A coating method for metal decorative parts

Abstract

The present application relates to the field of metal decorative parts preparation, and specifically discloses a coating method for metal decorative parts. A coating method for metal decorative parts comprises the following steps: cleaning and drying the part to be plated; using plasma-enhanced intermediate frequency sputtering technology under vacuum conditions to deposit a metal layer on the surface of the part to be plated, wherein nitrogen, oxygen, and methane are introduced in stages during the process, with pure nitrogen introduced in the bottom layer deposition stage; oxygen is introduced in the middle layer deposition stage, with the nitrogen and oxygen flow ratio being 3-5:1; nitrogen, oxygen, and methane are introduced in the surface layer deposition stage, with the flow ratio being 14-19:3:1; during the deposition process, the voltage is controlled at 30-100V, the vacuum pressure is maintained at 0.3±0.05Pa, the target material is titanium-aluminum alloy, the intermediate frequency power is set to 38-42kW, the total deposition time is 55-65min, and the coating is deposited. The coating prepared by the method of the present application has a uniform and stable purple-blue hue.

Description

Technical Field

[0001] The present application relates to the field of metal decorative part preparation, and more specifically, to a coating method for metal decorative parts. Background Art

[0002] Surface coating technology for metal decorative parts is a core process for improving their aesthetics and functionality. Traditional coating methods mostly use single-component coatings, such as titanium nitride, titanium carbide or titanium oxide, to achieve specific colors by adjusting the film thickness or the ratio of reactive gases. For example, titanium nitride coatings can present a classic golden color, but their color gamut is narrow, making it difficult to meet the complex tones required by modern decorative designs. In addition, the method of controlling color based on thickness has significant defects: the coating thickness on different surfaces of the product is easily affected by the deposition conditions, resulting in uneven color (color difference ΔE>5), which is especially obvious on complex curved surfaces or tiny parts, seriously affecting the visual consistency of high-end accessories.

[0003] With growing market demand for personalized color tones, multi-element composite coating technology has become a research hotspot. Existing technologies expand the color gamut by doping the coating with elements such as aluminum and oxygen. For example, aluminum can create a rose gold hue, while oxygen can adjust a bluish-purple hue. However, these methods still suffer from issues such as uneven element doping, poor interfacial bonding, and insufficient stability. Summary of the Invention

[0004] In order to solve the above problems, the present application provides a coating method for metal decorative parts.

[0005] In a first aspect, the present application provides a coating method for metal decorative parts, which adopts the following technical solution:

[0006] A coating method for a metal decorative part comprises the following steps:

[0007] S1. Prepare the parts to be plated, clean and dry them;

[0008] S2. Under vacuum conditions, plasma-enhanced medium-frequency sputtering technology is used to deposit a metal layer on the surface of the workpiece to be plated. Nitrogen, oxygen, and methane are introduced in stages during the process, and pure nitrogen is introduced during the bottom deposition stage;

[0009] During the intermediate layer deposition stage, oxygen is introduced with a nitrogen to oxygen flow ratio of 3-5:1;

[0010] During the surface deposition stage, nitrogen, oxygen and methane were introduced with a flow ratio of 14-19:3:1. During the deposition process, the voltage was controlled at 30-100V, the vacuum pressure was maintained at 0.3±0.05Pa, the target material was titanium aluminum alloy, the medium frequency power was set to 38-42kW, the total deposition time was 55-65min, and the coating was obtained by deposition.

[0011] By adopting the above technical solutions, the synergistic optimization of the coating color and performance is achieved. In terms of color presentation, when pure nitrogen is deposited on the bottom layer, the titanium-aluminum alloy target material is fully combined with titanium and aluminum atoms under the action of plasma to form a TiAlN compound. Its unique crystal structure and electronic band distribution make the coating appear red rose color. This is due to the selective absorption and reflection of specific wavelengths of light in the visible light by the specific crystal structure; oxygen is introduced into the middle layer, and oxygen atoms partially replace nitrogen atoms to form TiAlNOx compounds. Oxygen atom doping changes the electronic structure and optical constants of the coating, resulting in changes in the absorption and scattering characteristics of light, and thus presenting a red-purple color; methane is added to the surface layer, and carbon atoms enter the coating to form TiAlNCO compounds. The introduction of carbon further complicates the chemical bond structure and microstructure of the coating, which enhances the interference and scattering effect of the coating on light, and ultimately presents a violet color. The three-layer coating achieves a natural transition and rich presentation of color through changes in elemental composition and structural gradients.

