CoCrNi-TiC composite coating and preparation method thereof

Abstract

The invention relates to a CoCrNi-TiC composite coating and a preparation method thereof, and belongs to the technical field of coatings. The preparation method comprises the following steps that S1, CoCrNi alloy powder and TiC particles are mixed, and composite powder is obtained; s2, the CoCrNi alloy powder and the composite powder are alternately prepared into a CoCrNi alloy layer and a CoCrNi-TiC composite layer on a metal substrate through a laser cladding technology, and a CoCrNi-TiC composite coating is obtained; wherein the CoCrNi alloy layers are directly prepared on the surface of the metal substrate, and the number of the CoCrNi alloy layers and the number of the CoCrNi-TiC composite layers are both 4-6. Through the combination of TiC and CoCrNi and the design of a thickness alternating structure, the optimization of the CoCrNi-TiC composite coating in the aspects of hardness, wear resistance, toughness, thermal shock resistance, fatigue resistance and the like is realized, and the performance of the CoCrNi-TiC composite coating under complex working conditions is further improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of coatings, and particularly relates to a CoCrNi-TiC composite coating and a preparation method thereof. Background Art

[0002] Existing surface strengthening technologies, such as heat treatment and spraying, although they can improve the hardness and wear resistance of materials, often cannot meet multiple requirements such as high wear resistance, corrosion resistance, and toughness at the same time. Laser cladding technology has become an effective surface treatment method because it can precisely control the composition and structure of the cladding layer. However, existing laser cladding technologies mostly focus on the enhancement of single materials and lack precise control over the composition gradient of composite materials. CoCrNi-TiC composite materials are widely used due to their excellent properties, but traditional preparation methods for metal matrix composite materials have certain problems in terms of composition uniformity and interfacial bonding strength:

[0003] One is the brittleness problem of the coating: In some cases, especially when the coating contains a high proportion of hard particles such as TiC, the laser-cladded coating will become more brittle due to thermal stress concentration or grain coarsening. This makes the coating more likely to crack or peel when subjected to loads such as impact and vibration, affecting its durability and reliability.

[0004] The second is the heat-affected zone problem: Although the heat-affected zone of laser cladding technology is smaller than that of other heat treatment methods, under high-power laser irradiation, the temperature in local areas is still relatively high. This thermal effect may cause deformation, hardness reduction of the substrate material, and even affect the microstructure of the substrate material. Especially for some heat-sensitive materials (such as aluminum alloys, titanium alloys, etc.), it will reduce the overall performance of the substrate.

[0005] The third is the unsatisfactory bonding between the coating and the substrate: Although laser cladding can achieve metallurgical bonding between the coating and the substrate, due to uneven composition ratios, too thin or too thick cladding layers, the bonding strength between the cladding layer and the substrate is poor, and delamination is likely to occur during use, affecting the service life of the material.

[0006] The fourth is the coating thickness and uniformity problem: Traditional laser cladding technology relies on the adjustment of laser parameters and scanning paths to control the coating thickness. It is often difficult to ensure the thickness uniformity of the entire coating. Especially on complex or large-area surfaces, the coating may be uneven, the bonding strength of the cladding layer is weak, the local thickness is inconsistent, and cracks or interlayer detachment are likely to occur, which will also affect the performance of the coating, such as wear resistance and corrosion resistance.

[0007] Fifthly, the paradox between strength and plasticity: In traditional CoCrNi-TiC composite coatings, a higher TiC content helps to improve hardness and wear resistance, but an excessive TiC content will lead to an increase in the brittleness of the material, thus affecting its impact resistance and toughness. This performance conflict makes it impossible for a single-component or fixed-ratio composite coating to meet multiple performance requirements in some application scenarios.

[0008] Sixthly, the surface properties are insufficient to meet the requirements of multiple working conditions: Most of the existing laser cladding technologies focus on the surface strengthening of single materials. Although they can improve surface hardness and wear resistance, they cannot optimize multiple properties such as wear resistance, corrosion resistance, and toughness of the material at the same time. Under extreme working conditions, although the surface of the material has high hardness, problems such as brittle fracture or insufficient impact resistance may occur.

