Protective coating with bionic structure, and preparation method and use thereof

Abstract

A protective coating having a bionic bone or tortoise shell structure comprises a rigid mesh 1 having a high hardness and an electrically conductive and thermally conductive soft material 2 located within interstices in the rigid mesh, wherein forming the rigid mesh first and the soft material second by laser cladding results in a stress removal and relaxation effect being formed on the rigid mesh. The rigid mesh may be formed from 70 - 90 weight percentage of metal powder and 10 - 30 weight percentage of ceramic powder, preferably titanium nitride, titanium carbide, titanium boride, tungsten carbide, boron carbide or silicon carbide powder. The soft material may be formed from copper, chromium and zirconium powder. Use of the protective coating in marine equipment, aerospace, rail transportation or chemical machinery is disclosed.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of metal material surface processing. The present disclosure is aimed at key components that fail due to poor surface wear resistance and low lifespan when working under extreme working conditions, especially non-ferrous metal components such as copper and copper alloys, which have low hardness and poor wear resistance, while improving wear resistance reduces electrical conductivity and thermal conductivity. The present disclosure designs a structure-function integrated protective coating with a bionic structure, which has a bionic animal bone structure and a bionic tortoise shell structure and is wear-resistant as well as electrically conductive and thermally conductive, and a preparation method thereof, to achieve high-efficiency and high-quality surface strengthening of the non-ferrous metal components such as copper and copper alloys. The protective coating is suitable for the protection of key components such as pantographs, catapult rails, heat exchangers, and condensers in the fields of marine engineering, petroleum, chemical industry, electric power, and transportation. BACKGROUND

[0002] Key components of marine equipment, aerospace, rail transit, and chemical machinery, especially non-ferrous metal components such as copper and copper alloys, have low hardness, poor wear resistance, and high-temperature softening. When serving in extreme wear and high-temperature environments, these components may be affected by wear and softening to cause short material service life and great safety hazards. Forming a strong protective coating through surface treatment is an effective way to improve the surface strength and wear resistance of copper alloys. Chinese Patent No. 202211655694.3 has disclosed a preparation method of a conductive copper-chromium-zirconium alloy, in which an alloy powder, a binder, and acetone are laid on an alloy end surface after grinding and polishing, and then laser cladding is conducted after drying to obtain the conductive copper-chromium-zirconium alloy. Chinese Patent No. 201980046310.8 has disclosed a copper-based surface-hardened alloy, in which a hard phase (such as silicide, boride, or carbide) is formed in a copper matrix to improve wear resistance of the alloy. The process substantially eliminates the use of precious Co, Mn, Mo, Ta, V, and W, thereby reducing the high hardness of such silicides and improving crack resistance and machinability of the alloy. Chinese patent No. 202010219677.X has disclosed a multi-scale titanium carbide particle-reinforced copper-based composite coating, and a preparation method and use thereof, where multi-scale titanium carbide particles are added into copper and a coppertitanium matrix, and then spark discharge sintering is conducted to obtain a high-hardness, friction-reducing, and wear-resistant composite coating. This multi-scale strengthening phase particle-reinforced copper-based composite coating can be used in copper alloy molds, copper alloy crystallizers, and electromagnetic gun guide rails. Chinese patent No. 202210274501.3 has disclosed an additive manufacturing method based on plasma combined with laser, where a cyclic sequence of plasma cladding followed by laser cladding is conducted on a workpiece surface to obtain a surface layer, which has a strong and tough combination of a wavy wearresistant belt and a stainless steel soft adhesive belt, as well as alternating soft and hard layers. This additive manufacturing method effectively reduces a residual stress between the wearresistant belt and the adhesive belt, achieves strong binding, and thus improves wear resistance, impact resistance, corrosion resistance, and corrosion wear force-electric coupling damage resistance on a surface of the key components.

[0003] The copper alloy surface strengthening and coating design and preparation techniques in the above patents can improve surface properties of the copper alloys, increase a bonding strength between the coating and the substrate, and improve mechanical properties of the surface and a service life of the workpiece. However, there are no reports on the design of a protective coating with a bionic structure that has integrated structure and function on the surface of nonferrous metal components such as copper and copper alloys, and a preparation process thereof, where the protective coating exhibits wear resistance, electrical conductivity, and thermal conductivity. SUMMARY

[0004] In order to overcome the above problems in the prior art, an objective of the present disclosure is to provide a method for designing and preparing a coating with structural and functional integration as well as a bionic animal bone structure and a bionic tortoise shell structure on the surface of non-ferrous metal components such as copper and copper alloys. The preparation method innovatively proposes to design a bionic structure that not only forms a rigid mesh belt with structural properties such as hardness and wear resistance, but also forms a soft channel with functional properties such as electrical conductivity and thermal conductivity. The rigid mesh belt and the soft channel are metallurgically bonded and then prepared by laser cladding to achieve alternative distribution. When working, the rigid mesh belt supports friction pair and improves wear resistance, while the soft channel in the middle is made of materials with desirable electrical conductivity and thermal conductivity to form a continuous effect of the electrical conductivity and thermal conductivity from the substrate to the surface.