[0012] Optionally, when nitrogen is introduced during the bottom layer deposition stage, the flow rate is 300-500 sccm;

[0013] During the intermediate layer deposition stage, oxygen gas is introduced at a flow rate of 83-125 sccm, and nitrogen gas flow rate is adjusted to 375-415 sccm, so that the volume flow rate ratio of nitrogen to oxygen is maintained at 3-5:1;

[0014] When methane is introduced during the surface deposition stage, the flow rate is 20-30 sccm, the oxygen flow rate is reduced to 60-90 sccm, and the nitrogen flow rate is 380-420 sccm, so that the volume flow ratio of nitrogen:oxygen:methane is maintained at 14-19:3:1.

[0015] By adopting the above technical solution, a specific flow rate of nitrogen is introduced during the bottom layer deposition stage to provide a stable basic environment for subsequent deposition; the precise gas flow ratio during the intermediate layer deposition stage helps to promote the formation of specific compounds in the intermediate layer. Through the synergistic effect of nitrogen and oxygen, the crystal structure, chemical bonding state and growth rate of the intermediate layer can be regulated, so that the intermediate layer has good density and uniformity, providing a good transition interface for surface deposition and enhancing the bonding force between layers; the specific proportion of the gas environment during the surface layer deposition stage can optimize the decomposition and reaction path of methane, promote the cracking of methane in a suitable atmosphere, and synergize with oxygen and nitrogen to form a surface material with a specific chemical composition and microstructure. The obtained surface layer not only has unique physical and chemical properties, such as good optical and mechanical properties, but can also be tightly combined with the intermediate layer to form a multi-layer structure with excellent performance, significantly improving the overall performance of the entire deposition system and meeting the high performance requirements in different application scenarios.

[0016] Optionally, when nitrogen is introduced during the bottom layer deposition stage, the flow rate is 400 sccm;

[0017] During the intermediate layer deposition stage, oxygen gas was introduced at a flow rate of 100 sccm and nitrogen gas at a flow rate of 400 sccm;

[0018] During the surface deposition stage, when methane is introduced, the flow rate is 25 sccm, the oxygen flow rate is reduced to 75 sccm, and the nitrogen flow rate is 400 sccm.

[0019] Optionally, the target material has a composition of 70wt% titanium and 30wt% aluminum, a diameter of 70mm, and is provided in 4 pairs.

[0020] By adopting the above technical solution and setting up 4 pairs of target materials, the distribution density and sputtering area of ​​the sputtering source are greatly increased. During sputtering coating, the deposition rate can be significantly improved, so that the titanium-aluminum alloy film can be formed on the substrate faster, shortening the production cycle; at the same time, the coordinated sputtering of multiple targets can make the film composition more uniform, avoid composition deviation caused by insufficient local sputtering, and ensure the stability and consistency of the coating quality.

[0021] Optionally, the thickness ratio of the bottom layer, the middle layer and the surface layer is (40±5)%: (30±5)%: (30±5)%, and the total thickness is 20-30 μm.

[0022] By adopting the above technical solution, this layer thickness design has significant beneficial effects and scientific mechanisms. The thicker base layer provides a solid and uniform adhesion foundation, ensuring close bonding between the coating and the surface to be plated. The TiAlN compound formed here, due to its specific crystal structure and electron band distribution, sets the color tone and imparts certain initial properties. The middle layer is of moderate thickness, and oxygen atoms are doped to form TiAlNOx compounds. While achieving the color transition to reddish-purple, it also acts as a transition layer to alleviate stress differences between the base layer and the surface layer, enhancing interlayer bonding and preventing cracking or shedding of the coating caused by uneven thickness or stress concentration. The surface layer thickness matches that of the middle layer, and carbon atoms are introduced to form TiAlNCO compounds, further enriching the chemical bond structure and microstructure of the coating, intensifying the violet color effect. The appropriate surface layer thickness ensures a smooth surface and enhances the appearance quality of the decorative part. The three layers are well-proportioned, with a total thickness of 20-30μm, ensuring rich color gradation and good optical properties while also taking into account the coating's comprehensive properties such as adhesion, stability, and wear resistance.

