Method for controllably preparing micro-arc oxidation ceramic layer on surface of copper and alloy thereof

Abstract

This application relates to the field of metal surface modification technology and provides a method for preparing a ceramic layer, applicable to the controllable preparation of a micro-arc oxidation ceramic layer on the surface of copper or copper alloys. The method for preparing the ceramic layer includes: pretreating the surface of the component; scanning a portion of the component surface using a pulsed laser to form an oxide layer in that region; and performing micro-arc oxidation treatment on the component as an anode to obtain a micro-arc oxidation ceramic layer on the surface of the oxide layer on the component. The micro-arc oxidation treatment employs constant current bipolar control. This method enables the generation of a ceramic layer only in areas of the copper or copper alloy that require wear, while omitting the generation in areas requiring electrical and thermal conductivity, thus expanding the application range of copper or copper alloys.

Description

Technical Field

[0001] This application relates to the field of metal surface modification technology, and in particular to a method for preparing a ceramic layer, applicable to the controllable preparation of micro-arc oxidation ceramic layers on copper or copper alloy surfaces. Background Technology

[0002] Copper and its alloys are widely used in various industrial fields such as electronics, power, aircraft carriers and ships, transportation, machinery, aerospace, and defense due to their excellent electrical and thermal conductivity. However, copper and its alloys have insufficient hardness and wear resistance, thus requiring surface modification treatment to ensure that copper and its alloys have a long service life in special applications. Currently, common surface modification methods include ion implantation, anodizing, thermal spraying, electroplating, and chemical plating. Micro-arc oxidation technology, as a surface modification technology for in-situ growth of ceramic layers on the surface of valve metals (Al, Mg, Ti, etc.) and their alloys, mainly utilizes spark discharge to generate a ceramic layer on the alloy surface. This ceramic layer has a strong bond with the substrate and exhibits excellent corrosion resistance, wear resistance, and thermal shock resistance. It also has the advantages of simple process, high efficiency, and no pollution, and is gradually becoming a commonly used surface treatment method for valve metals and their alloys.

[0003] However, micro-arc oxidation technology is generally considered unsuitable for some non-valve metals, such as steel, nickel, copper, and their alloys. This typically refers to metals that do not possess valve metal properties during electrolysis. Valve metals, such as aluminum, magnesium, and titanium, exhibit a resistance to anolytical current in the electrolyte, exhibiting high resistance and unidirectional conductivity. Non-valve metals, on the other hand, lack these properties, typically exhibiting lower resistance and higher conductivity during electrolysis, making it difficult to establish stable plasma discharge. Furthermore, the oxide layer is generally formed as a full-coverage layer. However, this full-coverage coating significantly reduces the electrical and thermal conductivity of copper and its alloys, limiting its application range. Therefore, a method for controllably preparing micro-arc oxidation ceramic layers is needed, forming the ceramic layer only on the areas of the copper or its alloy surface that require abrasion, while leaving the areas requiring electrical and thermal conductivity untouched. Summary of the Invention

[0004] In view of this, this application aims to propose a method for preparing a ceramic layer, applicable to the controllable preparation of a micro-arc oxidation ceramic layer on the surface of copper or copper alloy, so as to achieve the generation of a ceramic layer only in the areas of copper or copper alloy that need to be worn, while not generating a ceramic layer in areas that need to conduct electricity and heat, thereby expanding the application range.

[0005] To achieve the above objectives, the technical solution of this application is implemented as follows:

[0006] A method for preparing a ceramic layer, suitable for controllably preparing a micro-arc oxidation ceramic layer on the surface of a component made of copper or its alloy, the method comprising:

[0007] The surface of the component is pretreated;

[0008] A portion of the component's surface is scanned using a pulsed laser, forming an oxide layer in that area.

[0009] The component is used as an anode to undergo micro-arc oxidation treatment, and a micro-arc oxidized ceramic layer is obtained on the surface of the oxide layer on the component.

[0010] The micro-arc oxidation process employs constant current bipolar control.

[0011] Furthermore, the pretreatment of the component surface includes:

[0012] The surface of the component is polished using sandpaper of gradually increasing number.

[0013] After grinding, the surface of the component is polished, cleaned with a mixture of acetone and water, and then dried.

