Crn-based composite conductive wear-resistant coating and preparation method thereof, and power connector

Abstract

The application relates to a CrN-based composite conductive wear-resistant coating and a preparation method thereof, and a power connector, the coating comprising a bearing support and a plurality of conductive units arranged in the bearing support, the bearing support comprising a diffusion barrier layer, a stress transition layer and a CrN-based wear-resistant layer, the conductive unit comprising a conductive root arranged in contact and a conductive main body, the conductive main body being located in the CrN-based wear-resistant layer and exposing one side to the CrN-based wear-resistant layer, the conductive root extending at least to the diffusion barrier layer from one end away from the conductive main body, the conductive main body comprising at least one conductive subunit, the conductive subunit comprising a conductive reserve part and a conductive neck part, and the lateral cross-sectional area of the conductive reserve part being greater than that of the conductive neck part. The bearing support formed by the CrN-based material and the conductive unit embedded in the bearing support make the coating have excellent wear resistance and conductivity, and the variable cross-section design of the conductive unit enables the coating to change the surface conductive area according to the wear degree.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, and particularly relates to a CrN-based composite conductive wear-resistant coating and its preparation method, as well as a power connector. Background Technology

[0002] DC charging stations are the core infrastructure for enabling rapid charging of electric vehicles, and their power terminals are key components that establish the electrical connection between the charging gun and the vehicle's charging dock. With the rapid development of high-power charging technology for electric vehicles, the power terminals of DC charging stations need to be able to operate continuously under high charging current conditions.

[0003] Each time a charging gun and a vehicle charging dock are connected and disconnected, the power terminal contact surface is subjected to a combination of normal contact pressure, axial or circumferential tangential friction, environmental corrosion, and current thermal effects. As the frequency of use increases, repeated connection and disconnection causes gradual wear on the power terminal contact surface, reducing the local contact area. This reduction in contact area leads to a significant increase in contact resistance, which directly causes a sharp rise in Joule heating. This Joule heating, in turn, accelerates oxidation and material softening on the contact surface, further reducing the effective contact area and increasing contact resistance. This creates a vicious cycle between contact resistance and Joule heating, resulting in increased terminal temperature rise, derating charging, and thermal aging of insulation components. In severe cases, it can lead to safety hazards such as terminal burning or connection failure.

[0004] Existing technologies address the aforementioned problems by coating the surface of power terminals. Power terminals typically use copper or copper alloys as the conductive substrate. Applying silver, tin, nickel, gold, or corresponding alloy coatings to the conductive substrate can effectively reduce initial contact resistance, but after repeated insertions and removals, scratches, plastic coating, material transfer, and wear debris accumulation can easily occur, leading to localized wear through the coating and oxidation or corrosion of the conductive substrate, resulting in a rapid increase in contact resistance. Applying a CrN coating to the conductive substrate can improve its wear and corrosion resistance, but it is not conducive to reducing contact resistance. Coatings made of soft conductive metals and CrN can also be applied to the conductive substrate, but it is difficult to simultaneously maintain the advantages of high wear resistance and good conductivity. Therefore, there is an urgent need for a surface protection solution for power terminals that can balance high wear resistance and good conductivity to fundamentally solve the problem of contact performance degradation of power terminals under long-term high-current charging and repeated insertion and removal conditions. Summary of the Invention

[0005] To address the aforementioned technical problems, this application provides a CrN-based composite conductive wear-resistant coating, its preparation method, and a power connector.

[0006] In a first aspect, embodiments of this application disclose a CrN-based composite conductive wear-resistant coating, comprising: The support structure includes a diffusion barrier layer, a stress transition layer and a CrN-based wear-resistant layer stacked sequentially, wherein the diffusion barrier layer is used to contact the surface to be coated. Multiple conductive units are embedded in a support bracket and spaced apart from each other. The support bracket covers at least the sidewall of each conductive unit. There is a phase interface between the support bracket and each conductive unit. Each conductive unit includes a conductive root and a conductive body that are in contact with each other along a preset direction. The conductive body is located in a CrN-based wear-resistant layer. The surface of the conductive body away from the conductive root is exposed on the side of the CrN-based wear-resistant layer away from the diffusion barrier layer. One end of the conductive root is located in the CrN-based wear-resistant layer and contacts the conductive body. The other end extends at least to the side of the diffusion barrier layer facing the CrN-based wear-resistant layer. The conductive body includes one conductive sub-unit or multiple conductive sub-units that are in contact with each other along a preset direction. Each conductive sub-unit includes a conductive reserve and a conductive neck that are in contact with each other along a preset direction. The conductive reserve in each conductive sub-unit is located on the side of the conductive neck near the conductive root. The transverse cross-sectional area of ​​the conductive reserve in the preset direction is larger than the transverse cross-sectional area of ​​the conductive neck in the preset direction.

[0007] In some possible embodiments, the surface of the conductive body portion away from the conductive root portion is not higher than the surface of the CrN-based wear-resistant layer away from the diffusion barrier layer, and the distance between the surface of the conductive body portion away from the conductive root portion and the surface of the CrN-based wear-resistant layer away from the diffusion barrier layer is in the range of 0-1 micrometer.

[0008] In some possible embodiments, the end of the conductive root away from the conductive body extends to the side of the diffusion barrier layer facing the CrN-based wear-resistant layer. Alternatively, the conductive root extends from one end away from the conductive body to the side of the diffusion barrier layer away from the CrN-based wear-resistant layer. Alternatively, the end of the conductive root that is away from the conductive body protrudes from the side of the diffusion barrier layer that is away from the CrN-based wear-resistant layer.

[0009] In some possible embodiments, the conductive body includes a plurality of conductive sub-units, and in any two conductive sub-units, the cross-sectional area of ​​the conductive reserve portion in the conductive sub-unit closer to the conductive root in the predetermined direction is greater than the cross-sectional area of ​​the conductive reserve portion in the conductive sub-unit farther from the conductive root in the predetermined direction.

[0010] In some possible embodiments, the transverse cross-sectional area of ​​each conductive reservoir in a predetermined direction gradually increases from the end of the conductive reservoir away from the conductive root to the end of the conductive reservoir closer to the conductive root. Alternatively, the lateral cross-sectional area of ​​each conductive reservoir is constant in a preset direction; Alternatively, the transverse cross-sectional area of ​​each conductive reservoir in a preset direction gradually decreases from the middle region of the conductive reservoir towards both ends of the conductive reservoir.

[0011] In some possible embodiments, the ratio of the transverse cross-sectional area of ​​the conductive reserve portion in each conductive subunit to the transverse cross-sectional area of ​​the conductive neck in the predetermined direction ranges from 1.5 to 20.

[0012] In some possible embodiments, the diffusion barrier layer includes one or more diffusion barrier sublayers stacked together, and the material of the diffusion barrier sublayer includes at least one of Cr, Ni, NiCr alloy, NiCrMo alloy and CrCu alloy.

[0013] In some possible embodiments, the material of the stress transition layer includes CrN. x , 0≤x<1, the nitrogen content in the stress transition layer gradually increases from the side of the stress transition layer in contact with the diffusion barrier layer to the side of the stress transition layer in contact with the CrN-based wear-resistant layer.

[0014] In some possible embodiments, the material of the CrN-based wear-resistant layer includes one selected from the group consisting of: CrN; A mixed phase of Cr2N and CrN; CrN-TiN; CrN-SiN; The CrN phase accounts for more than or equal to 50% of the volume in the CrN-based wear-resistant layer.

[0015] In some possible embodiments, the material of the CrN-based wear-resistant layer also includes a modifying element selected from at least one of Al, Ti, Si, Mo, and C.

[0016] In some possible embodiments, the materials of the conductive root, conductive reservoir, and conductive neck all include one of Ag, Cu, Ag-Cu alloy, Ag-Pd alloy, Cu-Ag-Sn alloy, and Ag-Sn alloy.

[0017] Secondly, embodiments of this application disclose a method for preparing a CrN-based composite conductive wear-resistant coating, comprising: S1 forms a diffusion barrier layer; S2 forms a stress transition layer and a plurality of spaced conductive roots. The stress transition layer is located on the diffusion barrier layer. One end of the conductive root is higher than the upper surface of the stress transition layer, and the other end extends at least to the upper surface of the diffusion barrier layer. S3 forms a conductive reserve at each conductive root; S4 forms the first CrN-based wear-resistant sublayer, which is located on the stress transition layer and covers the sidewalls of the conductive root and the sidewalls of the conductive reserve. S5 forms a conductive neck on each conductive reservoir, the transverse cross-sectional area of ​​the conductive neck is smaller than the transverse cross-sectional area of ​​the conductive reservoir, and the conductive reservoir and the conductive neck form a conductive subunit. S6 When the CrN-based composite conductive wear-resistant coating includes multiple conductive sub-units, a new conductive reserve is formed on each conductive neck, and a second CrN-based wear-resistant sub-layer is formed on the first CrN-based wear-resistant sub-layer. The second CrN-based wear-resistant sub-layer is located on the first CrN-based wear-resistant sub-layer and covers the sidewall of the conductive neck and the sidewall of the newly formed conductive reserve. Then, a new conductive neck is formed on each newly formed conductive reserve. This process is repeated until a predetermined number of conductive sub-units are formed. S7 After step S5 or step S6, a third CrN-based wear-resistant sublayer is formed. The third CrN-based wear-resistant sublayer is located on the first CrN-based wear-resistant sublayer or the second CrN-based wear-resistant sublayer and covers the sidewall of the newly formed conductive neck. The upper surface of the conductive neck is exposed in the third CrN-based wear-resistant sublayer.