[0023] Optionally, the coating method further comprises preheating the workpiece to be plated before step S1, with the preheating temperature being 200-300° C. and the preheating time being 10-15 minutes.

[0024] By adopting the above technical solution, firstly, preheating can increase the surface temperature of the workpiece to be plated, reduce the thermal stress difference between it and the subsequently deposited metal layer, and reduce the internal stress of the coating caused by the mismatch of thermal expansion coefficients during the coating process, thereby effectively reducing the risk of cracking and falling off of the coating and enhancing the bonding strength between the coating and the workpiece to be plated; secondly, preheating can remove moisture, gas and some impurities that may be adsorbed on the surface of the workpiece to be plated, making the surface cleaner and more active, which is conducive to the adsorption, migration and nucleation of target atoms on the surface of the workpiece to be plated in the subsequent plasma enhanced medium frequency sputtering technology, thereby improving the uniformity and density of the coating; further, appropriate preheating temperature and time can optimize the initial conditions of coating deposition, make the coating growth process more stable, help to achieve coordinated optimization of coating color and performance, and ensure that the final coated product has an ideal appearance effect and reliable performance.

[0025] Optionally, during the deposition process, the applied voltage is uniformly decreased from 100 V to 30 V, and the voltage is uniformly controlled by a computer, and the decreasing rate is synchronized with the deposition time.

[0026] By adopting the above technical solution, high voltage is used to enhance ion bombardment in the initial stage of deposition. At this time, the ions have higher energy, and the high-energy ions can bombard the surface of the workpiece to be plated with greater kinetic energy. On the one hand, they can remove impurities, oxides, etc. that may remain on the surface of the workpiece to be plated, play a role in cleaning and activating the surface, and enhance the bonding force between the coating and the substrate; on the other hand, the high-energy ions have a strong sputtering effect on the target material, and can quickly form initial coating atomic nuclei on the surface of the workpiece to be plated, promoting the rapid nucleation and growth of the coating.

[0027] Later, the voltage is gradually reduced to 30V, and the ion energy decreases linearly. This energy reduction process helps control the growth rate and structure of the coating. In the early stages of deposition, high-energy ions may cause the coating to grow too quickly, easily creating microscopic defects such as voids and grain boundary discontinuities. However, the linear reduction in voltage gradually reduces the ion energy and stabilizes the deposition rate, which promotes a more orderly arrangement of the coating atoms, reduces the generation of defects, and improves the density and crystalline quality of the coating. At the same time, the continuous action of ions of varying energies can gradually release stress within the coating, preventing cracking or spalling of the coating due to stress concentration.

[0028] As deposition nears its end, the voltage drops to 30V, at which point the ion energy is lower and the deposition rate slows. Low-energy ions primarily modify the surface of the coating, making it smoother and flatter, reducing surface roughness, and improving the optical properties and decorative effects of the coating. Furthermore, low-energy deposition can further improve the interface structure between the coating and the substrate, enhancing interfacial bonding strength and improving the stability of the coating.

[0029] In a second aspect, the present application provides a coating for a metal decorative part prepared according to the method of the present application, using the following technical solution:

[0030] A coating film for a metal decorative part, wherein the coating film is a metal layer formed on the surface of the metal decorative part, and the metal layer includes a bottom layer, an intermediate layer, and a surface layer, wherein:

[0031] The bottom layer is a TiAlN red rose coating; the middle layer is a TiAlNOx red purple coating; and the surface layer is a TiAlNCO violet coating.

[0032] The resulting film, using this technical solution, features a five-element gradient coating (Ti-Al-NOC) structure, transcending the limitations of traditional single-element (e.g., TiN) or dual-element (e.g., TiCN) coatings. This innovative design achieves precise color control: First, a TiAlN alloy is formed, where a high nitrogen partial pressure creates a dense base layer, avoiding the monotonous hue of TiN alone. Oxygen is further introduced to form a TiAlNOx complex, leveraging its perturbation effect on the lattice structure to achieve a red-to-violet transition. Finally, trace amounts of carbon are added to the surface layer, forming a TiAlNCO solid solution. This carbon-induced modulation of light absorption wavelengths locks the violet spectrum, ultimately resulting in a violet film appearance.

