High-entropy alloy powder, coating layer for brake disc and method for preparing coating layer

Abstract

The present application provides high-entropy alloy powder, a coating layer for a brake disc, and a method for preparing the coating layer. The preparation method comprises the following steps: (1) mixing Al powder, Co powder, Ni powder, Cu powder, and Ti powder in a molar ratio, then carrying out gas atomization to prepare powder, and sieving the powder to obtain high-entropy alloy powder; (2) preheating the high-entropy alloy powder obtained in step (1) to obtain alloy powder to be used; and (3) taking, as a raw material, the alloy powder to be used to perform atmospheric plasma spraying on the surface of a pretreated brake disc substrate to obtain the coating layer for a brake disc. By optimizing spraying parameters, the present application achieves maximized optimization of the microscopic morphology of the coating layer, obtaining the spraying parameters of the coating layer including optimal wear resistance and corrosion resistance; in addition, the coating layer for a brake disc has good interlayer bonding, a dense structure, and excellent wear resistance and corrosion resistance.

Description

High entropy alloy powder, coating for brake disc, and coating preparation method Cross-references

[0001] This application claims priority to Chinese patent application No. 202410386755.3 filed on April 1, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present application relates to the field of metal coating materials and thermal spraying technology, and particularly to a high entropy alloy powder, a coating for a brake disc, and a method for preparing the coating. Background Art

[0003] A brake disc, also known as a brake rotor, is a metal disc made of alloy steel and fixed to the wheel, rotating with it. When the brakes are applied while the vehicle is moving, the brake caliper clamps the disc to slow or stop the vehicle. Brake discs typically have circular holes to reduce weight and increase friction. There are many different types of brake discs, characterized by thin walls and sand cores forming the disc and center. Different types of brake discs vary in disc diameter, disc thickness, and the gap between the discs. The thickness and height of the disc hub also vary.

[0004] Although gray cast iron is very suitable for manufacturing brake discs, its hardness is low, approximately 200HV, and its wear resistance is limited. Brake discs are consumable parts in the braking system. If the brake discs are severely worn, the actual braking distance will differ significantly from the expected braking distance, thus affecting driving controllability and safety. At present, the main material used for brake discs in my country is gray cast iron, which is low-cost, high-strength, durable, has a high melting point, and is not easily softened by the heat energy generated by friction. However, with the development of science and the advancement of technology, this traditional metal material can no longer meet the service requirements of multiple working conditions due to its single mechanical properties, easy oxidation and rusting, poor thermal fatigue resistance, braking performance, and wear resistance. It is difficult to adapt to the current development of the automotive brake disc industry. Therefore, there is an urgent need for technical upgrades to brake discs.

[0005] High-entropy alloys (HEAs), a new class of alloys developed in the past decade, exhibit four key properties: the high-entropy effect in thermodynamics, the slow diffusion effect in kinetics, the lattice mismatch effect in crystal structure, and the cocktail effect in performance. These alloys exhibit numerous outstanding properties, including high strength and hardness, as well as excellent wear resistance, corrosion resistance, low-temperature resistance, high-temperature oxidation resistance, and resistance to temper softening.

[0006] Thermal spraying technology has its own unique advantages compared with other technologies, mainly including the following aspects: (1) There are more than ten spraying methods, which can be comprehensively selected based on factors such as performance requirements, substrate type, equipment conditions, and production efficiency; (2) There are a wide variety of spraying materials, and the temperature in the high-temperature zone is high enough to spray refractory materials; (3) It has a wide range of applications and is not limited by the size of the workpiece or the site; (4) The coating thickness is controllable.

[0007] CN106756717A discloses a method for preparing a high-strength, wear-resistant copper-nickel-tin alloy coating. It specifically discloses that a Cu15Ni8SnNb coating is prepared on a stainless steel substrate by a thermal spraying method. The wear resistance of the prepared alloy coating is better than that of an alloy block of the same material, and the wear scar depth of the coating is significantly smaller than that of an alloy material of the same material. However, compared with the present application, its wear rate is still higher.

[0008] Therefore, it is necessary to provide an alloy coating with better wear resistance and corrosion resistance for the automotive brake disc industry. Summary of the Invention

[0009] In response to the shortcomings of the prior art, the present application aims to provide a high entropy alloy powder, a brake disc coating, and a method for preparing the coating. The brake disc coating provided in the present application has good interlayer bonding, a dense structure, and excellent wear and corrosion resistance.

[0010] To achieve this goal, this application adopts the following technical solutions:

[0011] In a first aspect, the present application provides a high entropy alloy powder, wherein raw materials for preparing the high entropy alloy powder include Al powder, Co powder, Ni powder, Cu powder and Ti powder;

[0012] The molar ratio of the metal elements Al, Co, Ni, Cu and Ti in the high entropy alloy powder is 1:1:1:1:(0.7-1.3), for example, it can be 1:1:1:1:0.7, 1:1:1:1:0.8, 1:1:1:1:0.9, 1:1:1:1:1, 1:1:1:1:1:1.1, 1:1:1:1:1:2 or 1:1:1:1:1:3, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0013] The high entropy alloy powder has a single BCC (Body-Centered Cubic) crystal structure.

[0014] In some embodiments, the particle size of the high entropy alloy powder is 25 to 75 μm, for example, it can be 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm or 75 μm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0015] In some embodiments, the purity of the Al powder, Co powder, Ni powder, Cu powder and Ti powder is ≥99.9%, for example, it can be 99.9%, 99.92%, 99.94%, 99.96%, 99.98% or 99.999%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0016] In some embodiments, the present application uses Al powder, Co powder, Ni powder, Cu powder and Ti powder with a purity of ≥99.9% as raw materials to obtain high entropy alloy powder with a particle size range of 25 to 75 μm, so that the high entropy alloy powder has a high purity, and the high entropy alloy powder has a crystal structure of a BCC solid solution phase and thus has a high entropy effect, which can improve the solubility of the alloy system and the metal compound, and improve the bonding strength between the alloy and the metal compound.