[0018] Thirdly, embodiments of this application disclose a power connector, including a connection terminal and the aforementioned CrN-based composite conductive wear-resistant coating. The surface of the connection terminal includes a plug-in contact area, the CrN-based composite conductive wear-resistant coating is located in the plug-in contact area, and the diffusion barrier layer is in contact with the connection terminal.

[0019] In some possible embodiments, the plug-in contact area includes a high contact pressure area, a medium contact pressure area, and a low contact pressure area distributed sequentially from the inside to the outside on the surface of the connection terminal. The number density of conductive units in the CrN-based composite conductive wear-resistant coating located in the high contact pressure area, the number density of conductive units in the CrN-based composite conductive wear-resistant coating located in the medium contact pressure area, and the number density of conductive units in the CrN-based composite conductive wear-resistant coating located in the low contact pressure area decreases sequentially.

[0020] The technical solution provided in this application has the following technical effects: The CrN-based composite conductive wear-resistant coating of this application includes a support bracket and multiple conductive units. The support bracket comprises a diffusion barrier layer, a stress transition layer, and a CrN-based wear-resistant layer stacked sequentially. The diffusion barrier layer is used to contact the surface to be coated. Multiple conductive units are embedded in the support bracket and spaced apart from each other. The support bracket at least covers the sidewall of each conductive unit, and there is a phase interface between the support bracket and each conductive unit. Each conductive unit includes a conductive root and a conductive body portion that are contacted along a predetermined direction. The conductive body portion is located in the CrN-based wear-resistant layer, and one end of the conductive root portion is located in the CrN-based wear-resistant layer. The conductive body is in contact with the conductive main body, and the other end extends at least to the side of the diffusion barrier layer facing the CrN-based wear-resistant layer. The surface of the conductive main body away from the conductive root is exposed on the side of the CrN-based wear-resistant layer away from the diffusion barrier layer. The conductive main body includes one conductive sub-unit or multiple conductive sub-units that are contacted and arranged along a preset direction. The conductive sub-unit includes a conductive reserve portion and a conductive neck that are contacted and arranged along the preset direction. The conductive reserve portion in each conductive sub-unit is located on the side of the conductive neck near the conductive root. The transverse cross-sectional area of ​​the conductive reserve portion in the preset direction is larger than the transverse cross-sectional area of ​​the conductive neck in the preset direction. In the embodiments of this application, the coating has excellent wear resistance and conductivity simultaneously through the support bracket formed by the CrN-based material and the conductive unit embedded in the support bracket. Furthermore, the variable cross-section design of the conductive unit allows the coating to change the surface conductive area according to the degree of wear, thereby enabling the coating to take into account the advantages of conductivity, wear resistance, corrosion resistance, and precious metal conservation. Attached Figure Description

[0021] To more clearly illustrate the technical solutions and advantages in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of a DC charging gun and a vehicle-side socket; Figure 2 and Figure 3 These are schematic diagrams of a CrN-based composite conductive wear-resistant coating provided in the embodiments of this application. Figure 1 and indication Figure 2 ; Figure 4 This is a partial structural schematic diagram of a power connector provided in an embodiment of this application; Figure 5 This is a schematic diagram of the conductive area of ​​the CrN-based composite conductive wear-resistant coating in the unworn state in the embodiments of this application; Figure 6This is a schematic diagram of the conductive area of ​​the CrN-based composite conductive wear-resistant coating in the embodiments of this application when it is worn down to the first-level conductive reserve. Figure 7 This is a schematic diagram of the conductive area of ​​the CrN-based composite conductive wear-resistant coating in the embodiments of this application when it is worn down to the second-level conductive reserve. Figure 8 This is a schematic flowchart of a method for preparing a CrN-based composite conductive wear-resistant coating according to an embodiment of this application. Detailed Implementation

[0023] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0024] It should be noted that the term "an embodiment" or "embodiment" in the specification of the embodiments of this application refers to a specific feature, structure, or characteristic that can be included in at least one implementation of this application. It should be understood that in the specification, claims, and accompanying drawings of the embodiments of this application, the terms "upper," "lower," "top," "bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" and "second" may explicitly or implicitly include one or more of that feature. Moreover, the terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, in the description of this embodiment, unless otherwise stated, "a plurality of" means two or more. Additionally, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, for example, a process, method, system, or product that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or devices.

[0025] It should be understood that when a device or component is referred to as being "on," "adjacent to," or "connected to" other devices or components, it may be directly on, adjacent to, or connected to other devices or components, or there may be intervening devices or components. Conversely, when a device or component is referred to as being "directly on," "directly adjacent to," or "directly connected to" other devices or components, there are no intervening devices or components. It should be understood that although the terms first, second, third, etc., may be used to describe various components, areas, layers, and / or parts, these components, areas, layers, and / or parts should not be limited by these terms. These terms are only used to distinguish one component, area, layer, or part from another component, area, layer, or part. Therefore, without departing from the teachings of this application, the first component, area, layer, or part discussed below may be referred to as the second component, area, layer, or part. And the discussion of the second component, area, layer, or part does not imply that the first component, area, layer, or part necessarily exists in this application.

[0026] To make the objectives, technical solutions, and advantages disclosed in the embodiments of this application clearer, the embodiments of this application will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the embodiments of this application and are not intended to limit the embodiments of this application.

[0027] Figure 1 This is a schematic diagram of the DC charging gun and the vehicle-side socket, as shown below. Figure 1 As shown, the DC charging gun has a high-current connection terminal at the position for insertion into the vehicle-side socket. The high-current connection terminal can be made of copper, brass, CuCrZr alloy, CuNiSi alloy, beryllium copper, or other copper alloy conductive materials. To prevent wear on the surface of the connection terminal, a coating is typically applied. Preferably, the coating is only applied to the actual insertion contact area of ​​the connection terminal; the crimping area, soldering area, and cable connection area of ​​the connection terminal can be kept uncoated by using a mask.

[0028] This application provides a coating that combines excellent wear resistance and conductivity, which can be applied to the connection terminals of DC charging guns, as well as to other devices to be protected.

[0029] Figure 2 and Figure 3 These are schematic diagrams of a CrN-based composite conductive wear-resistant coating provided in the embodiments of this application. Figure 1 and indication Figure 2 ,like Figure 2 or Figure 3As shown, the coating includes a support bracket 1 and multiple conductive units 2. The support bracket 1 includes a diffusion barrier layer 11, a stress transition layer 12, and a CrN-based wear-resistant layer 13 stacked sequentially. The diffusion barrier layer 11 is used to contact the surface to be coated. Multiple conductive units 2 are embedded in the support bracket 1 and spaced apart from each other. The support bracket 1 at least covers the sidewall of each conductive unit 2. There is a phase interface between the support bracket 1 and each conductive unit 2. The conductive unit 2 includes a conductive root 21 and a conductive body portion that are contacted along a predetermined direction. The conductive body portion is located in the CrN-based wear-resistant layer 13. The surface of the conductive body portion facing away from the conductive root 21 is exposed on the side of the CrN-based wear-resistant layer 13 facing away from the diffusion barrier layer 11. One end of the conductive root 21 is located in the CrN-based wear-resistant layer 13 and contacts the conductive body portion. The other end extends at least to the side of the diffusion barrier layer 11 facing the CrN-based wear-resistant layer 13. The conductive body portion includes a conductive sub-unit 22 (e.g., Figure 2 As shown, Figure 2 There is one conductive sub-unit 22) or multiple conductive sub-units 22 arranged in contact along a preset direction (e.g., Figure 3 As shown, Figure 3 There are two conductive sub-units 22 (the serial number 22 indicates one of them). The conductive sub-unit 22 includes a conductive reserve portion 221 and a conductive neck 222 that are contacted and disposed along a preset direction. The conductive reserve portion 221 in each conductive sub-unit 22 is located on the side of the conductive neck 222 near the conductive root portion 21. The transverse cross-sectional area of ​​the conductive reserve portion 221 in the preset direction is greater than the transverse cross-sectional area of ​​the conductive neck 222 in the preset direction.

[0030] In this embodiment, the coating possesses both excellent wear resistance and conductivity through the support bracket 1 formed of CrN-based material and the conductive unit 2 embedded in the support bracket 1. Furthermore, the variable cross-section design of the conductive unit 2 allows the coating to change its surface conductive area according to the degree of wear, thereby enabling the coating to combine the advantages of conductivity, wear resistance, corrosion resistance, and precious metal conservation.

