A protective coating with a biomimetic structure and a preparation method and application thereof

Abstract

The application discloses a protective coating with a bionic structure and a preparation method and application thereof, and adopts a laser cladding technology to prepare hard net belts with high hardness first, and then prepares soft channels with electric conduction and heat conduction, realizes interphase distribution, and fills the soft channels in the gaps of the hard net belts to make the two interphase distributed, so that the protective coating has an animal bone structure and a turtle shell structure. When the bionic structure coating works, each hard net belt and the soft channel form a unit, when encountering wear or ablation damage, can play a limited role, limits the damage in one or several adjacent units, avoids the damage from expanding in a large range, further plays a protective role, and prolongs the service life of the workpiece.

Description

Technical Field

[0001] This invention relates to the field of metal material surface processing technology. It addresses the critical failure of key components, particularly non-ferrous metal parts such as copper and copper alloys, which operate under extreme conditions and suffer from poor surface wear resistance and short lifespan. These components often exhibit low hardness and poor wear resistance, while improving wear resistance reduces electrical and thermal conductivity. The invention presents a biomimetic structural coating and preparation technology that integrates wear resistance, electrical conductivity, and thermal conductivity, mimicking animal bone and tortoise shell structures. This achieves high-efficiency, high-quality surface strengthening of non-ferrous metal parts such as copper and copper alloys, and is applicable to the protection of critical components such as conductive pantographs, catapult rails, heat exchangers, and condensers in marine engineering, petroleum, chemical, power, and transportation industries. Background Technology

[0002] Key components in marine equipment, aerospace, rail transportation, and chemical machinery, especially non-ferrous metal parts such as copper and copper alloys, suffer from low hardness, poor wear resistance, and high-temperature softening. These issues lead to short service life and significant safety hazards when subjected to extreme wear and high-temperature environments. Forming a robust protective coating through surface treatment is an effective way to improve the surface strength and wear resistance of copper alloys. Chinese Patent Application No. 202211655694.3 discloses a method for preparing conductive copper-chromium-zirconium alloys. After grinding, alloy powder, binder, and acetone are laid on the alloy end face, and after drying, laser cladding is performed to obtain the conductive copper-chromium-zirconium alloy. Chinese Patent Application No. 201980046310.8 discloses a copper-based surface-hardening alloy that forms a hard phase (such as silicides, borides, or carbides) in the copper matrix, improving the alloy's wear resistance. This method is essentially free of precious elements such as Co, Mn, Mo, Ta, V, and W, thereby reducing the high hardness of these silicides and improving the alloy's crack resistance and machinability. Chinese Patent Application No. 202010219677.X discloses a multi-scale titanium carbide particle-reinforced copper-based composite coating, its preparation method, and its application. By adding multi-scale titanium carbide particles to copper and copper-titanium matrices, a high-hardness, friction-reducing, and wear-resistant composite coating is obtained through spark discharge sintering. This multi-scale reinforced phase particle-reinforced copper-based composite coating can be applied to copper alloy molds, copper alloy crystallizers, and electromagnetic railgun guides. Chinese Patent Application No. 202210274501.3 discloses a plasma-laser composite additive manufacturing method. Using a cyclical sequence of plasma cladding followed by laser cladding on the workpiece surface, a strong and tough bond between a wavy wear-resistant band and a soft stainless steel bonding band, and an alternating soft and hard surface layer, is obtained. This method effectively reduces the residual stress between the wear-resistant band and the bonding band, achieving a strong bond, thereby improving the wear resistance, impact resistance, corrosion resistance, and resistance to corrosion-wear force-electric coupling damage of key components.