[0014] Furthermore, a portion of the component's surface is scanned using a pulsed laser to form an oxide layer in that area, including:

[0015] A pulsed laser with a power between 600W and 1000W, a duty cycle between 10% and 50%, a frequency between 50 and 2000kHz, and a scanning speed of 10-150mm / s is used to scan a portion of the surface of the component, forming an oxide layer in that area.

[0016] Furthermore, the pulsed laser scanning is performed in an oxygen atmosphere.

[0017] Furthermore, the roughness Ra of the oxide layer is between 0.2 and 3 μm.

[0018] Furthermore, the micro-arc oxidation process employs constant current bipolar control, including:

[0019] The forward current density of the micro-arc oxidation treatment is 1-20 A / cm. 2 Between these ranges, the negative current density is 1-20 A / cm². 2 Between these values, the ratio R of negative current to positive current is between 0.5 and 3, the positive duty cycle is between 5% and 40%, the negative duty cycle is between 5% and 40%, and the frequency is between 50 and 2000 Hz.

[0020] Furthermore, the electrolyte used in the micro-arc oxidation treatment is a mixed aqueous solution of NaAlO2, NaH2PO4 and NaF;

[0021] The micro-arc oxidation treatment time is between 5 min and 120 min.

[0022] Furthermore, in the electrolyte, the concentration of NaAlO2 is between 5 g / L and 20 g / L, the concentration of NaH2PO4 is between 2 g / L and 8 g / L, and the concentration of NaF is between 0.5 g / L and 3 g / L.

[0023] Compared with related technologies, this application has the following advantages:

[0024] The method for preparing the ceramic layer in this application involves scanning a portion of the surface of a copper or copper alloy workpiece with a pulsed laser before micro-arc oxidation. This scans an oxide layer on the scanned area, while the unscanned area remains a metal surface. Under specific electrical parameters, the laser-oxidized area generates fine, dense bubbles, forming a dense film. The untreated area, however, produces large bubbles, preventing the formation of an AAP (Al₂O₃, AlPO₄) insulating layer by the electrolyte. This makes it difficult for the untreated area to undergo plasma discharge breakdown, thus achieving controllable preparation. The micro-arc oxidation ceramic layer is generated in the laser-oxidized area, while the untreated area remains exposed on the metal surface. This micro-arc oxidation ceramic layer significantly improves the wear resistance of copper and its alloys while maintaining their electrical conductivity.

[0025] This application also proposes a non-valve metal component, which is made of copper or a copper alloy and has a ceramic layer on its surface, the ceramic layer being prepared by the above-described method for preparing ceramic layers.

[0026] Furthermore, the copper alloy is a Cu-Cr-Zr alloy, a Cu-Zn alloy, or a Cu-W alloy.

[0027] The non-valve metal components described in this application have a ceramic layer with excellent wear resistance in the areas to be worn, resulting in higher wear resistance. At the same time, they also have the electrical and thermal conductivity of metals, making them more widely applicable. Attached Figure Description

[0028] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0029] Figure 1 This is a flowchart illustrating the method for preparing the ceramic layer as described in the embodiments of this application;

[0030] Figure 2 Here are macroscopic surface views of the workpiece in Example 1 of this application, where (a) is a macroscopic surface view of the workpiece after mechanical grinding in step S1 of Example 1, and (b) is a macroscopic surface view of the workpiece after mechanical grinding in step S1 and laser oxidation in step S2 of Example 1.

[0031] Figure 3 The images shown are morphological images of the workpiece after laser oxidation in Example 1 of this application. Among them, (a) is a confocal three-dimensional morphological image of the laser oxidation region on the surface of the laser workpiece obtained in Example 1, (b) is a confocal two-dimensional morphological image of the oxidation region of the laser workpiece obtained in Example 1, and (c) is a three-dimensional morphological contour curve of the laser workpiece obtained in Example 1.

[0032] Figure 4 The images show macroscopic surface views of the workpieces obtained in Examples 1, 2 and Comparative Example 1 of this application, where (a) is a macroscopic surface view of the workpiece after laser oxidation treatment in Example 1, (b) is a macroscopic surface view of the workpiece obtained in Example 2, and (c) is a macroscopic surface view of the workpiece obtained in Comparative Example 1.

[0033] Figure 5 SEM images of the surface and cross-section of the ceramic layer of the workpiece obtained in Example 2 of this application, wherein (a) is an SEM image of the surface of the micro-arc oxidation ceramic layer obtained in Example 2, and (b) is an SEM image of the cross-section of the micro-arc oxidation ceramic layer obtained in Example 2.