[0017] In a second aspect of some embodiments of this specification, a coating for a brake disc is provided. The coating for a brake disc is prepared using the high entropy alloy powder provided in the first aspect.

[0018] As a preferred technical solution of the present application, the thickness of the brake disc coating is 200 to 300 μm, for example, it can be 200 μm, 220 μm, 240 μm, 260 μm, 280 μm or 300 μm, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable, preferably 250 to 300 μm.

[0019] In some embodiments, the thickness of the coating for the brake disc described in the present application is 200 to 300 μm. If the coating thickness is too large, the bonding strength between the coating and the substrate will be insufficient, and the coating will easily fall off over a long period of time, which will increase costs and reduce product competitiveness. If the coating thickness is too small, the coating will easily crack, fall off, etc., affecting the durability of the coating, and it will be easily corroded by corrosive media, thereby reducing the corrosion resistance of the coating. At the same time, it will be easily worn, thereby exposing the substrate and causing damage to the substrate.

[0020] In a third aspect, the present application provides a method for preparing a brake disc coating as provided in the second aspect, the preparation method comprising the following steps:

[0021] (1) Al powder, Co powder, Ni powder, Cu powder, and Ti powder are mixed in molar ratio, and then atomized and sifted to obtain high entropy alloy powder;

[0022] (2) preheating the high entropy alloy powder obtained in step (1) to obtain an alloy powder to be used;

[0023] (3) Using the alloy powder to be used as a raw material, atmospheric plasma spraying is performed on the surface of the pretreated brake disc substrate to obtain the brake disc coating.

[0024] This application adopts the gas atomization method to prepare high-entropy alloy powder with good powder sphericity, so as to ensure good fluidity of the powder during the spraying process; then adopts the atmospheric plasma spraying method and adjusts the spraying parameters to achieve the maximum optimization of the micromorphology of the brake disc coating; finally, a brake disc coating with good interlayer bonding, dense structure, and excellent wear resistance and corrosion resistance is obtained.

[0025] In some embodiments, the high entropy alloy powder of the present application has a single BCC crystal structure. After the atmospheric plasma spraying described in step (3), Ni in the alloy occupies some of the node positions of Cu atoms as solute atoms and undergoes a solid solution reaction to generate Cu 0.81 Ni 0.19 alloy phase, obtained with Cu 0.81 Ni 0.19 The FCC (face-centered cubic) crystal structure represented by TiCo3 significantly improves the tensile strength, wear resistance, corrosion resistance, electrocatalytic performance and thermoelectric lamp performance of the coating.

[0026] In some embodiments of the present specification, the gas atomization powder preparation in step (1) includes: under the protection of inert gas, repeatedly smelting Al powder, Co powder, Ni powder, Cu powder and Ti powder until the melt drips, and then performing high-pressure atomization.

[0027] In some embodiments, the vacuum degree in the aerosol powder making is 2.5×10 -4 ~3.5×10 -4 Pa, for example, can be 2.5×10 -4 Pa, 2.7×10 -4 Pa, 2.9×10 -4 Pa, 3.1×10 -4 Pa, 3.3×10 -4 Pa or 3.5×10 - 4 Pa, but not limited to the listed values, other values ​​not listed within the numerical range are also applicable.

[0028] In some embodiments, the smelting power is 30-40 kW, for example, 30 kW, 32 kW, 34 kW, 36 kW, 38 kW or 40 kW, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0029] In some embodiments, the repeated smelting is performed 3 to 5 times, for example, 3 times, 4 times, or 5 times.

[0030] In some embodiments, the gas used for the high-pressure atomization includes argon.

[0031] In some embodiments, the pressure of the high-pressure atomization is 7.5 to 8.5 MPa, for example, 7.5 MPa, 7.7 MPa, 7.9 MPa, 8.1 MPa, 8.3 MPa or 8.5 MPa, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0032] The pressure of the high-pressure atomization described in this application is 7.5~8.5MPa. If the pressure is too high, the gas consumption will increase, and the powder particle size will be too small, which is not conducive to spraying to form a coating. If the pressure is too low, the powder fluidity will be poor, the loose-pack ratio will be small, the particle size will increase and become irregular and uneven.

[0033] In some embodiments of the present specification, the temperature of the preheat treatment in step (2) is 180-230°C, for example, it can be 180°C, 190°C, 200°C, 210°C, 220°C or 230°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0034] In some embodiments, the preheating time in step (2) is 150 to 200 minutes, for example, 150 minutes, 160 minutes, 170 minutes, 180 minutes, 190 minutes or 200 minutes, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0035] In some embodiments of the present specification, the pretreatment in step (3) includes: sequentially performing sandblasting pretreatment, cleaning, and drying on the surface of the brake disc substrate.

[0036] In some embodiments, the sandblasting material used in the sandblasting pretreatment is brown corundum sand.

[0037] In some embodiments, the particle size of the brown corundum sand is any one of 16#, 18#, 20#, 22# or 24#, or a combination of at least two of them. Typical but non-limiting combinations include: a combination of 16# brown corundum sand and 18# brown corundum sand, a combination of 22# brown corundum sand and 24# brown corundum sand, a combination of 16# brown corundum sand, 18# brown corundum sand, 20# brown corundum sand and 24# brown corundum sand, or a combination of 16# brown corundum sand, 18# brown corundum sand, 20# brown corundum sand, 22# brown corundum sand and 24# brown corundum sand.

[0038] In some embodiments, the compressed air pressure in the sandblasting pretreatment is 0.3 to 0.8 MPa, for example, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa or 0.8 MPa, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0039] In some embodiments, the angle between the spray gun and the surface of the brake disc substrate in the sandblasting pretreatment is 40-50°, for example, it can be 40°, 41°, 42°, 43°, 44°, 45°, 46°, 47°, 48°, 49° or 50°, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0040] In some embodiments, the cleaning includes cleaning with a degreasing agent.

