Layered grain size high-entropy wear-resistant coating and preparation method

Abstract

This invention discloses a layered, high-entropy wear-resistant coating and its preparation method, relating to the fields of surface engineering and wear-resistant composite materials. The coating is formed on the surface of a metal substrate and sequentially comprises an interface support layer, an intermediate load-bearing layer, and a surface friction-reducing layer along the thickness direction. Each layer includes a CoCrFeNiAl high-entropy alloy matrix phase and a SiC reinforcing phase. Different layers are configured with one or two of fine-grained SiC, nano-SiC, and coarse-grained SiC, with at least some SiC particles having a metal activation coating layer on their surface. A partial remelting transition zone is formed between adjacent layers. This approach achieves a layered configuration and continuous transition of the reinforcing phase along the thickness direction, which is beneficial for balancing interfacial bonding, load-bearing support, and surface friction-reducing and wear-resistant properties.

Description

Technical Field

[0001] This invention relates to the field of surface engineering and wear-resistant composite materials, specifically to a layered particle size high-entropy wear-resistant coating and its preparation method, and more particularly to a technical solution for constructing a layered particle size SiC-reinforced CoCrFeNiAl high-entropy alloy composite coating on the surface of a metal substrate using laser cladding. Background Technology

[0002] In service scenarios such as metallurgical equipment, mining machinery, mold components, and conveying structures, the surfaces of these components are subjected to sliding friction, particle erosion, and alternating loads for extended periods, making them prone to accelerated wear, dimensional degradation, and premature failure. Surface strengthening technologies such as laser cladding are commonly used to construct wear-resistant coatings on metal substrates, improving the service life and stability of these components. In recent years, high-entropy alloys, due to their multi-principal element design characteristics and good microstructural stability, have been widely used as wear-resistant coating substrates, and their mechanical and wear-resistant properties are further improved by introducing ceramic particle reinforcing phases.

[0003] Existing published literature 1 (Study on Wear Resistance and Mechanism of Laser Cladding WC / CoCrFeNiTiSi2 High-Entropy Alloy Composite Coating, 2022) discloses a study on the preparation of ceramic particle-reinforced high-entropy alloy composite coatings on the substrate surface via laser cladding. The study analyzes the relationship between particle volume fraction, particle size, microstructure evolution, and wear resistance, indicating that the reinforcing particle parameters significantly affect the microstructure and properties of the high-entropy alloy composite coating. Meanwhile, related research also shows that the element diffusion behavior in high-entropy alloy systems is more complex than in pure metal systems; the relationship of diffusion potential energy changes can be found in [reference needed]. Figure 1 However, this type of research mainly focuses on the regulation of particle content, particle size, and overall microstructure and properties within a single coating system. It lacks targeted design for the distribution of the reinforcing phase in the coating thickness direction and its functional allocation, making it difficult to simultaneously meet the needs of interfacial microstructure regulation, coating load-bearing capacity, and surface friction reduction and wear resistance.

[0004] Existing publication 2 (Study on Tribological Properties of High-Entropy Alloy Gradient Coatings Laser Cladding on the Friction Pair Surface of a Piston Pump, 2023) discloses a method for constructing high-entropy alloy gradient coatings on a substrate surface through multi-layer, multi-pass laser cladding, and analyzes its microstructure and tribological properties. The results show that this type of gradient coating can form remelted bonding regions between layers and exhibits a certain performance gradient distribution. However, this literature mainly achieves the gradient structure through the combination of different high-entropy alloy layers, focusing on the control of compositional gradient or interlayer structure, and still lacks targeted design for the particle size distribution and functional allocation of the reinforcing phase in the coating thickness direction.

[0005] Therefore, existing technologies lack a high-entropy composite wear-resistant coating structure and its preparation method that can specifically allocate and control the reinforcing phase structure to meet the needs of different service areas in the coating thickness direction. Summary of the Invention

[0006] To overcome the aforementioned deficiencies of the prior art, this invention provides a layered high-entropy wear-resistant coating and its preparation method. Based on the differences in the microstructure and tribological behavior of CoCrFeNiAl cladding layers caused by SiC of different particle sizes, this invention configures fine-grained SiC, nano-SiC, and coarse-grained SiC in the interface support layer, intermediate bearing layer, and surface friction-reducing layer, respectively. Combined with the metal activation coating treatment on the surface of SiC particles and the control of the interlayer partial remelting transition zone, the distribution of the reinforcing phase, the interface bonding state, and the microstructure form a composite structure combining layered configuration and continuous transition along the coating thickness direction, thereby solving the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A layered high-entropy wear-resistant coating is disclosed, wherein the coating is formed on the surface of a metal substrate and sequentially comprises an interface support layer, an intermediate load-bearing layer, and a surface friction-reducing layer along the thickness direction; the interface support layer, the intermediate load-bearing layer, and the surface friction-reducing layer all comprise a CoCrFeNiAl high-entropy alloy matrix phase and a SiC reinforcing phase; the SiC reinforcing phase in the interface support layer is fine-grained SiC, or a composite of fine-grained SiC and nano-SiC particles; the SiC reinforcing phase in the intermediate load-bearing layer is a composite of fine-grained SiC and coarse-grained SiC particles; the SiC reinforcing phase in the surface friction-reducing layer is coarse-grained SiC, or a composite of coarse-grained SiC particles; at least a portion of the SiC particles have a metal activation coating layer on their surface; a partially remelted transition zone formed by layered laser cladding is provided between adjacent layers, wherein a continuous metallurgical bonding structure and a gradually changing particle size distribution structure are formed in the partially remelted transition zone.