[0031] In this embodiment, the coating comprises a support bracket 1 and multiple conductive units 2 embedded in the support bracket 1. The multiple conductive units 2 are spaced apart from each other, and a relatively clear phase interface is formed between the support bracket 1 and each conductive unit 2. The support bracket 1 forms the main support skeleton of the coating in the form of a continuous phase structure, which is used to withstand the contact pressure and tangential friction during the insertion process of the connection terminal, and to prevent water vapor, chloride ions and oxidizing media from penetrating into the connection terminal. The multiple conductive units 2 are distributed at intervals to form the wear compensation conductive system of the coating. Their sides are covered and surrounded by the support bracket 1, and at least one end of their surface is exposed outside the support bracket 1 to achieve electrical connection with other structures. The support bracket 1 is formed of a wear-resistant and corrosion-resistant CrN-based material, giving the coating excellent wear resistance. The conductive units 2 are made of a metal material with good conductivity, giving the coating excellent conductivity.

[0032] In this embodiment of the application, the support bracket 1 includes a support along a first direction (such as...). Figure 2 or Figure 3 The diffusion barrier layer 11, stress transition layer 12 and CrN-based wear-resistant layer 13 are sequentially stacked in the Y direction shown, wherein the diffusion barrier layer 11 is used to contact the surface to be coated.

[0033] In this embodiment, the diffusion barrier layer 11 can be disposed between the surface to be coated and the stress transition layer 12 to improve the interfacial bonding force between the structure to be protected (such as a copper alloy terminal) and the coating, and to inhibit the diffusion of elements in the structure to be protected (such as copper in the copper alloy terminal) into the CrN-based wear-resistant layer 13.

[0034] In some embodiments, the diffusion barrier layer 11 includes one or more diffusion barrier sublayers stacked together. The material of each diffusion barrier sublayer includes at least one of Cr, Ni, NiCr alloy, NiCrMo alloy, and CrCu alloy, and the materials of different diffusion barrier sublayers may be the same or different.

[0035] In some embodiments, the thickness of the diffusion barrier layer 11 (as shown in the figure) Figure 2 or Figure 3 The length in the Y direction shown is 0.05-1.0 micrometers, for example, 0.2 micrometers, 0.5 micrometers, 0.8 micrometers, etc.

[0036] In one alternative embodiment, the diffusion barrier layer 11 has a higher Cr content on the side closer to the stress transition layer 12 and a higher Ni content on the side farther from the stress transition layer 12.

[0037] In this embodiment, the stress transition layer 12 is located between the diffusion barrier layer 11 and the CrN-based wear-resistant layer 13, and is used to alleviate the differences in hardness and thermal expansion between the structure to be protected (such as a copper alloy terminal), the diffusion barrier layer 11, and the CrN-based wear-resistant layer 13. The material composition of the stress transition layer 12 is CrN. x Where 0 ≤ x < 1. The material of the stress transition layer 12 near the diffusion barrier layer 11 is Cr or CrN with low nitrogen content. x The stress transition layer 12 is made of CrN with a high nitrogen content on the side closest to the CrN-based wear-resistant layer 13. x .

[0038] In some embodiments, the nitrogen content in the stress transition layer 12 gradually increases from the side of the stress transition layer 12 in contact with the diffusion barrier layer 11 to the side of the stress transition layer 12 in contact with the CrN-based wear-resistant layer 13, so that the material of the stress transition layer 12 achieves a gradual transition from metallic Cr or low-nitrogen CrNx to CrN.

[0039] In some embodiments, the thickness of the stress transition layer 12 is 0.1-1.5 micrometers, such as 0.4 micrometers, 0.8 micrometers, 1.2 micrometers, etc.

[0040] In this embodiment, the CrN-based wear-resistant layer 13 has a continuous phase structure. The material of the CrN-based wear-resistant layer 13 can be CrN, a mixture of Cr2N and CrN, CrN-TiN, or CrN-SiN. To ensure the wear resistance of the CrN-based wear-resistant layer 13, the volume percentage of the CrN phase in the CrN-based wear-resistant layer 13 is required to be greater than or equal to 50%.

[0041] In some possible embodiments, a small amount of modifying elements, such as Al, Ti, Si, Mo, and C, are also added to the CrN-based wear-resistant layer 13. Al primarily enhances oxidation and corrosion resistance; Ti primarily improves hardness, load-bearing capacity, and thermal stability; Si helps refine grains, increase density, and reduce through-porosity; Mo can improve toughness and tribological properties; and C can form CrCN-like structures and is used to adjust toughness, internal stress, and frictional properties. These modifying elements are optional components; in specific applications, one or more modifying elements can be selected to improve the coating's performance based on the emphasis on wear resistance, corrosion prevention, or low friction.

[0042] In some embodiments, the thickness of the CrN-based wear-resistant layer 13 is 1-10 micrometers. Preferably, the thickness of the CrN-based wear-resistant layer 13 is 2-6 micrometers, such as 3 micrometers, 4 micrometers, 5 micrometers, etc.

[0043] In this embodiment, multiple conductive units 2 are spaced apart from each other in the support bracket 1 along their respective preset directions. The preset directions may be parallel to the first direction or partially deviate from the first direction (the deviation angle is less than 30 degrees). The preset directions of different conductive units 2 may be the same or different. Each conductive unit 2 includes a conductive root portion 21 and a conductive body portion that are contacted and disposed along the preset direction. The conductive body portion is located in the CrN-based wear-resistant layer 13, and the surface of the conductive body portion facing away from the conductive root portion 21 is exposed in the CrN-based wear-resistant layer 13. One end of the conductive root portion 21 is in contact with the conductive body portion in the CrN-based wear-resistant layer 13, and the other end extends toward the diffusion barrier layer 11.

[0044] In some embodiments, the exposed side of the conductive body is flush with or slightly lower than the CrN-based wear-resistant layer 13 to avoid localized stress concentration, abnormal scratching, or soft metal detachment during insertion and removal of the connection terminals. The height difference between the exposed side of the conductive body and the surface of the CrN-based wear-resistant layer 13 away from the diffusion barrier layer 11 (as shown in...) Figure 2 or Figure 3 The length in the Y direction shown does not exceed 1 micrometer, preferably not exceeding 0.3 micrometers, for example 0.3 micrometers, 0.2 micrometers, 0.1 micrometers, etc. When the conductive body portion is recessed relative to the CrN-based wear-resistant layer 13, the risk of the conductive body portion being impacted and smeared first when the coating comes into contact with other objects can be reduced, but if the recess is too large, the initial contact resistance will increase.

[0045] In some embodiments, the conductive root 21 extends from one end away from the conductive body portion to the side of the diffusion barrier layer 11 facing the CrN-based wear-resistant layer 13 (e.g., Figure 2 (As shown). Since the diffusion barrier layer 11 itself can achieve continuous electrical connection with the copper alloy terminal, there is no need for the conductive unit 2 to enter the interior of the copper alloy terminal. The bottom end of the conductive unit 2 can directly contact the upper surface of the diffusion barrier layer 11.

[0046] In some embodiments, the conductive root 21 extends from one end away from the conductive body to the side of the diffusion barrier layer 11 away from the CrN-based wear-resistant layer 13. In this case, the conductive unit 2 can directly contact the copper alloy terminal through the conductive root 21 to enhance the electrical connection.

[0047] In some embodiments, one end of the conductive root 21, which is away from the conductive body, protrudes from the side of the diffusion barrier layer 11 that is away from the CrN-based wear-resistant layer 13 (the protruding length can be 0.1-2 micrometers). In this case, the conductive unit 2 can enter the groove provided in the copper alloy terminal through the conductive root 21 to enhance the electrical connection and the interface mechanical locking capability.

[0048] In this embodiment, at least one conductive sub-unit 22 is provided in the conductive main body. Each conductive sub-unit 22 includes a conductive reserve portion 221 and a conductive neck 222 that are contacted and arranged along a preset direction. When only one conductive sub-unit 22 is provided in the conductive main body, one end of the conductive reserve portion 221 is contacted and connected to the conductive root portion 21, and the other end is contacted and connected to the conductive neck 222. When multiple conductive sub-units 22 that are contacted and arranged along a preset direction are provided in the conductive main body, the conductive reserve portion 221 in each conductive sub-unit 22 is closer to the conductive root portion 21 than the conductive neck 222. The conductive reserve portion 221 in the conductive sub-unit 22 adjacent to the conductive root portion 21 is in direct contact with the conductive root portion 21. The entire conductive unit 2 is arranged in the manner of "conductive root portion 21 - conductive reserve portion 221 - conductive neck 222 - conductive reserve portion 221 - conductive neck 222...".