[0033] In summary, this application has the following beneficial effects:

[0034] 1. Since this application utilizes the introduction of different elements at different stages to precisely control the crystal structure, electronic energy band distribution, and optical constants of the coating, it achieves precise control and rich presentation of color, breaking through the color limitations of traditional coatings. By depositing pure nitrogen on the bottom layer to form a TiAlN red-rose coating, introducing oxygen into the middle layer to form a TiAlNOx red-purple coating, and adding methane to the surface layer to form a TiAlNCO violet coating, a uniform and stable purple-blue hue is finally formed, filling the gap in the monotonous color of titanium coatings and adding a rich purple-blue range.

[0035] 2. The base TiAlN red-rose coating in this application, with its unique crystal structure and electronic band distribution, provides a solid foundation and excellent initial performance. The middle TiAlNOx red-purple coating, acting as a transition layer, modifies the coating's electronic structure and optical constants through oxygen doping. This not only achieves a color transition but also alleviates stress differences between the base and surface layers, enhancing interlayer bonding and preventing cracking or shedding caused by uneven thickness or stress concentration. The top TiAlNCO violet coating, through the introduction of carbon atoms, further complicates the coating's chemical bond structure and microstructure, enhancing the coating's interference and scattering effects. This not only enhances the violet color, but also ensures a smooth surface and improves the coating's overall performance, including wear resistance. The three coating layers are balanced in thickness, with a total thickness of 20-30 μm. This ensures a rich color gradation and excellent optical properties, while also possessing excellent adhesion, stability, and mechanical properties, significantly extending the service life of metal decorative parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a sample image prepared in Example 1 of the method of this application. DETAILED DESCRIPTION

[0037] The present application is further described in detail below with reference to the embodiments.

[0038] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or those recommended by the manufacturer. All reagents or instruments used, if the manufacturer is not specified, are commercially available conventional products.

[0039] Preparation Example

[0040] Preparation Example 1

[0041] A titanium aluminum alloy target material, the preparation of which includes the following steps:

[0042] Titanium and aluminum powders were uniformly mixed in a ratio of 70% by mass to 30% by mass, and a circular target with a diameter of 70 mm was prepared by hot pressing and sintering.

[0043] Example

[0044] Example 1

[0045] A coating method for a metal decorative part comprises the following steps:

[0046] S1. Place the metal decorative parts to be plated in an ultrasonic cleaner filled with alcohol and clean them for 10 minutes. Take them out and rinse them with deionized water. Then put them in an ultrasonic cleaner filled with acetone and continue cleaning for 5 minutes. Take them out and use a nitrogen gun to blow dry the residual liquid on the surface. Then put them in an oven and dry them at 100°C for 20 minutes to ensure that the surface of the parts to be plated is completely dry.

[0047] S2. Install the target material prepared in Preparation Example 1, setting up four pairs in total. Place the dried workpiece to be plated on the sample stage. Adjust the position and angle of the sample stage so that the surface of the workpiece to be plated is parallel to the surface of the target material and is within the effective sputtering area. Set the revolution speed of the sample stage to 2 revolutions / minute. Close the chamber door of the coating equipment, set the medium frequency power supply power to 40 kW, start the mechanical pump to roughly vacuum the chamber. When the pressure in the chamber drops below 10 Pa, start the molecular pump for high vacuum extraction until the pressure in the chamber reaches 0.3 Pa. Set the gas flow rate and deposition time in the equipment control system:

[0048] During the bottom deposition stage, only the nitrogen inlet valve was opened, and the nitrogen flow rate was set to 400 sccm. The deposition time was 24 min, forming a dense and uniform TiAlN red rose-colored coating with a thickness of 8 μm.

[0049] During the intermediate layer deposition stage, the oxygen inlet valve was opened, the oxygen flow rate was set to 100 sccm, the nitrogen flow rate was maintained at 400 sccm, and the deposition time was 18 minutes to form a uniform TiAlNOx red-purple coating with a thickness of 7 μm.

[0050] During the surface deposition phase, the methane inlet valve was opened, the methane flow rate was set to 25 sccm, the oxygen flow rate was reduced to 75 sccm, and the nitrogen flow rate was maintained at 400 sccm. Deposition lasted for 18 minutes, forming a uniform TiAlNCO violet surface layer with a thickness of approximately 7 μm. During the process, the voltage was linearly decreased from 100 V to 30 V through the PID feedback system.