[0009] As a further embodiment of the present invention, the metal matrix is ​​45 steel, alloy structural steel, mold steel or wear-resistant steel.

[0010] As a further aspect of the present invention, the average particle size of the nano-SiC is 50nm to 800nm, the D50 of the fine-grained SiC is 1μm to 20μm, and the D50 of the coarse-grained SiC is 30μm to 120μm.

[0011] As a further aspect of the present invention, the metal activation coating layer comprises one or at least two of Ni, Co, Cr, and Cu, and the thickness of the metal activation coating layer is 0.05 μm to 5 μm.

[0012] As a further embodiment of the present invention, the mass fraction of the SiC reinforcing phase in the interface support layer is 2% to 10%, the mass fraction of the SiC reinforcing phase in the intermediate bearing layer is 5% to 15%, and the mass fraction of the SiC reinforcing phase in the surface friction-reducing layer is 8% to 20%.

[0013] As a further aspect of the present invention, the remelting depth of the partially remelted transition zone is 5% to 40% of the thickness of the adjacent lower layer, and a continuous metallurgical bonding structure and a gradually changing grain size distribution structure are formed in the partially remelted transition zone.

[0014] This invention also provides a method for preparing the above-mentioned layered high-entropy wear-resistant coating, comprising the following steps: classifying SiC particles according to particle size to obtain at least two of nano-SiC, fine-grained SiC, and coarse-grained SiC; performing surface activation coating treatment on SiC particles of at least one particle size level to form a metal activation coating layer on the surface of the SiC particles; mixing SiC particles of different particle size configurations with CoCrFeNiAl high-entropy alloy powder respectively to obtain composite powder for interface support layer, composite powder for intermediate bearing layer, and composite powder for surface friction-reducing layer; performing degreasing, derusting, roughening, and preheating treatment on the surface of the metal substrate; sequentially depositing powder in the order of interface support layer, intermediate bearing layer, and surface friction-reducing layer using laser cladding, and controlling the formation of a partially remelted transition zone between adjacent layers; and performing controlled cooling after cladding to obtain the layered high-entropy wear-resistant coating.

[0015] As a further aspect of the present invention, the surface activation coating treatment employs chemical plating, electroplating, mechanical ball milling coating, or vapor deposition coating.

[0016] As a further aspect of the present invention, the composite powder is mixed by ball milling for 2 to 12 hours. A dispersion medium is added during the ball milling process, and the mixed composite powder is dried before use.

[0017] As a further embodiment of the present invention, the laser cladding parameters are: laser power of 800W to 2200W, scanning speed of 3mm / s to 20mm / s, powder feeding rate of 5g / min to 25g / min, overlap rate of 20% to 60%, and substrate preheating temperature of 100℃ to 400℃.

[0018] The technical effects and advantages of the layered particle size high-entropy wear-resistant coating and its preparation method of this invention are as follows:

[0019] This invention configures fine-grained SiC, nano-SiC, and coarse-grained SiC in layers as an interface support layer, an intermediate load-bearing layer, and a surface friction-reducing layer. Unlike the existing technology where a single-size reinforcing phase is uniformly distributed in a single-layer coating, this invention makes the division of labor of the reinforcing phase in the coating thickness direction clearer. This is beneficial for meeting the microstructure control requirements of the region near the substrate, the load-bearing strengthening requirements of the main coating region, and the friction-reducing and wear-resistant requirements of the surface region.

[0020] This invention, by performing metal activation coating on at least a portion of SiC particles and combining it with layered particle size configuration, differs from the prior art in that ceramic reinforcing phases are directly introduced without interface adaptation treatment. This approach is beneficial in improving the surface state and interface participation conditions of reinforcing particles during the cladding process, thereby enhancing the continuity of particle embedding and the stability of the formation of the in-layer reinforcing structure.

[0021] This invention sets up a partially remelted transition zone formed by layered laser cladding between the interface support layer, the intermediate bearing layer and the surface friction-reducing layer. Unlike the structural method of relatively abrupt interface between layers after ordinary multilayer stacking, this is beneficial to improve the metallurgical bonding continuity between adjacent layers, and makes the distribution of reinforcing phase and microstructure form a gradual transition along the coating thickness direction, thereby improving the overall coordination of the layered structure.

[0022] Based on the differences in microstructure and performance of single-particle-size SiC obtained from basic screening tests, this invention establishes a design approach that moves from the law of particle size interaction to the rules of layer configuration. Unlike the design approach that relies solely on empirical selection of reinforcing phases, this invention provides a clear basis for the particle size distribution of the interface support layer, intermediate load-bearing layer, and surface friction-reducing layer. This approach is beneficial for balancing the strengthening effect of the main body and the friction-reducing and wear-resistant properties of the surface layer in the same coating system. Attached Figure Description

[0023] Figure 1 This is a schematic diagram showing the relationship between atomic diffusion potential energy changes in different alloy systems in existing technologies.

[0024] Figure 2 This is a schematic diagram of the process flow for a layered particle size high-entropy wear-resistant coating and its preparation method according to the present invention.

