Method for preparing high wear-resistant and high-conductive copper-based composite material by selective laser melting and application thereof

Abstract

The application is suitable for the field of metal additive manufacturing, and provides a method for preparing high-wear-resistance high-conductivity copper-based composite material by selective laser melting and application, which comprises the following steps: providing copper powder and high-vanadium wear-resistant steel powder, and weighing the copper powder and the high-vanadium wear-resistant steel powder according to a predetermined proportion; pretreating the weighed powder, wherein the pretreatment comprises: uniformly mixing the copper powder and the high-vanadium wear-resistant steel powder in a three-dimensional motion mixer by using a step-by-step incremental mixing method, and then placing the mixed powder in a vacuum drying box for drying treatment; printing the pretreated mixed powder into a shape by using a selective laser melting process to obtain a printed copper-based composite material, and then performing stress relief annealing treatment, so that the high-wear-resistance high-conductivity copper-based composite material is obtained. The application utilizes the ultrafast cooling characteristics of SLM to inhibit macrosegregation, forms a uniform and fine dual-phase heterogeneous structure, and enables the composite material to have excellent conductivity and high strength.

Description

Technical Field

[0001] This invention relates to the field of metal additive manufacturing, specifically a method and application for preparing high wear-resistant and high conductivity copper-based composite materials by selective laser melting. Background Technology

[0002] Copper and copper alloys, with their excellent electrical and thermal conductivity and good corrosion resistance, are widely used in current-carrying friction components in electronics, rail transportation, aerospace, and other fields. These applications typically require materials to possess both high conductivity (to reduce transmission losses) and high wear resistance (to extend service life) under harsh conditions of high loads, high sliding speeds, and strong current carrying capacity. However, pure copper and ordinary copper alloys have relatively low strength and hardness, and insufficient wear resistance, making it difficult to meet the aforementioned requirements for long-term stable service.

[0003] To improve the overall performance of copper-based materials, existing technologies often employ the addition of reinforcing phases (such as ceramic particles, carbides, or intermetallic compounds) to prepare copper-based composites. However, existing reinforcement systems have the following shortcomings: First, ceramic reinforcing phases exhibit poor wettability with the copper matrix, resulting in weak interfacial bonding and a tendency to introduce pores or cracks, severely deteriorating the electrical conductivity. Second, some reinforcing phases are prone to agglomeration or decomposition during high-temperature preparation, leading to uneven microstructure. Third, while conventional metal particle reinforcements offer good interfacial compatibility, their improvement in wear resistance is limited and often comes at the cost of reduced conductivity. In particular, when iron (Fe) is used as a reinforcing element, the Cu-Fe binary alloy system is immiscible in the liquid state, and the two components have different densities. During traditional casting solidification, severe macroscopic segregation and liquid-liquid phase separation easily occur, forming coarse and unevenly distributed iron-rich phases that severely impair the material's plasticity and mechanical properties.

[0004] In recent years, Selective Laser Melting (SLM) technology has provided a new approach for preparing high-performance copper-based composite materials due to its advantages such as near-net-shape forming, high design freedom, and ultrafast cooling rate. The ultrafast cooling rate and extremely small molten pool characteristics of SLM can suppress macroscopic segregation and retain the metastable liquid-phase separation characteristics of Cu-Fe alloys, forming uniform and fine iron-rich droplets and obtaining a unique two-phase heterostructure. However, copper-based materials have extremely high reflectivity (typically >95%) to near-infrared lasers (e.g., 1064 nm wavelength) widely used in industrial SLM equipment, resulting in low energy absorption, poor molten pool stability, and an extremely narrow forming window, making it difficult to directly prepare high-density, low-defect copper-based composite materials via SLM. Existing reports indicate that reinforcements (such as carbides and oxides) used to improve copper laser absorption can improve formability to some extent, but often result in a significant decrease in the conductivity of the composite material due to excessively high or unevenly distributed interfacial resistance between the reinforcing phase and the copper matrix, failing to meet the requirements of high current-carrying conditions. Therefore, in view of the above situation, there is an urgent need to provide a method and application for preparing high wear-resistant and high conductivity copper-based composite materials by selective laser melting, so as to overcome the shortcomings in current practical applications. Summary of the Invention

[0005] The purpose of this invention is to provide a method and application for preparing high wear-resistant and high conductivity copper-based composite materials by selective laser melting, aiming to solve the problems in the background art.

[0006] This invention is achieved through a method for preparing highly wear-resistant and highly conductive copper-based composite materials by selective laser melting, comprising the following steps:

[0007] S1: Provide copper powder and high vanadium wear-resistant steel powder, and weigh the copper powder and high vanadium wear-resistant steel powder in a predetermined ratio;

[0008] S2: The well-balanced powder is pretreated, which includes: mixing copper powder and high-vanadium wear-resistant steel powder evenly in a three-dimensional motion mixer using a stepwise incremental mixing method, and then placing it in a vacuum drying oven for drying.

[0009] S3: The pretreated mixed powder is printed into a printed copper-based composite material by selective laser melting process, and then stress-relief annealing is performed to obtain the high wear-resistant and high conductivity copper-based composite material.

