A lead-free copper alloy self-lubricating bimetallic material containing a high-entropy alloy and a preparation method thereof

Abstract

The application discloses a kind of high-entropy alloy-containing lead-free copper alloy self-lubricating bimetallic materials, a layer of high-entropy alloy-containing lead-free copper alloy is constructed on the surface of alloy steel base material as lubricating wear-resistant layer, the components of the lubricating wear-resistant layer are as follows in percentage by weight: high-entropy alloy 0.5-2%, bismuth 1%-7%, tin 6%-13%, and the balance is copper.The application can greatly improve the lubricity, wear resistance and anti-seizure performance of the friction pair under the harsh working conditions of oil starvation by manufacturing a layer of high-entropy alloy-containing self-lubricating lead-free copper alloy on the surface of alloy steel base material, thereby improving the overall service life of mechanical equipment.Therefore, it can be used as the inner wall surface of cylinder bore, sliding shoe, flow distribution disc and inner curved surface of plunger ball hinge of hydraulic pump motor, bearing material, etc., and has a wide application prospect.

Description

Technical Field

[0001] This invention relates to a copper alloy self-lubricating material, and more particularly to a lead-free copper alloy self-lubricating bimetallic material containing a high-entropy alloy and its preparation method, belonging to the fields of engineering materials and engineering hydraulic machinery technology. Background Technology

[0002] The friction pair materials in mechanical equipment not only need excellent lubricity to avoid decreased transmission efficiency, kinetic energy loss, frictional heat, and noise caused by frictional resistance, but also need good wear resistance to prevent increased clearance, decreased precision, and even component damage and failure caused by wear. Copper alloys, with their high melting point, strong corrosion resistance, high load-bearing capacity, good thermal conductivity and heat resistance, and excellent friction reduction and wear resistance, have long been a widely used self-lubricating metal material. They are not only used as bearing lubrication layers but were also one of the earliest self-lubricating materials used in piston pump friction pairs.

[0003] Currently, copper alloys, primarily in the form of copper-tin alloys and lead bronze, are used in various friction pairs. However, with increasing environmental awareness, the use of lead alloys is being restricted. Therefore, non-toxic, low-melting-point bismuth has become an important metallic element replacing lead in friction pair materials. However, with the introduction of bismuth, during friction, the low-melting-point bismuth precipitates onto the substrate surface, making the substrate surface more prone to peeling under stress. Therefore, while bismuth-containing copper alloy samples possess good self-lubricating properties, they are often accompanied by significant wear. Furthermore, during start-up, shutdown, and turning of engineering equipment, the friction pairs are often in a state of poor lubrication due to insufficient oil, which places higher demands on the low-oil lubrication properties of the lubricating materials.

[0004] High-entropy alloys are crystals composed of five or more elements, with each element comprising between 5% and 35% of the atoms, and each element's atoms randomly occupying a lattice site. High-entropy alloys have attracted widespread attention due to their excellent mechanical properties, corrosion resistance, and superior thermal stability. Previous studies have also shown that high-entropy alloys possess good tribological properties (Jian Wu, Yujie Chen, Heguo Zhu. A Review on the Tribological Performances of High-Entropy Alloys). Advanced Engineering Materials , 2022, 24 (8) 2101548.) Among them, the high-entropy alloy composed of CoCrFeNiMo has high microhardness due to its high grain boundary strength and dislocation strength. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention proposes a lead-free copper alloy self-lubricating bimetallic material containing a high-entropy alloy and its preparation method.

[0006] I. Preparation of lead-free copper alloy self-lubricating bimetallic materials containing high-entropy alloys

[0007] The present invention relates to a lead-free copper alloy self-lubricating bimetallic material containing a high-entropy alloy, which is constructed on the surface of an alloy steel substrate as a lubricating and wear-resistant layer containing a high-entropy alloy.

[0008] The components of the lubricating and wear-resistant layer, by weight percentage, are: 0.5-2% high-entropy alloy, 1-7% bismuth, 6-13% tin, and the balance being copper. The high-entropy alloy contains five metallic elements—cobalt, chromium, iron, nickel, and molybdenum—in approximately equal weight percentages.