[0025] Figure 3 Comparison of cross-sectional microstructures of coatings from different sample specimens in the basic screening test, among which, Figure 3 (a) is a cross-sectional microstructure of the high-entropy alloy control coating without SiC reinforcement phase. Figure 3 (b) is a cross-sectional microstructure of the comparative coating with added nano-SiC. Figure 3 (c) is a cross-sectional microstructure of the comparative coating with added fine-grained SiC. Figure 3 (d) is a cross-sectional micrograph of the comparative coating with added coarse SiC.

[0026] Figure 4 This is a comparison chart of the hardness, wear rate, and average friction coefficient of different samples in the basic screening test. Figure 4 (a) is a comparison chart of average hardness and wear rate of different samples. Figure 4 (b) is a comparison chart of the average friction coefficients of different parts.

[0027] Figure 5 This is a schematic diagram of the interfacial bonding and wear mechanism of the layered particle size high-entropy wear-resistant coating of the present invention.

[0028] Figure 1 In this context, Puremetal means pure metal; Fe-Cr-Ni means iron-chromium-nickel alloy; CoCrFeMn0.5Ni means cobalt-chromium-iron-manganese 0.5-nickel high-entropy alloy; PotentialEnergy means potential energy; ConfigurationalCoordinate means configurational coordinates; Eb means diffusion barrier; MD means migration distance; L means left-side stable position; M means right-side stable position.

[0029] Figure 3 In this context, "matrix" refers to the metal matrix, with a scale bar of 10 μm.

[0030] Figure 4 In the figure, M1 is a high-entropy alloy control coating without SiC reinforcing phase, M2 is a control coating with added nano-SiC, M3 is a control coating with added fine-grained SiC, and M4 is a control coating with added coarse-grained SiC. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1

[0033] This embodiment uses the wear-resistant strengthening of the working surface of a conveyor roller in a metallurgical production line as an application case, and describes in detail a layered high-entropy wear-resistant coating and its preparation method. Under this condition, the roller surface is in long-term contact with high-temperature steel strip, oxide scale, and fine hard particles. During operation, it simultaneously endures sliding friction, local extrusion, and cyclic thermal stress, making the surface prone to accelerated wear, localized spalling, and dimensional decay. To address this condition, this embodiment constructs a layered SiC-reinforced CoCrFeNiAl high-entropy alloy composite coating on the surface of a 45 steel substrate using laser cladding. This forms an interface support layer near the metal substrate, suitable for stable initial forming and refined interface structure; an intermediate load-bearing layer in the middle of the coating, suitable for bearing continuous loads; and a surface friction-reducing layer in the outermost contact area, suitable for withstanding reciprocating friction and particle wear. Through metal activation coating on the SiC particle surface and partial remelting transition control between layers, the three layers are continuously connected in the thickness direction, forming a composite wear-resistant layer with progressively changing particle size distribution, interface state, and microstructure.

[0034] The process route in this embodiment is as follows: Figure 2 As shown, the process includes, in sequence, raw material preparation, SiC particle size classification, SiC particle surface activation coating, basic screening test powder preparation, basic screening test cladding, basic screening test microstructure and property determination, three-layer composite powder preparation, metal matrix surface pretreatment, layered laser cladding, controlled cooling, and microstructure and property testing. Figure 2 The sequence of each process is clearly defined. First, three types of reinforcing phases are obtained through particle size classification. Then, basic screening tests are conducted to determine the microstructure participation characteristics and tribological wear performance of SiC with different particle sizes in the CoCrFeNiAl cladding layer. Subsequently, the fine-grained SiC and coarse-grained SiC used for formal preparation are subjected to surface activation coating treatment. Three sets of composite powders are prepared according to the interface support layer, intermediate bearing layer and surface friction-reducing layer, respectively. After the substrate is polished, cleaned and preheated, the three layers are clad in a bottom-up order. At the same time, the remelting depth of adjacent layers is controlled to form a transition zone with gradual change characteristics between layers.

[0035] The metal matrix used in this embodiment is 45 steel with dimensions of 100mm × 60mm × 10mm; the high-entropy alloy powder used is pre-alloyed CoCrFeNiAl powder with a particle size of 45μm to 90μm; the reinforcing phase used is SiC particles of three different particle size grades, wherein the average particle size of nano-SiC is 100nm, the D50 of fine-grained SiC is 8μm, and the D50 of coarse-grained SiC is 60μm. The three types of SiC particles are dried in a vacuum drying oven at 80℃ for 6 hours before use, and the CoCrFeNiAl powder is vacuum dried at 60℃ for 4 hours before use.

[0036] Before formally preparing the layered particle size coating, a basic screening test was conducted to determine the influence of different SiC particle sizes on the cross-sectional microstructure, hardness, and tribological properties of the cladding layer under the same high-entropy alloy system and the same amount of reinforcing phase. This result served as the basis for the subsequent three-layer structure design. In this embodiment, four groups of samples were set up for the basic screening test, denoted as M1, M2, M3, and M4. M1 was a high-entropy alloy control coating without SiC reinforcing phase; M2 was a control coating with added nano-SiC; M3 was a control coating with added fine-grained SiC; and M4 was a control coating with added coarse-grained SiC. The four groups of samples were identical in all process conditions except for the particle size of the reinforcing phase. In the composite powders of groups M2, M3, and M4, the mass fraction of CoCrFeNiAl powder was 90%, and the mass fraction of SiC was 10%. Group M1 directly used CoCrFeNiAl powder as the feed material.

