of the transition layer is too thin, it cannot effectively relieve the physical property differences between the substrate and the surface ceramic layer, cannot effectively relieve the stress during the coating process, and deteriorates the film-substrate bonding force.

[0041] Preferably, the negative bias voltage during the deposition of the transition layer is 45-55 V. For example, it can be 45 V, 47 V, 49 V, 51 V, 53 V or 55 V, etc., but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0042] Preferably, the duty cycle during the deposition of the transition layer is 45-55%. For example, it can be 45%, 47%, 49%, 51%, 53% or 55%, etc., but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0043] Preferably, the flow rate of the arc-starting gas used during the deposition of the transition layer is 80-120 sccm. For example, it can be 80 sccm, 90 sccm, 100 sccm, 110 sccm or 120 sccm, etc., but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0044] In the present invention, the arc-starting gas used during the deposition of the transition layer is Ar.

[0045] As a preferred technical solution of the present invention, the film thickness of the functional layer is 2 to 2.5 μm. For example, it can be 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, etc., but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0046] The negative bias voltage during the deposition of the functional layer is 15 to 25 V. For example, it can be 15 V, 17 V, 19 V, 21 V, 23 V, 25 V, etc., but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0047] Preferably, the duty cycle during the deposition of the functional layer is 70 to 80%. For example, it can be 70%, 72%, 74%, 76%, 78%, 80%, etc., but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0048] Preferably, the target used during the deposition of the functional layer includes an alloy target of at least two elements among Cr, Ti, Zr, or W. Typical but non-limiting combinations include: CrTi target, CrZr target, TiZr target, CrTiZrW target, TiZrW target, ZrW target, or CrW target.

[0049] Preferably, the functional layer includes alternately arranged metal layers and nitride ceramic layers.

[0050] Preferably, the modulation ratio of the metal layer to the nitride ceramic layer is 1:0.8 to 1.2. For example, it can be 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, etc., but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0051] Preferably, the modulation period during the deposition of the functional layer is 5 to 20 nm. For example, it can be 5 nm, 10 nm, 15 nm, 20 nm, etc., but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0052] Preferably, the flow rate of argon used during the deposition of the functional layer is 80 to 120 sccm. For example, it can be 80 sccm, 90 sccm, 100 sccm, 110 sccm, 120 sccm, etc., but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0053] Preferably, during the deposition of the functional layer, the flow rate of nitrogen gas used for depositing the nitride ceramic layer is 80 - 120 sccm. For example, it can be 80 sccm, 90 sccm, 100 sccm, 110 sccm, or 120 sccm, etc., but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0054] In the present invention, the functional layer is an alternately deposited metal layer and nitride ceramic layer, and its function is to deposit a film layer material with a matching hardness and toughness and corrosion resistance on the transition layer. If the thickness of the functional layer is too thick, it will lead to a long film layer deposition time and affect production efficiency. On the contrary, if the thickness of the functional layer is too thin, the matching of the hardness and toughness of the metal layer / nitride layer will be lost, and thus the substrate cannot be effectively protected.

[0055] As a preferred technical solution of the present invention, the film layer thickness of the color layer is 0.5 - 1 μm. For example, it can be 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, or 1 μm, etc., but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0056] In the present invention, the function of the color layer is to provide color on the surface. If the thickness of the color layer is too thick, it will lead to a long deposition time and affect production efficiency. On the contrary, if the thickness of the color layer is too thin, local color differences will occur in the color layer.

[0057] Preferably, the target used during the deposition of the color layer includes an alloy target of any one or at least two elements selected from Cr, Si, or W. Typical but non - limiting combinations include: CrW target, CrSi target, SiW target, or CrSiW target.

[0058] Preferably, the pressure during the deposition of the color layer is 0.5 - 1.5 Pa. For example, it can be 0.5 Pa, 0.7 Pa, 0.9 Pa, 1.1 Pa, 1.3 Pa, or 1.5 Pa, etc., but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0059] Preferably, the gases used during the deposition of the color layer include argon, acetylene gas, and nitrogen.