[0005] In order to achieve the above objective, the present disclosure adopts the following technical solutions:

[0006] The present disclosure provides a protective coating with a bionic structure, including a wear-resistant rigid mesh belt formed primarily and an electrically conductive and thermally conductive soft channel formed secondarily, where the soft channel fills gaps in the rigid mesh belt, such that the rigid mesh belt and the soft channel achieve alternative distribution and the protective coating has a bionic animal bone structure and a bionic tortoise shell structure; and the rigid mesh belt, the soft channel, and a substrate are metallurgically bonded, and the soft channel formed secondarily exerts a stress removal and relaxation effect on the rigid mesh belt formed primarily.

[0007] Further, the rigid mesh belt and the soft channel are preferably formed by laser cladding.

[0008] Further, the rigid mesh belt is prepared by an electrically conductive and thermally conductive metal powder and a ceramic powder, and the soft channel is prepared by the electrically conductive and thermally conductive metal powder.

[0009] Further, a structure of the rigid mesh belt includes but is not limited to a mesh structure in which a hexagon, a rhombus, and a rectangle are connected mutually.

[0010] Further, the rigid mesh belt includes 70% to 90% of the electrically conductive and thermally conductive metal powder and 10% to 30% of the ceramic powder by mass percentage.

[0011] Further, the electrically conductive and thermally conductive metal powder is a CuCrZr powder including 0.1% to 0.8% of a Cr powder, 0.3% to 0.6% of a Zr powder, and a Cu powder as a balance, and has a particle size of 40 pm to 120 pm; and a composition of the electrically conductive and thermally conductive metal powder is consistent with a composition of the substrate to reduce a difference in a thermophysical properties between the protective coating and the substrate and then reduce a stress.

[0012] Further, the ceramic powder is one or more selected from the group consisting of TiN, TiC, TiB2, WC, B4C, and SiC nanopowders, and the ceramic powder is synthesized in situ or directly introduced and has a particle size of 50 nm to 200 nm.

[0013] The present disclosure further provides a preparation method of the protective coating with a bionic structure, including the following steps:

[0014] step 1, preparing powders:

[0015] designing a coating composition according to actual demands of a metal workpiece to be treated, preparing a rigid mesh belt powder and a soft channel powder, and then drying for later use;

[0016] step 2, conducting workpiece surface pretreatment:

[0017] descaling a surface of a metal workpiece substrate for later use;

[0018] step 3, programming a cladding motion trajectory as needed:

[0019] programming a laser scanning motion trajectory according to a shape, a size, and a cladding area of the metal workpiece, setting synchronous powder feeding parameters, and setting motion trajectories of different types of bionic structures for the rigid mesh belt and the soft channel to allow cladding; and

[0020] step 4, conducting laser cladding:

[0021] preparing the rigid mesh belt with a high hardness by the laser cladding, filling the electrically conductive and thermally conductive soft channel in the gaps of the rigid mesh belt to achieve alternative distribution, and then obtaining the protective coating on the surface of the metal workpiece by synchronous powder feeding.

[0022] Further, where the laser cladding includes the following parameters: a laser power of 1 kW to 4 kW, a spot diameter of 2 mm to 4 mm, a cladding speed of 280 mm / min to 600 mm / min, and a powder feeding rate of 20 g / min to 50 g / min; and an overlap rate is 10% to 30% between the rigid mesh belt and the soft channel and between different cladding passes of the soft channel.

[0023] The present disclosure further provides use of the protective coating with a bionic structure in a key component of marine equipment, aerospace, rail transportation, or chemical machinery.