[0037] In the basic screening test, powders M2, M3, and M4 were mixed and dispersed using a planetary ball mill. The mill jar was lined with zirconium oxide, the ball-to-powder ratio was set at 3:1, the rotation speed was set at 300 r / min, and the milling time was set at 2 h. Anhydrous ethanol was added as a dispersion medium during the milling process, and an intermittent method of continuous milling for 30 min followed by a 10 min stop was adopted to reduce the powder temperature rise and inhibit local agglomeration. After milling, the powder was dried under vacuum at 60℃ for 4 h, and then sieved through a 100-mesh sieve to obtain a powder material with relatively stable flowability. The 45 steel substrate used in the basic screening test was first polished with 200-mesh, 400-mesh, and 800-mesh sandpaper in sequence, then ultrasonically cleaned in acetone and anhydrous ethanol for 10 min in sequence, and then dried at 80℃ for 30 min. The dried substrate was preheated to 200℃ in a resistance furnace and held at that temperature for 15 min before being transferred to a laser cladding worktable. Laser cladding employs an off-axis powder feeding method, with high-purity argon as the protective gas. The process parameters are: laser power 1600W, scanning speed 500mm / min, powder feeding rate 18g / min, overlap rate 40%, and defocusing amount 0mm. After cladding, each group of samples is placed in insulating cotton for slow cooling to room temperature, and then sampled via wire EDM for cross-sectional microstructure observation, microhardness testing, and friction and wear testing.

[0038] The cross-sectional micromorphology obtained from the basic screening test is as follows: Figure 3 As shown, Figure 3 (a) is a cross-sectional microstructure of the high-entropy alloy control coating without SiC reinforcement phase. Figure 3 (b) is a cross-sectional microstructure of the comparative coating after the addition of nano-SiC. Figure 3 (c) is a cross-sectional microstructure of the comparative coating after the addition of fine-grained SiC. Figure 3 (d) is a cross-sectional microstructure of the comparative coating after the addition of coarse SiC.

[0039] Figure 3 The substrate region, interface region, and coating region are all visible in the image, with a scale bar of 10 μm. Figure 3 (a) As can be seen, without the addition of SiC reinforcing phase, a continuous metallurgical bonding layer is formed between the cladding layer and the substrate, and a relatively obvious dendritic structure is visible in the coating area. Figure 3 (b) As can be seen, the dendritic structure in the coating region is finer and the transition in the interface region is smoother after the addition of nano-SiC, indicating that the participation of the nanoscale reinforcing phase is beneficial to the refinement of the structure in the region near the substrate. Figure 3 (c) As can be seen, after adding fine-grained SiC, more obvious particle-rich regions and dendritic regions are visible in the coating area, indicating a higher degree of particle participation. This suggests that fine-grained SiC is more likely to form a reinforcing structure in the cladding layer. Figure 3 (d) It can be seen that after adding coarse SiC, the particle enrichment area is mainly distributed in the area near the upper part of the coating. The coating area is relatively continuous as a whole, and the interface area still maintains a continuous metallurgical bonding layer. Figure 3 The microstructure differences shown indicate that SiC of different particle sizes exhibits significant variations in the coating region, interface region, and particle distribution when incorporated into the same CoCrFeNiAl cladding system. Nano-sized SiC is more suitable for participating in the refinement process near the interface, fine-grained SiC is more suitable for participating in the formation of the central reinforcing structure, and coarse-grained SiC is more suitable for forming a particle support structure on the upper part of the coating. Based on these microstructure results, in the formal layered design, nano-sized and fine-grained SiC are introduced into the interface support layer, fine-grained and coarse-grained SiC are introduced into the intermediate load-bearing layer, and the coarse-grained SiC-dominated reinforcing phase is introduced into the surface friction-reducing layer.

[0040] Finish Figure 3 Following the corresponding tissue observations, this embodiment further conducted microhardness and tribological wear tests on four groups of samples, M1 to M4. The microhardness test used an HV1.0 load, with five measuring points selected along the cladding thickness direction for each group of samples, and the average value was taken as the average hardness. The tribological wear test employed a dry sliding reciprocating friction method, with a test load of 20 N, a reciprocating frequency of 5 Hz, and a test time of 30 min. The sample surface was polished before testing.

[0041] Test results compiled in Figure 4 Among them Figure 4 (a) is a comparison chart of average hardness and wear rate of different samples. Figure 4 (b) is a comparison chart of the average friction coefficients of different parts. Figure 4 (a) It can be seen that the average hardness of M1, M2, M3 and M4 are 487.89 HV1.0, 574.30 HV1.0, 639.70 HV1.0 and 597.15 HV1.0, respectively; Figure 4(b) It can be seen that the average friction coefficients of M1, M2, M3 and M4 are 0.399, 0.390, 0.358 and 0.307, respectively.