[0060] Preferably, the flow rate of the argon gas is 80 - 120 sccm. For example, it can be 80 sccm, 90 sccm, 100 sccm, 110 sccm, or 120 sccm, etc., but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0061] Preferably, the flow rate of the acetylene gas is 15 - 25 sccm. For example, it can be 15 sccm, 17 sccm, 19 sccm, 21 sccm, 23 sccm, 25 sccm, etc., but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0062] Preferably, the flow rate of the nitrogen gas is 5 - 15 sccm. For example, it can be 5 sccm, 7 sccm, 9 sccm, 11 sccm, 13 sccm, 15 sccm, etc., but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0063] It should be noted that in the present invention, the matching of the hardness and toughness of the thin film is achieved by alternately depositing the metal / ceramic layer. During the alternate deposition and the gradient transition deposition of the PVD film layer components, by controlling the nitrogen gas flow rate during the deposition process, the proportion of the metal and the nitride in the thin film is achieved, thereby regulating the hardness value of the thin film.

[0064] It should be noted that after the PVD coating treatment in the present invention, it also includes the preparation of a surface polymer on the coated aluminum alloy substrate.

[0065] The numerical range described in the present invention not only includes the point values listed above, but also includes any point values between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the range.

[0066] Compared with the prior art, the present invention has the following beneficial effects:

[0067] (1) The method provided by the present invention solves the problem of a large hardness difference between the aluminum alloy substrate and the PVD coating by combining sandblasting treatment and a unique PVD coating treatment;

[0068] (2) The method provided by the present invention controls the roughness of the pretreated substrate by electrolytic polishing, further improves the film-substrate bonding force between the PVD coating and the aluminum alloy substrate, and at the same time improves its corrosion resistance and scratch resistance. Specific Embodiments

[0069] The technical solution of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0070] In a specific embodiment, the present invention provides a method for improving the film-substrate bonding force between aluminum alloy and PVD coating, and the method includes the following steps:

[0071] (1) Under the pressure condition of 3 - 5 bar, the aluminum alloy substrate is sandblasted with abrasive materials of 200 - 600 mesh for 20 - 40 minutes, and then, under the voltage condition of 10 - 20 V, electrolytic polishing treatment is carried out for 5 - 10 minutes with an electrolyte of concentrated phosphoric acid and ethanol with a volume ratio of 1:1 - 2. After ultrasonic cleaning treatment, vacuum drying is carried out at 70 - 90 °C for 50 - 70 minutes to obtain a pre - treated substrate with a roughness of 0.01 - 0.2 μm;

[0072] (2) The pre - treated substrate obtained in step (1) is put into a PVD furnace, and glow cleaning is carried out for 20 - 40 minutes under the conditions of a voltage of 600 - 800 V, a duty cycle of 45 - 55%, and a temperature of < 80 °C, and then PVD coating treatment is carried out under the temperature condition of 50 - 80 °C;

[0073] The PVD coating treatment includes sequentially depositing a transition layer, a functional layer, and a color layer on the surface of the pre - treated substrate;

[0074] Among them, the film thickness of the transition layer is 1 - 1.5 μm. The target used in the deposition process includes an alloy target of any one or at least two elements among Cr, Ti, or Zr. The negative bias voltage is 45 - 55 V, the duty cycle is 45 - 55%, and the flow rate of the starting arc gas (Ar) is 80 - 120 sccm;

[0075] The film thickness of the functional layer is 2 - 2.5 μm; the negative bias voltage during the deposition process is 15 - 25 V, the duty cycle is 70 - 80%, and the target used includes an alloy target of at least two elements among Cr, Ti, Zr, or W;

[0076] The functional layer includes alternately arranged metal layers and nitride ceramic layers; the modulation ratio of the metal layer and the nitride ceramic layer is 1:0.8 - 1.2, and the modulation period is 5 - 20 nm; the flow rate of argon used during the deposition of the functional layer is 80 - 120 sccm, and the flow rate of nitrogen used during the deposition of the nitride ceramic layer is 80 - 120 sccm;

[0077] The film thickness of the color layer is 0.5 - 1 μm; the target used in the deposition process includes an alloy target of any one or at least two elements among Cr, Si, or W. The pressure is 0.5 - 1.5 Pa, and the gases used include argon, acetylene gas, and nitrogen; the flow rate of argon is 80 - 120 sccm, the flow rate of acetylene gas is 15 - 25 sccm, and the flow rate of nitrogen is 5 - 15 sccm.