[0010] As a further aspect of the present invention: in S1, the mass ratio of copper powder to high vanadium wear-resistant steel powder is 9:1;

[0011] The particle size of both the copper powder and the high-vanadium wear-resistant steel powder is 15-90 micrometers, and the mixed powder of copper powder and high-vanadium wear-resistant steel powder adopts a multi-modal gradation, wherein the fine powder has a particle size of 15-35 micrometers, the medium powder has a particle size of 35-65 micrometers, and the coarse powder has a particle size of 65-90 micrometers, and the mass fractions of the fine powder, medium powder, and coarse powder are 55-70%, 25-35%, and 10-25%, respectively.

[0012] As a further aspect of the present invention: in S1, the composition of the high-vanadium wear-resistant steel powder, by mass percentage, is: C 1.5-2.8%, Si 0.5-1.5%, Cr 4.0-6.5%, V 5.0-9.0%, with the balance being Fe and unavoidable impurities; the high-vanadium wear-resistant steel powder is prepared using an air atomization powder preparation process;

[0013] The copper powder is pure copper powder, and phosphorus is added as a deoxidizer during the preparation process.

[0014] As a further aspect of the present invention: in S2, the step-by-step incremental mixing method specifically refers to:

[0015] First, take all of the high-vanadium wear-resistant steel powder and an equal mass of copper powder and mix them evenly in a three-dimensional motion mixer. Then, add the remaining copper powder in batches, with the mass of copper powder added each time being equal to the total mass of the current mixture. Mix step by step until all copper powder has been added.

[0016] Mixing is carried out under argon protection at a speed of 20-60 rpm, with a single mixing time of 45-90 minutes.

[0017] The drying process is carried out in a vacuum drying oven at a temperature of 100-220℃ for 2-6 hours, with a vacuum degree ≤133 Pa.

[0018] As a further aspect of the present invention: in S3, the selected area laser melting process uses a near-infrared laser with a wavelength of 1064 nm as the forming light source.

[0019] As a further aspect of the present invention: in S3, the processing parameters of the selected area laser melting process are as follows:

[0020] Laser power 140-225 W, scanning speed 200-500 mm / s, scanning spacing 0.03-0.06 mm, powder layer thickness 0.02-0.04 mm, strip scanning strategy, interlayer rotation angle 45°-67°, oxygen content in the printing chamber <500 ppm during printing, protective gas flow rate 2.1-2.4 m / s, powder compensation factor 200%-320%.

[0021] As a further aspect of the present invention: the powder spreading compensation factor is the ratio of the volume of powder supplied in a single powder spreading operation to the volume formed by a single descent of the processing platform.

[0022] As a further aspect of the present invention: in S3, the stress-relief annealing treatment is carried out under an argon atmosphere, the annealing temperature is 350-550℃, and the holding time is 1-3 hours.

[0023] The present invention also provides a high wear-resistant and high conductivity copper-based composite material, which is prepared by the method described above, and the high wear-resistant and high conductivity copper-based composite material is used for components under current-carrying friction conditions.

[0024] As a further aspect of the present invention: the microstructure of the high wear-resistant and high conductivity copper-based composite material comprises an iron-rich phase uniformly distributed in the copper matrix, as well as VC carbides and (Cr,Fe). 23 C6 carbides, of which VC carbides are dominant;

[0025] The high wear-resistant and high conductivity copper-based composite material has an electrical conductivity of 55.6% IACS and a microhardness of 140.7 HV. 0.2 It has a density of over 99.63%, a yield strength of 295 MPa, and a tensile strength of 439 MPa;

[0026] Under the conditions of a normal load of 15 N, a loading current of 30 A, a sliding speed of 0.05 m / s, and a grinding time of 30 min, the volumetric wear rate was 1.65 × 10⁻⁶. -4 mm 3 / (N·m).

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] This invention innovatively introduces high-vanadium wear-resistant steel particles (HVWRS) as a reinforcing phase in a high-wear-resistant and high-conductivity copper-based composite material. Unlike conventional wear-resistant steel or ceramic reinforcing phases, HVWRS particles pre-contain VC and (Cr,Fe). 23 Hard phases such as C6 can play a multi-scale strengthening and wear-resistant enhancement role in composite materials, thereby significantly improving the strength, hardness and wear resistance of the materials.

[0029] This invention addresses the high reflectivity issue in near-infrared laser-assisted lithography (SLM) forming of Cu and Cu alloys. Due to the high reflectivity of copper and low laser energy utilization, forming stability is generally poor. This invention introduces Fe-based HVWRS particles, significantly improving the absorption capacity of the mixed powder for laser light, promoting stable molten pool formation, thereby widening the process window and increasing forming density.

[0030] This invention avoids the problem of uneven powder mixing when the powder density is similar and the flowability is good during traditional whole-powder mixing by using a step-by-step incremental powder mixing method; at the same time, the mixed powder is dried to reduce the impact of moisture and surface adsorbed gas on the forming process, further ensuring the printing quality.

[0031] This invention utilizes the ultrafast cooling rate, extremely small molten pool, and cyclic heating characteristics of selective laser melting to suppress macroscopic segregation, preserving the metastable liquid-phase separation characteristics of Cu-Fe alloys to form uniform, fine, iron-rich droplets. This ultimately yields a unique two-phase heterostructure, significantly improving the overall mechanical properties of the copper-iron alloy. The resulting high-wear-resistant, high-conductivity copper-based composite material exhibits the following properties: electrical conductivity of 55.6% IACS and microhardness of 140.7 HV. 0.2 It has a density of over 99.53%, a yield strength of 295 MPa, and a tensile strength of 439 MPa, exhibiting good wear resistance under current-carrying friction and wear conditions. Attached Figure Description

[0032] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0033] Figure 1 The diagram shows a comparison of the nanomodulus and nanohardness of the high wear-resistant and high conductivity copper-based composite materials prepared in Example 1 and Comparative Examples 1-3.