[0003] The aforementioned copper alloy surface strengthening and coating design and preparation technology can improve the surface properties of copper alloys, increase the bonding strength between the coating and the substrate, and improve the mechanical properties of the surface and the service life of the workpiece. However, no reports have been found on the design and preparation technology of biomimetic structural coatings that integrate structure and function on the surface of non-ferrous metal parts such as copper and copper alloys, which also possess wear resistance, electrical conductivity, and thermal conductivity. Summary of the Invention

[0004] To overcome the aforementioned problems in the prior art, this invention provides a method for designing and preparing a coating with an integrated structure-function, mimicking animal bone and tortoise shell structures on the surface of non-ferrous metal parts such as copper and copper alloys. This method innovatively proposes a biomimetic structure that forms both a hard mesh strip with structural properties such as hardness and wear resistance, and a soft channel with functional properties such as electrical and thermal conductivity. Laser cladding technology is used to prepare the metallurgically bonded hard mesh strip and soft channels, achieving an alternating phase distribution. During operation, the mesh strip formed by the hard material supports the friction pair, improving wear resistance, while the soft channels in the middle are made of materials with good electrical and thermal conductivity, forming a continuous electrical and thermal conductivity effect from the base layer to the surface.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A protective coating with a biomimetic structure is characterized in that it is a coating composed of a first-formed wear-resistant hard mesh strip and a second-formed conductive and thermally conductive soft channel. The soft channel fills the gaps in the hard mesh strip, so that the two are distributed alternately, thereby giving the protective coating a structure that mimics animal bones and tortoise shells. The hard mesh strip and soft channel are metallurgically bonded to the substrate, and the second-formed soft channel plays a role in stress relief and relaxation of the first-formed hard mesh strip.

[0007] Furthermore, the rigid mesh belt and the flexible channel are preferably formed by laser cladding process.

[0008] Furthermore: the rigid mesh belt is composed of conductive and thermally conductive metal powder and ceramic powder; the soft channel is formed of conductive and thermally conductive metal powder, which is the same as the metal powder in the rigid mesh belt.

[0009] Furthermore, the specific structure of the rigid mesh belt can be a mesh of interconnected hexagons, rhombuses, rectangles, etc.

[0010] Furthermore, the rigid mesh belt contains 70-90% metal powder and 10-30% ceramic powder by mass.

[0011] Furthermore, the composition of the conductive and thermally conductive metal powder is consistent with that of the substrate, preferably CuCrZr powder, with the mass ratio of each element being Cr: 0.1-0.8%, Zr: 0.3-0.6%, and the remainder being Cu powder, with a particle size of 40-120μm, in order to reduce the difference in thermal properties between the coating and the substrate and reduce stress.

[0012] Furthermore, the ceramic powder is selected from one or more nano-powders with a particle size of 50nm-200nm, such as TiN, TiC, TiB2, WC, B4C, and SiC, and the ceramic powder is used through in-situ synthesis or direct introduction.

[0013] To obtain the above coating, the present invention employs the following method, specifically including the following steps:

[0014] Step 1: Powder preparation and workpiece surface pretreatment

[0015] The coating composition is designed according to the actual needs of the workpiece. Hard mesh belt powder and soft channel powder are prepared separately and then dried for later use. The surface of the metal workpiece substrate is descaled and then set aside for later use.

[0016] Step 2: Programming the cladding motion trajectory as needed

[0017] Based on the workpiece shape, size, and cladding area, a laser scanning motion trajectory is programmed, synchronous powder feeding parameters are set, and different types of biomimetic structural motion trajectories for rigid mesh belts and soft channels are set for cladding.

[0018] Step 4: Laser cladding

[0019] The laser cladding method is used to first prepare a hard mesh belt with high hardness, and then fill the gaps in the hard mesh belt to prepare a soft channel that is conductive and thermally conductive, so as to achieve phase distribution. A protective coating is obtained on the surface of the workpiece by synchronous powder feeding.

[0020] Furthermore, the laser cladding parameters are as follows: laser power 1-4kW, spot diameter 2-4mm, cladding speed 280-600mm / min, powder feeding rate 20-50g / min, and overlap rate of 10-30% between the rigid mesh belt and the soft channel, and between different cladding passes of the soft channel.

[0021] The method for preparing protective coatings provided by this invention is suitable for key components in marine equipment, aerospace, rail transportation, chemical machinery, and especially for non-ferrous metal parts such as copper and copper alloys.