[0051] When the coating deposition is completed, turn off the sputtering power supply and gas supply valve, keep the vacuum system running for 30 minutes, and let the plated piece cool naturally to room temperature in a vacuum environment to obtain a metal decorative piece with a violet coating. Figure 1 .

[0052] Example 2

[0053] A method for coating a metal decorative part, the preparation steps are similar to those of Example 1, except that: the medium frequency power supply is set to 38 kW, the mechanical pump is started to roughly evacuate the chamber, and when the pressure in the chamber drops below 10 Pa, the molecular pump is started to perform high vacuum extraction until the pressure in the chamber reaches 0.35 Pa. In the control system of the equipment, the gas flow rate and deposition time are set:

[0054] During the bottom deposition stage, only the nitrogen inlet valve was opened, and the nitrogen flow rate was set to 500 sccm. The deposition time was 26 min, forming a dense and uniform TiAlN red rose-colored coating with a thickness of 13.5 μm.

[0055] During the intermediate layer deposition stage, the oxygen inlet valve was opened, the oxygen flow rate was set to 125 sccm, the nitrogen flow rate was 375 sccm, and the deposition time was 17 min, forming a uniform TiAlNOx red-purple coating with a thickness of 9 μm.

[0056] During the surface deposition stage, the methane inlet valve was opened, the methane flow rate was set to 20 sccm, the oxygen flow rate was reduced to 60 sccm, and the nitrogen flow rate was 380 sccm. The deposition lasted for 14 minutes to form a uniform TiAlNCO violet surface layer with a thickness of about 7.5 μm.

[0057] Example 3

[0058] A method for coating a metal decorative part, the preparation steps are similar to those of Example 1, except that: the medium frequency power supply is set to 42 kW, the mechanical pump is started to roughly evacuate the chamber, and when the pressure in the chamber drops below 10 Pa, the molecular pump is started to perform high vacuum extraction until the pressure in the chamber reaches 0.25 Pa. In the control system of the equipment, the gas flow rate and deposition time are set:

[0059] During the bottom deposition stage, only the nitrogen inlet valve was opened, the nitrogen flow rate was set to 300 sccm, and the deposition time was 25 min, forming a dense and uniform TiAlN red rose-colored coating with a thickness of 7 μm.

[0060] During the intermediate layer deposition stage, the oxygen inlet valve was opened, the oxygen flow rate was set to 83 sccm, and the nitrogen flow rate was 415 sccm. The deposition was carried out for 20 minutes to form a uniform TiAlNOx red-purple coating with a thickness of 7 μm.

[0061] During the surface deposition stage, the methane inlet valve was opened, the methane flow rate was set to 30 sccm, the oxygen flow rate was reduced to 90 sccm, and the nitrogen flow rate was 420 sccm. The deposition lasted for 20 minutes to form a uniform TiAlNCO violet surface layer with a thickness of about 6 μm.

[0062] Example 4

[0063] A coating method for metal decorative parts, which is different from Example 1 in that the voltage is fixed at 100V.

[0064] Example 5

[0065] A coating method for metal decorative parts, which is different from Example 1 in that the voltage is fixed at 30V.

[0066] Example 6

[0067] A method for coating a metal decorative part is different from that of Example 1 in that the part to be coated is preheated before step S1, with a preheating temperature of 200° C. and a preheating time of 15 minutes.

[0068] Example 7

[0069] A method for coating a metal decorative part is different from that of Example 1 in that the part to be coated is preheated before step S1, with a preheating temperature of 300° C. and a preheating time of 10 minutes.

[0070] Example 8

[0071] A method for coating a metal decorative part, which differs from Example 1 in that during the bottom deposition stage, nitrogen is introduced at a flow rate of 290 sccm;

[0072] During the intermediate layer deposition stage, oxygen gas was introduced at a flow rate of 130 sccm, and nitrogen gas flow was adjusted to 300 sccm.

[0073] During the surface deposition stage, when methane is introduced, the flow rate is 15 sccm, the oxygen flow rate is reduced to 100 sccm, and the nitrogen flow rate is 430 sccm; the remaining operations are the same as in Example 1.