[0034] Figure 2 The phase XRD patterns of the high wear-resistant and high conductivity copper-based composite materials prepared in Example 1 and Comparative Examples 1-3 are shown.

[0035] Figure 3 SEM micrographs of the high wear-resistant and high conductivity copper-based composite materials prepared in Example 1 and Comparative Examples 1-3 are shown.

[0036] Figure 4 The tensile stress-strain curves of the high wear-resistant and high conductivity copper-based composite materials prepared in Example 1 and Comparative Example-3 are shown.

[0037] Figure 5 The diagram shows the volumetric wear of the high wear-resistant and high conductivity copper-based composite materials prepared in Example 1 and Comparative Examples 1-3 during current-carrying tribo-wear tests. Detailed Implementation

[0038] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0039] The present invention will be further explained below with reference to specific embodiments.

[0040] This invention provides a method for preparing high-wear-resistant and high-conductivity copper-based composite materials by selective laser melting, comprising the following steps:

[0041] S1: Provide copper powder and high vanadium wear-resistant steel powder, and weigh the copper powder and high vanadium wear-resistant steel powder in a predetermined ratio;

[0042] The mass ratio of copper powder to high-vanadium wear-resistant steel powder is 9:1;

[0043] The particle size of both the copper powder and the high-vanadium wear-resistant steel powder is 15-90 micrometers, and the mixed powder of copper powder and high-vanadium wear-resistant steel powder adopts a multi-modal gradation, wherein the fine powder has a particle size of 15-35 micrometers, the medium powder has a particle size of 35-65 micrometers, and the coarse powder has a particle size of 65-90 micrometers, and the mass fractions of the fine powder, medium powder, and coarse powder are 55-70%, 25-35%, and 10-25%, respectively.

[0044] The high-vanadium wear-resistant steel powder, by mass percentage, comprises: C 1.5-2.8%, Si 0.5-1.5%, Cr 4.0-6.5%, V 5.0-9.0%, with the balance being Fe and unavoidable impurities; the high-vanadium wear-resistant steel powder is prepared using an air atomization powdering process, specifically:

[0045] (1) Weigh the raw materials according to the above chemical composition, and melt them in a medium frequency induction melting furnace. Control the melting temperature to 1550-1650 ℃. After the raw materials are completely melted, refine them for 15-30 min to obtain a steel liquid with uniform composition.

[0046] (2) The molten steel is transferred to an intermediate ladle and, under vacuum or inert gas protection, a gas atomization powder making process is adopted, with high pressure inert gas as the atomization medium and atomization pressure of 2.5 to 6.0 MPa. The atomized powder is collected, cooled, and sieved to obtain high vanadium wear-resistant steel powder.

[0047] The copper powder used is 100% pure copper powder, and the preparation method is the same as that of wear-resistant steel powder. The melting temperature is 1150-1200 ℃. An appropriate amount (0.01-0.05 wt.%) of phosphorus (P) is added as a deoxidizer during the melting process.

[0048] S2: The well-balanced powder is pretreated, which includes: mixing copper powder and high-vanadium wear-resistant steel powder evenly in a three-dimensional motion mixer using a stepwise incremental mixing method, and then placing it in a vacuum drying oven for drying.

[0049] The step-by-step incremental mixing method is specifically as follows:

[0050] First, take all of the high-vanadium wear-resistant steel powder and an equal mass of copper powder and mix them evenly in a three-dimensional motion mixer. Then, add the remaining copper powder in batches, with the mass of copper powder added each time being equal to the total mass of the current mixture. Mix step by step until all copper powder has been added.

[0051] Mixing is carried out under argon protection at a speed of 20-60 rpm, with a single mixing time of 45-90 minutes.

[0052] The drying process is carried out in a vacuum drying oven at a temperature of 100-220℃ for 2-6 hours, with a vacuum degree ≤133 Pa.

[0053] S3: The pretreated mixed powder is printed into a printed copper-based composite material by selective laser melting process, and then stress-relief annealing is performed to obtain the high wear-resistant and high conductivity copper-based composite material.

[0054] The selective laser melting process uses a near-infrared laser with a wavelength of 1064 nm as the forming light source. It improves the laser absorption characteristics of copper powder by using HVWRS powder. Compared with the current industry situation where pure copper can only be printed with green light, it improves the energy absorption rate of copper powder to red laser and uses red laser to complete the preparation of high wear-resistant and high conductivity copper-based composite materials.

[0055] The processing parameters for the selected area laser melting process are:

[0056] Laser power 140-225 W, scanning speed 200-500 mm / s, scanning spacing 0.03-0.06 mm, powder layer thickness 0.02-0.04 mm, strip scanning strategy, interlayer rotation angle 45°-67°, oxygen content in the printing chamber <500 ppm during printing, protective gas flow rate 2.1-2.4 m / s, powder compensation factor 200%-320%;

[0057] The powder-laying compensation factor is the ratio of the volume of powder supplied in a single powder-laying operation to the volume formed by the single descent of the processing platform. The method of over-powder-laying compensation ensures the stability of the powder bed filling height, thereby ensuring the stability of the molding process and the density of the parts.

[0058] The stress-relief annealing process is carried out under an argon atmosphere at an annealing temperature of 350-550℃ and a holding time of 1-3 hours.