[0049] In this embodiment, the conductive main body adopts a variable cross-section design, enabling the coating to change its surface conductive area according to the degree of wear. In each conductive sub-unit 22, the lateral cross-sectional area of ​​the conductive reserve portion 221 in a preset direction is greater than the lateral cross-sectional area of ​​the conductive neck 222 in a preset direction; when the conductive reserve portion 221 and / or the conductive neck 222 adopt a variable cross-section design, the maximum lateral cross-sectional area of ​​the conductive reserve portion 221 in the preset direction is greater than the maximum lateral cross-sectional area of ​​the conductive neck 222 in the preset direction. In a conductive main body with multiple conductive sub-units 22, in any two conductive sub-units 22, the lateral cross-sectional area of ​​the conductive reserve portion 221 in the preset direction of the conductive sub-unit 22 closer to the conductive root 21 is greater than the lateral cross-sectional area of ​​the conductive reserve portion 221 in the preset direction of the conductive sub-unit 22 farther from the conductive root 21, that is, the lateral cross-sectional area of ​​the conductive reserve portion 221 closer to the conductive root 21 is larger.

[0050] In some embodiments, the conductive body portion has a cross-section in a predetermined direction that is a continuously expanding triangle, trapezoid, or multiple stacked rectangles. With this design, the conductive body portion has a larger lateral cross-sectional area in the region farther away from the working surface of the CrN-based wear-resistant layer 13 (i.e., the side of the CrN-based wear-resistant layer 13 facing away from the diffusion barrier layer 11), thereby gradually increasing the surface conductive area of ​​the coating as the wear degree increases.

[0051] In some embodiments, in a conductive body portion having multiple conductive sub-units 22, different conductive reserve portions 221 gradually increase in cross-section as they approach the conductive root portion 21, ensuring that the conductive body portion can increase the surface conductive area of ​​the coating as the wear level increases.

[0052] In some embodiments, the lateral cross-sectional area of ​​each conductive reservoir 221 in a predetermined direction may be constant or variable. For example, the lateral cross-sectional area of ​​the conductive reservoir 221 in the predetermined direction gradually increases from the end of the conductive reservoir 221 away from the conductive root 21 to the end of the conductive reservoir 221 near the conductive root 21; or, the lateral cross-sectional area of ​​the conductive reservoir 221 in the predetermined direction is constant; or, the lateral cross-sectional area of ​​the conductive reservoir 221 in the predetermined direction gradually decreases from the middle region of the conductive reservoir 221 to both ends of the conductive reservoir 221. The variation of the lateral cross-sectional area of ​​the conductive reservoirs 221 in different conductive subunits 22 may be the same or different.

[0053] In some embodiments, all conductive necks 222 maintain a low lateral cross-sectional area, with the lateral cross-sectional area of ​​each conductive neck 222 being lower than that of the conductive reservoir 221 with the smallest lateral cross-sectional area. The conductive neck 222 located between two conductive reservoirs 221 not only maintains the electrical connection between the two conductive reservoirs 221 on either side, but also reduces the overall volume percentage of soft conductive metal in the CrN-based wear-resistant layer 13, thereby saving conductive metal and retaining a larger volume percentage for the support bracket 1.

[0054] In some embodiments, in each conductive subunit 22, the ratio of the transverse cross-sectional area of ​​the conductive reserve portion 221 in a predetermined direction to the transverse cross-sectional area of ​​the conductive neck 222 in a predetermined direction ranges from 1.5 to 20, preferably from 2 to 8, for example 4, 6, etc.

[0055] In some embodiments, in each conductive subunit 22, the ratio of the height of the conductive reservoir 221 to the height of the conductive neck 222 is 0.3-5, preferably 0.6-2.5, and the specific ratio can be determined according to the planned wear depth to be exposed.

[0056] In some embodiments, the width (length in the X direction) of the conductive neck 222 is 1-30 micrometers, preferably 3-15 micrometers, such as 5 micrometers, 10 micrometers, etc.; the height (length in the Y direction) of the conductive neck 222 is 0.2-2.0 micrometers, preferably 0.5-1.2 micrometers, such as 0.8 micrometers, 1 micrometer, etc. The height of the conductive neck 222 located between two conductive reservoirs 221 is determined by the thickness of the CrN-based wear-resistant layer 13 that needs to be retained between two adjacent conductive reservoirs 221.

[0057] In some embodiments, the height of the conductive reservoir 221 is 0.2-1.5 micrometers, such as 0.8 micrometers, 1.2 micrometers, etc.

[0058] In some embodiments, the width of the conductive root 21 is 2-20 micrometers, preferably 4-10 micrometers, such as 5 micrometers, 7 micrometers, 9 micrometers, etc.

[0059] In some embodiments, the conductive root 21, conductive reservoir 221, and conductive neck 222 can be made of Ag, Cu, Ag-Cu alloy, Ag-Pd alloy, Cu-Ag-Sn alloy, or Ag-Sn alloy, or a composite material with Ag or Cu as the main conductive phase. Preferably, Ag-Cu alloy or Ag-Pd alloy, which have good conductivity, are used. The conductive root 21, conductive reservoir 221, and conductive neck 222 are preferably made of the same material, but they can also be made of different materials.

[0060] This application also provides a power connector. The power connector includes a connection terminal 3 and the aforementioned CrN-based composite conductive and wear-resistant coating. Figure 4 This is a partial structural schematic diagram of a power connector provided in an embodiment of this application. The surface of the connection terminal 3 includes a plug-in contact area 4. A CrN-based composite conductive wear-resistant coating is located in the plug-in contact area 4, and the diffusion barrier layer 11 is in contact with the connection terminal 3.

[0061] In this embodiment, based on finite element analysis, pressure film testing, wear track analysis, or surface morphology after insertion and removal, the insertion contact area 4 is divided into a high contact pressure area 41, a medium contact pressure area 42, and a low contact pressure area 43. From the high contact pressure area 41 to the medium contact pressure area 42 and then to the low contact pressure area 43, the number density of conductive units 2 in the CrN-based composite conductive wear-resistant coating, and / or the number of conductive sub-units 22 in each conductive unit 2, and / or the lateral cross-sectional area of ​​the conductive reserve portion 221 decreases sequentially. This design can improve the lifespan of the main current-carrying area and reduce the amount of precious metals used in the low-wear area.

[0062] In some embodiments, such as Figure 4 As shown, the insertion contact area 4 includes a high contact pressure area 41, a medium contact pressure area 42, and a low contact pressure area 43 distributed sequentially from the inside to the outside on the surface of the connecting terminal 3. The conductive unit 2 in the CrN-based composite conductive wear-resistant coating located in the high contact pressure area 41 is a conductive unit 2. Figure 4 The number density of conductive units 2 (where number 2 indicates one of them) decreases sequentially from the number density of conductive units 2 in the CrN-based composite conductive wear-resistant coating located in the medium contact pressure region 42 to the number density of conductive units 2 in the CrN-based composite conductive wear-resistant coating located in the low contact pressure region 43.

[0063] In some embodiments, the number density of conductive units 2 in the high contact pressure region 41 is 1.2 to 4 times that of the number density of conductive units 2 in the low contact pressure region 43.

[0064] In some embodiments, the high contact pressure region 41 employs a dual-stage wear compensation conductive unit 2 (a dual-stage wear compensation conductive unit 2 refers to a conductive unit 2 including two conductive sub-units 2); the medium contact pressure region 42 may employ a smaller number of large-size dual-stage wear compensation conductive units 2 or a larger number of small-size dual-stage wear compensation conductive units 2; the low contact pressure region 43 employs a smaller number of dual-stage conductive units 2 or only a single-stage wear compensation conductive unit 2 (a single-stage wear compensation conductive unit 2 refers to a conductive unit 2 including one conductive sub-unit 2).

[0065] In this embodiment, the coating gradually wears off during repeated insertion and removal of the power connector. The following is an example... Figure 3 The following example, including the coating with dual-stage wear compensation conductive unit 2, illustrates the wear state of the coating at different stages. Figure 5 This is a schematic diagram showing the conductive area of ​​the CrN-based composite conductive wear-resistant coating in the unworn state in the embodiments of this application. Figure 6 This is a schematic diagram of the conductive area of ​​the CrN-based composite conductive wear-resistant coating in this embodiment when it wears down to the first-level conductive reserve 221 (the conductive reserve 221 that is far from the conductive root 21). Figure 7 This is a schematic diagram of the conductive area of ​​the CrN-based composite conductive wear-resistant coating in this embodiment when it wears down to the second-level conductive reservoir 221 (the conductive reservoir 221 in contact with the conductive root 21); Figure 5 , Figure 6 or Figure 7 In the diagram, the top graphic is a schematic diagram of the working surface of the coating, the bottom graphic is a cross-sectional view of the coating, and the top graphic is a top view of the bottom graphic.

[0066] like Figure 5 As shown, during the initial use phase, the coating did not show significant wear. In the conductive unit 2, only the surface conductive neck 222 was exposed to the working surface of the connection terminal 3, and the material of the CrN-based wear-resistant layer 13 occupied the main area of ​​the working surface. The CrN-based wear-resistant layer 13 bore the main contact pressure and frictional load, and the surface conductive neck 222 formed a dispersed low-resistance conductive path. Since the surface conductive neck 222 was basically flush with the surface of the CrN-based wear-resistant layer 13, the resilient contact of the socket would not be pressed solely onto the soft Ag-Cu material, thus reducing the plastic coating and material migration of the soft metal.