[0009] The thickness of the lubricating and wear-resistant layer is 0.1 mm to 2 mm.

[0010] The preparation of a lead-free copper alloy self-lubricating bimetallic material containing a high-entropy alloy according to the present invention includes the following process steps:

[0011] (1) Surface pretreatment of the substrate: Polish the surface of the alloy steel substrate to remove burrs, remove surface oil stains and dirt, and electroplate copper on its surface as a transition layer to improve the bonding strength of the bimetallic interface. The thickness of the copper plating layer is 1 μm ~ 5 μm.

[0012] (2) Raw material mixing and activation: The copper, tin, and bismuth powders, which form the lubricating and wear-resistant layer, and the high-entropy alloy powder are mechanically mixed and activated in a V-type or roller mixer for 5-24 hours, and then dried at a constant temperature of 80℃-100℃ for 10-12 hours to obtain uniform copper alloy powder. The copper, tin, and bismuth powders are elemental metal powders with a particle size of 50 μm-200 μm, or they can be spherical water-atomized alloy powders of copper, tin, and bismuth; or they can be spherical gas-atomized alloy powders of copper, tin, and bismuth. The high-entropy alloy powder is made by mechanically alloying five elemental metal powders of cobalt, chromium, iron, nickel, and molybdenum in equal weights, with a particle size distribution of 50 μm-200 μm. In the raw material mixing and activation process, the high-entropy alloy powder is mechanically mixed with the copper, tin, and bismuth powders. During the mixing process, anhydrous ethanol or acetone is added at 5%-15% of the total weight of the raw material powder to improve the mixing efficiency and final uniformity.

[0013] (3) Formation of copper alloy layer: The mechanically mixed copper alloy powder is used to form a copper alloy layer with a thickness of 0.3 mm to 3 mm on the substrate surface by plasma spraying or powder metallurgy.

[0014] (4) Sintering: The copper alloy layer on the surface of the substrate is sintered in a reducing atmosphere at 750℃~950℃ for 40 min~90 min, and then naturally cooled in a reducing atmosphere;

[0015] (5) Rolling: Roll the surface of the substrate with the sintered copper alloy layer to ensure that the surface copper alloy layer is flat and its thickness is close to the required copper alloy layer thickness.

[0016] (6) Secondary sintering and rolling: Repeat steps (3) and (4) on the substrate until the final copper alloy layer thickness is between 0.1 and 2 mm;

[0017] (7) Surface post-treatment: The copper alloy layer of the substrate is leveled, milled, ground and polished until the thickness of the copper alloy layer is between 0.1 mm and 2 mm; the surface roughness is between Ra0.2 and Ra3.0.

[0018] II. Properties of Lead-Free Copper Alloy Self-Lubricating Bimetallic Materials Containing High-Entropy Alloys

[0019] This invention significantly improves the lubrication, wear resistance, and anti-galling performance of friction pairs under harsh conditions of insufficient oil by fabricating a layer of high-entropy alloy-containing self-lubricating lead-free copper alloy on the surface of an alloy steel substrate, thereby extending the overall service life of mechanical equipment. The following example uses a metal sheet with a high-entropy alloy self-lubricating copper alloy layer prepared in Example 2, compared with a metal sheet without a high-entropy alloy copper alloy layer, to illustrate the self-lubricating and wear-resistant properties of the high-entropy alloy-containing lead-free copper alloy self-lubricating bimetallic material of this invention.

[0020] Figure 1 This is a comparison of the friction coefficients of a metal sheet with a high-entropy alloy self-lubricating copper alloy layer and a metal sheet without a high-entropy alloy copper alloy layer prepared in Example 2 of the present invention under oil-depleted conditions. Figure 1 As can be seen, the friction coefficient of Cu-Sn-Bi alloy plate without the addition of the CoCrFeNiMo high-entropy alloy component is 0.11 under oil-depleted conditions, while the friction coefficient is reduced to below 0.1 after the addition of the high-entropy alloy component. This indicates that the high-entropy alloy CoCrFeNiMo component has a significant effect on improving the self-lubricating properties of Cu-Sn-Bi alloy.