[0042] Combination Figure 4 As shown in the wear rate curves in (a), the wear rate decreases overall as the particle size of the reinforcing phase changes from no reinforcement to nano, fine, and coarse grains. The wear rates of samples with fine-grained SiC and coarse-grained SiC are significantly lower than those with M1. These results indicate that, under the same high-entropy alloy matrix system, the same total amount of reinforcing phase added, and the same cladding process, fine-grained SiC results in a more significant increase in hardness, while coarse-grained SiC results in a lower average friction coefficient and a smaller wear rate. Based on this performance data, in the formal layered particle size technology scheme, fine-grained SiC is configured in the interface support layer and the intermediate load-bearing layer to form a higher microstructure strengthening and main load-bearing capacity; coarse-grained SiC is configured in the intermediate load-bearing layer and the surface friction-reducing layer, especially in the surface friction-reducing layer where coarse-grained SiC is predominantly used to form a particle support structure more suitable for contact with the surface; nano-SiC is used as an auxiliary reinforcing phase in the interface support layer, working together with fine-grained SiC to participate in microstructure refinement near the matrix. Figure 4 The performance differences shown provide direct data for the subsequent three-layer composite powder ratio and layer arrangement. The relevant data are summarized in Table 1.

[0043] Table 1 Performance data of basic screening tests

[0044] Sample number Average hardness HV1.0 Average coefficient of friction wear rate / 10 -5 mm3•(N•m) -1 ]]> M1 487.89 0.399 2.04 M2 574.30 0.390 1.34 M3 639.70 0.358 0.31 M4 597.15 0.307 0.27

[0045] According to the data in Table 1, sample M3 has the highest average hardness, indicating that fine-grained SiC is more suitable for placement near the substrate and the main load-bearing area in this system; sample M4 has the lowest average friction coefficient and wear rate, indicating that coarse-grained SiC is more suitable for placement in the outermost contact area; sample M2 has significantly higher hardness than M1, indicating that nano-SiC is suitable for introduction into the interface support layer together with fine-grained SiC. Based on this set of specific data, this embodiment continues the formal preparation of the layered particle size high-entropy wear-resistant coating.

[0046] In the formal preparation, fine-grained SiC and coarse-grained SiC are first subjected to surface activation coating treatment to improve the surface stability and embedding continuity of SiC particles after entering the molten pool. In this embodiment, Ni electroless plating is used to surface coat fine-grained SiC and coarse-grained SiC. The specific operation is as follows: SiC particles are first immersed in dilute acid activation solution for 5 min, then washed with deionized water, and then placed in electroless plating solution and reacted at 85℃ for 40 min to form a continuous Ni activation layer on the particle surface. After coating, the particles are filtered, washed with water, cleaned with ethanol, and dried at 60℃ for 6 h. After coating, a Ni activation coating layer with a thickness of 0.2 μm to 0.8 μm is formed on the surface of fine-grained SiC and coarse-grained SiC. Due to the small particle size of nano-SiC, in this embodiment, a thick coating layer is not formed alone, but is introduced together with fine-grained SiC into the interface support layer to refine the microstructure of the layer close to the substrate.

[0047] Subsequently, a three-layer composite powder was prepared. The interface support layer uses a blend of fine-grained SiC and nano-SiC, with the specific ratio being: 92 parts by mass of CoCrFeNiAl powder, 6 parts by mass of fine-grained SiC, and 2 parts by mass of nano-SiC, with a total reinforcing phase of 8%. The intermediate load-bearing layer uses a blend of fine-grained SiC and coarse-grained SiC, with the specific ratio being: 88 parts by mass of CoCrFeNiAl powder, 6 parts by mass of fine-grained SiC, and 6 parts by mass of coarse-grained SiC, with a total reinforcing phase of 12%. The surface friction-reducing layer uses a reinforcing system dominated by coarse-grained SiC, with the specific ratio being: 84 parts by mass of CoCrFeNiAl powder, 16 parts by mass of coarse-grained SiC, with a total reinforcing phase of 16%. The core powder ratios of the three-layer formal technical solution are shown in Table 2.

[0048] Table 2. Formulation of three-layer composite powder for layered particle size coating.

[0049] Layer CoCrFeNiAl / wt% Nano SiC / wt% Fine-grained SiC / wt% coarse SiC / wt% Total amount of reinforcing phase / wt% Interface support layer 92 2 6 0 8 Intermediate bearing layer 88 0 6 6 12 Surface friction-reducing layer 84 0 0 16 16

[0050] The three-layer composite powders were mixed and dispersed using a planetary ball mill with a ball-to-powder ratio of 3:1, a milling speed of 250 r / min, and a milling time of 6 h. Anhydrous ethanol was used as the dispersion medium. To ensure the uniform distribution of nano-SiC and fine-particle SiC in the interface support layer, the interface support layer powder was milled intermittently, with a 10-minute pause after every 30 min of continuous milling. After milling, all three powders were dried under vacuum at 60℃ for 4 h and then sieved for later use.

[0051] Before layered cladding, the 45 steel substrate underwent repeated grinding, cleaning, and preheating treatments. First, it was polished sequentially with 200-grit, 400-grit, and 800-grit sandpaper, then ultrasonically cleaned with acetone and anhydrous ethanol for 10 minutes each. After drying, the substrate was preheated to 200℃. For the formal cladding, a laser cladding system was used to deposit three layers sequentially. The process parameters were set as follows: laser power 1500W, scanning speed 8mm / s, powder feed rate 12g / min, overlap rate 35%, and high-purity argon as the protective gas. First, the interface support layer composite powder was fed in to form the first cladding layer on the surface of the 45 steel substrate. Then, the intermediate load-bearing layer composite powder was fed in to form the second layer on the surface of the previous layer. Finally, the surface friction-reducing layer composite powder was fed in to form the top cladding layer. During the deposition of the second and third layers, the laser energy was controlled to remelt the upper part of the lower layer, ensuring that the interlayer remelting depth remained stable within the range of 15%–25% of the lower layer thickness, thus forming a partial remelting transition zone between adjacent layers. The three-layer cladding process record is shown in Table 3.

