A copper alloy - ductile iron bimetallic wear - resistant and friction - reducing component and its preparation method

Abstract

The present invention is applicable to the technical field of wear-resistant and friction-reducing components, and provides a copper alloy-spheroidal graphite cast iron bimetallic wear-resistant and friction-reducing component and a preparation method thereof. Through laser additive manufacturing technology, a wear-resistant and friction-reducing layer powder composed of copper alloy spherical powder and reinforcing phase powder is melted and solidified layer by layer on the surface of spheroidal graphite cast iron to prepare a copper alloy wear-resistant and friction-reducing layer. Subsequently, ultrasonic rolling technology is used to mechanically strengthen the surface of the copper alloy wear-resistant and friction-reducing layer, thereby improving the wear resistance and friction-reducing performance of the copper alloy-spheroidal graphite cast iron bimetallic component. The copper alloy-spheroidal graphite cast iron bimetallic wear-resistant and friction-reducing component of the present invention not only has excellent wear resistance and friction-reducing performance, but also has good bonding between the copper alloy wear-resistant and friction-reducing layer and the spheroidal graphite cast iron matrix, and can meet the use requirements of the friction pair of high-pressure piston pumps.

Description

Technical Field

[0001] The present invention belongs to the technical field of wear-resistant and friction-reducing components, and particularly relates to a copper alloy - ductile iron bimetallic wear-resistant and friction-reducing component and a preparation method thereof. Background Art

[0002] In hydraulic systems such as high-pressure piston pumps, friction pair components (such as pistons, sleeves, etc.) need to withstand the severe challenges of high load, high speed, and complex working conditions, posing extremely high requirements for the wear resistance, friction reduction performance, fatigue resistance, and thermal stability of materials. As the core component of the hydraulic system, the performance of the piston pump directly determines the efficiency and reliability of the entire equipment. Therefore, how to improve the material properties of friction pair components, especially to ensure their stability under high pressure, high speed, and extreme working conditions, has become an important technical problem in the development of the hydraulic industry.

[0003] Most friction pair components in hydraulic systems adopt a copper alloy - steel bimetallic structure. Due to its excellent wear resistance, friction reduction performance, and corrosion resistance, copper alloy is widely used in the contact surface of the friction pair; steel is usually used as the matrix material because of its high strength and good impact resistance. At present, the processing technologies of copper alloy - steel bimetallic components mainly include fusion welding, gas welding, brazing, explosion welding, thermal spraying, solid-state diffusion welding, casting, mechanical inlay, vapor deposition, and powder metallurgy sintering. Under conventional working conditions of high pressure, low speed, and small temperature changes, copper alloy - steel bimetallic components can provide ideal wear resistance and friction reduction performance, meeting the application requirements of most low-load or relatively stable working environments in hydraulic systems; however, under long-term high load, high pressure, high speed, and complex working conditions, the impact resistance and dimensional stability of the steel matrix are often insufficient, which may lead to misalignment between the contact surfaces, reducing the sealing performance, and further causing faults such as insufficient flow, low pressure in the pump body, overheating, or jamming. In addition, the flow vibration and pressure pulsation in the hydraulic system may cause the fixing components to loosen, inducing resonance phenomena, thereby accelerating the damage of the hydraulic system, and seriously affecting the performance and service life of the whole machine in severe cases. To break through this bottleneck, the application of copper alloy - ductile iron bimetallic components has gradually become the focus of attention in the field of high-end hydraulic component manufacturing. Ductile iron not only has high strength, high plasticity, and excellent toughness, but also has excellent shock absorption and energy absorption capabilities, wear resistance, heat resistance, and corrosion resistance. Compared with steel, ductile iron shows higher stability and reliability under extreme working conditions such as high temperature, low temperature, impact, and vibration; replacing steel with ductile iron for friction pair components in the piston pump assembly not only significantly improves the strength, wear resistance, and shock absorption performance of the components, but also realizes multiple advantages of weight reduction and noise reduction while maintaining high dimensional accuracy; the application of copper alloy - ductile iron bimetallic components not only improves the overall performance of the hydraulic system, but also reduces its operating cost and maintenance cost to a certain extent.