[0021] Figure 2 This is a comparison chart of the wear rates of a metal sheet with a high-entropy alloy self-lubricating copper alloy layer and a metal sheet without a high-entropy alloy copper alloy layer prepared in Example 2 of the present invention under oil-depleted conditions. Figure 2 As can be seen, after adding the high-entropy alloy CoCrFeNiMo component to the Cu-Sn-Bi alloy, the wear under loads of 200N, 600N, and 1000N is significantly reduced, indicating that the high-entropy alloy CoCrFeNiMo component has a significant effect on improving the wear resistance of the Cu-Sn-Bi alloy.

[0022] Figure 3This is a comparison of the anti-galling load curves of the metal sheet with a high-entropy alloy self-lubricating copper alloy layer prepared in Example 2 of the present invention and the metal sheet without a high-entropy alloy copper alloy layer under oil-depleted conditions. Figure 3 As can be seen, under low-oil conditions, the friction coefficient and temperature of Cu-Sn-Bi without high-entropy alloy suddenly increased after 24 minutes, with the friction coefficient reaching 0.3 and the friction temperature approaching 200℃. However, after adding the high-entropy alloy CoCrFeNiMo component, the friction coefficient remained below 0.1, and the friction temperature did not exceed 90℃ throughout the entire test. This indicates that the high-entropy alloy CoCrFeNiMo component has a significant effect on improving the anti-galling properties of Cu-Sn-Bi alloy.

[0023] In summary, the present invention has the following advantages over the prior art:

[0024] 1. This invention adds a high-entropy alloy component to a copper-tin-bismuth alloy matrix. Due to the face-centered cubic (FCC) structure, high grain boundary strength, and high dislocation strength of the high-entropy alloy component, it has the effect of refining the grains of the copper-tin alloy matrix, thereby improving the overall strength of the copper alloy self-lubricating material. At the same time, it also makes the copper alloy self-lubricating material have excellent self-lubricating properties, wear resistance, and anti-galling properties. It can effectively reduce the wear of friction pairs under poor lubrication conditions, prevent the occurrence of galling between friction pairs, maintain the stable operation of mechanical equipment, and extend its service life.

[0025] 2. The high-entropy alloy of the present invention hinders the growth of copper-tin eutectic alloy grains during sintering, suppresses grain growth, and refines the matrix grains, thereby improving strength and wear resistance. Moreover, the high-entropy alloy can fill the voids left by tin entering copper during the copper-tin eutectic process, thereby enhancing the overall strength and wear resistance of the alloy by increasing the alloy density.

[0026] 3. The copper-tin-bismuth alloy doped with high-entropy alloy components of the present invention can be prepared on the plane and curved surfaces of friction pair parts by thermal spraying or powder metallurgy. Therefore, it can be used as a material for hydraulic pump motor slippers, distribution plates, cylinder components, bearing materials, as well as the inner wall surface of piston pump cylinder bores, inner curved surfaces of slippers and piston ball joints, etc., and has broad application prospects. Attached Figure Description

[0027] Figure 1 This invention compares the friction coefficients of metal plates containing a high-entropy alloy self-lubricating copper alloy layer and metal plates without a high-entropy alloy copper alloy layer under oil-depleted conditions.

[0028] Figure 2 This invention compares the wear rates of metal plates containing a high-entropy alloy self-lubricating copper alloy layer and those without a high-entropy alloy copper alloy layer under oil-depleted conditions.

[0029] Figure 3 This invention provides a comparison of the anti-seizure load curves of metal plates containing a high-entropy alloy self-lubricating copper alloy layer and metal plates without a high-entropy alloy copper alloy layer under oil-depleted conditions. Detailed Implementation

[0030] The preparation and application performance of the high-entropy alloy self-lubricating copper alloy material of the present invention will be further illustrated below through specific embodiments.

[0031] Example 1: Constructing a lead-free copper alloy lubricating and wear-resistant layer on the surface of a plunger pump slipper.