[0034] Figure 6 SEM images of the surface and cross-section of the ceramic layer of the workpiece obtained in Comparative Example 1 of this application are shown, wherein (a) is an SEM image of the surface of the micro-arc oxidation ceramic layer obtained in Comparative Example 1, and (b) is an SEM image of the cross-section of the micro-arc oxidation ceramic layer obtained in Comparative Example 1.

[0035] Figure 7 The time potential diagrams of the workpieces prepared in Example 2 and Comparative Example 1 of this application during 60 min of micro-arc oxidation treatment are shown.

[0036] Figure 8 The XRD patterns of the workpiece surfaces obtained in Example 2 and Comparative Example 1 of this application are shown.

[0037] Figure 9 The graph shows the friction and wear coefficients of the copper alloy matrix in the verification example of this application, Example 2 and Comparative Example 1, which are subjected to sliding friction with GCr15 steel balls under a load of 10N for 30 minutes.

[0038] Figure 10 The cross-sectional wear profiles of the copper alloy matrix in the verification example of this application, Example 2 and Comparative Example 1, are obtained by sliding friction with GCr15 steel balls under a load of 10N for 30 minutes.

[0039] Figure 11 The wear mass and wear rate of the copper alloy substrate in the verification example of this application, Example 2 and Comparative Example 1 are obtained by sliding friction with GCr15 steel balls under a load of 10N for 30 minutes.

[0040] Figure 12Two-dimensional friction and wear morphology images of the copper alloy matrix in the verification example of this application, Example 2 and Comparative Example 1, which were subjected to sliding friction with GCr15 steel balls under a load of 10N for 30 minutes;

[0041] Figure 13 The three-dimensional morphology of friction and wear of the copper alloy matrix in the verification example of this application, Example 2 and Comparative Example 1, is obtained by sliding friction with GCr15 steel balls under a load of 10N for 30 minutes.

[0042] Figure 14 This is a mechanism diagram of the method for preparing the ceramic layer according to an embodiment of this application. Detailed Implementation

[0043] To make the technical solution and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0044] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0045] For items where specific conditions are not specified in this application, conventional conditions or conditions recommended by the manufacturer of the equipment used shall apply. For items where the manufacturer of the reagents or instruments used is not specified, conventional products that can be purchased commercially shall be used. As for the technical means or processes involved, if specific conditions are not specified, they shall be carried out in accordance with the existing methods in the relevant field.

[0046] The first aspect of this application provides a method for preparing a ceramic layer, which is applicable to the controllable preparation of a micro-arc oxidation ceramic layer on the surface of copper or copper alloy. This method enables the generation of a ceramic layer only in areas of the copper or copper alloy that require wear, while areas that require electrical and thermal conductivity are not generated, thus expanding the application range.

[0047] In related technologies, micro-arc oxidation technology is generally considered unsuitable for some non-valent metals, such as steel, nickel, copper, and their alloys, because it is difficult to establish a stable plasma discharge. Recently, researchers have developed a micro-arc oxidation surface treatment method and products suitable for copper and its alloys, enabling the one-time preparation of micro-arc oxidation ceramic layers on copper and its alloy surfaces under specific electrolyte and electrical parameters. Furthermore, studies have shown that laser pretreatment can be used to prepare ceramic layers in situ on copper alloy surfaces, further improving the coating's density and high-temperature oxidation resistance.

[0048] While these methods have solved the problem of forming micro-arc oxidation ceramic layers on the surface of copper and its alloys, and the resulting coatings improve wear resistance and high-temperature oxidation resistance, this full-coverage coating significantly reduces the electrical and thermal conductivity of copper and its alloys. This increases the service life of copper and its alloys but reduces their application range. Therefore, a method for controllably preparing micro-arc oxidation ceramic layers is needed, which forms the ceramic layer only in the areas of the copper and its alloys surface that require wear, while leaving the ceramic layer blank in areas that require electrical and thermal conductivity.

[0049] In view of this, in order to overcome the shortcomings of related technologies, the ceramic layer preparation method of this embodiment combines... Figure 1 In terms of overall design, this method is suitable for controllably preparing micro-arc oxidation ceramic layers on the surface of components made of copper or its alloys, specifically including:

[0050] Step S1: Pre-treat the surface of the component.