[0004] The manufacturing of copper alloy-ductile iron bimetallic components faces many technical difficulties. The main challenges come from the significant differences in the physical, chemical and mechanical properties of the two materials. Since copper alloy and ductile iron have obvious differences in expansion coefficient, melting temperature and fluidity, during hot working processes such as welding and casting, the connection between the two often has defects such as pores, cracks and hardened structure, which seriously affect the mechanical properties and long-term stability of the bimetallic components; in addition, the difference in expansion coefficient may induce thermal stress during the cooling process, thereby leading to the formation of interface cracks. Ductile iron is very easy to form hardened quenching structure during the cooling stage of hot working. The presence of this structure will further reduce the bonding strength of the composite layer, especially under high temperature or high pressure environment. If these defects are not effectively controlled, it may lead to the failure of copper alloy-ductile iron bimetallic components.

[0005] In view of the difficulties and defects in the above-mentioned manufacturing process, laser additive manufacturing technology, as a high-precision and high-efficiency manufacturing method, provides a feasible solution for the preparation of copper alloy-ductile iron bimetallic composite parts. Laser additive manufacturing technology has unique advantages such as one-time forming, moldless forming and high material utilization rate, and can flexibly meet the manufacturing needs of complex structural parts; by accurately designing the composition of copper alloy powder and optimizing additive manufacturing process parameters, laser additive manufacturing technology can achieve the regulation of the wear resistance, friction reduction and strength of the copper alloy layer. However, how to use laser additive manufacturing technology to overcome the performance differences between materials and ensure the stability and reliability of copper alloy-ductile iron bimetallic parts under extreme working conditions, so as to meet the use needs of hydraulic components, is still a key issue that needs to be solved urgently. Summary of the invention

[0006] The purpose of the embodiments of the present invention is to provide a method for preparing a copper alloy-ductile iron bimetallic wear-resistant and friction-reducing component, aiming to solve the problems raised in the above-mentioned background technology.

[0007] The embodiment of the present invention is implemented as follows: a method for preparing a copper alloy-ductile iron bimetallic wear-resistant and friction-reducing component comprises the following steps:

[0008] Treat the surface of ductile iron and smooth the surface;

[0009] Place the processed ductile iron in a sealed chamber, adjust the powder feeding speed of the wear-resistant and friction-reducing layer powder to 5-8 g / min, and heat the ductile iron to 150-200 °C through a preheating platform at the same time; wherein, the wear-resistant and friction-reducing layer powder includes 6%-8% of reinforcing phase powder by mass percentage, and the rest is copper alloy spherical powder; the reinforcing phase powder includes 13%-15% of lanthanum hexaboride ceramic powder by mass percentage, and the rest is nickel-coated graphite powder; the copper alloy spherical powder includes the following raw materials by mass percentage: Cr 1%-1.5%, Ni 0.5%-1.2%, Zr 0.2%-0.4%, Si 0.1%-0.3%, Nb 0.01%-0.02%, and the balance is Cu;

[0010] Under the process parameters of a laser power of 800-1000 W, a scanning speed of 6-8 mm / s, a defocus amount of 0, and an overlap rate of 40%-50%, use laser additive manufacturing technology to stack copper alloy layer by layer on the surface of ductile iron to form a copper alloy wear-resistant and friction-reducing layer;

[0011] Perform a leveling treatment on the copper alloy layer and an ultrasonic rolling treatment to obtain a copper alloy-ductile iron bimetallic wear-resistant and friction-reducing component.

[0012] Preferably, the copper alloy spherical powder is prepared by a gas atomization method, and the prepared copper alloy spherical powder has a particle size of 50-150 μm and a loose bulk density of 4-4.5 g / cm 3 , and a fluidity of 17.0-18.0 s / 50 g.

[0013] Preferably, the nickel-coated graphite powder has a particle size of 50-150 μm and a nickel coating thickness of 1-5 μm; the lanthanum hexaboride ceramic powder has a particle size of 150-300 nm; the preparation method of the reinforcing phase powder is: pour the nickel-coated graphite powder and lanthanum hexaboride ceramic powder into a vacuum ball mill for ball milling treatment to make the nickel-coated graphite powder and lanthanum hexaboride ceramic powder evenly mixed to obtain the reinforcing phase powder.

[0014] Preferably, the preparation method of the wear-resistant and friction-reducing layer powder is: pour the copper alloy powder and the reinforcing phase powder into a vacuum ball mill for ball milling treatment, perform a sieving treatment on the ball-milled powder, control the powder particle size to be 50-150 μm, and then perform a vacuum drying treatment on the sieved powder.

[0015] Preferably, in the step of stacking copper alloy layer by layer on the surface of ductile iron by using laser additive manufacturing technology, stack 5-7 layers, and the thickness of the copper alloy wear-resistant and friction-reducing layer is 4-5 mm.