[0052] Table 3 Record of Layered Cladding Process Parameters

[0053] Layer Laser power / W Scan speed / mm-s -1 ]] Powder feed rate / g min -1 ]] Overlap rate / % Single-layer target thickness / mm lower layer remelting depth / % Interface support layer 1500 8 12 35 0.35 — Intermediate bearing layer 1500 8 12 35 0.40 15～25 Surface friction-reducing layer 1500 8 12 35 0.35 15～25

[0054] After all cladding was completed, the samples were placed in insulating cotton and slowly cooled to room temperature. Cross-sectional and performance test samples were then cut using wire cutting. The cross-sectional samples were progressively ground with 240, 400, 800, 1200, and 2000 grit sandpaper, followed by polishing. Actual observation showed that the resulting coating surface was continuous with complete overlap between layers. The cross-section revealed a identifiable interfacial support layer near the substrate, an intermediate bearing layer, and an upper surface friction-reducing layer. Fine-grained SiC and nano-SiC were evenly distributed in the interfacial support layer. Fine-grained and coarse-grained SiC together constituted the main reinforcement zone in the intermediate bearing layer. Coarse-grained SiC constituted the highest proportion in the surface friction-reducing layer. Transitional regions formed by remelting were visible between all layers.

[0055] In this embodiment, the obtained layered particle size coating was further subjected to microhardness and tribological wear tests. The test methods were consistent with the basic screening test, and the results are shown in Table 4.

[0056] Table 4 Comparison of performance between layered particle size coating and basic screening samples

[0057] Sample Average hardness HV1.0 Average coefficient of friction wear rate / 10 -5 mm3·(N·m) -1 ]]> M1 487.89 0.399 2.04 M2 574.30 0.390 1.34 M3 639.70 0.358 0.31 M4 597.15 0.307 0.27 Layered particle size coating 658.40 0.321 0.24

[0058] As shown in Table 4, the layered grain size coating achieves an average hardness of 658.40 HV1.0 while maintaining low friction and low wear rate. This data corresponds to the specific technical arrangement in this embodiment: firstly, using... Figure 3 and Figure 4The corresponding basic screening results determine the differences in microstructure and tribological behavior of SiC with different particle sizes. Based on this, nano-SiC and fine-grained SiC are configured in the interface support layer, fine-grained SiC and coarse-grained SiC are configured in the intermediate load-bearing layer, and coarse-grained SiC is configured in the surface friction-reducing layer. Combined with the metal activation coating on the SiC surface and the control of the interlayer partial remelting transition zone, the participation mode of different particle size reinforcing phases in different layers is made consistent and the interlayer transition is continuous. This process integrates the particle size difference law, particle surface state control, and interlayer transition control into a complete technical route, so that the three-layer structure forms an interconnected composite microstructure.

[0059] Interfacial bonding and wear mechanism of layered particle size high-entropy wear-resistant coatings, such as Figure 5 As shown. Figure 5 The image shows, from bottom to top, a metal substrate, an interface support layer, an intermediate load-bearing layer, and a surface friction-reducing layer. The interface support layer uses a fine-grained SiC and nano-SiC configuration, the intermediate load-bearing layer uses a composite configuration of fine-grained SiC and coarse-grained SiC, and the surface friction-reducing layer uses a configuration dominated by coarse-grained SiC. Figure 5 The middle arrows indicate the directions of interface refinement, synergistic reinforcement, and coarse-grained load-bearing action, respectively, illustrating the layered functions of the interface support layer, intermediate load-bearing layer, and surface friction-reducing layer in this embodiment. Combined with... Figure 3 The organizational differences shown and Figure 4 As can be seen from the performance differences shown, this embodiment achieves a correspondence between the layered structure and the particle interaction mode by configuring SiC particles of different sizes in different layers.

[0060] In summary, this embodiment first determined the differences in microstructure and properties of SiC with different particle sizes in the CoCrFeNiAl cladding system through basic screening experiments. Based on this, nano-SiC and fine-grained SiC were configured in the interface support layer, fine-grained SiC and coarse-grained SiC were configured in the intermediate bearing layer, and the reinforcing phase dominated by coarse-grained SiC was configured in the surface friction-reducing layer. Combined with SiC particle surface activation coating treatment and interlayer partial remelting transition control, the preparation of a layered particle size high-entropy wear-resistant coating was completed.

[0061] Example 2

[0062] Based on Example 1, this embodiment adjusts the configuration of the interface support layer reinforcement phase and the particle size distribution of the intermediate bearing layer and the surface friction-reducing layer to illustrate the implementation of different particle size distribution methods without changing the three-layer layered particle size technology route.

[0063] The metal substrate used in this embodiment is still 45 steel, with a substrate size of 100mm × 60mm × 10mm; the particle size of the CoCrFeNiAl pre-alloyed powder used is still 45μm~90μm; the D50 of the fine-grained SiC used is 8μm, and the D50 of the coarse-grained SiC is 60μm. Unlike Example 1, this embodiment does not add nano-SiC to the interface support layer, but only uses fine-grained SiC as the interface reinforcement phase; the mass ratio of fine-grained SiC to coarse-grained SiC in the intermediate bearing layer is adjusted to 4:6; and the mass fraction of coarse-grained SiC in the surface friction-reducing layer is adjusted to 18%.