[0051] The pretreatment of the component surface in step S1 above, as an exemplary implementation, may include, for example:

[0052] Use sandpaper of gradually increasing number to polish the surface of the component;

[0053] After grinding, the surface of the parts is polished, cleaned with a mixture of acetone and water, and then dried.

[0054] In this preferred embodiment, the surface of the component is polished by using sandpaper of gradually increasing number. For example, SiC sandpaper of 400#, 800#, 1000#, 1200#, 1500# and 2000# can be used to polish the surface of the component.

[0055] It is worth noting that the cleaning with a mixture of acetone and water in step S1 can remove oil and impurities from the alloy surface, making the oxide layer generated in this embodiment adhere better.

[0056] Step S2: Use a pulsed laser to scan a portion of the component surface to form an oxide layer in that area.

[0057] In step S2 above, a portion of the component surface is scanned using a pulsed laser to form an oxide layer in that region. As an exemplary implementation, this could include, for example:

[0058] A pulsed laser with a power between 600W and 1000W, a duty cycle between 10% and 50%, a frequency between 50 and 2000kHz, and a scanning speed of 10-150mm / s is used to scan a portion of the surface of the component, forming an oxide layer in that area.

[0059] Specifically, the roughness Ra of the formed oxide layer is preferably, for example, between 0.2 and 3 μm.

[0060] It is worth noting that the environment in which pulsed laser scanning is performed in step S2 is preferably, for example, in an oxygen atmosphere. By adjusting the concentration of the introduced gas, the oxide density of the oxide layer is adjusted, thereby achieving the adjustment of the density of the micro-arc oxidation ceramic layer.

[0061] Step S3: Use the component as an anode to perform micro-arc oxidation treatment to obtain a micro-arc oxidized ceramic layer on the oxide layer surface of the component;

[0062] The micro-arc oxidation process employs constant current bipolar control. As an exemplary implementation, it may include, for example:

[0063] The forward current density of micro-arc oxidation treatment is 1-20 A / cm. 2 Between these ranges, the negative current density is 1-20 A / cm². 2 Between these values, the ratio R of negative current to positive current is between 0.5 and 3, the positive duty cycle is between 5% and 40%, the negative duty cycle is between 5% and 40%, and the frequency is between 50 and 2000 Hz.

[0064] In the aforementioned micro-arc oxidation process, a preferred embodiment may employ a constant current with a positive current between 2A and 4A, a negative current between 1A and 4A, and a positive current density between 1 and 2A / cm². 2 Between these values, the negative current density is 1~2 A / cm². 2 Between these values, the ratio R of negative current to positive current is between 0.5 and 2, the positive duty cycle is between 10% and 30%, the negative duty cycle is between 10% and 30%, and the frequency is between 500 and 2000 Hz.

[0065] Meanwhile, in the above-mentioned micro-arc oxidation treatment, as an exemplary implementation, the constant current used can be between 4 and 10 A for the positive current and between 4 and 10 A for the negative current, with a positive current density of 2 to 5 A / cm². 2 Between these values, the negative current density is 2~5 A / cm². 2 Between these values, the ratio R of negative current to positive current is between 0.5 and 3, the positive duty cycle is between 10% and 20%, the negative duty cycle is between 10% and 20%, and the frequency is between 500 and 1000 Hz.

[0066] In the above-described micro-arc oxidation process, as an exemplary embodiment, the constant current used can be between 10 and 20 A for the positive current and between 10 and 20 A for the negative current, with a positive current density of 5 to 10 A / cm². 2Between these values, the negative current density is 5~10 A / cm. 2 Between these values, the ratio R of negative current to positive current is between 0.5 and 3, the positive duty cycle is between 20% and 30%, the negative duty cycle is between 20% and 30%, and the frequency is between 1000 and 2000 Hz.

[0067] Specifically, the electrolyte used in the micro-arc oxidation process is preferably a mixed aqueous solution of NaAlO2, NaH2PO4 and NaF.

[0068] The concentrations of the components in the electrolyte are preferably, for example, between 5 g / L and 20 g / L for NaAlO2, between 2 g / L and 8 g / L for NaH2PO4, and between 0.5 g / L and 3 g / L for NaF.

[0069] The duration of the micro-arc oxidation treatment is preferably between 5 min and 120 min.