[0016] Preferably, the process parameters of the ultrasonic rolling treatment are as follows: rolling speed 400 - 500 mm / min, step distance 0.1 - 0.3 mm, reduction 0.05 - 0.08 mm, static pressure 0.5 - 0.8 MPa, and ultrasonic frequency 22 - 25 kHz.

[0017] Another object of the embodiment of the present invention is to provide a copper alloy - ductile iron bimetallic wear - resistant and friction - reducing component, which is prepared by the above - mentioned preparation method.

[0018] The preparation method of a copper alloy - ductile iron bimetallic wear - resistant and friction - reducing component provided by the embodiment of the present invention avoids the formation of white - mouth structure and cracks due to the influence of rapid heating and cooling on ductile iron during the laser additive manufacturing process through pre - welding preheating. The micro - hardness of the copper alloy wear - resistant and friction - reducing layer prepared by the laser additive technology can reach 111.6 - 175.3 HV. Selecting GCr15 steel as the counter - friction pair, the dry friction coefficient of the wear - resistant and friction - reducing layer on the copper alloy surface is measured to be 0.11 - 0.34. The copper alloy - ductile iron bimetallic wear - resistant and friction - reducing component prepared by the preparation method of the embodiment of the present invention not only has excellent wear - resistance and friction - reducing performance, but also has good bonding between the copper alloy wear - resistant and friction - reducing layer and the ductile iron matrix, and can meet the use requirements of the friction pair of high - pressure piston pumps;

[0019] The copper alloy - ductile iron bimetallic wear - resistant and friction - reducing component prepared by the laser additive manufacturing technology has great potential for customization, can flexibly meet the requirements of complex structural parts. Through precise design and manufacturing, the processing cycle can be shortened, and the material consumption and manufacturing cost can be effectively reduced, opening up a new path for the wide application of this technology in the industrial field. Description of the Drawings

[0020] Figure 1 It is the micro - structure photograph of the copper alloy wear - resistant and friction - reducing layer in the copper alloy - ductile iron bimetallic wear - resistant and friction - reducing component prepared in Example 6 of the present invention;

[0021] Figure 2 It is the micro - structure photograph of the copper alloy - ductile iron interface in the copper alloy - ductile iron bimetallic wear - resistant and friction - reducing component prepared in Example 6 of the present invention;

[0022] Figure 3 It is the dry friction coefficient curve of the copper alloy wear - resistant and friction - reducing layer in the copper alloy - ductile iron bimetallic wear - resistant and friction - reducing component prepared in Example 6 of the present invention. Detailed Embodiments

[0023] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0024] In the embodiment of the present invention, considering that ductile iron has a relatively high carbon content and is prone to white-mouth tendency under the action of laser thermal cycle, resulting in cracks at the interface. To avoid this phenomenon during the laser additive manufacturing process, the ductile iron is preheated to prevent the formation of white-mouth structure in subsequent laser cladding. In addition, copper has a relatively weak absorption capacity for laser. By adding elements such as Cr, Ni, Zr, Si, and Nb, the embodiment of the present invention can significantly improve the laser absorption rate of the copper alloy and enhance its strength. However, the high solid solubility of these elements in copper will lead to a decrease in the thermal conductivity of the copper alloy. The added nano-sized lanthanum hexaboride particles in the embodiment of the present invention have a relatively low melting point and a small agglomeration tendency in liquid copper. During the laser melting process, the lanthanum hexaboride particles will dissolve in the molten pool and play a role in refining grains and enhancing the thermal conductivity of the copper alloy during the solidification process. In addition, the addition of nickel-coated graphite powder can further improve the friction and wear performance of the copper alloy. The metal nickel layer on its surface can prevent the excessive decomposition of graphite under the action of laser heat and avoid the adverse effects of excessive carbon elements on the performance of the copper alloy;

[0025] The copper alloy layer obtained by laser additive manufacturing exhibits as-cast microstructure characteristics, with a relatively loose structure and prone to defects such as pores, spheroidization, and cracks inside. Therefore, the embodiment of the present invention performs ultrasonic rolling on the copper alloy cladding layer of laser additive manufacturing. By introducing severe plastic deformation, the porosity can be reduced and the grains can be refined, thereby improving the service strength of the copper alloy surface.

[0026] The following describes the specific implementation of the present invention in detail with specific embodiments.