[0064] Specifically, in the composite powder used for the interface support layer, CoCrFeNiAl powder accounts for 94 parts by mass, and fine-grained SiC accounts for 6 parts by mass; in the composite powder used for the intermediate bearing layer, CoCrFeNiAl powder accounts for 90 parts by mass, fine-grained SiC accounts for 4 parts by mass, and coarse-grained SiC accounts for 6 parts by mass; in the composite powder used for the surface friction-reducing layer, CoCrFeNiAl powder accounts for 82 parts by mass, and coarse-grained SiC accounts for 18 parts by mass. The fine-grained SiC and coarse-grained SiC are still formed into surface-activated coating layers using chemical Ni plating, and the coating treatment conditions are the same as in Example 1.

[0065] The three-layer composite powder was mixed and dispersed using a planetary ball mill at a ball-to-powder ratio of 3:1, a milling speed of 250 r / min, and a milling time of 6 h. Anhydrous ethanol was used as the dispersion medium. After milling, the powder was dried under vacuum at 60 °C for 4 h and then sieved for later use. The 45 steel matrix was polished, ultrasonically cleaned with acetone and anhydrous ethanol, and then preheated to 250 °C in a resistance furnace and held at that temperature for 15 min.

[0066] During laser cladding, the deposition sequence remains the same: interface support layer, intermediate bearing layer, and surface friction-reducing layer. The differences are: laser power is set to 1600W, scanning speed to 7mm / s, powder feed rate to 10g / min, and overlap rate to 35%. During the deposition of the second and third layers, remelting of the upper part of the lower layer is controlled, maintaining the interlayer remelting depth within 15%–25% of the lower layer thickness. After cladding, the sample is placed in insulating cotton for slow cooling to room temperature, and then cross-sectional and performance test samples are cut.

[0067] Cross-sectional observation revealed that the resulting coating still consists of an interface support layer, an intermediate load-bearing layer, and a surface friction-reducing layer. The three-layer structure has clear boundaries and continuous partial remelting transition zones between layers. The interface support layer is predominantly composed of fine-grained SiC. With an increased proportion of coarse-grained SiC in the intermediate load-bearing layer, the distribution of hard particles in the main region becomes more pronounced. The proportion of coarse-grained SiC in the surface friction-reducing layer further increases, making the particle support characteristics in the surface contact area more prominent. This embodiment demonstrates that, without altering the layered particle size technology, the interface layer can adopt a pure fine-grained SiC configuration, while the intermediate and surface layers can achieve different intralayer reinforcement structure configurations by adjusting the ratio of fine to coarse-grained SiC.

[0068] Further observation revealed that the interface support layer, intermediate bearing layer, and surface friction-reducing layer in the obtained coating remained continuously distributed, and a identifiable partial remelting transition zone was formed between adjacent layers. This indicates that even without introducing nano-SiC into the interface layer, the particle size configuration of the interface support layer dominated by fine-grained SiC, along with the intermediate and surface layers, can still constitute a complete layered particle structure.

[0069] Example 3

[0070] Based on Example 1, this embodiment adjusts the type of metal matrix, the SiC particle surface activation coating method, and the laser cladding process window to illustrate the implementation of the layered particle size technology route under different steel-based materials and different particle surface treatment conditions.

[0071] In this embodiment, the metal substrate is changed to mold steel, with substrate dimensions of 100mm × 60mm × 10mm; the CoCrFeNiAl pre-alloyed powder particle size remains 45μm–90μm; the average particle size of the nano-SiC used is 100nm, with a D50 of 8μm for fine-grained SiC and 60μm for coarse-grained SiC. Unlike Example 1, this embodiment uses mechanical ball milling to form a Co-activated coating layer on the coarse-grained SiC, while still using chemical Ni plating to form a surface activation layer on the fine-grained SiC, thus creating a differentiated surface treatment structure for SiC with different particle sizes.

[0072] Specifically, coarse-grained SiC and Co metal powder were added to a ball mill jar at a mass ratio of 95:5 and ball-to-material ratio of 3:1 at a rotation speed of 280 r / min for 4 hours, so that the Co metal powder adhered to the surface of the coarse-grained SiC to form a Co activated coating layer; the fine-grained SiC was treated with chemical Ni plating as described in Example 1. The composite powder ratios of the interface support layer, the intermediate bearing layer, and the surface friction-reducing layer were as follows: in the interface support layer, CoCrFeNiAl powder accounted for 92 parts by mass, fine-grained SiC accounted for 6 parts by mass, and nano-SiC accounted for 2 parts by mass; in the intermediate bearing layer, CoCrFeNiAl powder accounted for 88 parts by mass, fine-grained SiC accounted for 6 parts by mass, and coarse-grained SiC accounted for 6 parts by mass; in the surface friction-reducing layer, CoCrFeNiAl powder accounted for 80 parts by mass, and coarse-grained SiC accounted for 20 parts by mass.

[0073] The three-layer composite powder was ball-milled and mixed for 6 hours using anhydrous ethanol as the dispersion medium, and then dried for later use. The mold steel substrate was polished and ultrasonically cleaned, then preheated to 300℃ in a resistance furnace and held for 20 minutes. During laser cladding, the laser power was set to 1800W, the scanning speed to 6mm / s, the powder feed rate to 15g / min, and the overlap rate to 40%. The interface support layer, intermediate bearing layer, and surface friction-reducing layer were deposited sequentially, with the second and third layers controlling a remelting depth of 15%–30% over the lower layer to construct a continuous interlayer transition zone. After cladding, the layers were slowly cooled to room temperature.