[0032] (1) Surface pretreatment of original parts: Polish the surface of the plunger pump slipper to remove burrs, remove surface oil stains and dirt, and electroplate copper on its surface with a copper plating layer thickness of 1 μm;

[0033] (2) Mechanical mixing: Copper, tin, bismuth powder and high-entropy alloy CoCrFeNiMo powder were weighed at 86%, 8%, 4%, and 2% by weight, respectively. All raw material powders were then mechanically mixed and activated in a V-type mixer. During the mixing process, anhydrous ethanol or acetone was added at 5% by weight of the raw material powder to improve the mixing efficiency and final uniformity. After mixing for 5 hours, the mixture was removed and dried at 80°C for 12 hours.

[0034] (3) Powder spreading: Pour a certain amount of mechanically mixed copper alloy powder onto the copper-plated slipper base and scrape it flat so that it is evenly and flatly spread on the surface of the plunger pump slipper, so that a copper alloy powder layer with a thickness of 3mm is formed on the surface of the part.

[0035] (4) Sintering: The parts are sintered at 750 °C for 40 min in a reducing atmosphere and then naturally cooled in a reducing atmosphere;

[0036] (5) Rolling: The copper alloy layer of the sintered parts is rolled to a thickness close to the required copper layer thickness of 2.5mm;

[0037] (6) Secondary sintering and rolling: Repeat steps 3 and 4 until the copper alloy layer thickness is 2 mm;

[0038] (7) Surface post-treatment: The copper alloy layer is leveled, milled, ground and polished until the thickness of the copper alloy layer is 2mm and the surface roughness is Ra2.0;

[0039] (8) Lubrication performance test: The coefficient of friction under oil-deficient conditions is 0.12, and the wear rate under loads of 200N, 600N, and 1000N is 3.0×10⁻⁶. -7 mm 3 / (N·m), 3.7×10 -7 mm 3 / (N·m), 4.0×10 -7 mm 3 / (N·m).

[0040] Example 2: Constructing a high-entropy lead-free copper alloy lubricating and wear-resistant layer on the surface of a metal sheet.

[0041] (1) Surface pretreatment of original parts: surface polishing and deburring, removing surface oil stains and dirt, and electroplating copper on its surface with a copper plating layer thickness of 3μm;

[0042] (2) Mechanical mixing: Copper, tin, bismuth powder and high-entropy alloy CoCrFeNiMo powder were weighed at 83%, 12%, 3.5% and 1.5% by weight, respectively. All raw material powders were then mechanically mixed and activated in a roller mixer. During the mixing process, anhydrous ethanol or acetone was added at 10% by weight of the raw material powder to improve the mixing efficiency and final uniformity. After mixing for 10 hours, the mixture was removed and dried at a constant temperature of 90°C for 12 hours.

[0043] (3) Powder spreading: Pour a certain amount of mechanically mixed copper alloy powder onto the surface of the copper-plated metal plate and scrape it flat so that it is evenly and flatly spread on the surface of the metal plate to form a copper alloy layer with a thickness of 0.8 mm.

[0044] (4) Sintering: The metal sheet is sintered at 750 °C for 40 min in a reducing atmosphere and then naturally cooled in a reducing atmosphere;

[0045] (5) Rolling: The copper alloy layer of the sintered parts is rolled to a thickness close to the required copper layer thickness of 0.5 mm;

[0046] (6) Secondary sintering and rolling: Repeat steps 3 and 4 until the copper alloy layer thickness is 0.3 mm;

[0047] (7) Surface post-treatment: The copper alloy layer is leveled, milled, ground and polished until the thickness of the copper alloy layer is 0.3mm and the surface roughness is Ra 1.5;

[0048] (8) Lubrication performance test: The coefficient of friction under oil-deficient conditions is 0.1, and the wear rate under loads of 200N, 600N, and 1000N is 2.8×10. -7 mm 3 / (N), 3.5×10 -7 mm 3 / (N·m), 3.8×10 -7 mm 3 / (N·m).

[0049] Example 3: Constructing a lead-free copper alloy lubricating and wear-resistant layer containing a high-entropy alloy on the surface of the plunger pump distributor plate.