[0041] In the pretreatment described in the present application, after the sandblasting treatment, the surface of the substrate is repeatedly blown with compressed air to make the surface clean and free of dust particles, and then cleaned with a degreasing agent and dried to remove any residual oil.

[0042] In some embodiments, the brake disc substrate is made of cast iron.

[0043] In some embodiments of the present specification, the spraying distance in the atmospheric plasma spraying in step (3) is 100 to 150 mm, for example, it can be 100 mm, 110 mm, 120 mm, 130 mm, 140 mm or 150 mm, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0044] In some embodiments, the hydrogen flow rate of the plasma gas flow in the atmospheric plasma spraying in step (3) is 3 to 6 L / min, for example, it can be 3 L / min, 3.5 L / min, 4 L / min, 4.5 L / min, 5 L / min, 5.5 L / min or 6 L / min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0045] In some embodiments, the argon flow rate in the atmospheric plasma spraying in step (3) is 30 to 50 L / min, for example, it can be 30 L / min, 34 L / min, 38 L / min, 42 L / min, 46 L / min or 50 L / min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0046] In some embodiments, the spraying current in the atmospheric plasma spraying in step (3) is 480 to 550 A, for example, 480 A, 490 A, 500 A, 510 A, 520 A, 530 A, 540 A or 550 A, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0047] In some embodiments, the spraying voltage in the atmospheric plasma spraying in step (3) is 50 to 60 V, for example, 50 V, 52 V, 54 V, 56 V, 58 V or 60 V, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0048] In some embodiments, the translation speed of the spray gun in the atmospheric plasma spraying in step (3) is 150 to 400 mm / s, for example, it can be 150 mm / s, 200 mm / s, 250 mm / s, 300 mm / s, 350 mm / s or 400 mm / s, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable; the translation spacing of the spray gun is 3 mm.

[0049] In some embodiments, the powder feeding rate in the atmospheric plasma spraying in step (3) is 2 to 10 g / min, for example, it can be 2 g / min, 3 g / min, 4 g / min, 5 g / min, 6 g / min, 7 g / min, 8 g / min, 9 g / min or 10 g / min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0050] In some embodiments, the powder feeding method of the atmospheric plasma spraying in step (3) includes vertical jet powder feeding.

[0051] In some embodiments, the atmospheric plasma spraying in step (3) is repeated 4 to 6 times, for example, 4 times, 5 times or 6 times.

[0052] The selection of process parameters during the atmospheric plasma spraying process in this application will affect the thickness and uniformity of the resulting brake disc coating. Only by strictly controlling the spraying parameters can the micromorphology of the brake disc coating be optimized to the greatest extent possible.

[0053] In some embodiments of this specification, the second aspect provides a method for preparing a brake disc coating, comprising the following steps:

[0054] (1) Al powder, Co powder, Ni powder, Cu powder, and Ti powder are mixed in molar ratio, and then atomized and pulverized to obtain a high entropy alloy powder with a particle size of 25 to 75 μm after sieving;

[0055] The gas atomization powder making comprises: under the protection of inert gas, repeatedly smelting Al powder, Co powder, Ni powder, Cu powder and Ti powder with a purity of ≥99.9% for 3 to 5 times until the melt drips, and then using argon gas for high-pressure atomization;

[0056] The vacuum degree in the gas atomization powder making is 2.5×10 -4 ~3.5×10 -4 Pa, the smelting power is 30-40KW, and the pressure of the high-pressure atomization is 7.5-8.5MPa;

[0057] (2) preheating the high entropy alloy powder obtained in step (1) to obtain an alloy powder to be used;

[0058] Wherein, the temperature of the preheating treatment is 180-230°C and the time is 150-200 minutes;

[0059] (3) using the alloy powder to be used as a raw material, performing atmospheric plasma spraying on the surface of the pretreated brake disc substrate to obtain the brake disc coating with a thickness of 200 to 300 μm;

[0060] The pretreatment includes: sandblasting pretreatment, cleaning and drying the surface of the cast iron brake disc substrate in sequence; the sandblasting material used in the sandblasting pretreatment includes brown corundum sand, the compressed air pressure is 0.3-0.8 MPa; the angle between the spray gun and the surface of the brake disc substrate is 40-50 degrees; the cleaning includes cleaning with a degreasing agent;

[0061] The spraying distance in the atmospheric plasma spraying is 100-150 mm; the hydrogen flow rate of the plasma gas flow is 3-6 L / min; the argon flow rate is 30-50 L / min; the spraying current is 480-550 A; the spraying voltage is 50-60 V; the spray gun translation speed is 150-400 mm / s, and the spray gun translation spacing is 3 mm; the powder feeding speed is 2-10 g / min; the powder feeding method includes vertical jet powder feeding; and the number of repeated passes is 4-6 times.

[0062] The numerical range described in this application includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, this application no longer exhaustively lists the specific point values ​​included in the range.

[0063] Compared with the prior art, this application has the following beneficial effects:

[0064] (1) The high entropy alloy powder provided in this application has a high entropy effect due to its special BCC solid solution phase crystal structure, which greatly improves the solubility of the alloy system and the metal compound and improves the bonding strength between the alloy and the metal compound;

[0065] (2) The present application adopts gas atomization to prepare high entropy alloy powder, so that the obtained powder has good sphericity and ensures good fluidity of the powder during the spraying process;

[0066] (3) The high entropy alloy powder provided in this application has a diffusion hysteresis effect. In the supersaturated solid solution, a hard phase is easily precipitated and plays a role in dispersion strengthening. Moreover, the precipitated hard phase easily forms an oxidized protective glaze layer during the friction process of the coating, thereby significantly improving the friction performance of the coating.