[0009] Therefore, how to optimize the comprehensive performance of CoCrNi-TiC composite coatings through the laser cladding process is still a difficult problem to be solved urgently at present. Summary of the Invention

[0010] To solve the above technical problems, the present invention provides a CoCrNi-TiC composite coating and a preparation method thereof. Through the combination of TiC and CoCrNi and the design of a thin-thick alternating structure, the CoCrNi-TiC composite coating is optimized in terms of hardness, wear resistance, toughness, thermal shock resistance, and fatigue resistance, further improving the performance of the CoCrNi-TiC composite coating under complex working conditions.

[0011] The first object of the present invention is to provide a CoCrNi-TiC composite coating and a preparation method thereof, including the following steps:

[0012] S1. Mix CoCrNi alloy powder and TiC particles to obtain composite powder;

[0013] S2. Through laser cladding technology, alternately form CoCrNi alloy layers and CoCrNi-TiC composite layers of CoCrNi alloy powder and composite powder on a metal substrate to obtain the CoCrNi-TiC composite coating; wherein, the CoCrNi alloy layer directly prepared on the surface of the metal substrate is the CoCrNi alloy layer, and the number of layers of both the CoCrNi alloy layer and the CoCrNi-TiC composite layer is 4-6 layers.

[0014] In an embodiment of the present invention, in S1, the mass ratio of Co, Cr, and Ni in the CoCrNi alloy powder is (34-36):(32-34):(31-33).

[0015] In one embodiment of the present invention, in S1, the particle size of the CoCrNi alloy powder is 50 μm - 150 μm to ensure good cladding performance and adhesion; the particle size of the TiC particles is 28 μm - 50 μm, which serves as a reinforcing phase to enhance the wear resistance of the composite coating. TiC is a ceramic material with extremely high hardness. Its addition to the CoCrNi alloy matrix can significantly improve the hardness and wear resistance of the composite coating. As a hardening reinforcement phase, TiC particles can prevent wear particles from eroding the CoCrNi alloy matrix, thereby reducing wear. The reinforcing effect of TiC particles enables the CoCrNi alloy matrix to effectively resist wear in a wear environment. Additionally, by adjusting the mass fraction of TiC particles and the thickness of the CoCrNi-TiC composite layer, the wear resistance can be optimized without causing brittleness problems due to excessive hardness.

[0016] In one embodiment of the present invention, in S1, the mass proportion of TiC particles in the composite powder is 5% - 25%, ensuring that the material has both high toughness and crack resistance while maintaining sufficient hardness.

[0017] In one embodiment of the present invention, in S2, the process parameters of the laser cladding technology are as follows: the laser power is 2300 W - 3000 W, the scanning speed is 6 mm / s - 10 mm / s, the powder feeding rate is 2.5 r / min - 4.0 r / min, and the laser beam diameter is 1.8 mm - 2.2 mm. By adjusting process parameters such as laser power, scanning speed, and powder feeding rate, the thickness and composition distribution of each layer can be precisely controlled to ensure firm interlayer bonding.

[0018] In one embodiment of the present invention, in S2, the protective gas for the laser cladding technology is argon, and the gas flow rate is 9 L / min - 11 L / min.

[0019] In one embodiment of the present invention, in S2, the thickness of the CoCrNi alloy layer is 0.1 mm - 2 mm, and the thickness of the CoCrNi-TiC composite layer is 0.1 mm - 3 mm. The thickness of each layer of the CoCrNi alloy layer and the thickness of each layer of the CoCrNi-TiC composite layer are the same. The same thickness means that in the entire cladding layer, the distribution of CoCrNi and TiC is uniform. It can ensure that the distribution of hardness and wear resistance is relatively consistent on the entire surface.