[0067] like Figure 6As shown, when the wear depth reaches the location of the first-level conductive reserve 221, the first-level conductive reserve 221 begins to be exposed. The lateral cross-sectional area of ​​the first-level conductive reserve 221 is larger than that of the surface conductive neck 222, therefore, the exposed conductive metal area of ​​a single conductive unit 2 on the working surface increases with wear. The increase in the exposed conductive metal area can compensate for the increase in contact resistance caused by the following factors: changes in the actual contact area of ​​the CrN-based wear-resistant layer 13; slight oxidation or contamination on the coating surface; partial wear of the surface conductive neck 222; and slight attenuation of the contact pressure of the socket's elastic contact.

[0068] like Figure 7 As shown, when the wear depth reaches the location of the second-level conductive reservoir 221, the second-level conductive reservoir 221 is exposed to the working surface. Since the lateral dimension of the second-level conductive reservoir 221 is larger than that of the first-level conductive reservoir 221, its exposure can further increase the effective contact area of ​​the conductive material. At this time, although the coating has entered the later stage of its life, the conductive path can still be maintained through the second-level conductive reservoir 221, thereby avoiding the problem of a sudden increase in contact resistance after ordinary CrN coatings are worn through or partially damaged.

[0069] In some embodiments, such as Figure 5 As shown, the total exposed area of ​​all surface conductive necks 222 on the working surface accounts for 2%-20% of the area of ​​the plug contact region 4, preferably 4%-12%; as Figure 6 As shown, when wear reaches the first-stage conductive reserve 221, the surface exposed area of ​​the conductive unit 2 increases to 1.5-5 times the initial exposed area; as Figure 7 As shown, when wear reaches the second-level conductive reserve section 221, the surface exposed area of ​​the conductive unit 2 increases again. The specific ratio can be determined based on the rated current, terminal contact pressure, allowable temperature rise, and designed insertion / removal life.

[0070] This application also provides a method for preparing a CrN-based composite conductive wear-resistant coating. Figure 8 This is a schematic flowchart illustrating a method for preparing a CrN-based composite conductive wear-resistant coating according to an embodiment of this application. Figure 8 As shown, the preparation method includes the following steps: S1 forms a diffusion barrier layer; S2 forms a stress transition layer and a plurality of spaced conductive roots. The stress transition layer is located on the diffusion barrier layer. One end of the conductive root is higher than the upper surface of the stress transition layer, and the other end extends at least to the upper surface of the diffusion barrier layer. S3 forms a conductive reserve at each conductive root; S4 forms the first CrN-based wear-resistant sublayer, which is located on the stress transition layer and covers the sidewalls of the conductive root and the sidewalls of the conductive reserve. S5 forms a conductive neck on each conductive reservoir, the transverse cross-sectional area of ​​the conductive neck is smaller than the transverse cross-sectional area of ​​the conductive reservoir, and the conductive reservoir and the conductive neck form a conductive subunit. S6 When the CrN-based composite conductive wear-resistant coating includes multiple conductive sub-units, a new conductive reserve is formed on each conductive neck, and a second CrN-based wear-resistant sub-layer is formed on the first CrN-based wear-resistant sub-layer. The second CrN-based wear-resistant sub-layer is located on the first CrN-based wear-resistant sub-layer and covers the sidewall of the conductive neck and the sidewall of the newly formed conductive reserve. Then, a new conductive neck is formed on each newly formed conductive reserve. This process is repeated until a predetermined number of conductive sub-units are formed. S7 After step S5 or step S6, a third CrN-based wear-resistant sublayer is formed. The third CrN-based wear-resistant sublayer is located on the first CrN-based wear-resistant sublayer or the second CrN-based wear-resistant sublayer and covers the sidewall of the newly formed conductive neck. The upper surface of the conductive neck is exposed in the third CrN-based wear-resistant sublayer.

[0071] The following describes in detail the preparation method of the CrN-based composite conductive wear-resistant coating provided in this application, taking the preparation of the CrN-based composite conductive wear-resistant coating on the surface of the connecting terminal 3 in the charging gun as an example.

[0072] Before preparing the CrN-based composite conductive wear-resistant coating, the connecting terminal 3 needs to be pretreated. The specific steps are: degreasing, ultrasonic cleaning, deionized water cleaning, and drying of the copper alloy connecting terminal 3; placing the copper alloy connecting terminal 3 into a vacuum chamber for argon ion etching or plasma activation to remove the oxide film and surface contaminants on the surface of the copper alloy connecting terminal 3. Afterwards, the non-contact areas of the copper alloy connecting terminal 3 need to be masked to expose the areas to be coated. Specifically, the crimping area, welding area, cable connection area, and dimensional mating surfaces that do not require coating are mechanically masked or protected with removable masks.

[0073] After completing the above preparations, the CrN-based composite conductive wear-resistant coating can be prepared according to the following process steps: In step S1, a diffusion barrier layer 11 is formed on the surface of the connecting terminal 3.

[0074] As an example, in an argon atmosphere, a diffusion barrier layer 11 is deposited on the surface of the area to be coated using a Cr target, a Ni target, or a NiCr alloy target. An example process window is: terminal temperature of 80-250 degrees Celsius, working pressure of 0.2-1.0 Pa, and terminal bias of -20 V to -150 V.

[0075] In some embodiments, the thickness of the formed diffusion barrier layer 11 is 0.05-1.0 micrometers.

[0076] In step S2, a stress transition layer 12 and a plurality of spaced conductive roots 21 are formed. The stress transition layer 12 is located on the diffusion barrier layer 11, and one end of the conductive root 21 is higher than the upper surface of the stress transition layer 12, while the other end extends at least to the upper surface of the diffusion barrier layer 11.

[0077] In some embodiments, a plurality of spaced-apart conductive roots 21 are first formed, followed by the formation of a stress transition layer 12. The specific operation of forming the conductive roots 21 first involves: forming a plurality of spaced-apart conductive roots 21 on the diffusion barrier layer 11 using a microporous mask; or, first forming a plurality of spaced-apart through-holes in the diffusion barrier layer 11, and then filling each through-hole with conductive material protruding from the upper surface of the diffusion barrier layer 11. The operation of forming the stress transition layer 12 subsequently involves: forming the stress transition layer 12 on the diffusion barrier layer 11, such that it covers the sidewalls of the conductive roots 21 protruding from the diffusion barrier layer 11, and the upper surface of the stress transition layer 12 is lower than the upper surface of the conductive roots 21.

[0078] In other embodiments, a stress transition layer 12 is formed first, followed by the formation of a plurality of spaced conductive roots 21. Specifically, the stress transition layer 12 is first formed on the diffusion barrier layer 11, then holes are made from the upper surface of the stress transition layer 12 to the upper or lower surface of the diffusion barrier layer 11, and then each hole is filled with conductive material protruding from the upper surface of the stress transition layer 12 to obtain the conductive roots 21.

[0079] As an example, the specific process for forming the stress transition layer 12 is as follows: In an argon atmosphere, nitrogen gas is gradually introduced, and a Cr target is used to deposit the stress transition layer 12 on the surface of the diffusion barrier layer 11. During the deposition process, by gradually introducing nitrogen gas and adjusting the Cr target power, the material of the stress transition layer 12 is gradually transitioned from metallic Cr or low-nitrogen CrNx to CrN.

[0080] In step S3, a conductive reserve portion 221 is formed on each conductive root portion 21.

[0081] As an example, using a first patterned mask or local selective deposition method, a conductive reservoir 221 with a large lateral dimension is formed on each conductive root 21 using an Ag target, Cu target or alloy target, and connected to the conductive root 21.

[0082] In step S4, a first CrN-based wear-resistant sublayer is formed on the stress transition layer 12. The first CrN-based wear-resistant sublayer covers the sidewalls of the conductive root portion 21 and the sidewalls of the conductive reserve portion 221.

[0083] As an example, the first pattern mask is removed or switched, and a first CrN-based wear-resistant sublayer is deposited on the stress transition layer 12 by reactive magnetron sputtering, so that it surrounds the sidewalls of the conductive root portion 21 protruding from the upper surface of the stress transition layer 12 and the sidewalls of the conductive reservoir portion 221.

[0084] In step S5, a conductive neck 222 is formed on each conductive reservoir 221. The lateral cross-sectional area of ​​the conductive neck 222 is smaller than the lateral cross-sectional area of ​​the conductive reservoir 221, and the conductive reservoir 221 and the conductive neck 222 form a conductive subunit 22.

[0085] As an example, a second patterned mask or local selective deposition method with a smaller window size aligned with the conductive reservoir 221 is used to form a conductive neck 222 on each conductive reservoir 221 using an Ag target, Cu target, or alloy target, and connect it to the conductive reservoir 221.

[0086] When only one conductive sub-unit 22 is provided in the required CrN-based composite conductive wear-resistant coating, step S7 is executed directly after step S5.