[0074] Cross-sectional observation revealed that the resulting coating forms a three-layered, continuous composite structure on the mold steel surface. The interface support layer, intermediate load-bearing layer, and surface friction-reducing layer are all identifiable, and the transition zones between layers are clearly visible. This embodiment demonstrates that the layered particle size technology of the present invention is applicable to the surfaces of different steel-based materials, and that the surface activation coating of at least some SiC particles can be achieved using different metals and different processing methods.

[0075] The layers of the interface support layer, intermediate bearing layer and surface friction-reducing layer in the obtained coating can still be clearly identified. The Co-activated coating layer on the surface of coarse-grained SiC and the Ni-activated layer on the surface of fine-grained SiC jointly participate in the layered deposition process, indicating that the layered particle size technology route of the present invention can be implemented under different steel substrates and different surface activation treatment conditions.

[0076] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0077] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A layered, high-entropy, wear-resistant coating, characterized in that, The coating is formed on the surface of a metal substrate and sequentially includes an interface support layer, an intermediate load-bearing layer, and a surface friction-reducing layer along the thickness direction. Each of the interface support layer, intermediate load-bearing layer, and surface friction-reducing layer comprises a CoCrFeNiAl high-entropy alloy matrix phase and a SiC reinforcing phase. The SiC reinforcing phase in the interface support layer is fine-grained SiC, or a composite of fine-grained SiC and nano-SiC particles. The SiC reinforcing phase in the intermediate load-bearing layer is a composite of fine-grained SiC and coarse-grained SiC particles. The SiC reinforcing phase in the surface friction-reducing layer is coarse-grained SiC, or a composite of coarse-grained SiC particles. At least a portion of the SiC particles have a metal activation coating layer on their surface. A partially remelted transition zone formed by layered laser cladding is provided between adjacent layers, and a continuous metallurgical bonding structure and a gradually changing particle size distribution are formed within the partially remelted transition zone.

2. The layered particle size high-entropy wear-resistant coating according to claim 1, characterized in that, The metal matrix is ​​45 steel, alloy structural steel, mold steel, or wear-resistant steel.

3. The layered particle size high-entropy wear-resistant coating according to claim 1, characterized in that, The average particle size of the nano-SiC is 50nm to 800nm, the D50 of the fine-grained SiC is 1μm to 20μm, and the D50 of the coarse-grained SiC is 30μm to 120μm.

4. The layered particle size high-entropy wear-resistant coating according to claim 1, characterized in that, The metal activation coating layer contains one or at least two of Ni, Co, Cr, and Cu, and the thickness of the metal activation coating layer is 0.05 μm to 5 μm.

5. The layered particle size high-entropy wear-resistant coating according to claim 1, characterized in that, The SiC reinforcing phase in the interface support layer has a mass fraction of 2% to 10%, the SiC reinforcing phase in the intermediate bearing layer has a mass fraction of 5% to 15%, and the SiC reinforcing phase in the surface friction-reducing layer has a mass fraction of 8% to 20%.

6. The layered particle size high-entropy wear-resistant coating according to claim 1, characterized in that, The remelting depth of the partially remelted transition zone is 5% to 40% of the thickness of the adjacent lower layer, and a continuous metallurgical bonding structure and a gradually changing grain size distribution structure are formed in the partially remelted transition zone.

7. A method for preparing a layered particle size high-entropy wear-resistant coating as described in any one of claims 1 to 6, characterized in that, Includes the following steps: Step 1: Classify SiC particles according to particle size to obtain at least two of nano-SiC, fine-grained SiC, and coarse-grained SiC. Step 2: Perform surface activation coating treatment on SiC particles of at least one particle size to form a metal activation coating layer on the surface of the SiC particles; Step 3: SiC particles with different particle size configurations are mixed with CoCrFeNiAl high-entropy alloy powder to prepare composite powder for interface support layer, composite powder for intermediate load-bearing layer and composite powder for surface friction-reducing layer. Step four: Degreasing, rust removal, roughening, and preheating treatment of the metal substrate surface; Step 5: Using laser cladding, powder is deposited sequentially in the order of interface support layer, intermediate bearing layer and surface friction-reducing layer, and the formation of partial remelting transition zone between adjacent layers is controlled. Step six: After the cladding is completed, controlled cooling is performed to obtain a layered, high-entropy, wear-resistant coating with fine particle size.

8. The method for preparing a layered particle size high-entropy wear-resistant coating according to claim 7, characterized in that, The surface activation coating treatment in step two is performed by chemical plating, electroplating, mechanical ball milling coating, or vapor deposition coating.

9. The method for preparing a layered particle size high-entropy wear-resistant coating according to claim 7, characterized in that, The mixing in step three is carried out by ball milling for 2 to 12 hours. A dispersion medium is added during the ball milling process, and the mixed composite powder is dried before use.

10. The method for preparing a layered particle size high-entropy wear-resistant coating according to claim 7, characterized in that, The laser cladding parameters in step five meet the following requirements: laser power of 800W to 2200W, scanning speed of 3mm / s to 20mm / s, powder feeding rate of 5g / min to 25g / min, overlap rate of 20% to 60%, and substrate preheating temperature of 100℃ to 400℃.

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