[0059] This invention also provides a high wear-resistant and high conductivity copper-based composite material, which is prepared by the method described above. The high wear-resistant and high conductivity copper-based composite material is used for components under current-carrying friction conditions.

[0060] The microstructure of the high wear-resistant and high conductivity copper-based composite material comprises an iron-rich phase uniformly distributed in the copper matrix, as well as VC carbides and (Cr,Fe). 23 C6 carbides, of which VC carbides are dominant;

[0061] The high wear-resistant and high conductivity copper-based composite material has an electrical conductivity of 55.6% IACS and a microhardness of 140.7 HV. 0.2 It has a density of over 99.63%, a yield strength of 295 MPa, and a tensile strength of 439 MPa;

[0062] Under the conditions of a normal load of 15 N, a loading current of 30 A, a sliding speed of 0.05 m / s, and a grinding time of 30 min, the volumetric wear rate was 1.65 × 10⁻⁶. -4 mm 3 / (N·m).

[0063] In this embodiment, a compound containing VC, (Cr, Fe) is introduced into the copper matrix. 23 Metallic reinforcements with hard phases such as C6 can significantly improve the mechanical properties and wear resistance of materials, while effectively addressing the high reflectivity problem of Cu and Cu alloys in SLM forming. Furthermore, leveraging the advantage of SLM technology that allows for layer-by-layer control of material composition, copper-based composite materials with dense structure, good electrical conductivity, and high wear resistance can be prepared.

[0064] The alloying elements in wear-resistant steel powder include silicon (Si), chromium (Cr), molybdenum (Mo), vanadium (V), and niobium (Nb). These elements play a unique role in improving material properties and interfacial characteristics through mechanisms such as solid solution strengthening and second-phase strengthening (precipitation strengthening and dispersion strengthening). Carbon (C) can combine with Fe or other strong carbide-forming elements (such as Cr, Mo, and Nb) to form a stable, dispersed hard phase in situ within Fe-based particles, improving the hardness and wear resistance of the reinforcing phase. Silicon can improve carbide morphology; chromium primarily enhances corrosion resistance and oxidation resistance; molybdenum improves hardenability and hardenability; vanadium increases carbide hardness and improves the wear resistance of castings; and niobium can form NbC, significantly increasing the hardness of the carbide.

[0065] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and comparative examples.

[0066] Example 1:

[0067] This embodiment provides a method for preparing high-wear-resistant and high-conductivity copper-based composite materials by selective laser melting, including the following steps:

[0068] S1) Preparation of raw powder:

[0069] Copper powder and high-vanadium wear-resistant steel powder (HVWRS) are provided. The wear-resistant steel powder and copper powder are weighed and mixed at a mass ratio of 1:9. The fine powder has a particle size of 15-35 micrometers, the medium powder has a particle size of 35-65 micrometers, and the coarse powder has a particle size of 65-90 micrometers, with the fine powder accounting for 65%, the medium powder 25%, and the coarse powder 10%. The composition of the high-vanadium wear-resistant steel powder (HVWRS) is: 2.3 wt.% C, 0.9 wt.% Si, 5 wt.% Cr, 8.5 wt.% V, with the balance being Fe and unavoidable impurities.

[0070] The high-vanadium wear-resistant steel powder is prepared using a gas atomization powder preparation process, specifically:

[0071] (1) Weigh the raw materials according to the above chemical composition, and melt them in a medium frequency induction melting furnace. Control the melting temperature to 1550-1650 ℃. After the raw materials are completely melted, refine them for 15-30 min to obtain a steel liquid with uniform composition.

[0072] (2) The molten steel is transferred to an intermediate ladle and, under vacuum or inert gas protection, a gas atomization powder making process is adopted, with high pressure inert gas as the atomization medium and atomization pressure of 2.5 to 6.0 MPa. The atomized powder is collected, cooled, and sieved to obtain high vanadium wear-resistant steel powder.

[0073] The Cu powder used is 100% pure copper powder, and the preparation method is the same as that of wear-resistant steel powder. The melting temperature is 1150-1200 ℃. An appropriate amount (0.01-0.05 wt.%) of phosphorus (P) is added as a deoxidizer during the melting process.

[0074] S2) Powder pretreatment: mixing and drying the weighed powder according to the specified ratio.

[0075] First, all high-vanadium wear-resistant steel powder and an equal mass of copper powder are placed in a three-dimensional motion mixer and mixed evenly. Then, copper powder is gradually added, with each addition equal to the current mass of the mixture. This process is continued until all copper powder has been added. Argon gas is introduced for protection during mixing, the mixing speed is 60 rpm, and each mixing cycle takes 80 minutes. After mixing, the powder is removed and placed in a vacuum drying oven to dry. The oven temperature is 150℃, the drying time is 5 hours, and the vacuum degree is ≤133Pa.

[0076] S3) Preparation of high wear-resistant and high conductivity copper-based composite materials:

[0077] The pretreated mixed powder was laid on a 316L stainless steel substrate and printed using an SLM (Silicon-to-Layer) machine. The laser power was 170W, the scanning speed was 500mm / s, the scanning spacing was 0.04mm, the layer thickness was controlled at 0.02mm, and a strip scanning method was used. The interlayer rotation angle was set to 67°. Argon gas was continuously introduced during the printing process, and the oxygen content in the printing chamber was controlled to be <500ppm. The gas flow rate was controlled at 2.2m / s, and the powder laying compensation factor was 280%. The stress-relief annealing process was carried out at 500℃ for 3 hours under an argon atmosphere.