[0078] Example 1

[0079] This example provides a method for improving the film - substrate bonding force between aluminum alloy and PVD coating. The method includes the following steps:

[0080] (1) Under the condition of 4 bar pressure, the aluminum alloy substrate was sandblasted with emery of 400 mesh for 30 min, and then under the condition of 15 V voltage, electrolytic polishing treatment was carried out for 5 min with an electrolyte of concentrated phosphoric acid and ethanol with a volume ratio of 1:1. After ultrasonic cleaning treatment, vacuum drying was carried out at 80 °C for 60 min to obtain a pre-treated substrate with a roughness of 0.05 μm;

[0081] (2) The pre-treated substrate obtained in step (1) was placed in a PVD furnace, and glow cleaning was carried out for 30 min under the conditions of 700 V voltage, 50% duty cycle, and 70 °C temperature, and then PVD coating treatment was carried out under the condition of 75 °C temperature;

[0082] The PVD coating treatment includes sequentially depositing a transition layer, a functional layer, and a color layer on the surface of the pre-treated substrate;

[0083] Among them, the film thickness of the transition layer is 1.25 μm, the target material used in the deposition process is CrTi target, the negative bias voltage is 50 V, the duty cycle is 50%, and the flow rate of the starting arc gas (Ar) used is 100 sccm;

[0084] The film thickness of the functional layer is 2.25 μm; the negative bias voltage during the deposition process is 20 V, the duty cycle is 75%, and the target material used is CrTi target;

[0085] The functional layer is an alternately arranged metal layer and a nitride ceramic layer; the modulation ratio of the metal layer and the nitride ceramic layer is 1:1, and the modulation period is 15 nm; the flow rate of argon gas used during the deposition of the functional layer is 100 sccm, and the flow rate of nitrogen gas used during the deposition of the nitride ceramic layer is 100 sccm;

[0086] The film thickness of the color layer is 0.75 μm; the target material used in the deposition process is CrSi target, the pressure is 0.75 Pa, and the gases used include argon gas, acetylene gas, and nitrogen gas; the flow rate of argon gas is 100 sccm, the flow rate of acetylene gas is 20 sccm, and the flow rate of nitrogen gas is 10 sccm.

[0087] Example 2

[0088] This example provides a method for improving the film-substrate adhesion between aluminum alloy and PVD coating, and the method includes the following steps:

[0089] (1) Under the condition of 3 bar pressure, the aluminum alloy substrate was sandblasted with abrasive of 600 mesh for 40 min, and then under the condition of 10 V voltage, electrolytic polishing treatment was carried out for 10 min with an electrolyte of concentrated phosphoric acid and ethanol with a volume ratio of 1:1.5. After ultrasonic cleaning treatment, vacuum drying was carried out at 70 °C for 70 min to obtain a pre-treated substrate with a roughness of 0.01 μm;

[0090] (2) Put the pretreated substrate obtained in step (1) into a PVD furnace, perform glow cleaning for 40 min under the conditions of a voltage of 600 V, a duty cycle of 45%, and a temperature of 70 °C, and then perform PVD coating treatment under the condition of a temperature of 55 °C;

[0091] The PVD coating treatment includes sequentially depositing a transition layer, a functional layer, and a color layer on the surface of the pretreated substrate;

[0092] Among them, the film thickness of the transition layer is 1 μm, the target used in the deposition process is a TiZr target, the negative bias voltage is 45 V, the duty cycle is 45%, and the flow rate of the starting arc gas (Ar) used is 80 sccm;

[0093] The film thickness of the functional layer is 2 μm; the negative bias voltage during the deposition process is 15 V, the duty cycle is 70%, and the target used is a TiZr target;