[0020] In one embodiment of the present invention, in S2, the thickness of the CoCrNi-TiC composite layer is greater than that of the CoCrNi alloy layer. The thinner CoCrNi alloy layer has better ductility and toughness, and can absorb a part of the energy when subjected to external forces, preventing the material from brittle fracture due to excessive hardening; while the thicker CoCrNi-TiC composite layer can provide stronger hardness and wear resistance, thus extending the service life of the material. Through this structure design of alternating thin and thick layers, strong wear resistance can be achieved on the surface, while good crack resistance and toughness can be maintained in the substrate. It can better disperse the externally applied stress, avoid local stress concentration, and thus effectively improve the fatigue resistance and impact resistance. It can maintain stability for a long time under high loads, and at the same time avoid the brittleness problem caused by too high hardness alone.

[0021] In one embodiment of the present invention, in S2, by adjusting parameters such as the laser power and scanning speed of the laser during the laser cladding process, the thicknesses of different coatings are adjusted to form a structure with different layers, that is, a heterogeneous structure. Based on this design of the thin-thick heterogeneous structure, the surface area of the coating can have higher hardness to improve wear resistance, while the bottom layer has good toughness and crack resistance to enhance its impact resistance. By adjusting the thicknesses of the CoCrNi alloy layer and the CoCrNi-TiC composite layer, the hardness, toughness and wear resistance of the CoCrNi-TiC composite coating can be effectively optimized. When adopting the heterogeneous structure, it can not only reduce the thermal stress between the coating and the substrate, but also effectively improve the adhesion of the coating. It can also avoid the formation of coating peeling or cracks by precisely controlling the combination of the coating and the substrate, increasing the service life and reliability of the material.

[0022] In one embodiment of the present invention, in S2, the metal substrate is selected from H13 steel, H11 steel, H21 steel plate, H22 steel, H233 steel or H45 steel.

[0023] The second object of the present invention is to provide a CoCrNi-TiC composite coating prepared by the described preparation method.

[0024] The technical solution of the present invention has the following advantages compared with the prior art:

[0025] (1) The preparation method described in the present invention improves the hardness and wear resistance of the CoCrNi alloy matrix by adding TiC particles; through the alternating design of the CoCrNi alloy layer and the CoCrNi-TiC composite layer, the bonding force between the CoCrNi-TiC composite layer and the CoCrNi alloy layer is achieved, reducing delamination or crack propagation caused by thermal expansion differences and external stresses, thereby enhancing the hardness, wear resistance, toughness and stability of the CoCrNi-TiC composite coating in high-temperature and high-stress environments. By adjusting the TiC content and the thickness of the alternating layers, the performance of the CoCrNi-TiC composite coating in practical applications is improved.

[0026] (2) The preparation method described in the present invention realizes the uniform and stable distribution of TiC particles inside the CoCrNi-TiC composite layer by precisely controlling the process parameters of the laser cladding technology, the addition amount of TiC particles, and the particle sizes of the CoCrNi alloy powder and TiC particles, significantly enhancing the hardness, wear resistance, stability and reliability of the CoCrNi-TiC composite coating.

[0027] (3) The CoCrNi-TiC composite coating described in the present invention adopts an alternating structure design of the CoCrNi alloy layer and the CoCrNi-TiC composite layer. The CoCrNi-TiC composite layer provides higher hardness and wear resistance, and the CoCrNi alloy layer provides good toughness and impact resistance. The two cooperate to improve the wear resistance, heat resistance and fatigue resistance of the CoCrNi-TiC composite coating. In addition, the alternating layered structure design of the CoCrNi alloy layer and the CoCrNi-TiC composite layer can effectively disperse thermal stress and mechanical stress, thereby reducing the propagation of thermal cracks and fatigue cracks. Moreover, materials of different layers can provide different thermal expansion adaptabilities when heated, enhancing the thermal shock resistance of the material and at the same time improving its fatigue resistance under repeated loads. The thickness and number of layers of the CoCrNi alloy layer and the CoCrNi-TiC composite layer can be adjusted according to actual application requirements, especially in important mechanical components such as aeroengines, automotive engine components, and turbine blades in high-temperature, high-pressure, wear and corrosion environments. Brief Description of the Drawings

[0028] In order to make the content of the present invention easier to be clearly understood, the following further details the present invention according to specific embodiments of the present invention in conjunction with the drawings, wherein:

[0029] Figure 1 SEM images of the CoCrNi alloy powder (a), TiC particles (b) and composite powder (c) in Example 1 of the present invention;

[0030] Figure 2Schematic diagram of the CoCrNi-TiC composite coating in Embodiment 2 of the present invention;

[0031] Figure 3 Microhardness test results of the CoCrNi-TiC composite coating prepared in the example in Test Example 1 of the present invention;

[0032] Figure 4 Microhardness test results of the CoCrNi-TiC composite coating prepared in the comparative example in Test Example 1 of the present invention. Detailed implementation manners

[0033] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and be able to implement it. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. It should be understood that the specific embodiments are only used to explain the present invention, but the exemplified embodiments do not limit the present invention.

[0034] In the present invention, unless otherwise specified, the technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the technical field to which the present invention belongs.

[0035] In the present invention, unless otherwise specified, the term "and / or" includes any and all combinations of one or more of the related listed items.

[0036] In the present invention, unless otherwise specified, the experimental methods used in the embodiments of the present invention are all conventional methods without special instructions, and the materials, reagents, etc. used can be obtained from commercial channels without special instructions.

[0037] In the present invention, unless otherwise specified, the equipment used for laser cladding in the embodiments of the present invention includes: the laser cladding system includes a high-power laser, a powder feeding system, a control system, and a moving platform. The laser generates a high-intensity laser beam, which is focused onto the surface of the substrate through a focusing mirror to form a high-temperature local molten pool. The powder feeding system feeds CoCrNi alloy powder and composite powder into the molten pool through nozzles respectively. The powder melts under the action of the heat of the laser and combines with the surface of the substrate. As the laser scans, the molten pool continuously expands, gradually cools and solidifies to form a uniform cladding layer. In order to achieve the structure of alternating superposition of CoCrNi-TiC composite layers and CoCrNi alloy layers with different thicknesses, during the process of laser cladding, parameters such as the scanning speed and the powder feeding rate are adjusted to precisely control the thickness, composition, and structure of the cladding layer. By adjusting the distribution of the powder and the cooling rate of the molten pool, CoCrNi alloy powder and composite powder can be alternately formed into a multi-layer structure. In addition, due to the high energy density of laser cladding, the temperature of the molten pool is very high, and TiC particles are quickly melted and evenly distributed in the CoCrNi alloy matrix.

[0038] In the present invention, unless otherwise specified, the mass ratio of Co, Cr, and Ni in the CoCrNi alloy powder used in the embodiments of the present invention is 35:33:32.

[0039] In the present invention, unless otherwise specified, the purity of the TiC particles used in the embodiments of the present invention is 99%.

[0040] Example 1

[0041] The CoCrNi-TiC composite coating of the present invention and its preparation method specifically include the following steps:

[0042] S1. Preparation of the substrate: Use an H13 steel plate as the substrate. In order to enhance the interfacial bonding strength between the cladding layer and the substrate surface, the substrate surface is polished with 600-mesh sandpaper to ensure a certain roughness on the substrate surface. After polishing, the polished substrate surface is cleaned with anhydrous ethanol to ensure that there is no oxide layer or impurity on the substrate surface, and to avoid peeling of the coating after cladding due to poor interfacial bonding; Use a hair dryer to air-dry the polished surface to ensure that the substrate surface is dry;

[0043] S2. Preparation of the composite powder: Mix CoCrNi alloy powder with a particle size of 50 μm - 150 μm and TiC particles with a particle size of 28 μm - 50 μm, and then use a planetary ball mill for sufficient ball milling. The ball-to-powder ratio is 2:1, and the ball milling time is 4 h to obtain a composite powder with a TiC mass fraction of 5% ( Figure 1 );

[0044] S3. By means of laser cladding technology, CoCrNi alloy powder and composite powder are alternately made on a metal substrate to form a CoCrNi alloy layer with a thickness of 0.2 mm and a CoCrNi-TiC composite layer with a thickness of 0.4 mm, obtaining a CoCrNi-TiC composite coating; among them, the CoCrNi alloy layer is directly prepared on the substrate surface, and the number of layers of both the CoCrNi alloy layer and the CoCrNi-TiC composite layer is 5 layers;