[0070] In summary, the ceramic layer preparation method of this embodiment involves scanning the surface of a copper or its alloy workpiece with a pulsed laser before micro-arc oxidation treatment. This results in a uniform oxide layer with adjustable roughness on one part of the copper or alloy surface, while the other part remains a metal surface. Under specific parameters, the laser oxidation region generates fine, dense bubbles to form a dense film, while the untreated region generates large bubbles as in traditional preparation methods. This prevents the formation of an AAP (Al2O3, AlPO4) insulating layer by the electrolyte, making it difficult for the untreated region to undergo plasma discharge breakdown, thus achieving controllable preparation. The micro-arc oxidation ceramic layer is generated in the laser oxidation region, while the untreated region remains exposed on the metal surface. The generated micro-arc oxidation ceramic layer significantly improves the wear resistance of copper or its alloy while maintaining its electrical conductivity, expanding the application range of copper or its alloy workpieces.

[0071] An embodiment of the second aspect of this application provides a non-valve metal component made of copper or a copper alloy, and the surface of the non-valve metal component has a ceramic layer, which is prepared by the above-described method for preparing ceramic layers.

[0072] Specifically, the preferred copper alloys are, for example, Cu-Cr-Zr alloys, Cu-Zn alloys, or Cu-W alloys.

[0073] It is worth noting that, regarding the method for preparing the ceramic layer in this embodiment, based on the above exemplary implementations, the following examples can be referred to in specific implementations.

[0074] In the following examples and comparative examples, the pulsed laser can be generated by a pulsed laser, such as the GZ-GL1000-D pulsed laser, the pulsed micro-arc oxidation power supply model FL7-MAO010X, the sliding friction and wear testing machine Bruker (CETR) UMT-2, and the wear rate formula is... ω is the volumetric wear rate, V is the wear volume, X is the load, and L is the total sliding distance.

[0075] Example 1

[0076] Example 1 uses a 3mm thick Cu-Cr-Zr copper alloy sheet as the processing object and performs laser oxidation treatment on the copper alloy, including the following steps:

[0077] Step S1: Use SiC sandpaper of 400#, 800#, 1000#, 1200#, 1500# and 2000# in sequence to polish the surface of the copper alloy thin plate, then polish it with a polishing machine. After that, use a mixture of acetone and deionized water to clean it in an ultrasonic device to remove surface oil and impurities. Take it out and dry it for later use.

[0078] Step S2: Use a pulsed laser to scan the pretreated workpiece surface in an oxygen atmosphere. The scanning power is 600W, the duty cycle is 20%, the frequency is 1000kHz, and the scanning speed is 150mm / s to obtain a workpiece with a part of the surface having a uniform oxide layer and a part of the surface being a metal surface.

[0079] After the laser oxidation treatment is completed, the treated workpiece is removed, rinsed with deionized water, and then dried.

[0080] Example 2

[0081] Example 2 provides a method for preparing a ceramic layer, using a 3mm thick Cu-Cr-Zr copper alloy sheet as the processing object, including the following steps:

[0082] Step S1: Use SiC sandpaper of 400#, 800#, 1000#, 1200#, 1500# and 2000# in sequence to polish the surface of the copper alloy thin plate, then polish it with a polishing machine. After that, use a mixture of acetone and deionized water to clean it in an ultrasonic device to remove surface oil and impurities. Take it out and dry it for later use.

[0083] Step S2: Use a pulsed laser to scan the pretreated workpiece surface in an oxygen atmosphere. The scanning power is 600W, the duty cycle is 20%, the frequency is 1000kHz, and the scanning speed is 150mm / s to obtain a workpiece with a part of the surface having a uniform oxide layer and a part of the surface being a metal surface.

[0084] Step S3: A bipolar pulsed micro-arc oxidation power supply is used, operating in bipolar constant current mode (2A positive current, 1A negative current). A stainless steel electrolytic cell is used as the negative electrode, and the workpiece obtained in S2, with a portion of its surface having a uniform oxide layer and a portion having a metallic surface, is used as the positive electrode. The positive electrode is completely immersed in the electrolyte. The frequency and positive / negative duty cycles are set to 1000Hz and 20%, respectively, with a positive current density of 1A / cm². 2 The negative current density is 0.5 A / cm². 2 The ratio of negative current to positive current, R, is 0.5, and the oxidation time is 60 min. The electrolyte used contains 10 g / L NaAlO2, 2 g / L NaH2PO4, and 1 g / L NaF.