[0022] The beneficial effects of this invention are:

[0023] 1. The biomimetic structural coating obtained by the method of this invention has both a hard mesh strip with good structural properties such as hardness and wear resistance, and a soft channel with good electrical and thermal conductivity. The hard mesh strip can be hexagonal, rhomboid, rectangular, etc. The hard mesh strip and the soft channel are distributed alternately. During operation, the mesh strip formed by the hard material supports the friction pair and improves wear resistance. The soft channel in the middle is made of a material with good electrical and thermal conductivity, forming a continuous electrical and thermal conductivity effect from the base to the surface, so that the protective coating has both wear resistance, ablation resistance, electrical conductivity, and thermal conductivity. Tests have shown that when the cladding layer thickness is 0.5-1mm, the average hardness is 500-700 HV, the same as the hard mesh strip. 0.1 Between these values, the hardness of the soft channel is approximately 200 HV. 0.1 The bonding force between the entire protective coating and the substrate is greater than 200MPa, and the wear resistance is 3-5 times higher than that of the unprotected CuCrZr substrate, while the electrical and thermal conductivity are basically the same and there is no significant reduction.

[0024] 2. Laser cladding technology is used to prepare a metallurgically bonded hard mesh belt and soft channel. First, a high-hardness hard mesh belt is prepared, followed by a conductive and thermally conductive soft channel. The hard mesh belt, soft channel, and substrate exhibit a metallurgical bond. Because the hard mesh belt, soft channel, and substrate use the same metal powder, the compatibility between the three components in terms of melting point and coefficient of thermal expansion is further improved, reducing stress between the coating and the substrate. This avoids the formation of a hard and brittle intermetallic compound layer at the interfaces of the hard mesh belt and soft channel, the hard mesh belt and substrate, and the soft channel and substrate, which would reduce the bonding strength, when using different metal powders. Furthermore, the subsequently formed soft channel further relieves stress and relaxes the previously formed hard mesh belt through heating, resulting in a low-stress, metallurgically bonded protective coating. This is beneficial for improving the adhesion between the protective layer and the substrate and extending service life.

[0025] 3. When the biomimetic structure coating is in operation, each rigid mesh belt and soft channel form a unit. When encountering wear or ablation damage, it can play a confining role, limiting the damage to one or a few adjacent units, preventing the damage from spreading over a large area, and further playing a protective role.

[0026] 4. In biomimetic structural coatings, different materials of rigid mesh belts and soft channels can be designed based on actual needs. Biomimetic structures with different trajectories can also be set. This is suitable not only for surface strengthening of key components such as conductive pantographs, electrical contacts, catapult rails, heat exchangers, and condensers in marine engineering, petroleum, chemical, power, and transportation fields, but also for surface strengthening of civil aircraft landing gear, airfoil control bearings, and hydraulic plunger cylinders. Compared with traditional copper alloy surface strengthening methods, it combines wear resistance, electrical and thermal conductivity, and integrates structural-functionality, low stress, and metallurgical bonding into one, resulting in high efficiency and controllable thickness. It can effectively solve the contradiction in the performance of surface strengthening layers for copper and copper alloys and other non-ferrous metal parts under extreme working conditions, and is suitable for surface strengthening of key components such as conductive pantographs, electrical contacts, catapult rails, heat exchangers, and condensers in marine engineering, petroleum, chemical, power, and transportation fields. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the laser cladding process for rigid mesh belts.

[0029] Figure 2 This is a schematic diagram of the laser cladding process for soft channels.

[0030] Figure 3 A schematic diagram of the protective coating for the combination of rigid mesh belt and soft channel prepared in Example 1;

[0031] Figure 4 This is a schematic diagram of the protective coating for the combination of rigid mesh belt and flexible channel prepared in Example 2;

[0032] Figure 5 This is a schematic diagram of the protective coating of the rigid mesh belt and soft channel combination prepared in Example 3.