[0074] Example 9

[0075] A coating method for a metal decorative part, which differs from Example 1 in that during the bottom deposition stage, nitrogen is introduced at a flow rate of 510 sccm;

[0076] During the intermediate layer deposition stage, oxygen gas was introduced at a flow rate of 75 sccm, and nitrogen gas flow was adjusted to 420 sccm.

[0077] During the surface deposition stage, when methane is introduced, the flow rate is 35 sccm, the oxygen flow rate is reduced to 50 sccm, and the nitrogen flow rate is 370 sccm; the remaining operations are the same as in Example 1.

[0078] Comparative Example

[0079] Comparative Example 1

[0080] A method for coating a metal decorative part, which differs from Example 1 in that no layered deposition is performed and the film is deposited directly on the surface of the part to be plated, specifically comprising the following steps:

[0081] S1. Place the metal decorative parts to be plated in an ultrasonic cleaner filled with alcohol and clean them for 10 minutes. Take them out and rinse them with deionized water. Then put them in an ultrasonic cleaner filled with acetone and continue cleaning for 5 minutes. Take them out and use a nitrogen gun to blow dry the residual liquid on the surface. Then put them in an oven and dry them at 100°C for 20 minutes to ensure that the surface of the parts to be plated is completely dry.

[0082] S2. Install the target material prepared in Preparation Example 1, with a total of four pairs. Place the dried workpiece to be plated on the sample stage, adjust the position and angle of the sample stage so that the surface of the workpiece to be plated is parallel to the surface of the target material and is within the effective sputtering area, set the revolution speed of the sample stage to 2 revolutions / minute, close the chamber door of the coating equipment, set the medium frequency power supply power to 40kw, start the mechanical pump to roughly vacuum the chamber, and when the pressure in the chamber drops below 10Pa, start the molecular pump for high vacuum extraction until the pressure in the chamber reaches 0.3Pa. In the control system of the equipment, set the gas flow rate and deposition time: open the methane inlet valve, set the methane flow rate to 25sccm, the oxygen flow rate to 75sccm, the nitrogen flow rate to 400sccm, and deposit for 60min to form a violet surface layer; during the coating process, the voltage is controlled to decrease linearly from 100v to 30v through the PID feedback system;

[0083] The remaining steps are the same as in Example 1.

[0084] Performance testing

[0085] Color difference: Use a colorimeter to measure the color performance of the coating, record the Lab* value, and compare it with the standard sample to obtain the color difference △E of the coated part;

[0086] Adhesion: Use a scratch tester to perform scratch tests under different loads to observe whether the coating falls off and record the critical load value (HF);

[0087] Wear resistance index: Taber test shows that the wear loss is only 2.3μm after 12,000 times (compared to the patented test of 5μm after 8,000 times).

[0088] Table 1 Test data

[0089]

[0090] Combining Examples 1-3 with Comparative Example 1 and Table 1, it can be seen that the experimental data of Examples 1-3 are all superior to Comparative Example 1. This demonstrates that the staged deposition method for forming a TiAlN / TiAlNOx / TiAlNCO three-layer coating offers significant advantages over the single-component monolithic deposition method in terms of color control, functional gradient optimization, and film-substrate bonding. Layered deposition, by introducing different gases at different stages, forms a base layer, intermediate layer, and surface layer with specific chemical compositions and structures. The synergy between these layers not only helps achieve rich color transitions but also effectively alleviates internal stress concentration issues, improving the overall performance of the coating.

[0091] Combining Example 1 and Example 4-Example 5 and Table 1, it can be seen that the various experimental data of Example 1-Example 3 are better than those of Example 4-Example 5, indicating that the coating process with linearly decreasing voltage is better than the coating process with fixed voltage. In Examples 1-3, high voltage is used to enhance ion bombardment in the early stage of deposition, effectively cleaning and activating the surface of the workpiece to be plated, and promoting the rapid nucleation and growth of the coating; in the later stage, the voltage is gradually reduced to control the growth rate and structure of the coating, reduce the generation of defects, improve the density and crystallization quality of the coating, and release the internal stress of the coating to avoid cracking or peeling. However, Examples 4 and 5 have fixed voltages of 100V and 30V respectively, and cannot achieve this dynamic regulation.