[0078] Example 2:

[0079] This embodiment provides a method for preparing high-wear-resistant and high-conductivity copper-based composite materials by selective laser melting, including the following steps:

[0080] S1) Preparation of raw powder:

[0081] Copper powder and high-vanadium wear-resistant steel powder (HVWRS) were prepared according to the method in Example 1. The wear-resistant steel powder and copper powder were weighed in a mass ratio of 1:9. The fine powder had a particle size of 15-35 micrometers, the medium powder had a particle size of 35-65 micrometers, and the coarse powder had a particle size of 65-90 micrometers. The fine powder accounted for 70%, the medium powder for 20%, and the coarse powder for 10%. The composition of the high-vanadium wear-resistant steel powder (HVWRS) was: 2.2 wt.% C, 1 wt.% Si, 5.2 wt.% Cr, 8 wt.% V, and the balance was Fe.

[0082] S2) Powder pretreatment: mixing and drying the weighed powder according to the specified ratio.

[0083] First, take all the high-vanadium wear-resistant steel powder and an equal mass of copper powder and mix them evenly in a three-dimensional motion mixer. Then, gradually add copper powder, with each addition equal to the current mass of the mixture, mixing step by step until all the copper powder has been added. During mixing, argon gas is introduced for protection, the speed is 58 rpm, and the mixing time for each cycle is 90 minutes. After mixing, the powder is removed and placed in a vacuum drying oven to dry the mixed powder. The drying oven temperature is 180℃, the drying time is 5.5 hours, and the vacuum degree is ≤133Pa.

[0084] S3) Preparation of high wear-resistant and high conductivity copper-based composite materials:

[0085] The pretreated mixed powder was laid on a 316L stainless steel substrate and printed using an SLM (Silicon-to-Layer) machine. The laser power was 175W, the scanning speed was 450mm / s, the scanning spacing was 0.045mm, the layer thickness was controlled at 0.02mm, and a strip scanning method was used. The interlayer rotation angle was set to 67°. Argon gas was continuously introduced during the printing process, and the oxygen content in the printing chamber was controlled to be <500ppm. The gas flow rate was controlled at 2.2m / s, and the powder laying compensation factor was 290%. The stress-relief annealing process was carried out at 520℃ for 2.5h under an argon atmosphere.

[0086] Example 3:

[0087] This embodiment provides a method for preparing high-wear-resistant and high-conductivity copper-based composite materials by selective laser melting, including the following steps:

[0088] S1) Preparation of raw powder:

[0089] Copper powder and high-vanadium wear-resistant steel powder (HVWRS) were prepared according to the method in Example 1. The wear-resistant steel powder and copper powder were weighed in a mass ratio of 1:9. The fine powder had a particle size of 15-35 micrometers, the medium powder had a particle size of 35-65 micrometers, and the coarse powder had a particle size of 65-90 micrometers. The fine powder accounted for 68%, the medium powder for 21%, and the coarse powder for 11%. The composition of the high-vanadium wear-resistant steel powder (HVWRS) was: 2.4 wt.% C, 1.2 wt.% Si, 5.3 wt.% Cr, 8.7 wt.% V, and the balance was Fe.

[0090] S2) Powder pretreatment: mixing and drying the weighed powder according to the specified ratio.

[0091] First, take all the high-vanadium wear-resistant steel powder and an equal mass of copper powder and mix them evenly in a three-dimensional motion mixer. Then, gradually add copper powder, with each addition equal to the current mass of the mixture, mixing step by step until all the copper powder has been added. During mixing, argon gas is introduced for protection, the speed is 55 rpm, and the mixing time for each cycle is 85 minutes. After mixing, the powder is removed and placed in a vacuum drying oven to dry the mixed powder. The drying oven temperature is 185℃, the drying time is 6 hours, and the vacuum degree is ≤133Pa.

[0092] S3) Preparation of high wear-resistant and high conductivity copper-based composite materials:

[0093] The pretreated mixed powder was laid on a 316L stainless steel substrate and printed using an SLM (Silicon-Laser Transformer) machine. The laser power was 172W, the scanning speed was 480mm / s, the scanning spacing was 0.05mm, the layer thickness was controlled at 0.03mm, and a strip scanning method was used. The interlayer rotation angle was set to 67°. Argon gas was continuously introduced during the printing process, and the oxygen content in the printing chamber was controlled to be <500ppm. The gas flow rate was controlled at 2.2m / s, and the powder laying compensation factor was 300%. The stress-relief annealing process was carried out at 550℃ for 3 hours under an argon atmosphere.

[0094] Comparative Example 1:

[0095] Compared with Example 1, the difference is that the wear-resistant steel powder in S1 is replaced with coarse wear-resistant steel powder with a particle size range of 90-150 micrometers, while the composition and the ratio of pure copper powder remain unchanged.

[0096] Comparative Example 2:

[0097] Compared with Example 1, the difference is that the wear-resistant steel powder in S1 is replaced with low-alloy wear-resistant steel NM400 with lower V and Cr content (alloy composition: V ≤0.08wt.%, Cr ≤1.4wt.%, C ≤0.25wt.%, Si ≤0.70wt.%, Mn ≤1.60wt.%, P ≤0.025wt.%, S ≤0.010wt.%), while the particle size and the ratio with pure copper powder remain unchanged.