[0033] In the diagram: 1- Rigid mesh belt, 2- Flexible channel. Detailed Implementation

[0034] To enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. However, this is not the only description; all aspects not described in detail herein are based on conventional techniques in the art.

[0035] Example 1:

[0036] Step 1: Powder Preparation

[0037] The coating composition is designed and the powder is prepared according to the actual requirements of the workpiece. The coating powder consists of metal powder and ceramic powder. The metal powder is mainly CuCrZr powder, or other conductive and thermally conductive powders, with a particle size of 70μm. The ceramic reinforcing phase can be introduced directly or through in-situ reaction synthesis, and is selected from TiB2 nanoparticles with a particle size of 100nm. In the rigid mesh belt, the mass percentage of metal powder is 80%, and the mass percentage of ceramic powder is 20%, while the soft channel is made of CuCrZr powder, or other conductive and thermally conductive powders. The rigid mesh belt powder is weighed and mixed evenly, and then dried separately from the soft channel powder for later use.

[0038] Step 2: Surface pretreatment of the workpiece

[0039] The metal workpiece substrate is CuCrZr block, with the same composition as CuCrZr powder. It can also be other substrates that require protection. The workpiece is immersed in an acid solution to remove dirt, then washed with water, then soaked in alkaline water to neutralize the residual acid solution, and finally washed with warm water and dried.

[0040] Step 3: Program the cladding motion trajectory as needed.

[0041] Based on the workpiece shape, size, and cladding area, a laser scanning motion trajectory is programmed, synchronous powder feeding parameters are set, and the biomimetic structure motion trajectory of the hard mesh belt and soft channel is set to hexagonal, and cladding is performed separately.

[0042] Step 4: Laser Cladding

[0043] Using laser cladding, first prepare Figure 1 The high-hardness rigid mesh belt shown is subsequently prepared. Figure 2 The conductive and thermally conductive soft channels shown achieve phase distribution, and the powder is fed synchronously onto the workpiece surface to obtain a... Figure 3 The protective coating is shown. Laser cladding parameters are: laser power 3kW, spot diameter 3mm, cladding speed 400mm / min, powder feed rate 40g / min. The overlap rate between the rigid mesh belt and the flexible channel, and between different cladding passes in the flexible channel, is 20%. The cladding layer thickness is 0.8mm, and the average hardness is 600HV (the same as the rigid mesh belt). 0.1 The hardness of soft channel 2 is approximately 200 HV. 0.1 The bonding force between the entire protective coating and the substrate is greater than 200MPa, the wear resistance is 4 times higher than that of the unprotected CuCrZr substrate, and the electrical conductivity is ≥60%IACS.

[0044] from Figure 3As shown in the schematic diagram of the combination of rigid mesh belt 1 and soft channel 2, the biomimetic structure prepared in Example 1 has a hexagonal motion trajectory. The rigid mesh belt 1 is a mesh structure with interconnected hexagons. The soft channel 2 fills the hexagonal gaps in the rigid mesh belt 1, so that the soft channel 2 is a columnar channel from the surface of the protective coating to the substrate interface.

[0045] Example 2:

[0046] Step 1: Powder preparation: Except that the powder is selected from SiC, the rest is the same as in Example 1.

[0047] Step 2 is the same as in Example 1.

[0048] Step 3 is the same as in Example 1, except that the biomimetic structure's motion trajectory is a rhomboid structure.

[0049] Step 4: Laser cladding: The laser power is 4kW, the spot diameter is 3mm, the cladding speed is 400mm / min, the powder feed rate is 50g / min, the cladding layer thickness is 1.0mm, and the average hardness is 700HV (equivalent to the hardness of a rigid conveyor belt). 0.1 The wear resistance is 5 times higher than that of the unprotected CuCrZr matrix, the electrical conductivity is ≥55% IACS, and the rest is the same as in Example 1.