[0045] The process parameters of the CoCrNi alloy layer are as follows: the laser power is 2400 ± 10 W, the scanning speed is 10 mm / s, the powder feeding rate is 2.5 r / min, and the laser beam diameter is 2 mm; the protective gas is argon, and the gas flow rate is 10 L / min;

[0046] The process parameters of the CoCrNi-TiC composite layer are as follows: the laser power is 2400 ± 10 W, the scanning speed is 10 mm / s, the powder feeding rate is 4.0 r / min, and the laser beam diameter is 2 mm; the protective gas is argon, and the gas flow rate is 10 L / min.

[0047] Example 2

[0048] Basically the same as Example 1, the difference is that the TiC content is replaced by 10% ( Figure 2 ), and the laser power is 2500 ± 10 W.

[0049] Example 3

[0050] Basically the same as Example 1, the difference is that the TiC content is replaced by 20%, and the laser power is 2700 ± 10 W.

[0051] Comparative Example 1

[0052] Basically the same as Example 1, the difference is that the TiC content is replaced by 30%, and the laser power is 2900 ± 10 W.

[0053] Comparative Example 2

[0054] Basically the same as Example 1, the difference is that the TiC content is replaced by 40%, and the laser power is 3100 ± 10 W.

[0055] Comparative Example 3

[0056] Basically the same as Example 1, the difference is that the TiC content is replaced by 0.

[0057] Test Example 1

[0058] The CoCrNi-TiC composite coatings of Examples 1-3 and Comparative Examples 1-2 were subjected to hardness testing. The surface of the CoCrNi-TiC composite coating was polished using diamond sandpaper to ensure the flatness of the test surface and the absence of significant defects. The samples were placed on a Vickers hardness tester for testing. The hardness of each layer was measured using a Vickers hardness tester (load 100 g), and the holding time was 10 s. The hardness of each layer was detected separately. To ensure the feasibility of the experimental data, 12 points were taken for the hardness of each layer, and the average value of the hardness was used as the final hardness data for that layer. Then, with the layer number as the abscissa and the hardness as the ordinate, a hardness curve was plotted. The results are as Figures 3 - 4 shown. As can be seen from Figures 3 - 4 it, when the TiC content in the CoCrNi-TiC composite layer increases, the microhardness of the CoCrNi-TiC composite layer increases significantly, which is directly related to the high hardness and wear-resistant characteristics of TiC ceramic particles. Through the alternating design of the CoCrNi alloy layer and the CoCrNi-TiC composite layer, a periodic change distribution of hardness can be formed in the CoCrNi-TiC composite coating structure, which can not only effectively improve the wear resistance of the material surface, but also slow down the thermal stress concentration inside the coating and between the coating and the substrate, and avoid the generation and propagation of cracks.

[0059] Test Example 2

[0060] The CoCrNi-TiC composite coatings of Examples 1-3 and Comparative Examples 1-3 were subjected to wear resistance testing. A ball-on-disk wear test was used, with the load set at 30 N, the rotation speed at 200 rpm, and the time at 0.5 h. The specific test results are shown in Table 1:

[0061] Table 1

[0062] Specimen Average friction coefficient <![CDATA[Wear rate mm 3 / (N*m)]]> Example 1 0.545 <![CDATA[1.92×10 -4 > Example 2 0.5804 <![CDATA[1.8×10 -4 > Example 3 0.5596 <![CDATA[7.5×10 -5 > Comparative Example 1 0.23 <![CDATA[3.24×10 -5 > Comparative Example 2 0.2137 <![CDATA[1.73×10 -6 > Comparative Example 3 0.5090 <![CDATA[2.05×10 -4 >

[0063] As can be seen from Table 1, with the increase of the TiC content, the average friction coefficient first increases and then decreases. That is, in the low content stage (0%-10%), the friction coefficient shows a certain increase, while when the TiC content is further increased (20% and above), the friction coefficient instead decreases to a lower level. The wear rate decreases significantly with the increase of the TiC content, indicating that the wear resistance of the CoCrNi-TiC composite coating is continuously improved.