[0024] The present disclosure has the following beneficial effects:

[0025] 1. The protective coating with a bionic structure obtained by the preparation method of the present disclosure includes a rigid mesh belt with desirable structural properties such as hardness and wear resistance, and a soft channel with desirable functional properties such as electrical conductivity and thermal conductivity, and the rigid mesh belt can be in the shape of a hexagon, a rhombus, or a rectangle. The rigid mesh belt and the soft channel achieve alternative distribution. When working, the rigid mesh belt supports friction pair and improves wear resistance, while the soft channel in the middle is made of materials with desirable electrical conductivity and thermal conductivity to form a continuous effect of the electrical conductivity and thermal conductivity from the substrate to the surface, such that the protective coating exhibits wear resistance, ablation resistance, electrical conductivity, and thermal conductivity. After testing, when a thickness of the cladding layer is (0.5-1) mm, an average hardness of the rigid mesh belt is (500-700) HVo.i, and an average hardness of the soft channel is 200 HVo.i. A bonding force between the entire protective coating and the substrate is greater than 200 MPa, and wear resistance is 3-5 times higher than that of the unprotected CuCrZr substrate, while the electrical conductivity and thermal conductivity are basically close with no significant decrease.

[0026] 2. Laser cladding is conducted to prepare the rigid mesh belt and soft channel that are metallurgically bonded. First, the rigid mesh belt with a high hardness is prepared, and then the electrically conductive and thermally conductive soft channel is prepared. The rigid mesh belt, soft channel, and substrate are metallurgically bonded. Since the rigid mesh belt, soft channel, and substrate are prepared using a same metal powder, a compatibility between the above three parts in terms of melting point and thermal expansion coefficient is further improved to reduce the stress between the coating and the substrate. Meanwhile, the preparation method avoids the formation of a hard and brittle intermetallic compound layer at an interface between the rigid mesh belt and the soft channel, an interface between the rigid mesh belt and the substrate, and an interface between the soft channel and the substrate by different metal powders, thereby reducing the bonding strength. Moreover, the soft channel formed secondarily further heats and removes stress and relaxes the rigid mesh belt formed primarily, thereby obtaining the protective coating with low stress and metallurgical bonding, which is beneficial to improving a bonding strength between the protective layer and the substrate and then extending the service life.

[0027] 3. When the protective coating with a bionic structure is working, each rigid mesh belt and each soft channel form a unit, which can play a limiting role when encountering wear or ablation damages, thus limiting the damages to one or several adjacent units. In this way, the protective coating can prevent the damages from spreading over a large area, and further play a protective role.

[0028] 4. In the protective coating with a bionic structure, the rigid mesh belt and soft channel of different materials can be designed based on actual demands, and bionic structures of different trajectories can also be set. The protective coating is not only suitable for the surface strengthening of key components such as pantographs, electrical contacts, ejection rails, heat exchangers, and condensers in the fields of marine engineering, petroleum, chemical industry, electricity, and transportation, but also suitable for the surface strengthening of civil aircraft landing gear, wing control bearings, and hydraulic plunger cylinders. Compared with traditional copper alloy surface strengthening methods, the protective coating shows wear resistance, electrical conductivity, and thermal conductivity, integrates structure-functionality, low stress, and metallurgical bonding, and has high efficiency and controllable thickness. The protective coating effectively solves the contradiction in the performance of surface strengthening layer of non-ferrous metal components such as copper and copper alloys under extreme working conditions, and is suitable for surface strengthening of key components such as pantographs, electrical contacts, ejection rails, heat exchangers, and condensers in the fields of marine engineering, petroleum, chemical industry, electric power, and transportation. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] To describe the technical solutions in embodiments of the present disclosure or in the prior art more clearly, the accompanying drawings required in the embodiments are briefly described below. Apparently, the accompanying drawings in the following description show merely some embodiments of the present disclosure, and other drawings can be derived from these accompanying drawings by those of ordinary skill in the art without creative efforts.

[0030] FIG. 1 shows a schematic diagram of a process of laser cladding on the rigid mesh belt;

[0031] FIG. 2 shows a schematic diagram of a process of laser cladding on the soft channel;

[0032] FIG. 3 shows a schematic diagram of the protective coating including the rigid mesh belt and the soft channel prepared in Example 1;

[0033] FIG. 4 shows a schematic diagram of the protective coating including the rigid mesh belt and the soft channel prepared in Example 2; and

[0034] FIG. 5 shows a schematic diagram of the protective coating including the rigid mesh belt and the soft channel prepared in Example 3; where

[0035] reference numerals are: 1 - rigid mesh belt, 2 - soft channel. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] In order to make the technical solutions in this specification better understood by the persons skilled in the art, the technical solutions in the examples of the present disclosure are described clearly and completely below in conjunction with the drawings in the implementation of the present disclosure, but are not limited thereto. Anything not described in detail in the present disclosure is based on conventional techniques in this field.