[0098] Comparative Example 3:

[0099] Compared with Example 1, the difference is that the powder mixing method in S2 is changed from incremental mixing to overall mixing, the mixing time is 5 hours, and other conditions remain unchanged.

[0100] Performance testing and evaluation:

[0101] (1) Mechanical and physical properties of the high wear-resistant and high conductivity copper-based composite materials prepared in Examples 1-3 were tested.

[0102] The density of the high wear-resistant and high conductivity copper-based composite materials prepared in Examples 1-3 was measured according to GB / T 3850-2015 "Method for Determination of Density of Dense Sintered Metallic Materials and Hard Alloys"; the conductivity of the high wear-resistant and high conductivity copper-based composite materials prepared in Examples 1-3 was measured according to GB / T 351-2019 "Method for Measurement of Resistivity of Metallic Materials"; the hardness of the high wear-resistant and high conductivity copper-based composite materials prepared in Examples 1-3 was tested according to the method in GB / T4340.1-2024 Vickers Hardness Test of Metallic Materials. Seven data points were collected for the test, and the average value was taken after removing the extreme values. The density, conductivity and hardness results are shown in Table 1.

[0103] Table 1. Density, conductivity, and hardness of the high wear-resistant and high conductivity copper-based composite materials prepared in Examples 1-3.

[0104] sample Example 1 Example 2 Example 3 average value Density / % 99.63 99.32 99.49 99.48 Conductivity / IACS 55.6% 54.1% 55.2% 55.0 <![CDATA[Microhardness / HV 0.2 > 140.7 137.6 139.7 139.3

[0105] As shown in Table 1, the microstructure density of the three high-wear-resistant and high-conductivity copper-based composite materials prepared in Examples 1-3 is not significantly different; the electrical conductivity of the high-wear-resistant and high-conductivity copper-based composite materials remains above 50% IACS, proving that their conductivity is not significantly reduced due to strengthening; in addition, the average microstructure hardness of the three high-wear-resistant and high-conductivity copper-based composite materials reaches 139.3 HV. 0.2 The hardness of all three copper alloys is much greater than that of pure copper (annealed pure copper is approximately 68 HV). 0.2 ).

[0106] (2) The mechanical and physical properties of the high wear-resistant and high conductivity copper-based composite materials in Example 1 and Comparative Examples 1-3 were tested.

[0107] According to GB / T 3850-2015 "Method for Determination of Density of Dense Sintered Metallic Materials and Hard Alloys", the density of the high wear-resistant and high conductivity copper-based composite materials in Examples 1 and Comparative Examples 1-3 was tested; according to GB / T 351-2019 "Method for Measurement of Resistivity of Metallic Materials", the conductivity of the high wear-resistant and high conductivity copper-based composite materials prepared in Examples 1 and Comparative Examples 1-3 was measured; according to the method in GB / T4340.1-2024 Vickers Hardness Test of Metallic Materials, the hardness of the high wear-resistant and high conductivity copper-based composite materials prepared in Examples 1 and Comparative Examples 1-3 was tested; according to GB / T 22458-2008 "General Rules for Instrumented Nanoindentation Test Methods", nanoindentation tests were performed on the iron-rich phase in the microstructure of the high wear-resistant and high conductivity copper-based composite materials prepared in Examples 1 and Comparative Examples 1-3. The density, conductivity, and microhardness results of the high wear-resistant and high conductivity copper-based composite materials are shown in Table 2, and the nanohardness test results are as follows. Figure 1 As shown.

[0108] Table 2. Density, conductivity, and hardness of the high wear-resistant and high conductivity copper-based composite materials prepared in Example 1 and Comparative Examples 1-3.

[0109] sample Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Density / % 99.63 99.14 99.03 99.29 Conductivity / IACS 55.6% 51.8% 49.2% 50.5 <![CDATA[Microhardness / HV 0.2 > 140.7 130.3 118.5 133.6

[0110] From Table 2, Figure 1 As can be seen from the data, the microhardness in Example 1 is 140.7 HV. 0.2The density was 99.63%. The high wear-resistant and high-conductivity copper-based composite material in Example 1 exhibited higher density, conductivity, and microhardness than the high wear-resistant and high-conductivity copper-based composite materials in Comparative Examples 1-3. Simultaneously, the average nanomodulus and hardness of the iron-rich phase in the microstructure of Example 1 were also higher than those of the high wear-resistant and high-conductivity copper-based composite materials in Comparative Examples 1-3. This is because in Comparative Example 1, the coarse and fine powders were not properly graded, and only coarse powder was used, resulting in uneven mixing of the wear-resistant steel powder. In Comparative Example 2, the V and Cr contents were low, failing to form sufficient VC and (Cr,Fe) during the SLM printing process. 23 The C6 hard phase has poor microhardness and nanohardness of the iron-rich phase; in Comparative Example 3, the lack of stepwise powder mixing and uneven mixing of copper powder and wear-resistant steel powder resulted in slightly worse performance than in Example 1.

[0111] (3) Phase analysis was performed on the high wear-resistant and high conductivity copper-based composite material in Example 1 and the high wear-resistant and high conductivity copper-based composite materials in Comparative Examples 1-3.

[0112] According to YB / T 5320-2006 "Quantitative Phase Analysis of Metallic Materials - X-ray Diffraction K-value Method", the high wear-resistant and high conductivity copper-based composite materials in Example 1 and Comparative Examples 1-3 were subjected to XRD phase analysis. Figure 2 As shown.