[0064] Analyze the variation trend of the friction coefficient: The average friction coefficient of the pure CoCrNi alloy (without TiC) is about 0.5090. When a small amount of TiC reinforcing particles (5%) are added, the friction coefficient slightly increases (about up to 0.545). As the TiC content continues to increase to 10%, the friction coefficient reaches the peak. In the experimental data, the average friction coefficient of the composite material containing about 10% TiC is the highest, up to 0.5804. However, when the TiC content is further increased to a higher level (above 20%), the friction coefficient starts to decrease instead. When the TiC content reaches 40%, the friction coefficient drops to about 0.2137, even much lower than the friction coefficient without adding TiC. This non-monotonic change of "first increasing and then decreasing" indicates that the content of TiC reinforcing particles has a complex effect on tribological behavior: the frictional resistance increases at medium content and decreases at high content.

[0065] Analyze the variation trend of the wear rate: Different from the friction coefficient, the wear rate shows a monotonic decreasing trend with the increase of TiC content. The volumetric wear rate of the pure CoCrNi alloy is the highest, about 2.05×10 -4 , showing relatively low wear resistance of the matrix alloy. After adding TiC, the wear rate decreases significantly: for example, when containing 5% TiC, the wear rate drops to about 1.92×10 -4 , and when containing 10% TiC, the wear rate is about 1.8×10 -4 . Thereafter, as the TiC content increases from 20% to 40%, the wear rate further decreases slightly, tending to about 10 -6 order of magnitude. Finally, the wear rate of the 40% TiC composite material has an order-of-magnitude reduction compared with the non-reinforced alloy, and the wear resistance is greatly improved. It shows that ceramic particles can significantly improve the wear resistance of the CoCrNi-TiC composite coating. In addition, when the TiC content is further increased from 30% to 40%, the decreasing amplitude of the wear rate becomes smaller, indicating that when the reinforcing particles form a relatively continuous strengthening phase, the improvement of wear resistance tends to be saturated.

[0066] Formation of TiC particle reinforcement network and its effect on friction: With the increase of TiC content, a reinforcement "network" composed of TiC hard phase is gradually formed inside the CoCrNi-TiC composite coating. At low content, TiC particles are sparsely distributed in the matrix and far away from each other, and the support and reinforcement effect on the matrix is ​​limited. At this time, the material is still mainly loaded by the soft CoCrNi matrix, and large plastic deformation and adhesion are prone to occur during friction contact, causing a certain degree of adhesive wear and surface material transfer, and the friction coefficient is relatively low (because the soft matrix is ​​easily flattened and forms smooth contact during friction). When the TiC content increases to a medium level, the distance between particles is shortened, and some TiC particles begin to form connections or aggregations in the matrix, providing a significant second phase reinforcement effect. The hardness and strength of the CoCrNi matrix increase with the increase of TiC content (indicating that the hard ceramic phase significantly improves the load-bearing capacity and deformation resistance). However, at this stage, TiC has not yet formed a completely continuous network, the interface area between the matrix and the particles increases, and local stress concentration may occur at the interface. If the TiC particles are unevenly distributed or poorly bonded to the matrix, these particles may loosen or fall off during the friction process, causing abrasive particles to be mixed in the friction interface, increasing the friction resistance. In the "semi-strengthening" state, the surface of the material may show uneven hardness and softness: the hard TiC protrudes to bear part of the load, and the surrounding softer matrix is ​​constrained and deformed, which easily causes fluctuations in microscopic contact during friction, and the friction coefficient increases at this stage. When the TiC content is further increased to a high level (such as 30%-40%), the TiC particles form a relatively continuous skeleton or network structure in the material. The matrix metal is divided and surrounded by the hard phase, and the composite material presents a "dual-phase" (FCC matrix + TiC ceramic) structure. This continuous TiC network greatly enhances the overall hardness and rigidity of the material, making it difficult for the surface to produce large plastic deformation or furrows under friction loads. The hard network can hinder the cutting of abrasive particles and reduce the actual contact area, thereby significantly reducing the contribution of the plastic plowing component to the friction resistance. At the same time, the presence of the TiC phase reduces the area of ​​direct contact between the metal matrices and weakens the effect of adhesive wear. Therefore, at high TiC content, the material exhibits a low stable friction coefficient and excellent wear resistance. The strengthening network formed by 40% TiC content is expected to maintain the friction coefficient at a low level (about 0.21), and wear occurs at a very low rate. In addition, if the TiC content is too high, resulting in increased particle aggregation or interface defects, the brittleness of the CoCrNi-TiC composite coating increases. When the TiC content is high, the distance between the particles is very close, and clusters and microcracks are easily formed during sintering or solidification. Therefore, for the CoCrNi-TiC composite coating, although 40% TiC provides a strong strengthening network and wear resistance, it is necessary to ensure uniform distribution and good interface in the process to avoid local spalling caused by embrittlement, which has an adverse effect on friction performance.