[0037] Example 1:

[0038] Stepl,preparing powders:

[0039] A coating composition was designed and powders were prepared according to the actual demands of a workpiece. The powder included a metal powder and a ceramic powder, where the metal powder was mainly a CuCrZr powder or other electrically conductive and thermally conductive powders with a particle size of 70 pm; a ceramic reinforcement phase could be introduced by direct introduction or in-situ reaction synthesis, and was selected from TiB2 nanopowder with a particle size of 100 nm. The rigid mesh belt included 80% by mass of metal powder and 20% by mass of ceramic powder, while the soft channel was a CuCrZr powder or other electrically conductive and thermally conductive powders. The rigid mesh belt powder was weighed and mixed evenly, and then dried separately with the soft channel powder for later use.

[0040] Step 2, conducting workpiece surface pretreatment:

[0041] A metal workpiece substrate was a CuCrZr block, which had a same composition as that of the CuCrZr powder, or might be other substrates that need protection. The metal workpiece was immersed in an acid solution to remove dirt, washed with water, immersed in alkaline water to neutralize the residual acid solution, and then washed with warm water and dried.

[0042] Step 3, programming a cladding motion trajectory as needed:

[0043] A laser scanning motion trajectory was programmed according to a shape, a size, and a cladding area of the metal workpiece, synchronous powder feeding parameters were set, and motion trajectories of bionic structures for the rigid mesh belt and the soft channel were set to be a hexagon to allow cladding.

[0044] Step 4, conducting laser cladding:

[0045] The rigid mesh belt with a high hardness shown in FIG. 1 was prepared by the laser cladding, the electrically conductive and thermally conductive soft channel shown in FIG. 2 was filled in the gaps of the rigid mesh belt to achieve alternative distribution, and then the protective coating shown in FIG. 3 was obtained on the surface of the metal workpiece by synchronous powder feeding. The laser cladding included the following parameters: a laser power of 3 kW, a spot diameter of 3 mm, a cladding speed of 400 mm / min, and a powder feeding rate of 40 g / min; and an overlap rate was 20% between the rigid mesh belt and the soft channel and between different cladding passes of the soft channel. A thickness of the cladding layer was 0.8 mm, an average hardness of the rigid mesh belt 1 was 600 HVo.i, and an average hardness of the soft channel 2 was 200 HVo.i. A bonding force between the entire protective coating and the substrate was greater than 200 MPa, and wear resistance was 4 times higher than that of the unprotected CuCrZr substrate, while the electrical conductivity was >60% IACS.

[0046] From a schematic diagram of the combination of the rigid mesh belt 1 and the soft channel 2 in FIG. 3, it was seen that the motion trajectory of the bionic structure prepared in Example 1 was a hexagonal structure. The rigid mesh belt 1 was a mesh structure composed of hexagons connected to each other, while the soft channel 2 filled hexagonal gaps in the rigid mesh belt 1, such that the soft channel 2 was a columnar channel from the surface of the protective coating to the substrate interface.

[0047] Example 2:

[0048] Step 1, preparing powders: except for SiC powder, other steps were the same as those in Example 1.

[0049] Step 2 was the same as that in Example 1.

[0050] In step 3, except that the motion trajectory of the bionic structure was a rhombus, other steps were the same as those in Example 1.

[0051] Step 4, conducting laser cladding: except that a laser power of 4 kW, a spot diameter of 3 mm, a cladding speed of 400 mm / min, and a powder feeding rate of 50 g / min; a thickness of the cladding layer was 1.0 mm, an average hardness of the rigid mesh belt was 700 HVo.i; and wear resistance was 5 times higher than that of the unprotected CuCrZr substrate, while the electrical conductivity was >55% IACS, other steps were the same as those in Example 1.

[0052] FIG. 4 showed a schematic diagram of the protective coating including the rigid mesh belt 1 and the soft channel 2 prepared in Example 2. From FIG. 4, the rigid mesh belt 1 was a mesh structure composed of rhombuses connected to each other, while the soft channel 2 filled rhombic gaps in the rigid mesh belt 1, such that the soft channel 2 was a columnar channel from the surface of the protective coating to the substrate interface.

[0053] Example 3:

[0054] Step 1, preparing powders: except that powder was TiN+TiB2, each accounting for 50% by mass percentage, other steps were the same as those in Example 1.

[0055] Step 2 was the same as that in Example 1.

[0056] In step 3, except that the motion trajectory of the bionic structure was a rectangle, other steps were the same as those in Example 1.

[0057] Step 4, conducting laser cladding: except that an average hardness of the rigid mesh belt was 500 HVo.i; and wear resistance was 3 times higher than that of the unprotected CuCrZr substrate, while the electrical conductivity was >50% IACS, other steps were the same as those in Example 1.