[0067] (4) This application adopts plasma spraying technology to prepare the coating for brake discs, which has low cost and is suitable for industrial production. The prepared coating has the characteristics of high hardness, wear resistance and corrosion resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] This specification will be further described in the form of exemplary embodiments, which will be described in detail with reference to the accompanying drawings. These embodiments are not limiting, and in these embodiments, like numbers represent like structures, wherein:

[0069] FIG1 is an XRD pattern of a brake disc coating and a high entropy alloy powder provided in Example 3 of the present application;

[0070] FIG2 is a cross-sectional SEM image of the brake disc coating provided in Example 3 of the present application;

[0071] FIG3 is a SEM image of the coating surface after the friction test of the brake disc coating provided in Example 3 of the present application;

[0072] FIG4 is a SEM image of the coating surface after the corrosion test of the brake disc coating provided in Example 3 of the present application. DETAILED DESCRIPTION

[0073] The technical solution of the present application will be further described below with reference to the accompanying drawings and through specific implementation methods. Those skilled in the art should understand that the embodiments are only for the purpose of helping to understand the present application and should not be regarded as specific limitations of the present application.

[0074] The following examples and comparative examples provide friction and wear tests of the coatings using a GCr15 steel ball, a load of 10 N, a frequency of 4 Hz, a wear scar length of 5 m, and a total sliding distance of 100 m. In the corrosion tests, a CHI 604E electrochemical workstation was used to simulate the corrosion behavior of the alloy coating in seawater (3.5% NaCl solution).

[0075] Example 1

[0076] This embodiment provides a brake disc coating, wherein the raw material for preparing the brake disc coating is high entropy alloy powder; the preparation method of the brake disc coating comprises the following steps:

[0077] (1) Al powder, Co powder, Ni powder, Cu powder, and Ti powder were mixed in a molar ratio of 1:1:1:1:1:1, and then atomized and sifted to obtain a high entropy alloy powder with a particle size of 50 to 60 μm and a single BCC (Body-Centered Cubic) crystal structure;

[0078] The gas atomization powder making comprises: under the protection of inert gas, repeatedly smelting Al powder, Co powder, Ni powder, Cu powder and Ti powder with a purity of ≥99.9% for 4 times until the melt drips, and then using argon gas for high-pressure atomization;

[0079] The vacuum degree in the gas atomization powder making is 3×10 -4 Pa, the smelting power is 40KW, and the pressure of the high-pressure atomization is 8MPa;

[0080] (2) preheating the high entropy alloy powder obtained in step (1) to obtain an alloy powder to be used;

[0081] Wherein, the temperature of the preheating treatment is 200°C and the time is 180 minutes;

[0082] (3) The pre-treated brake disc substrate surface was subjected to atmospheric plasma spraying using the alloy powder to be used as raw material, and a thickness of 287 μm and a hardness of 309 HV were obtained. 0.1 The brake disc coating;

[0083] The pretreatment includes: sandblasting pretreatment, cleaning and drying the surface of the cast iron brake disc substrate in sequence; the sandblasting material used in the sandblasting pretreatment is 20# brown corundum sand, the compressed air pressure is 0.5MPa; the angle between the spray gun and the surface of the brake disc substrate is 45°; the cleaning includes cleaning with a degreasing agent;

[0084] The spraying distance in the atmospheric plasma spraying is 100 mm; the hydrogen flow rate of the plasma gas flow is 6 L / min; the argon flow rate is 40 L / min; the spraying current is 519 A; the spraying voltage is 55 V; the spray gun translation speed is 200 mm / s, and the spray gun translation spacing is 3 mm; the powder feeding speed is 2.5 g / min; the powder feeding method includes vertical jet powder feeding; and the number of repeated passes is 5 times.

[0085] Example 2

[0086] This embodiment provides a brake disc coating, wherein the raw material for preparing the brake disc coating is high entropy alloy powder; the preparation method of the brake disc coating comprises the following steps:

[0087] (1) Al powder, Co powder, Ni powder, Cu powder, and Ti powder were mixed in a molar ratio of 1:1:1:1:0.7, and then atomized and sifted to obtain a high entropy alloy powder with a particle size of 30 to 70 μm and a single BCC crystal structure;

[0088] The gas atomization powder making comprises: under the protection of inert gas, repeatedly smelting Al powder, Co powder, Ni powder, Cu powder and Ti powder with a purity of ≥99.9% for 3 times until the melt drips, and then using argon gas for high-pressure atomization;

[0089] The vacuum degree in the gas atomization powder making is 3.5×10 -4 Pa, the smelting power is 40KW, and the pressure of the high-pressure atomization is 7.5MPa;

[0090] (2) preheating the high entropy alloy powder obtained in step (1) to obtain an alloy powder to be used;

[0091] Wherein, the temperature of the preheating treatment is 180°C and the time is 200 minutes;

[0092] (3) The pre-treated brake disc substrate surface was subjected to atmospheric plasma spraying using the alloy powder to be used as raw material, and a thickness of 213 μm and a hardness of 257 HV were obtained. 0.1 The brake disc coating;

[0093] The pretreatment includes: sandblasting pretreatment, cleaning and drying the surface of the cast iron brake disc substrate in sequence; the sandblasting material used in the sandblasting pretreatment is 20# brown corundum sand, the compressed air pressure is 0.3MPa; the angle between the spray gun and the surface of the brake disc substrate is 40°; the cleaning includes cleaning with a degreasing agent;

[0094] The spraying distance in the atmospheric plasma spraying is 150 mm; the hydrogen flow rate of the plasma gas flow is 3 L / min; the argon flow rate is 50 L / min; the spraying current is 550 A; the spraying voltage is 60 V; the spray gun translation speed is 150 mm / s, and the spray gun translation spacing is 3 mm; the powder feeding speed is 2 g / min; the powder feeding method includes vertical jet powder feeding; and the number of repeated passes is 4 times.