[0067] In summary, the strengthening network formed by TiC particles significantly improves the load-bearing capacity and hardness of the material, reduces the wear rate, and reduces the friction coefficient at high contents by reducing the soft matrix contact and plastic plowing effects. During this process, the friction mechanism of the material gradually changes from mainly adhesion / plastic deformation at low contents to mainly mild abrasive wear dominated by hard phases at high contents, thus showing a trend of first deterioration and then improvement in tribological properties.

[0068] Obviously, the above embodiments are merely examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A method for preparing a CoCrNi-TiC composite coating, characterized in that: The following steps are involved: S1, mixing CoCrNi alloy powder and TiC particles to obtain composite powder; S2. By laser cladding technology, CoCrNi alloy powder and composite powder are alternately prepared into CoCrNi alloy layers and CoCrNi-TiC composite layers on a metal substrate to obtain the CoCrNi-TiC composite coating; wherein the CoCrNi alloy layer is directly prepared on the surface of the metal substrate, and the number of layers of the CoCrNi alloy layer and the CoCrNi-TiC composite layer are both 4-6 layers.

2. The method for preparing the CoCrNi-TiC composite coating according to claim 1, characterized in that: In S1, the mass ratio of Co, Cr and Ni in the CoCrNi alloy powder is (34-36):(32-34):(31-33).

3. The method for preparing the CoCrNi-TiC composite coating according to claim 1, characterized in that: In S1, the particle size of the CoCrNi alloy powder is 50 μm-150 μm; the particle size of the TiC particles is 28 μm-50 μm.

4. The method for preparing the CoCrNi-TiC composite coating according to claim 1, characterized in that: In S1, the mass proportion of TiC particles in the composite powder is 5%-25%.

5. The method for preparing the CoCrNi-TiC composite coating according to claim 1, characterized in that: In S2, the process parameters of the laser cladding technology are: laser power is 2300W-3000W, scanning speed is 6mm / s-10mm / s, powder feeding rate is 2.5r / min-4.0r / min, and laser beam diameter is 1.8mm-2.2mm.

6. The method for preparing the CoCrNi-TiC composite coating according to claim 1, characterized in that: In S2, the protective gas of the laser cladding technology is argon gas, and the gas flow rate is 9L / min-11L / min.

7. The method for preparing the CoCrNi-TiC composite coating according to claim 1, characterized in that: In S2, the thickness of the CoCrNi alloy layer is 0.1 mm-2 mm, and the thickness of the CoCrNi-TiC composite layer is 0.1 mm-3 mm.

8. The method for preparing the CoCrNi-TiC composite coating according to claim 7, characterized in that: In S2, the thickness of the CoCrNi-TiC composite layer is greater than the thickness of the CoCrNi alloy layer.

9. The method for preparing the CoCrNi-TiC composite coating according to claim 1, characterized in that: In S2, the metal substrate is selected from H13 steel, H11 steel, H21 steel plate, H22 steel, H233 steel or H45 steel.

10. A CoCrNi-TiC composite coating prepared by the preparation method according to any one of claims 1 to 9.

Images