[0027] Embodiment 1. A copper alloy-ductile iron bimetallic wear-resistant and friction-reducing component, and its preparation method includes the following steps:

[0028] (1) Prepare copper alloy spherical powder: Prepared by gas atomization method. The copper alloy spherical powder contains the following elements in mass percentage (Wt%): Cr 1-1.5%, Ni 0.5-1.2%, Zr 0.2-0.4%, Si 0.1-0.3%, Nb 0.01-0.02%, and the balance is Cu. The prepared copper alloy spherical powder needs to meet the following standards: the particle size is 50-150 μm, the loose bulk density is 4-4.5 g / cm 3 , and the fluidity is 17.0-18.0 s / 50 g;

[0029] (2)Preparation of reinforcing phase powder: Pour nickel-coated graphite powder and lanthanum hexaboride ceramic powder into a vacuum ball milling tank, and ball mill for 3 hours using the vacuum ball milling tank to uniformly mix the two powders; by mass percentage (Wt%), the lanthanum hexaboride ceramic powder is 13 - 15%, and the rest is nickel-coated graphite powder. The particle size of the nickel-coated graphite powder is 50 - 150 μm, the nickel layer thickness is 1 - 5 μm, and the particle size of the lanthanum hexaboride ceramic powder is 150 - 300 nm;

[0030] (3)Preparation of wear-resistant and friction-reducing layer powder: Pour copper alloy spherical powder and reinforcing phase powder into a vacuum ball milling tank. By mass percentage (Wt / %), the reinforcing phase powder is 6 - 8%, and the rest is copper alloy spherical powder. After vacuum ball milling for 3 hours, screen the mixed powder to ensure that the particle size of the mixed powder is 50 - 150 μm. Put the screened mixed powder into a vacuum drying oven, evacuate to a vacuum degree of 5×E -1 Pa, adjust the heat preservation temperature to 70 °C, and the heat preservation time to 20 min to fully dry the mixed powder;

[0031] (4)Perform mechanical and chemical treatments on the surface of the ductile iron to remove oil stains, oxides, and flatten the plate surface. Then place the ductile iron in a closed chamber, and place a heating platform that can preheat the ductile iron and a laser powder feeding head that can move freely in the rectangular coordinate system in the chamber. Fill the chamber with argon with a purity of 99.99% to prevent oxidation of the copper alloy during the laser additive manufacturing process;

[0032] (5)The laser additive manufacturing technology is realized through a powder feeding device and a fiber laser. The specific process is as follows: Pour the wear-resistant and friction-reducing layer powder into the powder bin of the powder feeding device, adjust the powder feeding speed to 8 g / min, and preheat the ductile iron using the preheating platform in the closed chamber. The preheating temperature is 200 °C. Using the ductile iron as the substrate, use the laser additive manufacturing technology to stack copper alloy layer by layer on its surface. The laser additive manufacturing process parameters are: laser power 1000 W, scanning speed 8 mm / s, defocus amount 0, and ensure that the laser focus and the powder focus of the powder feeding head are the same point. Each layer of copper alloy is composed of copper alloy formed by parallel multi-pass laser additive manufacturing. The overlap rate of each pass of laser is 50%, the residence time between each pass is 1 min, the protective gas is argon with a purity of 99.99%, and the gas flow rate is 15 L / min. Use this process to prepare 5 layers of copper alloy vertically layer by layer. The total thickness of the prepared copper alloy wear-resistant and friction-reducing layer is 4 - 5 mm;

[0033] (6)Mechanically polish and flatten the copper alloy wear-resistant and friction-reducing layer obtained on the surface of the ductile iron, and perform ultrasonic rolling treatment. Finally, form a copper alloy - ductile iron bimetallic wear-resistant and friction-reducing component. The ultrasonic rolling parameters are: rolling rate 500 mm / min, step distance 0.3 mm, reduction 0.05 mm, static pressure 0.5 MPa, and ultrasonic frequency 25 kHz.

[0034] Comparative Example 1: Compared with Example 1, the difference lies in that the wear-resistant and friction-reducing layer powder used is 100% copper alloy spherical powder, and other steps and parameters remain unchanged.