[0095] Example 3

[0096] This embodiment provides a brake disc coating, wherein the raw material for preparing the brake disc coating is high entropy alloy powder; the preparation method of the brake disc coating comprises the following steps:

[0097] (1) Al powder, Co powder, Ni powder, Cu powder, and Ti powder were mixed in a molar ratio of 1:1:1:1:1.3, and then atomized and sifted to obtain a high entropy alloy powder with a particle size of 25 to 75 μm and a single BCC crystal structure;

[0098] The gas atomization powder making comprises: under the protection of inert gas, repeatedly smelting Al powder, Co powder, Ni powder, Cu powder and Ti powder with a purity of ≥99.9% for 5 times until the melt drips, and then using argon gas for high-pressure atomization;

[0099] The vacuum degree in the gas atomization powder making is 2.5×10 -4 Pa, the smelting power is 30KW, and the pressure of the high-pressure atomization is 8.5MPa;

[0100] (2) preheating the high entropy alloy powder obtained in step (1) to obtain an alloy powder to be used;

[0101] The preheating temperature is 230°C and the time is 150 min.

[0102] (3) The pre-treated brake disc substrate surface was subjected to atmospheric plasma spraying using the alloy powder to be used as raw material, and a thickness of 293 μm and a hardness of 321 HV were obtained. 0.1 The brake disc coating;

[0103] The pretreatment includes: sandblasting pretreatment, cleaning and drying the surface of the cast iron brake disc substrate in sequence; the sandblasting material used in the sandblasting pretreatment is 20# brown corundum sand, the compressed air pressure is 0.8MPa; the angle between the spray gun and the surface of the brake disc substrate is 50°; the cleaning includes cleaning with a degreasing agent;

[0104] The spraying distance in the atmospheric plasma spraying is 120 mm; the hydrogen flow rate of the plasma gas flow is 4.6 L / min; the argon flow rate is 30 L / min; the spraying current is 480 A; the spraying voltage is 50 V; the spray gun translation speed is 400 mm / s, and the spray gun translation spacing is 3 mm; the powder feeding speed is 10 g / min; the powder feeding method includes vertical jet powder feeding; and the number of repeated passes is 6 times.

[0105] The XRD patterns of the high entropy alloy powder and the brake disc coating provided in this embodiment are shown in FIG1 ; the cross-sectional SEM image of the brake disc coating is shown in FIG2 .

[0106] The SEM images of the coating surface after the friction test and the SEM images of the coating surface after the corrosion test of the brake disc coating provided in this embodiment are shown in FIG3 and FIG4 , respectively.

[0107] As shown in FIG3 , after friction, the brake disc coating provided in this embodiment has a very smooth friction surface with some small pits, and the wear marks are very shallow, and it is difficult to distinguish between the wear marks and the substrate, and the wear resistance is excellent.

[0108] As shown in FIG4 , the brake disc coating provided in this embodiment has a relatively smooth surface after corrosion, with less accumulation of corrosion products, only some small corrosion pits, fewer holes, and shallow corrosion depth, indicating good corrosion resistance.

[0109] The results of the friction and wear tests and corrosion tests on the brake disc coatings provided in Examples 1-3 are shown in Table 1.

[0110] Table 1

[0111] From the analysis of Table 1, it can be seen that the brake disc coating provided in the present application has excellent wear resistance and corrosion resistance; among them, the brake disc coating provided in Example 3 has the best wear resistance and corrosion resistance.

[0112] I. Effect of coating thickness on the performance of the brake disc coating

[0113] Example 4

[0114] This embodiment provides a coating for a brake disc. The raw material for preparing the coating for a brake disc is high entropy alloy powder. The preparation method of the coating for a brake disc differs from that of embodiment 3 only in that:

[0115] In this embodiment, the spraying distance in the atmospheric plasma spraying in step (3) is modified to 110 mm, and the hydrogen flow rate of the plasma gas flow is modified to 3 L / min.

[0116] The thickness of the brake disc coating prepared in this embodiment is 275 μm.

[0117] Example 5

[0118] This embodiment provides a coating for a brake disc. The raw material for preparing the coating for a brake disc is high entropy alloy powder. The preparation method of the coating for a brake disc differs from that of embodiment 3 only in that:

[0119] In this embodiment, the spraying distance in the atmospheric plasma spraying in step (3) is modified to 130 mm, and the hydrogen flow rate of the plasma gas flow is modified to 4 L / min.

[0120] The thickness of the brake disc coating prepared in this embodiment is 269 μm.

[0121] Example 6

[0122] This embodiment provides a coating for a brake disc. The raw material for preparing the coating for a brake disc is high entropy alloy powder. The preparation method of the coating for a brake disc differs from that of embodiment 3 only in that:

[0123] In this embodiment, the spraying distance in the atmospheric plasma spraying in step (3) is modified to 150 mm, and the hydrogen flow rate of the plasma gas flow is modified to 5 L / min.

[0124] The thickness of the brake disc coating prepared in this embodiment is 253 μm.

[0125] Example 7

[0126] This embodiment provides a coating for a brake disc. The raw material for preparing the coating for a brake disc is high entropy alloy powder. The preparation method of the coating for a brake disc differs from that of embodiment 3 only in that:

[0127] In this embodiment, the spraying distance in the atmospheric plasma spraying in step (3) is modified to 200 mm, and the hydrogen flow rate of the plasma gas flow is modified to 5.5 L / min.

[0128] The thickness of the brake disc coating prepared in this embodiment is 190 μm.

[0129] Example 8

[0130] This embodiment provides a coating for a brake disc. The raw material for preparing the coating for a brake disc is high entropy alloy powder. The preparation method of the coating for a brake disc differs from that of embodiment 3 only in that:

[0131] In this embodiment, the spraying distance in the atmospheric plasma spraying in step (3) is modified to 95 mm, and the hydrogen flow rate of the plasma gas flow is modified to 6.5 L / min.