[0094] The functional layer includes alternately arranged metal layers and nitride ceramic layers; the modulation ratio of the metal layer and the nitride ceramic layer is 1:0.8, and the modulation period is 5 nm; the flow rate of argon used during the deposition of the functional layer is 120 sccm, and the flow rate of nitrogen used during the deposition of the nitride ceramic layer is 80 sccm;

[0095] The film thickness of the color layer is 0.5 μm; the target used in the deposition process is a SiW target, the pressure is 0.5 Pa, and the gases used include argon, acetylene gas, and nitrogen; the flow rate of argon is 80 sccm, the flow rate of acetylene gas is 15 sccm, and the flow rate of nitrogen is 5 sccm.

[0096] Example 3

[0097] This example provides a method for improving the film-substrate adhesion between an aluminum alloy and a PVD coating. The method includes the following steps:

[0098] (1) Under the condition of a pressure of 5 bar, use abrasive particles with a mesh number of 200 to perform sandblasting on the aluminum alloy substrate for 20 min, and then under the condition of a voltage of 20 V, use an electrolyte with a volume ratio of 1:2 of concentrated phosphoric acid and ethanol to perform electrolytic polishing for 8 min. After ultrasonic cleaning, perform vacuum drying at 90 °C for 50 min to obtain a pretreated substrate with a roughness of 0.2 μm;

[0099] (2) Put the pretreated substrate obtained in step (1) into a PVD furnace, perform glow cleaning for 20 min under the conditions of a voltage of 600 V, a duty cycle of 55%, and a temperature of 65 °C, and then perform PVD coating treatment under the condition of a temperature of 80 °C;

[0100] The PVD coating treatment includes successively depositing a transition layer, a functional layer, and a color layer on the surface of a pretreated substrate;

[0101] Among them, the film thickness of the transition layer is 1.5 μm. During the deposition process, the target used is a CrTiZr target, the negative bias voltage is 55 V, the duty cycle is 55%, and the flow rate of the starting arc gas (Ar) used is 120 sccm;

[0102] The film thickness of the functional layer is 2.5 μm; the negative bias voltage during the deposition process is 25 V, the duty cycle is 80%, and the target used is a CrTiZr target;

[0103] The functional layer includes alternately arranged metal layers and nitride ceramic layers; the modulation ratio of the metal layer and the nitride ceramic layer is 1:1.2, and the modulation period is 20 nm; during the deposition process of the functional layer, the flow rate of argon used is 80 sccm, and the flow rate of nitrogen used during the deposition of the nitride ceramic layer is 120 sccm;

[0104] The film thickness of the color layer is 1 μm; the target used during the deposition process is a CrSiW target, the pressure is 0.75 Pa, and the gases used include argon, acetylene gas, and nitrogen; the flow rate of argon is 120 sccm, the flow rate of acetylene gas is 25 sccm, and the flow rate of nitrogen is 15 sccm.

[0105] Example 4

[0106] This example provides a method for improving the film-substrate adhesion between aluminum alloy and PVD coating. The difference between this method and that of Example 1 is only that:

[0107] In this example, the time of the sandblasting treatment described in step (1) is adjusted to 10 min.

[0108] Example 5

[0109] This example provides a method for improving the film-substrate adhesion between aluminum alloy and PVD coating. The difference between this method and that of Example 1 is only that:

[0110] In this example, the time of the sandblasting treatment described in step (1) is adjusted to 60 min.

[0111] Example 6

[0112] This example provides a method for improving the film-substrate adhesion between aluminum alloy and PVD coating. The difference between this method and that of Example 1 is only that:

[0113] In this example, the time of the electrolytic polishing described in step (1) is adjusted to 2 min.

[0114] Example 7

[0115] This embodiment provides a method for improving the film-substrate adhesion between aluminum alloy and PVD coating. The difference between this method and that of Embodiment 1 is only that:

[0116] In this embodiment, the time of the electrolytic polishing described in step (1) is adjusted to 15 min.