[0035] Performance test:

[0036] Based on the preparation method of Example 1, the added masses of nickel-coated graphite powder, lanthanum hexaboride ceramic powder, and copper alloy spherical powder were adjusted, and other steps and parameters remained unchanged. Five groups of experiments were carried out to obtain Examples 2 - 6. The hardness and friction coefficient of the copper alloy wear-resistant and friction-reducing layer of the prepared samples (selecting GCr15 steel as the counterbody) were analyzed and compared with the hardness and friction coefficient of the copper alloy layer of the sample prepared in Comparative Example 1. The results are shown in Table 1:

[0037] Table 1

[0038]

[0039] The sample prepared in Example 6 was analyzed, and the microstructural photograph of the copper alloy wear-resistant and friction-reducing layer is as Figure 1 shown, the microstructural photograph of the copper alloy - ductile iron interface is as Figure 2 shown, and the dry friction coefficient curve of the copper alloy wear-resistant and friction-reducing layer is as Figure 3 shown. According to Figure 1 and Figure 2 , it can be seen that the copper alloy wear-resistant and friction-reducing layer has good bonding with the ductile iron matrix and has no defects such as cracks and pores.

[0040] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a copper alloy-ductile iron bimetallic wear-resistant and friction-reducing component, characterized in that: The following steps are involved: Treat the surface of ductile iron and smooth the surface; The treated ductile iron is placed in a closed cabin, the powder feeding speed of the wear-resistant and friction-reducing layer powder is adjusted to 5-8 g / min, and the ductile iron is heated to 150-200° C. through a preheating platform; wherein the wear-resistant and friction-reducing layer powder includes 6%-8% of the reinforcing phase powder by mass, and the rest is the copper alloy spherical powder; the reinforcing phase powder includes 13%-15% of the lanthanum hexaboride ceramic powder by mass, and the rest is the nickel-coated graphite powder; the copper alloy spherical powder includes the following raw materials by mass percentage: Cr 1%-1.5%, Ni 0.5%-1.2%, Zr 0.2%-0.4%, Si 0.1%-0.3%, Nb 0.01%-0.02%, and the balance is Cu; Under the process parameters of laser power of 800-1000W, scanning speed of 6-8mm / s, defocus of 0, and overlap rate of 40%-50%, the copper alloy is deposited layer by layer on the surface of ductile iron by laser additive manufacturing technology to form a copper alloy wear-resistant and friction-reducing layer; The copper alloy wear-resistant and friction-reducing layer is flattened and subjected to ultrasonic rolling treatment to obtain a copper alloy-ductile iron bimetallic wear-resistant and friction-reducing component; The copper alloy spherical powder is prepared by a gas atomization method. The particle size of the prepared copper alloy spherical powder is 50-150 μm and the bulk density is 4-4.5 g / cm 3 , fluidity is 17.0-18.0s / 50g.

2. The method for preparing the copper alloy-ductile iron bimetallic wear-resistant and friction-reducing component according to claim 1, characterized in that: The particle size of the nickel-coated graphite powder is 50-150 μm, and the thickness of the nickel coating is 1-5 μm; the particle size of the lanthanum hexaboride ceramic powder is 150-300 nm; the preparation method of the reinforcement phase powder is: pouring the nickel-coated graphite powder and the lanthanum hexaboride ceramic powder into a vacuum ball mill and ball milling them, so that the nickel-coated graphite powder and the lanthanum hexaboride ceramic powder are evenly mixed to obtain the reinforcement phase powder.

3. The method for preparing the copper alloy-ductile iron bimetallic wear-resistant and friction-reducing component according to claim 1, characterized in that: The preparation method of the wear-resistant and friction-reducing layer powder is as follows: pouring copper alloy powder and reinforcing phase powder into a vacuum ball mill for ball milling, sieving the ball-milled powder to control the powder particle size to be 50-150 μm, and then vacuum drying the sieved powder.

4. The method for preparing the copper alloy-ductile iron bimetallic wear-resistant and friction-reducing component according to claim 1, characterized in that: The step of stacking copper alloy layer by layer on the surface of ductile iron using laser additive manufacturing technology is to stack 5-7 layers, and the thickness of the copper alloy wear-resistant and friction-reducing layer is 4-5 mm.

5. The method for preparing the copper alloy-ductile iron bimetallic wear-resistant and friction-reducing component according to claim 1, characterized in that: The process parameters of the ultrasonic rolling treatment are: rolling speed 400-500 mm / min, step distance 0.1-0.3 mm, pressing amount 0.05-0.08 mm, static pressure 0.5-0.8 MPa, and ultrasonic frequency 22-25 kHz.

6. A copper alloy-ductile iron bimetallic wear-resistant and friction-reducing component, characterized in that: The method is prepared by the method according to any one of claims 1 to 5.

Images