[0132] The thickness of the brake disc coating prepared in this embodiment is 305 μm.

[0133] The results of the friction and wear tests and corrosion tests on the brake disc coatings provided in Example 3 and Examples 4-8 are shown in Table 2.

[0134] Table 2

[0135] According to Table 2, it can be seen that when the coating thickness is between 250 and 300 μm, the brake disc coating has excellent wear resistance and corrosion resistance. Example 3 has the highest coating thickness and provides the best wear resistance and corrosion resistance. Therefore, it can be seen that the higher the coating thickness, the better the wear resistance and corrosion resistance.

[0136] However, analysis of Examples 3 and 8 shows that when the coating thickness is too large, the wear resistance and corrosion resistance of the coating do not continue to improve. Analysis of Examples 6 and 7 shows that when the coating thickness is too small, the wear rate and self-corrosion current density increase significantly.

[0137] Therefore, this application requires strict control of the thickness of the brake disc coating to ensure that it has better wear resistance and corrosion resistance.

[0138] II. Effect of High Entropy Alloy Powder Particle Size on the Performance of the Brake Disc Coating

[0139] Example 9

[0140] This embodiment provides a coating for a brake disc. The raw material for preparing the coating for a brake disc is high entropy alloy powder. The preparation method of the coating for a brake disc differs from that of embodiment 3 only in that:

[0141] In this embodiment, the particle size of the high entropy alloy powder obtained by gas atomization pulverization in step (1) is modified to 80-90 μm.

[0142] Example 10

[0143] This embodiment provides a coating for a brake disc. The raw material for preparing the coating for a brake disc is high entropy alloy powder. The preparation method of the coating for a brake disc differs from that of embodiment 3 only in that:

[0144] In this embodiment, the particle size of the high entropy alloy powder obtained by gas atomization pulverization in step (1) is modified to 25-40 μm.

[0145] Example 11

[0146] This embodiment provides a coating for a brake disc. The raw material for preparing the coating for a brake disc is high entropy alloy powder. The preparation method of the coating for a brake disc differs from that of embodiment 3 only in that:

[0147] In this embodiment, the particle size of the high entropy alloy powder obtained by gas atomization pulverization in step (1) is modified to ≤10 μm.

[0148] The results of the friction and wear tests and corrosion tests on the brake disc coatings provided in Example 3 and Examples 9-11 are shown in Table 3.

[0149] Table 3

[0150] Analysis of Table 3 shows that the particle size selection of the high entropy alloy powder in the preparation method provided in this application will affect the wear resistance and corrosion resistance of the brake disc coating;

[0151] Analysis of Example 3 and Example 9 shows that when the particle size of the selected high entropy alloy powder is too large, the wear resistance and corrosion resistance of the brake disc coating are both reduced; Analysis of Example 3 and Example 10 shows that when the particle size of the selected high entropy alloy powder is further reduced, the wear resistance and corrosion resistance are slightly improved, and the wear rate, self-corrosion current density and self-corrosion potential change less. This is because the raw material powder with a finer particle size has a higher speed and temperature during the spraying process, resulting in a stronger coating density, smaller surface porosity, fewer boundary defects, and better wear resistance. However, if the raw material size is too small (such as Example 11), the fracture toughness of the coating may be affected, and the smaller the particle size, the more complicated the powder making process and the higher the cost, so a suitable particle size is selected to make its comprehensive performance better.

[0152] III. Influence of the process on the performance of the brake disc coating

[0153] Example 12

[0154] This embodiment provides a coating for a brake disc. The raw material for preparing the coating for a brake disc is high entropy alloy powder. The preparation method of the coating for a brake disc differs from that of embodiment 3 only in that:

[0155] In this embodiment, the gas atomization powder preparation in step (1) is modified into a ball milling and mechanical alloying process performed sequentially.

[0156] The results of the friction and wear tests and corrosion tests on the brake disc coatings provided in Examples 3 and 12 are shown in Table 4.

[0157] Table 4

[0158] From the analysis of Table 4, it can be seen that compared with Example 3, the wear resistance and corrosion resistance of the coating provided in Example 12 are both reduced. It can be seen that the aerosol powder preparation provided by the present application can better ensure the fluidity of the powder during the spraying process, thereby ensuring the uniformity of the coating and the bonding strength with the metal compound, so as to achieve the purpose of improving the wear resistance and corrosion resistance of the coating.

[0159] IV. Effect of the Element Ratio of High Entropy Alloy Powder on the Performance of the Brake Disc Coating

[0160] Comparative Example 1

[0161] This comparative example provides a brake disc coating, wherein the raw material for preparing the brake disc coating is high entropy alloy powder; the preparation method of the brake disc coating differs from that of Example 3 only in that:

[0162] In this comparative example, the molar ratio of the metal elements Al, Co, Ni, Cu and Ti in the high entropy alloy powder described in step (1) was modified to 1:1:1:1:0.5.

[0163] Comparative Example 2

[0164] This comparative example provides a brake disc coating, wherein the raw material for preparing the brake disc coating is high entropy alloy powder; the preparation method of the brake disc coating differs from that of Example 3 only in that:

[0165] In this comparative example, the molar ratio of the metal elements Al, Co, Ni, Cu and Ti in the high entropy alloy powder described in step (1) is modified to 1:1:1:1:1.5.

[0166] The results of the friction and wear tests and corrosion tests on the brake disc coatings provided in Example 3 and Comparative Examples 1-2 are shown in Table 5.

[0167] Table 5

[0168] The molar ratio of the metal elements in the alloy powders provided in Comparative Examples 1 and 2 does not meet the high entropy requirement. The Ti powder content in the alloy powder provided in Comparative Example 1 is significantly reduced. Compared with Example 3, its corrosion resistance is improved, but its wear resistance is also significantly reduced.