[0117] Embodiment 8

[0118] This embodiment provides a method for improving the film-substrate adhesion between aluminum alloy and PVD coating. The difference between this method and that of Embodiment 1 is only that:

[0119] In this embodiment, the time of the glow cleaning described in step (2) is adjusted to 60 min.

[0120] Embodiment 9

[0121] This embodiment provides a method for improving the film-substrate adhesion between aluminum alloy and PVD coating. The difference between this method and that of Embodiment 1 is only that:

[0122] In this embodiment, the time of the glow cleaning described in step (2) is adjusted to 10 min.

[0123] Embodiment 10

[0124] This embodiment provides a method for improving the film-substrate adhesion between aluminum alloy and PVD coating. The difference between this method and that of Embodiment 1 is only that:

[0125] In this embodiment, the temperature of the glow cleaning described in step (2) is adjusted to 100 °C.

[0126] Embodiment 11

[0127] This embodiment provides a method for improving the film-substrate adhesion between aluminum alloy and PVD coating. The difference between this method and that of Embodiment 1 is only that:

[0128] In this embodiment, the temperature of the PVD coating process described in step (2) is adjusted to 30 °C.

[0129] Embodiment 12

[0130] This embodiment provides a method for improving the film-substrate adhesion between aluminum alloy and PVD coating. The difference between this method and that of Embodiment 1 is only that:

[0131] In this embodiment, the temperature of the PVD coating process described in step (2) is adjusted to 160 °C.

[0132] Embodiment 13

[0133] This embodiment provides a method for improving the film-substrate adhesion between aluminum alloy and PVD coating. The difference between this method and that of Embodiment 1 is only that:

[0134] In this embodiment, the functional layer described in step (2) is adjusted to a metal layer, that is, the deposition of the nitride ceramic layer is omitted.

[0135] Example 14

[0136] This embodiment provides a method for improving the film-substrate adhesion between aluminum alloy and PVD coating. The difference between this method and that of Example 1 is only that:

[0137] In this embodiment, the functional layer described in step (2) is adjusted to a nitride ceramic layer, that is, the deposition of the metal layer is omitted.

[0138] Comparative Example 1

[0139] This comparative example provides a method for improving the film-substrate adhesion between aluminum alloy and PVD coating. The difference between this method and that of Example 1 is only that:

[0140] This comparative example omits the sandblasting process described in step (1).

[0141] Comparative Example 2

[0142] This comparative example provides a method for improving the film-substrate adhesion between aluminum alloy and PVD coating. The difference between this method and that of Example 1 is only that:

[0143] This comparative example omits the electrolytic polishing process described in step (1).

[0144] Comparative Example 3

[0145] This comparative example provides a method for improving the film-substrate adhesion between aluminum alloy and PVD coating. The difference between this method and that of Example 1 is only that:

[0146] This comparative example omits the glow cleaning process described in step (2).

[0147] Comparative Example 4

[0148] This comparative example provides a method for improving the film-substrate adhesion between aluminum alloy and PVD coating. The difference between this method and that of Example 1 is only that:

[0149] This comparative example omits the deposition process of the transition layer in the PVD coating process described in step (2).

[0150] Comparative Example 5

[0151] This comparative example provides a method for improving the film-substrate adhesion between aluminum alloy and PVD coating. The difference between this method and that of Example 1 is only that:

[0152] This comparative example omits the deposition process of the functional layer in the PVD coating process described in step (2).

[0153] Comparative Example 6

[0154] This comparative example provides a method for improving the film - substrate adhesion between aluminum alloy and PVD coating. The difference between this method and that of Example 1 is only that:

[0155] This comparative example omits the deposition process of the color layer in the PVD coating process described in step (2).

[0156] Performance detection:

[0157] The aluminum alloy after PVD coating provided in the above - mentioned examples and comparative examples is subjected to film - substrate adhesion test, corrosion resistance test and hardness value (scratch resistance performance) test. The results are shown in Table 1;

[0158] Among them, the film - substrate adhesion test includes: using a multi - function scratch tester to test the adhesion between the coating and the substrate, and the test load is 0 - 20 N;

[0159] The corrosion resistance test includes: using an electrochemical workstation to measure the corrosion potential of each coating in 3.5 wt% NaCl aqueous solution;

[0160] The scratch resistance performance is reflected by the hardness value of the plated PVD coating.