[0058] FIG. 5 showed a schematic diagram of the protective coating including the rigid mesh belt 1 and the soft channel 2 prepared in Example 3. From FIG. 5, the rigid mesh belt 1 was a mesh structure composed of rectangles connected to each other, while the soft channel 2 filled rectangular gaps in the rigid mesh belt 1, such that the soft channel 2 was a columnar channel from the surface of the protective coating to the substrate interface.

[0059] The above are only three examples of the present disclosure and are not intended to limit the technical solutions of the present disclosure. The innovation of the present disclosure is mainly to propose a protective coating that has both a bionic animal bone structure and a bionic tortoise shell structure, and to provide a preparation method of such a coating. Although the selection of metal powder and ceramic powder used in the coating and the ratio of each component in the powder are also necessary technical features to achieve the purpose of the present disclosure, this is not the focus. It should be noted that a person of ordinary skill in the art can make several improvements and modifications without departing from the principle of the present disclosure, and such improvements and modifications should be deemed as falling within the protection scope of the present disclosure.

Claims

1. A protective coating with a bionic structure, comprising a wear-resistant rigid mesh belt formed primarily and an electrically conductive and thermally conductive soft channel formed secondarily, wherein the soft channel fills gaps in the rigid mesh belt, such that the rigid mesh belt and the soft channel achieve alternative distribution and the protective coating has a bionic animal bone structure and a bionic tortoise shell structure; and the rigid mesh belt, the soft channel, and a substrate are metallurgically bonded, and the soft channel formed secondarily exerts a stress removal and relaxation effect on the rigid mesh belt formed primarily.

2. The protective coating with a bionic structure according to claim 1, wherein the rigid mesh belt and the soft channel are formed by laser cladding.

3. The protective coating with a bionic structure according to claim 1, wherein the rigid mesh belt is prepared by an electrically conductive and thermally conductive metal powder and a ceramic powder, the soft channel is prepared by the electrically conductive and thermally conductive metal powder, and the rigid mesh belt comprises 70% to 90% of the electrically conductive and thermally conductive metal powder and 10% to 30% of the ceramic powder by mass percentage.

4. The protective coating with a bionic structure according to claim 3, wherein a composition of the electrically conductive and thermally conductive metal powder is consistent with a composition of the substrate to reduce a difference in a thermophysical properties between the protective coating and the substrate and then reduce a stress.

5. The protective coating with a bionic structure according to claim 4, wherein the electrically conductive and thermally conductive metal powder is a CuCrZr powder comprising 0.1% to 0.8% of a Cr powder, 0.3% to 0.6% of a Zr powder, and a Cu powder as a balance, and has a particle size of 40 pm to 120 pm.

6. The protective coating with a bionic structure according to claim 1, wherein a structure of the rigid mesh belt comprises but is not limited to a mesh structure in which a hexagon, a rhombus, and a rectangle are connected mutually.

7. The protective coating with a bionic structure according to claim 5, wherein the ceramic powder comprises but is not limited to one or more of TiN, TiC, TiB2, WC, B4C, and SiC nanopowders, and the ceramic powder is synthesized in situ or directly introduced and has a particle size of 50 nm to 200 nm.

8. A preparation method of the protective coating with a bionic structure according to claim 1, comprising the following steps:step 1, preparing powders:designing a coating composition according to actual demands of a metal workpiece to be treated, preparing a rigid mesh belt powder and a soft channel powder, and then drying for later use;step 2, conducting workpiece surface pretreatment:descaling a surface of a metal workpiece substrate for later use;step 3, programming a cladding motion trajectory as needed:programming a laser scanning motion trajectory according to a shape, a size, and a cladding area of the metal workpiece, setting synchronous powder feeding parameters, and setting motion trajectories of different types of bionic structures for the rigid mesh belt and the soft channel to allow cladding; andstep 4, conducting laser cladding:preparing the rigid mesh belt with a high hardness by the laser cladding, filling the electrically conductive and thermally conductive soft channel in the gaps of the rigid mesh belt to achieve alternative distribution, and then obtaining the protective coating on the surface of the metal workpiece by synchronous powder feeding.

9. The preparation method of the protective coating with a bionic structure according to claim 8, wherein the laser cladding comprises the following parameters: a laser power of 1 kW to 4 kW, a spot diameter of 2 mm to 4 mm, a cladding speed of 280 mm / min to 600 mm / min, and a powder feeding rate of 20 g / min to 50 g / min; and an overlap rate is 10% to 30% between the rigid mesh belt and the soft channel and between different cladding passes of the soft channel.

10. Use of the protective coating with a bionic structure according to claim 1 in a key component of marine equipment, aerospace, rail transportation, or chemical machinery.

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