[0169] The Ti powder content in the alloy powder provided in Comparative Example 2 is significantly increased, and compared with Example 3, its wear resistance and corrosion resistance are reduced (its self-corrosion potential is only 85% of the coating described in Example 3).

[0170] Therefore, this application requires strict control of the content of each metal element in the high-entropy alloy powder so that the brake disc coating has better wear resistance and corrosion resistance.

[0171] V. Effect of High Entropy Alloy Powder Type on the Performance of the Brake Disc Coating

[0172] Comparative Example 3

[0173] This comparative example provides a brake disc coating, wherein the raw material for preparing the brake disc coating is high entropy alloy powder; the preparation method of the brake disc coating differs from that of Example 3 only in that:

[0174] In this comparative example, the raw materials of the high entropy alloy powder described in step (1) are modified to Al powder, Co powder, Ni powder, Cu powder, Ti powder and Zr powder, and the molar ratio of the metal elements Al, Co, Ni, Cu, Ti and Zr is 1:1:1:1:1:1.

[0175] Comparative Example 4

[0176] This comparative example provides a brake disc coating, wherein the raw material for preparing the brake disc coating is high entropy alloy powder; the preparation method of the brake disc coating differs from that of Example 3 only in that:

[0177] In this comparative example, the raw materials of the high entropy alloy powder in step (1) are modified to Al powder, Co powder, Ni powder, Cr powder, Ti powder and Si powder, and the molar ratio of the metal elements Al, Co, Ni, Cr, Ti and Si is 1:1:1:1:1:1.

[0178] Comparative Example 5

[0179] This comparative example provides a brake disc coating, wherein the raw material for preparing the brake disc coating is high entropy alloy powder; the preparation method of the brake disc coating differs from that of Example 3 only in that:

[0180] In this comparative example, the raw materials of the high entropy alloy powder in step (1) are modified to Al powder, Co powder, Ni powder and Cu powder, and the molar ratio of the metal elements Al, Co, Ni and Cu is 1:1:1:1.

[0181] Comparative Example 6

[0182] This comparative example provides a brake disc coating, wherein the raw material for preparing the brake disc coating is high entropy alloy powder; the preparation method of the brake disc coating differs from that of Example 3 only in that:

[0183] In this comparative example, the raw materials of the high entropy alloy powder in step (1) are modified to Al powder, Co powder, Ni powder, Cu powder and Cr powder, and the molar ratio of the metal elements Al, Co, Ni, Cu and Cr is 1:1:1:1:1.

[0184] Comparative Example 7

[0185] This comparative example provides a brake disc coating, wherein the raw material for preparing the brake disc coating is high entropy alloy powder; the preparation method of the brake disc coating differs from that of Example 3 only in that:

[0186] In this comparative example, the raw materials of the high entropy alloy powder in step (1) are modified to Al powder, Co powder, Ni powder, Cu powder, Ti powder and Cr powder, and the molar ratio of the metal elements Al, Co, Ni, Cu, Ti and Cr is 1:1:1:1:1:1.

[0187] The results of the friction and wear tests and corrosion tests on the brake disc coatings provided in Example 3 and Comparative Examples 3-7 are shown in Table 6.

[0188] Table 6

[0189] Compared with Example 3, the high-entropy alloy powder provided in Comparative Example 3 adds Zr powder. The addition of Zr powder slightly improves the wear resistance of the alloy coating, but significantly reduces the corrosion resistance of the coating (the corrosion test results show that the surface self-corrosion current density is 1.5 times that of the coating in Example 3, and the self-corrosion potential is only 4 / 5 of that of the coating in Example 3).

[0190] Compared with Example 3, the high-entropy alloy powder provided in Comparative Example 4 adds Si powder. The increase of Si powder makes its wear rate slightly lower than that of Example 3, but its corrosion test results show that the surface self-corrosion current density reaches 1.5 times that of the coating described in Example 3, and the self-corrosion potential is only 4 / 5 of that of the coating described in Example 3. The corrosion resistance is quite different from that of Example 3.

[0191] Compared with Example 3, the high entropy alloy powder provided in Comparative Example 5 lacks Ti powder. Metal Ti has properties such as high strength and corrosion resistance. The lack of Ti powder will cause the wear resistance and corrosion resistance of the alloy to be greatly reduced.

[0192] Compared with Example 3, the high-entropy alloy powder provided in Comparative Example 6 is replaced with Cr powder by Ti powder. Compared with Comparative Example 5, its wear resistance and corrosion resistance are improved, but the addition of Cr powder does not achieve the effect of adding Ti powder, indicating that the addition of Ti powder is more helpful in obtaining the wear resistance and corrosion resistance of the alloy described in this application.

[0193] Compared with Example 3, Cr powder is added to the high-entropy alloy powder provided in Comparative Example 7. Those skilled in the art know that metal Cr has excellent corrosion resistance. However, analysis of Example 3 and Comparative Example 7 shows that the corrosion resistance of the brake disc coating obtained by adding Cr powder with high corrosion resistance does not reach the effect of Example 3, indicating that the addition of Cr powder will affect the corrosion resistance of the brake disc coating.

[0194] Therefore, this application requires strict control of the types of elements in the high-entropy alloy powder so that the brake disc coating has better wear resistance and corrosion resistance.

[0195] The applicant declares that the above is only a specific implementation method of the present application, but the protection scope of the present application is not limited thereto. Technical personnel in the relevant technical field should understand that any changes or substitutions that can be easily thought of by technical personnel in the relevant technical field within the technical scope disclosed in this application fall within the protection scope and disclosure scope of this application.