[0087] In step S7, which follows step S5, a third CrN-based wear-resistant sublayer is formed on the first CrN-based wear-resistant sublayer to obtain a CrN-based composite conductive wear-resistant coating. The third CrN-based wear-resistant sublayer covers the sidewall of the conductive neck 222, and the upper surface of the conductive neck 222 is exposed on the upper surface of the third CrN-based wear-resistant sublayer.

[0088] When multiple conductive sub-units 22 are provided in the required CrN-based composite conductive wear-resistant coating, steps S6 and S7 are executed sequentially after step S5.

[0089] In step S6, a new conductive reservoir 221 is formed on each conductive neck 222, and a second CrN-based wear-resistant sublayer is formed on the first CrN-based wear-resistant sublayer. The second CrN-based wear-resistant sublayer covers the sidewalls of the conductive neck 222 and the sidewalls of the newly formed conductive reservoir 221. Then, a new conductive neck 222 is formed on each newly formed conductive reservoir 221. This process is repeated, that is, the deposition operation is repeated in the order of "forming conductive reservoir 221 through a larger mask window - depositing CrN-based wear-resistant sublayer - forming conductive neck 222 through a smaller mask window" until a predetermined number of conductive sub-units 22 are formed in a stacked manner, thereby obtaining the desired conductive unit 2.

[0090] Specifically, the lateral cross-sectional area of ​​the conductive reserve portion 221 formed in different steps is different, and the lateral cross-sectional area of ​​the conductive reserve portion 221 formed later is smaller than that of the conductive reserve portion 221 formed earlier; the thickness of the conductive reserve portion 221 formed in different steps is different, and the thickness of the conductive reserve portion 221 formed later is smaller than that of the conductive reserve portion 221 formed earlier.

[0091] In some implementations, magnetron sputtering is used to form a conductive reservoir 221 with a large lateral cross-sectional area, and ion beam-assisted deposition or local electrodeposition is used to form a slender conductive neck 222.

[0092] In step S7, which follows step S6, a third CrN-based wear-resistant sublayer is formed on the newly formed second CrN-based wear-resistant sublayer to obtain a CrN-based composite conductive wear-resistant coating. The third CrN-based wear-resistant sublayer covers the sidewall of the newly formed conductive neck 222, and the upper surface of the newly formed conductive neck 222 is exposed on the upper surface of the third CrN-based wear-resistant sublayer.

[0093] After forming a CrN-based composite conductive wear-resistant coating on the surface of the connecting terminal 3 through the above steps, further surface treatment of the CrN-based composite conductive wear-resistant coating is required. The specific process is as follows: the coating surface is leveled using low-energy ion beam leveling, plasma polishing, precision grinding or other low-damage leveling processes, so that the top surface of the conductive neck 222 at the very top is basically flush with the working surface of the CrN-based wear-resistant layer 13; a smooth transition or thickness gradient area is formed at the edge of the coating to avoid stress concentration and peeling at the contact area boundary, the groove edge of the connecting terminal or the root of the elastic sheet; the connecting terminal 3 is subjected to low-temperature stabilization treatment in a vacuum or inert atmosphere to stabilize the interface between the diffusion barrier layer 11, the stress transition layer 12, the CrN-based wear-resistant layer 13 and the conductive unit 2. The treatment temperature is required not to exceed the temperature at which the material of the connecting terminal 3 will significantly soften or lose elasticity.

[0094] In some embodiments, the cryogenic treatment temperature is 160-190 degrees Celsius, and the cryogenic treatment time is 45-90 minutes.

[0095] The following focuses on the high-current positive terminal 3 of a DC charging gun, and describes the preparation of a CrN-based composite conductive wear-resistant coating in the insertion contact area 4 of the terminal 3. This coating employs a structure combining a continuous CrN-based support structure with a dual-stage wear-compensating conductive unit 2. This structure enables the terminal 3 to have high wear resistance during initial use, and as the coating gradually wears down, the effective conductive area is increased by progressively exposing conductive reserve sections 221 to suppress the rapid increase in contact resistance and terminal temperature with increasing insertion and removal cycles. The following is one embodiment, where the parameters can be adjusted according to the terminal specifications, rated current, insertion / removal life, and the specific conditions of the magnetron sputtering equipment.

[0096] I. Structure of Connecting Terminal 3 The connecting terminal 3 is made of CuCrZr copper alloy. The connecting terminal 3 has a cylindrical pin structure, with an outer diameter of 12 mm and an effective insertion length of 18 mm for the insertion portion. The outer circumferential surface of the connecting terminal 3 mates with the elastic contact of the vehicle-side socket connecting terminal to form electrical contact. Based on the contact position of the connecting terminal 3 after insertion into the socket, a 12 mm long area on the outer circumferential surface of the connecting terminal 3 is defined as the insertion contact area 4.

[0097] The cable crimping area, welding area and installation positioning area located at the tail of the connecting terminal 3 do not require the preparation of CrN-based composite coating. During the magnetron sputtering process, a detachable metal shielding sleeve is used to shield the non-contact area to avoid the hard coating affecting the crimping, welding and assembly of the connecting terminal 3.

[0098] Before coating preparation, the pressure distribution of the insertion contact area 4 in the connecting terminal 3 was determined through contact pressure simulation and pressure film testing, and it was divided into a high contact pressure area 41, a medium contact pressure area 42, and a low contact pressure area 43. The high contact pressure area 41 corresponds to the position where the socket elastic contact piece is mainly pressed, the medium contact pressure area 42 is located on both sides of the high contact pressure area 41, and the low contact pressure area 43 is located at the edge of the insertion contact area 4. Different density of conductive units 2 is used in different contact pressure areas to match the distribution of conductive units 2 with the actual wear degree of the connecting terminal 3.

[0099] II. Pre-treatment of connection terminal 3 First, the insertion contact area 4 of the CuCrZr connector 3 is mechanically polished to a surface roughness of no more than 0.20 micrometers. Then, the following steps are performed sequentially: The connector 3 is cleaned in an alkaline degreasing solution for 10 minutes to remove surface oil; the surface of the connector 3 is rinsed with deionized water; the connector 3 is ultrasonically cleaned sequentially in anhydrous ethanol and acetone for 10 minutes each time; the connector 3 is dried with nitrogen; the connector 3 is mounted on a rotating fixture in a magnetron sputtering device; metal shielding sleeves are installed on the crimping area, welding area, and positioning area of ​​the connector 3; the vacuum chamber is evacuated to a vacuum level no higher than 5 × 10⁻⁶. -4 Argon gas is introduced to perform argon ion etching cleaning on the connecting terminal 3 to remove the oxide layer and residual contaminants on the surface of the connecting terminal 3, and to improve the bonding force between the diffusion barrier layer 11 in the subsequently prepared coating and the copper alloy connecting terminal 3. The process conditions for argon ion etching are: working gas pressure of 0.4-0.6 Pa, connecting terminal bias voltage of -300 volts to -500 volts, and etching time of 8-15 minutes.

[0100] III. Coating Design The specific structure of the formed dual-stage wear-compensating conductive unit 2 can be referred to Figure 3 .

[0101] The diffusion barrier layer 11 is made of NiCr alloy, with a Ni to Cr mass ratio of 80:20, and a thickness of 0.35 micrometers. The NiCr diffusion barrier layer 11 improves the bonding force between the copper alloy connector 3 and the subsequently formed CrNx stress transition layer 12, and also inhibits the diffusion of copper elements from the copper alloy connector 3 to the subsequently formed CrN-based wear-resistant layer 13 during long-term high-temperature current carrying, thereby reducing coating interface degradation caused by copper migration.

[0102] The material of stress transition layer 12 is CrN x The thickness is 0.45 micrometers. CrN x The stress transition layer 12 can reduce the abrupt changes in hardness, elastic modulus and thermal expansion properties between the NiCr diffusion barrier layer 11 and the CrN-based wear-resistant layer 13, thereby reducing the risk of cracks or interface peeling of the coating under high current thermal cycling and insertion / extraction loads.

[0103] The CrN-based wear-resistant layer 13 is made of CrN and has a thickness of 4.2 micrometers. The CrN-based wear-resistant layer 13 mainly bears the normal contact load and tangential friction load during the insertion and removal of the connection terminal 3.

[0104] Multiple dual-stage wear-compensating conductive units 2 are spaced apart from each other to avoid excessive conductive phase, which would reduce the overall wear resistance. Each dual-stage wear-compensating conductive unit 2 is positioned along a direction away from the connecting terminal 3 (e.g., ...). Figure 3 The conductive unit 2 (shown in the Y direction) sequentially includes a conductive root 21, a second-stage conductive reservoir 221, an intermediate conductive neck 222, a first-stage conductive reservoir 221, and a surface conductive neck 222. These parts are interconnected, forming a low-resistance conductive path extending from the connection terminal 3 to the working surface of the coating. The conductive root 21 has a diameter of 7 micrometers; the second-stage conductive reservoir 221 is located near the bottom of the CrN-based wear-resistant layer 13, and is a laterally expanding elliptical or approximately circular disk shape with a maximum diameter of 26 micrometers and a thickness of 0.7 micrometers; the intermediate conductive neck 222 has a diameter of 6 micrometers and a thickness of 0.8 micrometers; the first-stage conductive reservoir 221 is located near the working surface of the coating, with a maximum diameter of 14 micrometers and a thickness of 0.5 micrometers; and the surface conductive neck 222 has a diameter of 5 micrometers and a thickness of 0.7 micrometers. All parts of the conductive unit 2 are made of Ag-Cu alloy, with a mass ratio of Ag to Cu of 92:8. Ag is the main conductive phase, which can reduce the contact resistance of the connection terminal 3; Cu is used to improve the interfacial bonding ability between the conductive unit 2, the NiCr diffusion barrier layer 11 and the copper alloy connection terminal 3, and reduce the possibility of excessive plastic flow of pure silver material under contact pressure.