[0113] from Figure 2 As can be seen from the data, the phase composition of the wear-resistant steel particle-reinforced high wear-resistant and high-conductivity copper-based composite material is mainly ε-Cu, γ-Fe, martensite, and (Cr,Fe). 23 Compared to the low-alloy wear-resistant steel in Comparative Example 2, the increased V content in high-vanadium wear-resistant steel promotes the formation of harder VC carbides, which are important reinforcing phases for improving the wear resistance of high-wear-resistant and high-conductivity copper-based composite materials.

[0114] (4) The microstructure of the high wear-resistant and high conductivity copper-based composite materials in Example 1 and Comparative Examples 1-3 was observed by SEM.

[0115] According to GB / T 16594-2021 "General Rules for Scanning Electron Microscopy Measurement Methods of Micrometer-Scale Lengths", the high wear-resistant and high conductivity copper-based composite materials prepared in Example 1 and Comparative Examples 1-3 were observed under a scanning electron microscope. The tissue morphology images are shown below. Figure 3 As shown.

[0116] from Figure 3As can be seen from the results, at low magnification, the surface forming quality of the composite material in Example 1 is good, with few defects such as cracks and pores, laying the foundation for a uniform and dense microstructure. This also indicates that the introduction of wear-resistant steel particles significantly improves the material's absorption rate of laser energy, further enhancing the stability of the molten pool. At high magnification, the Fe-rich phase particles in Example 1 are uniformly dispersed in the Cu matrix, further ensuring the uniformity of material properties. In contrast to Example 1, Comparative Examples 1 and 3 both exhibit a certain degree of iron-rich phase aggregation. The former is due to the excessively large particle size of the wear-resistant steel powder used, combined with the immiscible characteristics of Cu-Fe binary alloys in the liquid state, which easily lead to phase separation and aggregation, making it difficult for the reinforcing phase to disperse in the copper matrix. Comparative Example 3, due to the overall mixing during powder pretreatment, also resulted in slight Fe-rich phase aggregation because the two powders had similar densities and particle sizes. In Comparative Example 2, unfused areas appeared on the surface, which was caused by insufficient laser energy absorption due to compositional differences, resulting in incomplete melting of the powder.

[0117] (5) Tensile properties of the high wear-resistant and high conductivity copper-based composite materials in Example 1 and Comparative Examples 1-3 were tested.

[0118] According to GB / T 228.1-2021 "Metallic materials - Tensile testing - Part 1: Test method at room temperature", the high wear-resistant and high conductivity copper-based composite materials prepared in Example 1 and Comparative Examples 1-3 were subjected to tensile property testing. The stress-strain curves of the tensile tests are shown below. Figure 4 As shown.

[0119] from Figure 4 As can be seen from the data, the yield strength of the high-vanadium wear-resistant steel particle-reinforced high-wear-resistant and high-conductivity copper-based composite material in Example 1 reached 295 MPa, the tensile strength was 439 MPa, and the elongation was 18%, indicating that the addition of high-vanadium wear-resistant steel particles resulted in good mechanical properties of the high-wear-resistant and high-conductivity copper-based composite material. In Comparative Examples 1 and 3, the strength was slightly lower than that of Example 1, but the elongation was also lower. This was due to uneven powder mixing causing microstructure inhomogeneity. In Comparative Example 2, the insufficient wear-resistant steel powder reinforcement and insufficient laser energy absorption during selective laser melting printing resulted in low density, low strength, and low toughness.

[0120] (6) The high wear-resistant and high conductivity copper-based composite materials in Example 1 and Comparative Examples 1-3 were tested for their current-carrying tribological properties.

[0121] According to ASTM G133 - Standard Test Method for Linearly Reciprocating Ball-on-Flat Sliding Wear, the high wear-resistant and high-conductivity copper-based composite materials in Example 1 and Comparative Examples 1-3 were subjected to reciprocating friction tests under current-carrying conditions. The applied current was 30A, the load was 15N, the sliding speed was 0.05 m / s, and the friction time was 30 min. The three-dimensional wear volume is as follows: Figure 5 As shown in the figure; the volumetric wear rate is shown in Table 3.

[0122] Table 3. Current-carrying tribological wear rate of the high wear-resistant and high conductivity copper-based composite materials prepared in Examples 1 and Comparative Examples 1-3

[0123] sample Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 <![CDATA[Volume wear rate / mm 3 ·N -1 ·m -1 > <![CDATA[1.65×10 -4 ]]> <![CDATA[2.51×10 -4 ]]> <![CDATA[2.88×10 -4 ]]> <![CDATA[2.28×10 -4 ]]>

[0124] Depend on Figure 5 As shown in Table 3, under current-carrying conditions, the high-wear-resistant and high-conductivity copper-based composite material of Example 1 exhibits the lowest volumetric wear rate. This is because Example 1 has the best conductivity and a more uniform distribution of hard phase carbide particles, thus demonstrating good wear resistance during current-carrying friction and wear. In Comparative Examples 1 and 3, due to the uneven distribution and morphology of hard particles, and slightly lower conductivity compared to Example 1, their wear resistance under current-carrying conditions is lower than that of Example 1. In Comparative Example 2, the V and Cr content is low, and sufficient VC and (Cr, Fe) were not formed during the SLM printing process. 23 The C6 phase is a hard phase and also has the worst electrical conductivity, resulting in the lowest current-carrying triboelectric wear performance.