[0161] Table 1

[0162]

[0163] [[ID=…]]

[0164] It can be seen from Table 1 as follows:

[0165] (1) Through comprehensive analysis of Examples 1 - 3, it can be known that the method provided by the present invention can effectively reduce the hardness difference between the substrate and the PVD coating, and then obtain an aluminum alloy material with excellent film - substrate adhesion. Moreover, the PVD coating has excellent corrosion resistance and scratch resistance performance;

[0166] (2) Through comprehensive analysis of Example 1, Examples 4 - 7 and Comparative Examples 1 - 2, it can be known that the roughness of the pretreated substrate will affect the film - substrate adhesion and corrosion resistance performance;

[0167] More specifically, when the time of the sandblasting treatment is too long, it will lead to an increase in roughness, and then the corrosion resistance becomes poor; on the contrary, when the time is too short or the sandblasting treatment is directly omitted, the film - substrate adhesion and corrosion resistance will become poor;

[0168] When the time of the electrolytic polishing is too long, it will lead to a decrease in roughness, more stress layers are removed, and the purpose of sandblasting strengthening is lost; on the contrary, when the time is too short or the electrolytic polishing treatment is directly omitted, the roughness will be relatively large, affecting the corrosion resistance performance;

[0169] (3) By comprehensively analyzing Examples 1, 8 - 10 and Comparative Example 3, it can be seen that the glow cleaning will affect the film - substrate bonding strength and the corrosion resistance;

[0170] More specifically, when the time of the glow cleaning is too long, it will lead to a decrease in the film - substrate bonding strength; on the contrary, when the time is too short or the glow cleaning is directly omitted, it will lead to a decrease in the corrosion resistance;

[0171] When the temperature of the glow cleaning is too high, it will lead to a decrease in the film - substrate bonding strength and a deterioration of the corrosion resistance;

[0172] (4) By comprehensively analyzing Example 1 and Examples 11 - 12, it can be seen that a relatively low temperature during the PVD coating process will lead to a deterioration of the film - substrate bonding strength and the corrosion resistance; on the contrary, a relatively high temperature will lead to a deterioration of the film - substrate bonding strength;

[0173] (5) By comprehensively analyzing Example 1, Examples 12 - 14 and Comparative Examples 4 - 6, it can be seen that the design of the film layer structure during the PVD coating process will affect the film - substrate bonding strength and the corrosion resistance;

[0174] When the functional layer with alternately arranged metal / ceramic is adjusted to a single - metal layer or a single - ceramic layer, it will lead to a deterioration of the film - substrate bonding strength and the corrosion resistance;

[0175] When the functional layer is omitted, it will lead to a significant deterioration of the corrosion resistance; when the transition layer is omitted, it will lead to a significant decrease in the film - substrate bonding strength; when the color layer is omitted, it will lead to the film layer losing the use value of the color layer.

[0176] In summary, the method provided by the present invention solves the problem of a large difference in hardness between the aluminum - alloy substrate and the PVD coating by combining sand - blasting treatment and a unique PVD coating treatment; at the same time, by controlling the roughness of the pretreated substrate through electrolytic polishing, while further improving the film - substrate bonding strength between the PVD coating and the aluminum - alloy substrate, it also improves its corrosion resistance and scratch - resistance performance.

[0177] The applicant declares that the above - described specific embodiments have further detailed the purpose, technical solution and beneficial effects of the present invention. It should be understood that the above - described are only specific embodiments of the present invention and do not limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for improving the film-substrate adhesion between aluminum alloy and PVD coating, characterized in that The method includes the following steps: (1) Sandblasting treatment, electrolytic polishing treatment, cleaning treatment and vacuum drying are sequentially carried out on the aluminum alloy substrate to obtain a pretreated substrate; (2) The pretreated substrate obtained in step (1) is placed in a PVD furnace, and then glow cleaning and PVD coating treatment are sequentially carried out; The PVD coating treatment includes sequentially depositing a transition layer, a functional layer and a color layer on the surface of the pretreated substrate.