[0050] A schematic diagram of the combination of rigid mesh belt 1 and soft channel 2 prepared in Example 2 is shown below. Figure 4 ,from Figure 4 It can be seen that the rigid mesh belt 1 is a mesh structure with interconnected rhombuses, and the soft channel 2 fills the rhombus gaps in the rigid mesh belt 1, so that the soft channel 2 is a columnar channel from the protective coating interface to the substrate interface.

[0051] Example 3:

[0052] Step 1: Powder preparation: Except that the powder is selected from TiN+TiB2, with each accounting for 50% by mass, the rest is the same as in Example 1.

[0053] Step 2 is the same as in Example 1.

[0054] Step 3 is the same as in Example 1, except that the biomimetic structure's motion trajectory is a rectangular structure.

[0055] Step 4: Laser cladding: Except that the average hardness is between 500 HV0.1 and that of the hard mesh belt, the wear resistance is 3 times higher than that of the unprotected CuCrZr substrate, and the electrical conductivity is ≥50% IACS. The rest is the same as in Example 1.

[0056] A schematic diagram of the combination of rigid mesh belt 1 and soft channel 2 prepared in Example 3 is shown below. Figure 5 ,from Figure 5It can be seen that the rigid mesh belt 1 is a mesh structure with rectangles connected to each other, and the soft channel 2 fills the rectangular gaps in the rigid mesh belt 1, so that the soft channel 2 is a columnar channel from the surface of the protective coating to the substrate interface.

[0057] The above are merely three examples of the present invention and are not intended to limit the technical solutions of the present invention. The innovation of the present invention mainly lies in proposing a protective coating that simultaneously mimics the structure of animal bones and the structure of a tortoise shell, and providing a method for preparing such a coating. Although the selection of metal powder and ceramic powder used in the coating, as well as the proportion of each component in the powder, are also necessary technical features for achieving the purpose of the present invention, they are not the focus. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principles described in the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a protective coating with a biomimetic structure, characterized in that, Includes the following steps: Step 1: Prepare rigid mesh belt powder and soft channel powder. The rigid mesh belt powder is composed of conductive and thermally conductive metal powder and ceramic powder. The soft channel powder is composed of the same conductive and thermally conductive metal powder as the rigid mesh belt powder, and the composition of the conductive and thermally conductive metal powder is consistent with that of the matrix. Step 2: Using laser cladding technology, hard mesh powder is first clad onto the surface of the metal substrate to form a wear-resistant hard mesh. The hard mesh is a mesh structure in which hexagons, rhombuses or rectangles are connected to each other. The third step involves using laser cladding to clad soft channel powder in the gaps of the rigid mesh belt, forming conductive and thermally conductive soft channels. These soft channels fill the gaps in the rigid mesh belt and are distributed alternately with it, thus obtaining a protective coating with an animal bone structure and a tortoise shell structure. Both the rigid mesh belt and the soft channel are metallurgically bonded to the matrix, and the soft channel formed later can remove and relax the internal stress of the rigid mesh belt formed earlier. The conductive and thermally conductive metal powder is CuCrZr powder, with the mass ratio of each element being Cr: 0.1-0.8%, Zr: 0.3-0.6%, and the remainder being Cu powder; the laser power of the laser cladding process is 1-4kW; The rigid mesh belt contains 70-90% conductive and thermally conductive metal powder and 10-30% ceramic powder by mass.

2. The method for preparing a protective coating with a biomimetic structure as described in claim 1, characterized in that, The ceramic powder includes one or more of TiN, TiC, TiB2, WC, B4C and SiC nanoparticles. The ceramic powder is synthesized in situ or introduced directly, and has a particle size of 50nm-200nm.

3. The method for preparing a protective coating with a biomimetic structure as described in claim 1, characterized in that, The laser cladding parameters are as follows: spot diameter is 2~4mm, cladding speed is 280~600mm / min, powder feeding rate is 20~50g / min, and the overlap rate between the rigid mesh belt and the soft channel, and between different cladding passes of the soft channel is 10-30%.

4. The application of a protective coating with a biomimetic structure prepared by any one of claims 1-3 in key components of marine equipment, aerospace, rail transportation or chemical machinery.

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