[0105] Based on the contact pressure distribution of the connection terminals, conductive units 2 are arranged in different areas with different density. In the high contact pressure area 41, approximately 1500 conductive units 2 are arranged per square millimeter; in the medium contact pressure area 42, approximately 1000 conductive units 2 are arranged per square millimeter; and in the low contact pressure area 43, approximately 600 conductive units 2 are arranged per square millimeter.

[0106] IV. Coating Preparation The specific preparation process of the coating is as follows: (1) Deposition diffusion barrier layer 11 After pretreatment of the connector 3, reactive magnetron sputtering is performed on the insertion contact area 4 of the connector 3 using a NiCr alloy target to deposit a diffusion barrier layer 11. Specific deposition parameters are as follows: argon flow rate of 35-45 standard milliliters per minute; working pressure of 0.3-0.6 Pa; target power of 1.5-2.5 kW; connector bias voltage of -50 V to 100 V; connector temperature of 120-180 degrees Celsius; and connector rotation speed of 3-8 revolutions per minute.

[0107] (2) Formation of conductive roots 21 The structures of the two-stage wear-compensated conductive unit 2 were fabricated using a combination of replaceable microporous metal masks and layered magnetron sputtering. The masks were engaged with the rotating fixture of the connecting terminal 3 via positioning holes, allowing the deposition windows on different masks to be repeatedly aligned at the same location in the conductive unit 2.

[0108] The specific process for preparing the conductive root 21 is as follows: the connecting terminal 3 is rotated to a predetermined position, and the mask used to prepare the conductive root 21 in the first set of microporous masks is brought close to the surface of the connecting terminal 3; the conductive root 21 is obtained by depositing Ag-Cu alloy through a deposition window with a diameter of about 7 micrometers.

[0109] All parts of the conductive unit 2 are made of Ag-Cu alloy and use the same deposition parameters. Taking the conductive root 21 as an example, its deposition parameters are as follows: argon flow rate of 20-30 standard milliliters per minute, no nitrogen gas is introduced; working pressure of 0.25-0.45 Pa; Ag-Cu target power of 0.5-1.2 kW; bias voltage of the connection terminal of 0 volts to -30 volts; and connection terminal temperature not exceeding 180 degrees Celsius.

[0110] (3) Depositional stress transition layer 12 The mask used to prepare the conductive root 21 is removed from the surface of the connecting terminal 3, and then reactive magnetron sputtering is performed on the surface of the NiCr diffusion barrier layer 11 using a Cr target to deposit the stress transition layer 12. In the initial stage, only argon gas or a small amount of nitrogen gas is introduced to ensure that the material near the NiCr diffusion barrier layer 11 is composed of metallic Cr and low-nitrogen CrN. x The nitrogen flow rate is then gradually increased, causing the nitrogen content in the stress transition layer 12 to gradually increase in the direction away from the connecting terminal 3.

[0111] In this embodiment, the nitrogen flow rate was gradually increased from 0 to 10 standard milliliters per minute over 20 minutes, while the argon flow rate was maintained at 35 standard milliliters per minute. Other deposition parameters were: working pressure of 0.4-0.6 Pa; Cr target power of 1.8-2.5 kW; terminal bias voltage of -60 V to 100 V; and terminal temperature of 140-180 degrees Celsius.

[0112] (4) Forming a second-level conductive reserve section 221 Rotate the connecting terminal 3 to a predetermined position and bring the mask in the first set of microporous masks used to prepare the second-level conductive reservoir 221 close to the surface of the connecting terminal 3; deposit Ag-Cu alloy above the conductive root 21 to obtain the second-level conductive reservoir 221.

[0113] (5) Deposition of the first CrN-based wear-resistant sublayer After the second-stage conductive reservoir 221 is formed, a first CrN-based wear-resistant sublayer is deposited by reactive magnetron sputtering of the stress transition layer 12 using a Cr target in a mixed atmosphere of argon and nitrogen. During the deposition process, the upper surface of the conductive unit 2 is preserved by partially shielding or aligning the openings, so that the subsequently formed intermediate conductive neck 222 can be connected to the second-stage conductive reservoir 221.

[0114] In this embodiment, the deposition process of each CrN-based wear-resistant sublayer uses the same deposition parameters. Taking the first CrN-based wear-resistant sublayer as an example, its deposition parameters are as follows: argon flow rate of 30-40 standard milliliters per minute; nitrogen flow rate of 8-14 standard milliliters per minute; working pressure of 0.35-0.60 Pa; Cr target power of 1.8-2.8 kW; terminal bias voltage of -60 volts to -120 volts; terminal temperature of 140-200 degrees Celsius; and terminal rotation speed of 3-8 revolutions per minute.

[0115] (6) Forming an intermediate conductive neck 222 and a first-stage conductive reserve 221 A second set of microporous masks is installed on the surface of the first CrN-based wear-resistant sublayer, with the center of its window aligned with the center of the second-level conductive reservoir 221; an intermediate conductive neck 222 is deposited on the second-level conductive reservoir 221 through the mask with the smaller window; the mask with the larger window is replaced to form the first-level conductive reservoir 221 on the intermediate conductive neck 222.

[0116] (7) Deposition of the second CrN-based wear-resistant sublayer After forming the first-stage conductive reservoir 221, a second CrN-based wear-resistant sublayer is deposited by reactive magnetron sputtering using a Cr target in a mixed atmosphere of argon and nitrogen. The second CrN sublayer surrounds the intermediate conductive neck 222 and the sides of the first-stage conductive reservoir 221, with the upper surface of the first-stage conductive reservoir 221 exposed.

[0117] (8) Formation of surface conductive neck 222 and third CrN-based wear-resistant sublayer A mask with a deposition window of approximately 5 micrometers in diameter is used to deposit a surface conductive neck 222 on the first-stage conductive reserve 221. Then, a third CrN-based wear-resistant sublayer is deposited on the second CrN-based wear-resistant sublayer, bringing the CrN-based wear-resistant layer 13 to the designed thickness. The third CrN-based wear-resistant sublayer, the second CrN-based wear-resistant sublayer, and the first CrN-based wear-resistant sublayer together constitute the CrN-based support layer.

[0118] V. Post-coating treatment After the coating is formed, the coating surface is leveled by a combination of low-energy ion beam trimming and precision polishing, so that the height difference between the top surface of the conductive neck 222 and the top surface of the CrN-based wear-resistant layer 13 is no greater than 0.3 micrometers, the surface roughness of the coating is no greater than 0.20 micrometers, and there are no obvious Ag-Cu conductive blocks protruding on the coating surface.

[0119] After the surface is leveled, the connecting terminal 3 is placed in a vacuum or inert gas environment and subjected to a low-temperature treatment at 180 degrees Celsius for 60 minutes.

[0120] This application addresses the issues of coating wear, increased contact resistance, and increased local temperature rise in the high-current connection terminals 3 of DC charging piles after frequent insertion and removal. Multiple embedded wear-compensating conductive units 2 are incorporated within the continuous CrN-based wear-resistant layer 13. Each conductive unit 2 consists of a conductive neck 222 that is substantially flush with the working surface, one or more conductive reserve portions 221 with a lateral cross-sectional area larger than the conductive neck 222, and a conductive root portion 21 electrically connected to the connection terminal 3. In the initial use phase, only a small area of ​​the conductive neck 222 is exposed to maintain a high CrN bearing area, ensuring wear resistance and load-bearing capacity. As the coating wears deeper, the conductive reserve portions 221 are gradually exposed, increasing the effective conductive area of ​​the working surface with the degree of wear, thus delaying the increase in contact resistance and temperature rise. When the deepest conductive reserve portion 221 is consumed or the remaining thickness of the bearing support 1 reaches a threshold, the connection terminal 3 can be determined to be in a state close to maintenance or replacement.