[0085] After the micro-arc oxidation treatment, the treated workpiece was removed, rinsed with deionized water, and then dried. Using GCr15 steel balls, it was subjected to sliding friction under a 10N load for 30 minutes, resulting in a wear rate of 11.2 × 10⁻⁶. -4 mm 3 / N·m.

[0086] Comparative Example 1

[0087] This comparative example provides a method for preparing a ceramic layer, using a 3mm thick Cu-Cr-Zr copper alloy sheet as the processing object. The steps are similar to those in Example 2, except that the ratio R of the negative current to the positive current is increased. The specific steps are as follows:

[0088] Step S1: Use SiC sandpaper of 400#, 800#, 1000#, 1200#, 1500# and 2000# in sequence to polish the surface of the copper alloy thin plate, then polish it with a polishing machine. After that, use a mixture of acetone and deionized water to clean it in an ultrasonic device to remove surface oil and impurities. Take it out and dry it for later use.

[0089] Step S2: Use a pulsed laser to scan the pretreated workpiece surface in an oxygen atmosphere. The scanning power is 600W, the duty cycle is 20%, the frequency is 1000kHz, and the scanning speed is 150mm / s to obtain a workpiece with a part of the surface having a uniform oxide layer and a part of the surface being a metal surface.

[0090] Step S3: A bipolar pulsed micro-arc oxidation power supply is used, operating in bipolar constant current mode (2A positive current, 2A negative current). A stainless steel electrolytic cell is used as the negative electrode, and the workpiece obtained in S2, with a portion of its surface having a uniform oxide layer and a portion having a metallic surface, is used as the positive electrode. The positive electrode is completely immersed in the electrolyte. The frequency and positive / negative duty cycles are set to 1000Hz and 20%, respectively, with a positive current density of 1A / cm².2 The negative current density is 1 A / cm 2 The ratio of negative current to positive current, R, is 1, and the oxidation time is 60 min. The electrolyte used contains 10 g / L NaAlO2, 2 g / L NaH2PO4, and 1 g / L NaF.

[0091] After the micro-arc oxidation treatment, the treated workpiece was removed, rinsed with deionized water, and then dried. Using GCr15 steel balls, it was subjected to sliding friction under a 10N load for 30 minutes, resulting in a wear rate of 0.45 × 10⁻⁶. -4 mm 3 / N·m.

[0092] Verification Example

[0093] This verification example involves observing the surfaces of the workpieces obtained in Examples 1-2 and Comparative Example 1, testing the potential during the 60-minute micro-arc oxidation treatment in Examples 2 and Comparative Example 1, performing XRD tests on the surfaces of the workpieces obtained in Examples 2 and Comparative Example 1, and conducting friction and wear tests on an untreated CuCrZr copper alloy substrate, the treated workpieces obtained in Example 2, and the treated workpieces obtained in Comparative Example 1, using GCr15 steel balls under a 10N load for 30 minutes. These methods aim to verify the controllability of the ceramic layer preparation method and the wear resistance of the obtained ceramic layer.

[0094] Depend on Figure 2 As can be seen from (a) and (b), after pulsed laser scanning of the pretreated copper alloy workpiece, a uniform oxide layer is formed on part of the surface of the copper alloy workpiece, and the other part is a metal surface.

[0095] Depend on Figure 3 The three-dimensional and two-dimensional morphological images of the oxide layer formed on the surface of the copper alloy workpiece after pulsed laser scanning (a) and (b) show that the average surface roughness Sa = 0.98 μm after laser scanning in Example 1. The three-dimensional morphological contour image in Figure (c) shows that the width of each laser scan is 301.9 μm and the depth is 4.48 μm.

[0096] This indicates that after the copper alloy is laser-scanned, a uniform surface morphology and oxide layer are generated in this area. By changing parameters such as the laser power, the average roughness of the alloy surface can be changed, thereby allowing the generated uniform oxide layer to further act on the micro-arc oxidation preparation process. This ensures that only the laser oxidation area can generate a uniform micro-arc oxidation ceramic layer, thus completing the controllable preparation.

[0097] Depend on Figure 4 As can be seen, compared to the workpiece prepared in Example 1 after laser oxidation treatment, the controllable preparation in Comparative Example 1 is more precise, and the exposed metal area in the un-laser-oxidized region is larger. Example 2 corresponds to... Figure 4 In (b), the white area represents the generated CuAlO2, and the black area represents the generated Al2O3, which are the areas where the micro-arc oxide ceramic layer is formed after laser oxidation. This corresponds to the area in Comparative Example 1. Figure 4 (c) has a thicker coating in the black area.