Claims

1. A coating for a brake disc, characterized in that: The brake disc coating is prepared by using high entropy alloy powder; the raw materials for preparing the high entropy alloy powder are composed of Al powder, Co powder, Ni powder, Cu powder and Ti powder; The molar ratio of the metal elements Al, Co, Ni, Cu and Ti in the high entropy alloy powder is 1:1:1:1:(1.0-1.3); The high entropy alloy powder has a single BCC (Body-Centered Cubic) crystal structure.

2. The brake disc coating according to claim 1, wherein: The particle size of the high entropy alloy powder is 25-75 μm, and the purity of the Al powder, Co powder, Ni powder, Cu powder and Ti powder is ≥99.9%.

3. The brake disc coating according to claim 1, wherein: The thickness of the brake disc coating is 200 to 300 μm.

4. The brake disc coating according to claim 3, wherein: The thickness of the brake disc coating is 250 to 300 μm.

5. A method for preparing a brake disc coating according to any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: (1) Al powder, Co powder, Ni powder, Cu powder, and Ti powder are mixed in molar ratio, and then atomized and sifted to obtain high entropy alloy powder; (2) preheating the high entropy alloy powder obtained in step (1) to obtain an alloy powder to be used; (3) Using the alloy powder to be used as a raw material, atmospheric plasma spraying is performed on the surface of the pretreated brake disc substrate to obtain the brake disc coating.

6. The preparation method according to claim 5, characterized in that The gas atomization powder making in step (1) comprises: under the protection of inert gas, repeatedly smelting Al powder, Co powder, Ni powder, Cu powder and Ti powder until the melt drips, and then performing high-pressure atomization.

7. The preparation method according to claim 6, characterized in that The vacuum degree in the gas atomization powder making is 2.5×10 -4 ~3.5×10 -4 Pa, the smelting power is 30-40KW, the number of repeated smelting is 3-5 times, the gas used for the high-pressure atomization includes argon, and the pressure of the high-pressure atomization is 7.5-8.5MPa.

8. The preparation method according to claim 5, characterized in that The temperature of the preheating treatment in step (2) is 180 to 230° C., and the time of the preheating treatment in step (2) is 150 to 200 minutes.

9. The preparation method according to claim 5, characterized in that The pretreatment in step (3) includes: sandblasting pretreatment, cleaning and drying the surface of the brake disc substrate in sequence.

10. The preparation method according to claim 9, characterized in that The sandblasting material used in the sandblasting pretreatment includes brown corundum sand.

11. The preparation method according to claim 10, characterized in that: The particle size of the brown corundum sand is any one of 16#, 18#, 20#, 22# or 24#, or a combination of at least two of them.

12. The preparation method according to claim 9, characterized in that The compressed air pressure in the sandblasting pretreatment is 0.3-0.8 MPa.

13. The preparation method according to claim 9, characterized in that In the sandblasting pretreatment, the angle between the spray gun and the surface of the brake disc substrate is 40-50 degrees.

14. The preparation method according to claim 9, characterized in that The cleaning includes using a degreasing agent for cleaning.

15. The preparation method according to claim 5, characterized in that The brake disc substrate is made of cast iron.

16. The preparation method according to claim 5, characterized in that In the atmospheric plasma spraying in step (3), the spraying distance is 100-150 mm, the spray gun translation speed is 150-400 mm / s, the spray gun translation spacing is 3 mm, and the atmospheric plasma spraying is repeated 4-6 times.

17. The preparation method according to claim 5, characterized in that In the atmospheric plasma spraying in step (3), the argon flow rate is 30 to 50 L / min, and the hydrogen flow rate of the plasma gas flow is 3 to 6 L / min.

18. The preparation method according to claim 5, characterized in that The spraying current in the atmospheric plasma spraying in step (3) is 480-550A, and the spraying voltage is 50-60V.

19. The preparation method according to claim 5, characterized in that The powder feeding speed in the atmospheric plasma spraying in step (3) is 2 to 10 g / min, and the powder feeding method includes vertical jet powder feeding.

20. The preparation method according to claim 5, characterized in that The preparation method comprises the following steps: (1) Al powder, Co powder, Ni powder, Cu powder, and Ti powder are mixed in molar ratio, and then atomized and pulverized to obtain a high entropy alloy powder with a particle size of 25 to 75 μm after sieving; The gas atomization powder making comprises: under the protection of inert gas, repeatedly smelting Al powder, Co powder, Ni powder, Cu powder and Ti powder with a purity of ≥99.9% for 3 to 5 times until the melt drips, and then using argon gas for high-pressure atomization; The vacuum degree in the gas atomization powder making is 2.5×10 -4 ~3.5×10 -4 Pa, the smelting power is 30-40KW, and the pressure of the high-pressure atomization is 7.5-8.5MPa; (2) preheating the high entropy alloy powder obtained in step (1) to obtain an alloy powder to be used; Wherein, the temperature of the preheating treatment is 180-230°C and the time is 150-200 minutes; (3) using the alloy powder to be used as a raw material, performing atmospheric plasma spraying on the surface of the pretreated brake disc substrate to obtain the brake disc coating with a thickness of 200 to 300 μm; The pretreatment includes: sandblasting pretreatment, cleaning and drying the surface of the cast iron brake disc substrate in sequence; the sandblasting material used in the sandblasting pretreatment includes brown corundum sand, the compressed air pressure is 0.3-0.8 MPa; the angle between the spray gun and the surface of the brake disc substrate is 40-50 degrees; the cleaning includes cleaning with a degreasing agent; The spraying distance in the atmospheric plasma spraying is 100-150 mm; the hydrogen flow rate of the plasma gas flow is 3-6 L / min; the argon flow rate is 30-50 L / min; the spraying current is 480-550 A; the spraying voltage is 50-60 V; the spray gun translation speed is 150-400 mm / s, and the spray gun translation spacing is 3 mm; the powder feeding speed is 2-10 g / min; the powder feeding method includes vertical jet powder feeding; and the number of repeated passes is 4-6 times.

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