[0121] Compared with CrN coating, coating the surface of the high-current connection terminal 3 of the DC charging pile with the CrN-based composite conductive wear-resistant coating provided in this application has the following advantages: the continuously arranged CrN-based wear-resistant layer 13 bears the main mechanical load, and the dispersed conductive units 2 bear the low-resistance conductive function, which can avoid the decrease in hardness caused by uniformly adding a large amount of soft conductive metal to the CrN coating; the surface conductive neck 222 is basically flush with the CrN-based wear-resistant layer 13, which can reduce stress concentration and abnormal wear caused by conductive metal protrusions; as the coating wear degree increases, the conductive reserve part 221 is exposed step by step, so that the conductive metal area of ​​the working surface increases in stages, realizing conductive compensation corresponding to the wear depth; different contact pressure areas use conductive units 2 with different density and different levels, so that precious metal materials are concentrated in areas with more severe actual wear and more concentrated current carrying capacity, thereby improving the life of the connection terminal 3 while reducing the amount of precious metal materials used; the multi-level conductive reserve structure that can be repeatedly manufactured is formed by magnetron sputtering and patterned selective deposition, and the process operation is controllable. This coating combines the wear resistance and corrosion resistance of CrN coating with the low resistance of Ag-Cu alloy, taking into account the advantages of low resistance, wear resistance, corrosion resistance and precious metal saving. It can be prepared by magnetron sputtering combined with patterned selective deposition and is suitable for the positive and negative connection terminals of DC charging pile charging guns and the high current connection terminals in vehicle-side DC charging sockets.

[0122] It should be noted that the order of the embodiments described above is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. Furthermore, specific embodiments have been described above. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps described in the claims can be performed in a different order than that shown in the embodiments and still achieve the desired result. Additionally, the processes depicted in the drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0123] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the device embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0124] Those skilled in the art will understand that all or part of the steps of the above embodiments can be implemented by hardware or by a program instructing related hardware. The program can be stored in a computer-readable storage medium, such as a read-only memory, a disk, or an optical disk.

[0125] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A CrN-based composite conductive and wear-resistant coating, characterized in that, include: The support bracket includes a diffusion barrier layer, a stress transition layer and a CrN-based wear-resistant layer stacked sequentially, wherein the diffusion barrier layer is used to contact the surface to be coated; Multiple conductive units are embedded in the support bracket and spaced apart from each other. The support bracket at least covers the sidewall of each conductive unit. An interface is provided between the support bracket and each conductive unit. Each conductive unit includes a conductive root and a conductive body that are in contact with each other along a predetermined direction. The conductive body is located in the CrN-based wear-resistant layer. The surface of the conductive body away from the conductive root is exposed on the side of the CrN-based wear-resistant layer away from the diffusion barrier layer. One end of the conductive root is located in the CrN-based wear-resistant layer and contacts the conductive body. The other end extends at least to the side of the diffusion barrier layer facing the CrN-based wear-resistant layer. The conductive body includes one conductive sub-unit or multiple conductive sub-units that are in contact with each other along the predetermined direction. Each conductive sub-unit includes a conductive reserve portion and a conductive neck that are in contact with each other along the predetermined direction. The conductive reserve portion in each conductive sub-unit is located on the side of the conductive neck closer to the conductive root. The transverse cross-sectional area of ​​the conductive reserve portion in the predetermined direction is larger than the transverse cross-sectional area of ​​the conductive neck in the predetermined direction.

2. The CrN-based composite conductive wear-resistant coating according to claim 1, characterized in that, The surface of the conductive main body away from the conductive root is not higher than the surface of the CrN-based wear-resistant layer away from the diffusion barrier layer, and the distance between the surface of the conductive main body away from the conductive root and the surface of the CrN-based wear-resistant layer away from the diffusion barrier layer is 0-1 micrometer.

3. The CrN-based composite conductive wear-resistant coating according to claim 1, characterized in that, The conductive root extends from one end away from the conductive body to the side of the diffusion barrier layer facing the CrN-based wear-resistant layer. Alternatively, the conductive root extends from one end away from the conductive body to the side of the diffusion barrier layer away from the CrN-based wear-resistant layer. Alternatively, one end of the conductive root, away from the conductive body, protrudes from the side of the diffusion barrier layer away from the CrN-based wear-resistant layer.

4. The CrN-based composite conductive wear-resistant coating according to claim 1, characterized in that, The conductive main body includes a plurality of conductive sub-units, and in any two conductive sub-units, the lateral cross-sectional area of ​​the conductive reserve portion in the conductive sub-unit closer to the conductive root in the preset direction is greater than the lateral cross-sectional area of ​​the conductive reserve portion in the conductive sub-unit farther from the conductive root in the preset direction.

5. The CrN-based composite conductive wear-resistant coating according to claim 1, characterized in that, The transverse cross-sectional area of ​​each conductive reservoir in the preset direction gradually increases from the end of the conductive reservoir away from the conductive root to the end of the conductive reservoir close to the conductive root. Alternatively, the lateral cross-sectional area of ​​each of the conductive reservoirs in the preset direction is constant; Alternatively, the lateral cross-sectional area of ​​each of the conductive reservoirs in the preset direction gradually decreases from the middle region of the conductive reservoir to both ends of the conductive reservoir.

6. The CrN-based composite conductive wear-resistant coating according to claim 1, characterized in that, The ratio of the transverse cross-sectional area of ​​the conductive reserve portion in each conductive subunit to the transverse cross-sectional area of ​​the conductive neck in the preset direction ranges from 1.5 to 20.

7. The CrN-based composite conductive wear-resistant coating according to claim 1, characterized in that, The diffusion barrier layer includes one or more diffusion barrier sublayers stacked together, and the material of the diffusion barrier sublayer includes at least one of Cr, Ni, NiCr alloy, NiCrMo alloy and CrCu alloy.

8. The CrN-based composite conductive wear-resistant coating according to claim 1, characterized in that, The material of the stress transition layer includes CrN. x 0≤x<1, the nitrogen content in the stress transition layer gradually increases from the side of the stress transition layer in contact with the diffusion barrier layer to the side of the stress transition layer in contact with the CrN-based wear-resistant layer.

9. The CrN-based composite conductive wear-resistant coating according to claim 1, characterized in that, The material of the CrN-based wear-resistant layer includes one selected from the group consisting of: CrN; A mixed phase of Cr2N and CrN; CrN-TiN; CrN-SiN; The CrN phase accounts for more than or equal to 50% of the volume in the CrN-based wear-resistant layer.

10. The CrN-based composite conductive wear-resistant coating according to claim 9, characterized in that, The material of the CrN-based wear-resistant layer also includes modifying elements, which are selected from at least one of Al, Ti, Si, Mo and C.

11. The CrN-based composite conductive wear-resistant coating according to claim 1, characterized in that, The materials of the conductive root, the conductive reserve, and the conductive neck all include one of Ag, Cu, Ag-Cu alloy, Ag-Pd alloy, Cu-Ag-Sn alloy, and Ag-Sn alloy.

12. A method for preparing a CrN-based composite conductive wear-resistant coating, characterized in that, include: S1 forms a diffusion barrier layer; S2 forms a stress transition layer and a plurality of spaced conductive roots. The stress transition layer is located on the diffusion barrier layer. One end of the conductive root is higher than the upper surface of the stress transition layer, and the other end extends at least to the upper surface of the diffusion barrier layer. S3 forms a conductive reserve portion on each of the conductive roots; S4 forms a first CrN-based wear-resistant sublayer, which is located on the stress transition layer and covers the sidewalls of the conductive root and the sidewalls of the conductive reserve. S5 forms a conductive neck on each of the conductive reservoirs, the transverse cross-sectional area of ​​the conductive neck being smaller than the transverse cross-sectional area of ​​the conductive reservoir, and the conductive reservoir and the conductive neck together form a conductive subunit; S6 When the CrN-based composite conductive wear-resistant coating includes a plurality of conductive sub-units, a new conductive reserve portion is formed on each conductive neck, and a second CrN-based wear-resistant sub-layer is formed on the first CrN-based wear-resistant sub-layer. The second CrN-based wear-resistant sub-layer is located on the first CrN-based wear-resistant sub-layer and covers the sidewall of the conductive neck and the sidewall of the newly formed conductive reserve portion. Then, a new conductive neck is formed on each newly formed conductive reserve portion, and so on, until a predetermined number of conductive sub-units are formed. S7 After step S5 or step S6, a third CrN-based wear-resistant sublayer is formed. The third CrN-based wear-resistant sublayer is located on the first CrN-based wear-resistant sublayer or the second CrN-based wear-resistant sublayer and covers the sidewall of the newly formed conductive neck. The upper surface of the conductive neck is exposed in the third CrN-based wear-resistant sublayer.

13. A power connector, characterized in that, The device includes a connecting terminal and a CrN-based composite conductive wear-resistant coating as described in any one of claims 1 to 11, wherein the surface of the connecting terminal includes a plug-in contact area, the CrN-based composite conductive wear-resistant coating is located in the plug-in contact area, and the diffusion barrier layer is in contact with the connecting terminal.

14. The power connector according to claim 13, characterized in that, The insertion contact area includes a high contact pressure area, a medium contact pressure area, and a low contact pressure area distributed sequentially from the inside to the outside on the surface of the connection terminal. The number density of conductive units in the CrN-based composite conductive and wear-resistant coating located in the high contact pressure area, the number density of conductive units in the CrN-based composite conductive and wear-resistant coating located in the medium contact pressure area, and the number density of conductive units in the CrN-based composite conductive and wear-resistant coating located in the low contact pressure area decrease sequentially.

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