[0050] (1) Surface pretreatment of original parts: surface polishing and deburring, removing surface oil stains and dirt, and electroplating copper on its surface with a copper plating layer thickness of 5 μm;

[0051] (2) Mechanical mixing: Copper, tin, bismuth powder and high-entropy alloy CoCrFeNiMo powder were weighed at 92%, 6%, 1%, and 1% by weight, respectively. All raw material powders for the copper alloy layer were then mechanically mixed and activated in a roller mixer. During the mixing process, anhydrous ethanol or acetone was added at 15% by weight of the raw material powder to improve the mixing efficiency and final uniformity. After mixing for 24 hours, the mixture was removed and dried at 100°C for 12 hours.

[0052] (3) Powder spreading: Pour a certain amount of mechanically mixed copper alloy powder onto the copper-plated distribution plate substrate and spread it evenly and flatly on the distribution plate surface to form a copper alloy layer with a thickness of 1.5 mm on the surface of the part.

[0053] (4) Sintering: The parts are sintered at 950 °C for 90 min in a reducing atmosphere and then naturally cooled in a reducing atmosphere;

[0054] (5) Rolling: The copper alloy layer of the sintered parts is rolled to a thickness close to the required copper layer thickness of 1.2 mm;

[0055] (6) Secondary sintering and rolling: Repeat steps 3 and 4 until the copper alloy layer thickness is 1.0 mm;

[0056] (7) Surface post-treatment: The copper alloy layer is leveled, milled, ground and polished until the required thickness of 1.0 mm is reached and the surface roughness is Ra1.0;

[0057] (8) Lubrication performance test: The coefficient of friction under oil-deficient conditions is 0.08, and the wear rate under loads of 200N, 600N, and 1000N is 2.0×10⁻⁶. -7 mm 3 / (N·m), 3.0×10 -7 mm 3 / (N·m), 3.5×10 -7 mm 3 / (N·m).

[0058] Example 4: A lead-free copper alloy lubricating and wear-resistant layer containing a high-entropy alloy is constructed on the inner surface of the plunger ball joint of the plunger pump slipper.

[0059] (1) Surface pretreatment of original parts: surface polishing and deburring, removing surface oil stains and dirt, and electroplating copper on its surface with a copper plating layer thickness of 3μm;

[0060] (2) Mechanical mixing: Weigh copper, tin, bismuth powder and high-entropy alloy CoCrFeNiMo powder at weights of 79.5%, 13%, 7%, and 0.5%, respectively. Then, mechanically mix and activate all the raw material powders for the copper alloy layer in a V-type or roller mixer. During the mixing process, add anhydrous ethanol or acetone at 5% of the weight of the raw material powder to improve the mixing efficiency and final uniformity. After mixing for 18 hours, remove and dry at 90°C for 12 hours.

[0061] (3) Thermal spraying: The mechanically mixed copper alloy powder is uniformly sprayed onto the inner surface of the plunger ball joint of the plunger pump slip shoe using thermal spraying technology, so that a copper alloy layer with a thickness of 1mm is formed on its surface.

[0062] (4) Sintering: The parts are sintered at 950 °C for 90 min in a reducing atmosphere and then naturally cooled in a reducing atmosphere;

[0063] (5) Rolling: The copper alloy layer of the sintered parts is rolled to a thickness close to the required copper layer thickness of 0.5 mm;

[0064] (6) Secondary sintering and rolling: Repeat steps 3 and 4 until the copper alloy layer thickness is 0.3 mm;

[0065] (7) Surface post-treatment: The copper alloy layer is leveled, milled, ground and polished until the required thickness of 0.3 mm is reached and the surface roughness is Ra0.5;

[0066] (8) Lubrication performance test: The coefficient of friction under oil-deficient conditions is 0.09, and the wear rate under loads of 200N, 600N, and 1000N is 2.9×10. -7 mm 3 / (N·m), 3.2×10 -7 mm 3 / (N·m), 3.6×10 -7 mm 3 / (N·m).

[0067] In the above embodiments, the particle size of the metal raw materials copper, tin, and bismuth powder is 50 μm to 200 μm; the high-entropy alloy powder CoCrFeNiMo is prepared by mechanical alloying of five elemental metal powders: cobalt, chromium, iron, nickel, and molybdenum.