2. The method according to claim 1, wherein The abrasive used in the sandblasting treatment in step (1) includes any one or a combination of at least two of emery, glass beads, white fused alumina, garnet sand or quartz sand; Preferably, the mesh number of the abrasive used in the sandblasting treatment in step (1) is 200-600 mesh; Preferably, the time of the sandblasting treatment in step (1) is 20-40 min; Preferably, the pressure of the sandblasting treatment in step (1) is 3-5 bar.

3. The method according to claim 1 or 2, characterized in that, Cleaning treatment is also included before the electrolytic polishing treatment in step (1); Preferably, the electrolyte used in the electrolytic polishing treatment in step (1) includes concentrated phosphoric acid and ethanol; Preferably, the volume ratio of the concentrated phosphoric acid to ethanol is 1:1-2; Preferably, the voltage of the electrolytic polishing treatment in step (1) is 10-20 V; Preferably, the time of the electrolytic polishing treatment in step (1) is 5-10 min.

4. The method according to any one of claims 1 to 3, characterized in that, The cleaning treatment in step (1) includes ultrasonic cleaning; Preferably, the temperature of the vacuum drying in step (1) is 70-90 °C; Preferably, the time of the vacuum drying in step (1) is 50-70 min; Preferably, the roughness of the pretreated substrate in step (1) is 0.01-0.2 μm.

5. The method according to any one of claims 1 to 4, characterized in that, The voltage of the glow cleaning in step (2) is 600-800 V; Preferably, the duty cycle of the glow cleaning in step (2) is 45-55%; Preferably, the temperature of the glow cleaning in step (2) < 80 °C; Preferably, the time of the glow cleaning in step (2) is 20-40 min.

6. The method according to any one of claims 1-5, characterized in that The temperature in the PVD furnace during the PVD coating treatment in step (2) is 50-80 °C.

7. The method according to claim 6, wherein The film thickness of the transition layer is 1-1.5 μm; Preferably, the target used during the deposition of the transition layer includes an alloy target of any one or at least two elements of Cr, Ti or Zr; Preferably, the negative bias voltage during the deposition of the transition layer is 45-55 V; Preferably, the duty cycle during the deposition of the transition layer is 45-55%; Preferably, the flow rate of the starting arc gas used during the deposition of the transition layer is 80-120 sccm.

8. The method according to claim 6, characterized in that, The film thickness of the functional layer is 2-2.5 μm; The negative bias voltage during the deposition of the functional layer is 15-25 V; Preferably, the duty cycle during the deposition of the functional layer is 70-80%; Preferably, the target used during the deposition of the functional layer includes an alloy target of at least two elements of Cr, Ti, Zr or W.

9. The method according to claim 8, wherein The functional layer includes alternately arranged metal layers and nitride ceramic layers; Preferably, the modulation ratio of the metal layer to the nitride ceramic layer is 1:0.8-1.2; Preferably, the modulation period during the deposition of the functional layer is 5-20 nm; Preferably, the flow rate of argon used in the deposition process of the functional layer is 80 - 120 sccm; Preferably, during the deposition process of the functional layer, the flow rate of nitrogen used in the deposition of the nitride ceramic layer is 80 - 120 sccm.

10. The method according to claim 6, wherein The film thickness of the color layer is 0.5 - 1 μm; Preferably, the target used in the deposition process of the color layer includes an alloy target of any one or at least two elements among Cr, Si, or W; Preferably, the pressure during the deposition process of the color layer is 0.5 - 1.5 Pa; Preferably, the gases used in the deposition process of the color layer include argon, acetylene gas, and nitrogen; Preferably, the flow rate of argon is 80 - 120 sccm; Preferably, the flow rate of acetylene gas is 15 - 25 sccm; Preferably, the flow rate of nitrogen is 5 - 15 sccm.

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