[0092] Combining Example 1 with Examples 6 and 7 and Table 1, it can be seen that the data of Examples 6 and 7 are superior to those of Example 1, indicating that the preheating operation can significantly improve the coating effect. Preheating the workpiece before step S1 can increase the surface temperature of the workpiece, reduce the thermal stress difference between it and the subsequently deposited metal layer, and reduce the internal stress of the coating caused by the mismatch of thermal expansion coefficients, thereby effectively reducing the risk of cracking and shedding of the coating and enhancing the bonding strength between the coating and the workpiece. It also helps to improve the density and color consistency of the coating.

[0093] Combining Example 1 with Examples 8-9 and Table 1, it can be seen that the various data of Example 1 are better than those of Examples 8-9, indicating that the ideal violet TiAlNCO coating with good optical and mechanical properties can be obtained only when the gas flow rate is within the set range.

[0094] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A coating method for metal decorative parts, characterized in that: The steps include: S1. Prepare the parts to be plated, clean and dry them; S2. Under vacuum conditions, plasma-enhanced medium-frequency sputtering technology is used to deposit a metal layer on the surface of the workpiece to be plated. Nitrogen, oxygen, and methane are introduced in stages during the process, and pure nitrogen is introduced during the bottom deposition stage; During the intermediate layer deposition stage, oxygen is introduced with a nitrogen to oxygen flow ratio of 3-5:1; During the surface deposition stage, nitrogen, oxygen and methane were introduced with a flow ratio of 14-19:3:

1. During the deposition process, the voltage was controlled at 30-100V, the vacuum pressure was maintained at 0.3±0.05Pa, the target material was titanium aluminum alloy, the medium frequency power was set to 38-42kW, the total deposition time was 55-65min, and the coating was obtained by deposition.

2. The coating method for a metal decorative part according to claim 1, characterized in that: When nitrogen is introduced during the bottom layer deposition stage, the flow rate is 300-500 sccm; During the intermediate layer deposition stage, oxygen gas is introduced at a flow rate of 83-125 sccm, and nitrogen gas flow rate is adjusted to 375-415 sccm, so that the volume flow rate ratio of nitrogen to oxygen is maintained at 3-5:1; When methane is introduced during the surface deposition stage, the flow rate is 20-30 sccm, the oxygen flow rate is reduced to 60-90 sccm, and the nitrogen flow rate is 380-420 sccm, so that the volume flow ratio of nitrogen:oxygen:methane is maintained at 14-19:3:

1.

3. The coating method for a metal decorative part according to claim 2, characterized in that: When nitrogen is introduced during the bottom layer deposition stage, the flow rate is 400 sccm; During the intermediate layer deposition stage, oxygen gas was introduced at a flow rate of 100 sccm and nitrogen gas at a flow rate of 400 sccm; During the surface deposition stage, when methane is introduced, the flow rate is 25 sccm, the oxygen flow rate is reduced to 75 sccm, and the nitrogen flow rate is 400 sccm.

4. The coating method for a metal decorative part according to claim 1, characterized in that: The target material has a composition of 70wt% titanium and 30wt% aluminum, a diameter of 70mm, and is provided in 4 pairs.

5. The coating method for a metal decorative part according to claim 1, characterized in that: The thickness ratio of the bottom layer, the middle layer and the surface layer is (40±5)%: (30±5)%: (30±5)%, and the total thickness is 20-30 μm.

6. The coating method for a metal decorative part according to claim 1, characterized in that: The coating method further comprises preheating the workpiece before step S1, with the preheating temperature being 200-300° C. and the preheating time being 10-15 minutes.

7. The coating method for a metal decorative part according to claim 1, characterized in that: During the deposition process, the applied voltage is uniformly decreased from 100 V to 30 V. The voltage is uniformly controlled by a computer, and the decreasing rate is synchronized with the deposition time.

8. The coating method for a metal decorative part according to claim 1, characterized in that: During the deposition process, the revolution speed of the workpiece to be plated is set to 2 revolutions per minute.

9. A coating film for a metal decorative part prepared according to the method of any one of claims 1 to 8, characterized in that: The coating is a metal layer formed on the surface of the metal decorative part, and the metal layer includes a bottom layer, an intermediate layer and a surface layer, wherein: The bottom layer is a TiAlN red rose coating; the middle layer is a TiAlNOx red purple coating; and the surface layer is a TiAlNCO violet coating.

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