[0098] Depend on Figure 5 and Figure 6 It can be seen that the surface morphology of the micro-arc oxide ceramic layer generated in the laser oxidation region of the copper alloy workpiece, magnified 700 times under SEM, is similar to that of Example 2 and Comparative Example 1. Figure 5 The surface discharge pores of a and 6a) exhibit a crater-like morphology, similar to the microstructure of valve metal micro-arc oxidation.

[0099] Example 2: More black areas on the surface. (This area corresponds to...) Figure 4 The white area in the macroscopic image of (b) represents CuAlO2. The white area on the surface of Comparative Example 1 corresponds to... Figure 4 The black area in the macroscopic image in (c) is Al2O3. From Example 2 and Comparative Example 1 (… Figure 5 As can be seen from the cross-sectional images (b and 6b), the average thickness of the coating in Example 2 is 56.6 μm, while the average thickness of the coating in Comparative Example 1 is 62.4 μm. Compared to Example 2, the coating thickness of Comparative Example 1 is larger and more dense, and no large discharge channels were found.

[0100] Depend on Figure 7 As can be seen, compared with the electrical parameters of Example 2, the time to reach the breakdown voltage in Comparative Example 1 is significantly reduced, but the negative voltage remains higher than that in Example 2, and the voltage continues to rise. In contrast, the voltage in Example 2 tends to stabilize after reaching the breakdown voltage, which is due to the transition to the large arc discharge stage. The soft spark discharge stage in Comparative Example 1 takes longer, which is also the reason why the coating in Comparative Example 1 is denser.

[0101] Depend on Figure 8 As can be seen, the XRD test results of the micro-arc oxidation ceramic layers of Example 2 and Comparative Example 1 show that both coatings are composed of α-Al2O3, γ-Al2O3, CuAlO2, CuO, Cu2O, and AlPO4. However, the peak values ​​of Comparative Example 1 are higher than those of Example 2, which also proves that the coating thickness of the workpiece prepared by Comparative Example 1 is thicker.

[0102] Depend on Figure 9 It can be seen that the friction and wear coefficients of the substrate, Example 2, and Comparative Example 1 are obtained by sliding friction with GCr15 steel balls under a load of 10N for 30 minutes. Compared with the copper alloy substrate, the friction coefficient of Comparative Example 1 is lower and more stable with smaller fluctuations, while the friction coefficient of Example 2 is higher and fluctuates more.

[0103] Depend on Figure 10As can be seen from the cross-sectional friction wear profiles of the substrate, Example 2, and Comparative Example 1, which were subjected to sliding friction with GCr15 steel balls under a load of 10N for 30 minutes, the cross-sectional wear area of ​​Example 2 is larger than that of the copper alloy substrate. The coating was worn away and deposits formed on both sides of the wear track, which is due to the higher Cu2O content in the coating. The wear profile of Comparative Example 1 shows only a small amount of wear, indicating a higher coating density.

[0104] Depend on Figure 11 It can be seen that the wear masses of the substrate, Example 2, and Comparative Example 1, when subjected to sliding friction under a 10N load for 30 minutes using GCr15 steel balls, are 2.89 mg, 3.11 mg, and 1.42 mg, respectively, with wear rates of 6.8 × 10⁻⁶. -4 mm 3 / N·m,11.2×10 -4 mm 3 / N·m and 0.45×10 -4 mm 3 / N·m. Compared to the copper alloy substrate, the workpiece prepared in Example 2 has a greater wear mass because the coating and part of the substrate are worn away. The workpiece prepared in Comparative Example 1 has a smaller wear mass and higher wear resistance.

[0105] The wear rate data shows that the wear resistance of the workpiece prepared in Comparative Example 1 is about 15 times that of the substrate. Comparative Example 1, under controllable preparation conditions, produces a dense coating with high wear resistance.

[0106] Depend on Figure 12 and Figure 13 The results show the two-dimensional and three-dimensional morphologies of the substrate, Example 2, and Comparative Example 1 after frictional wear using GCr15 steel balls under a 10N load for 30 minutes. Compared to the copper alloy substrate, Example 2 shows a wider wear track that wears away the coating, while Comparative Example 1 only shows a partial wear track, indicating higher wear resistance.