Claims

1. A lead-free copper alloy self-lubricating bimetallic material containing a high-entropy alloy, characterized in that a layer of lead-free copper alloy containing a high-entropy alloy is constructed on the surface of an alloy steel substrate as a lubricating and wear-resistant layer; The components of the lead-free copper alloy lubricating wear-resistant layer are as follows in percentage by weight: high-entropy alloy 0.5-2%, bismuth 1-7%, tin 6-13%, and the balance being copper; the high-entropy alloy is formed by the same weight ratio of cobalt, chromium, iron, nickel, and molybdenum.

2. The lead-free copper alloy self-lubricating bimetallic material containing a high-entropy alloy according to claim 1, characterized in that: The thickness of the lubricating wear-resistant layer is 0.1-2 mm.

3. The preparation method of the lead-free copper alloy self-lubricating bimetallic material containing high-entropy alloy according to claim 1, comprising the following process steps: (1) surface pretreatment of the substrate: polishing the surface of the substrate to remove burrs, removing surface oil stains and dirt, and electroplating copper on the surface of the substrate, with the thickness of the copper plating layer being 1-5 μm; (2) mixing and activation of raw materials: mechanically mixing and activating copper, tin, and bismuth powders, which are the metal raw materials for forming the lubricating wear-resistant layer, and high-entropy alloy powder, which is formed by the same weight ratio of cobalt, chromium, iron, nickel, and molybdenum, in a V-type or roller-type mixer for 5-24 hours, and then drying at a constant temperature of 80-100 °C for 10-12 hours to obtain uniform copper alloy powder; during the mixing process, 5-15% of anhydrous ethanol or acetone is added according to the total weight of the raw material powder to improve the mixing efficiency and final uniformity; (3) formation of the copper alloy layer: forming a copper alloy layer with a thickness of 0.3-3 mm on the surface of the substrate by plasma spraying or powder metallurgy; (4) sintering: sintering the copper alloy layer on the surface of the substrate in a reducing atmosphere at 750-950 °C for 40-90 min, and then naturally cooling in a reducing atmosphere; (5) rolling: rolling the bimetallic part with the sintered copper alloy layer to ensure that the surface copper alloy layer is flat and its thickness is close to the required copper alloy layer thickness; (6) secondary sintering and rolling: recycling steps (3) and (4) for the bimetallic part until the final thickness of the copper alloy layer is between 0.1 and 2 mm; (7) surface post-treatment: leveling, milling, grinding, and polishing the copper alloy layer on the substrate until the thickness of the copper alloy layer is between 0.1 and 2 mm, and the surface roughness is between Ra0.2 and Ra3.

0.

4. The method of claim 3, wherein the high-entropy alloy-containing lead-free copper alloy bimetallic material is prepared by the steps of: preparing a high-entropy alloy-containing lead-free copper alloy layer; and preparing a self-lubricating layer on the high-entropy alloy-containing lead-free copper alloy layer. The metal raw materials copper, tin, and bismuth powders are metal elemental powders with a particle size of 50-200 μm.

5. The method of claim 3, wherein the high-entropy alloy-containing lead-free copper alloy bimetallic material is prepared by the steps of: preparing a high-entropy alloy-containing lead-free copper alloy layer; and preparing a self-lubricating layer on the high-entropy alloy-containing lead-free copper alloy layer. The metal raw materials copper, tin, and bismuth powders are copper, tin, and bismuth spherical water-atomized alloy powders; or copper, tin, and bismuth spherical gas-atomized alloy powders.

6. The method of claim 3, wherein the high-entropy alloy-containing lead-free copper alloy bimetallic material is prepared by the steps of: preparing a high-entropy alloy-containing lead-free copper alloy layer; and preparing a self-lubricating layer on the high-entropy alloy-containing lead-free copper alloy layer. The high-entropy alloy powder is made of cobalt, chromium, iron, nickel, and molybdenum elemental powders through a mechanical alloying process, with a particle size distribution of 50-200 μm.

Images