[0125] In summary, this invention innovatively introduces high-vanadium wear-resistant steel into a copper matrix and prepares a copper-based composite material using selective laser melting (SLM). On one hand, the high-vanadium wear-resistant steel contains VC, (Cr, Fe)... 23 Hard phases such as C6 can significantly improve the mechanical properties of the matrix. On the other hand, the addition of high-vanadium wear-resistant steel can effectively improve the high reflectivity problem of copper in selective laser melting, promote the stable formation of the molten pool, and improve the density of the alloy. In addition, compared with pure copper, the addition of iron has a smaller decrease in the conductivity of the alloy, basically retaining the excellent conductivity of pure copper. In this invention, the ultrafast cooling rate, extremely small molten pool, and cyclic heating characteristics of selective laser melting are utilized to suppress macroscopic segregation, retain the metastable liquid phase separation characteristics of Cu-Fe alloy, thereby forming uniform, fine, iron-rich droplets, and finally obtaining a unique two-phase heterostructure Cu-based composite material with both conductivity and wear resistance.

[0126] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing high-wear-resistant and high-conductivity copper-based composite materials by selective laser melting, characterized in that, Includes the following steps: S1: Provide copper powder and high vanadium wear-resistant steel powder, and weigh the copper powder and high vanadium wear-resistant steel powder in a predetermined ratio; S2: The well-balanced powder is pretreated, which includes: mixing copper powder and high-vanadium wear-resistant steel powder evenly in a three-dimensional motion mixer using a stepwise incremental mixing method, and then placing it in a vacuum drying oven for drying. S3: The pretreated mixed powder is printed into a printed copper-based composite material by selective laser melting process, and then stress-relief annealing is performed to obtain the high wear-resistant and high conductivity copper-based composite material.

2. The method according to claim 1, characterized in that, In S1, the mass ratio of copper powder to high-vanadium wear-resistant steel powder is 9:1; The particle size of both the copper powder and the high-vanadium wear-resistant steel powder is 15-90 micrometers, and the mixed powder of copper powder and high-vanadium wear-resistant steel powder adopts a multi-modal gradation, wherein the fine powder has a particle size of 15-35 micrometers, the medium powder has a particle size of 35-65 micrometers, and the coarse powder has a particle size of 65-90 micrometers, and the mass fractions of the fine powder, medium powder, and coarse powder are 55-70%, 25-35%, and 10-25%, respectively.

3. The method according to claim 1, characterized in that, In S1, the high-vanadium wear-resistant steel powder has the following composition by mass percentage: C 1.5-2.8%, Si 0.5-1.5%, Cr 4.0-6.5%, V 5.0-9.0%, with the balance being Fe and unavoidable impurities; the high-vanadium wear-resistant steel powder is prepared by gas atomization powder preparation process; The copper powder is pure copper powder, and phosphorus is added as a deoxidizer during the preparation process.

4. The method according to claim 1, characterized in that, In S2, the step-by-step incremental mixing method is specifically as follows: First, take all of the high-vanadium wear-resistant steel powder and an equal mass of copper powder and mix them evenly in a three-dimensional motion mixer. Then, add the remaining copper powder in batches, with the mass of copper powder added each time being equal to the total mass of the current mixture. Mix step by step until all copper powder has been added. Mixing is carried out under argon protection at a speed of 20-60 rpm, with a single mixing time of 45-90 minutes. The drying process is carried out in a vacuum drying oven at a temperature of 100-220℃ for 2-6 hours, with a vacuum degree ≤133 Pa.

5. The method according to claim 1, characterized in that, In S3, the selected area laser melting process uses a near-infrared laser with a wavelength of 1064 nm as the forming light source.

6. The method according to claim 1, characterized in that, In S3, the processing parameters of the selected area laser melting process are: Laser power 140-225 W, scanning speed 200-500 mm / s, scanning spacing 0.03-0.06 mm, powder layer thickness 0.02-0.04 mm, strip scanning strategy, interlayer rotation angle 45°-67°, oxygen content in the printing chamber <500ppm during printing, protective gas flow rate 2.1-2.4 m / s, powder compensation factor 200%-320%.

7. The method according to claim 6, characterized in that, The powder-spreading compensation factor is the ratio of the volume of powder supplied in a single powder-spreading operation to the volume formed by a single descent of the processing platform.

8. The method according to claim 1, characterized in that, In S3, the stress-relief annealing treatment is carried out under an argon atmosphere, with an annealing temperature of 350-550℃ and a holding time of 1-3 hours.

9. A high wear-resistant and high conductivity copper-based composite material, characterized in that, The high wear-resistant and high conductivity copper-based composite material, prepared by any one of claims 1-8, is used for components under current-carrying friction conditions.

10. The high wear-resistant and high conductivity copper-based composite material according to claim 9, characterized in that, The microstructure of the high wear-resistant and high conductivity copper-based composite material comprises an iron-rich phase uniformly distributed in the copper matrix, as well as VC carbides and (Cr,Fe). 23 C6 carbides, of which VC carbides are dominant; The high wear-resistant and high conductivity copper-based composite material has an electrical conductivity of 55.6% IACS and a microhardness of 140.7 HV. 0.2 It has a density of over 99.63%, a yield strength of 295 MPa, and a tensile strength of 439 MPa; Under the conditions of a normal load of 15 N, a loading current of 30 A, a sliding speed of 0.05 m / s, and a grinding time of 30 min, the volumetric wear rate was 1.65 × 10⁻⁶. -4 mm 3 / (N·m).

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