[0107] Depend on Figure 14 It can be seen that the mechanism of controllable micro-arc oxidation ceramic layer preparation on copper alloy surface is possible. Figure 14 (a) shows that a Cu2O oxide layer was generated in some areas and left untreated in others by laser-induced oxidation treatment. Figure 14 (b) shows that under specific parameters, the laser oxidation region generates fine, dense bubbles to form a dense film, while the untreated region generates large bubbles as in the conventional preparation mode. This prevents the formation of an AAP (Al2O3, AlPO4) insulating layer by the electrolyte, making it difficult for the untreated region to generate plasma discharge breakdown, thus achieving controllable preparation. A micro-arc oxidation film is formed in the laser oxidation region, while no film is formed in the untreated region, exposing the bare metal surface.

[0108] In summary, the method for preparing the ceramic layer of this application can generate a micro-arc oxidation ceramic layer in the region after laser oxidation, without forming a coating on the surface of copper and its alloys, thus maintaining the electrical and thermal conductivity required for the application and improving the application range of micro-arc oxidation technology for copper and its alloys.

[0109] Meanwhile, by controlling the ratio R of negative current to positive current in the micro-arc oxidation process, the thickness and wear resistance of the final obtained ceramic layer can be adjusted. When the value of R increases, the wear resistance of the workpiece is higher.

[0110] The above descriptions are merely some embodiments of this application and are not intended to limit this application. The technical features or structures in the foregoing different embodiments can be arbitrarily combined to form other specific technical solutions as needed. For those skilled in the art, this application can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of the claims of this application.

Claims

1. A method for preparing a ceramic layer, suitable for controllably preparing a micro-arc oxidation ceramic layer on the surface of a component made of copper or its alloy, characterized in that, The method includes: The surface of the component is pretreated; A portion of the component's surface is scanned using a pulsed laser, forming an oxide layer in that area. The component is used as an anode to undergo micro-arc oxidation treatment, and a micro-arc oxidized ceramic layer is obtained on the surface of the oxide layer on the component. The micro-arc oxidation process employs constant current bipolar control.

2. The method for preparing the ceramic layer according to claim 1, characterized in that, The pretreatment of the component surface includes: The surface of the component is polished using sandpaper of gradually increasing number. After grinding, the surface of the component is polished, cleaned with a mixture of acetone and water, and then dried.

3. The method for preparing the ceramic layer according to claim 1, characterized in that, A portion of the component's surface is scanned using a pulsed laser to form an oxide layer in that area, including: A pulsed laser with a power between 600W and 1000W, a duty cycle between 10% and 50%, a frequency between 50 and 2000kHz, and a scanning speed of 10-150mm / s is used to scan a portion of the surface of the component, forming an oxide layer in that area.

4. The method for preparing the ceramic layer according to claim 3, characterized in that: The pulsed laser scanning was performed in an oxygen atmosphere.

5. The method for preparing the ceramic layer according to claim 3, characterized in that: The roughness Ra of the oxide layer is between 0.2 and 3 μm.

6. The method for preparing the ceramic layer according to claim 1, characterized in that... The micro-arc oxidation process employs constant current bipolar control, including: The forward current density of the micro-arc oxidation treatment is 1-20 A / cm. 2 Between these ranges, the negative current density is 1-20 A / cm². 2 Between these values, the ratio R of negative current to positive current is between 0.5 and 3, the positive duty cycle is between 5% and 40%, the negative duty cycle is between 5% and 40%, and the frequency is between 50 and 2000 Hz.

7. The method for preparing the ceramic layer according to claim 6, characterized in that: The electrolyte used in the micro-arc oxidation treatment is a mixed aqueous solution of NaAlO2, NaH2PO4 and NaF. The micro-arc oxidation treatment time is between 5 min and 120 min.

8. The method for preparing the ceramic layer according to claim 6, characterized in that: In the electrolyte, the concentration of NaAlO2 is between 5 g / L and 20 g / L, the concentration of NaH2PO4 is between 2 g / L and 8 g / L, and the concentration of NaF is between 0.5 g / L and 3 g / L.

9. A non-valve metal component, characterized in that: The non-valve metal component is made of copper or a copper alloy, and the surface of the non-valve metal component has a ceramic layer, which is prepared by the method of any one of claims 1 to 8.

10. The non-valve metal component according to claim 9, characterized in that: The copper alloy is a Cu-Cr-Zr alloy, a Cu-Zn alloy, or a Cu-W alloy.

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