A low-friction coating for aluminum alloy cylinder blocks and its preparation method

Abstract

This application provides a low-friction coating for aluminum alloy cylinder blocks and its preparation method. The low-friction coating includes a bonding layer and a surface functional layer stacked on the cylinder block surface. The surface functional layer includes Fe314, Fe316L, Cr3C2, MoS2, Dy2O3, Gd2O3, WC, TiC, TiN, BN, ZrO, and FeAlCr. The bonding layer is FeNiCoCrAlY. Using the low-friction coating provided in this application on an aluminum alloy cylinder block eliminates the need for cast iron cylinder liners. While achieving weight reduction, the coefficient of friction and wear between the coating and piston rings are lower than those of cast iron cylinder liners, improving engine fuel economy. The low-friction coating of this application has a bonding strength greater than or equal to 35 MPa and a microhardness greater than or equal to 400 HV.

Description

Technical Field

[0001] This application relates to the field of cylinder block processing, and more specifically, to a low-friction coating for aluminum alloy cylinder blocks and a method for preparing the same. Background Technology

[0002] The cylinder block (or cylinder liner) and piston rings are a crucial friction pair in an engine, especially at the top dead center of the cylinder block (or cylinder liner). This area is considered low-oil zone, where a good lubricating film cannot form, leading to severe friction and wear. Currently, most engine cylinder blocks on the market are made of cast iron. Replacing cast iron with aluminum alloy can significantly reduce the overall engine weight. However, aluminum alloy has poor wear resistance, necessitating machining of the aluminum alloy cylinder block to improve its wear resistance. Summary of the Invention

[0003] The first objective of this application is to provide a low-friction coating for aluminum alloy cylinder blocks. Using the low-friction coating of this invention on an aluminum alloy cylinder block eliminates the need for cast iron cylinder liners, achieving weight reduction while simultaneously reducing the coefficient of friction and wear between the coating and piston rings compared to cast iron cylinder liners, thus improving engine fuel economy. The low-friction coating described in this application has a bonding strength greater than or equal to 35 MPa and a microhardness greater than or equal to 400 HV.

[0004] The second objective of this application is to provide a method for preparing a low-friction coating for aluminum alloy cylinder blocks.

[0005] To achieve the aforementioned first inventive objective, this application adopts the following specific technical solution:

[0006] A low-friction coating for aluminum alloy cylinder blocks, comprising a surface functional layer and a bonding layer;

[0007] The surface functional layer includes Fe314, Fe316L, Cr3C2, MoS2, Dy2O3, Gd2O3, WC, TiC, TiN, BN, ZrO and FeAlCr.

[0008] The bonding layer is FeNiCoCrAlY.

[0009] As one implementation, with the surface functional layer comprising 100% by mass, the surface functional layer includes the following components by mass fraction:

[0010]

[0011] In one implementation, all components of the surface functional layer and bonding layer exist in powder form.

[0012] In one embodiment, the thickness of the surface functional layer is 0.2-0.3 mm.

[0013] In one embodiment, the thickness of the bonding layer is 0.08-0.15 mm.

[0014] To achieve the second objective of this application, this application provides a method for preparing a low-friction coating for aluminum alloy cylinder blocks, comprising the following steps:

[0015] 1) Spray the raw material powder of the bonding layer onto the inner surface of the cylinder to form the bonding layer;

[0016] 2) Prepare a mixed powder according to the content of each component in the surface functional layer, and spray the mixed powder onto the surface of the bonding layer to form a surface functional layer on the bonding layer;

[0017] 3) Abrasive particles are used to grind the surface of the functional layer.

[0018] In one implementation, in steps 1) and 2), the spraying is atmospheric plasma thermal spraying.

[0019] In one implementation, in step 1), the thickness of the bonding layer is 0.08-0.15 mm.

[0020] In one implementation, in step 2), the thickness of the surface functional layer is 0.2-0.3 mm.

[0021] In one implementation, in steps 1) and 2), the spray gun power is 19-23kW.

[0022] In one implementation, the spraying spacing in steps 1) and 2) is 75-85mm.

[0023] In one implementation, in steps 1) and 2), the spray gun rotation speed is 150-200 rpm.

[0024] In one implementation, in step 3), the grinding particles are silicon carbide particles.

[0025] In one implementation, in step 3), the grinding time is 10-30 minutes.

[0026] Any range described in this application includes end values, any numerical values ​​between end values, and any subranges consisting of end values ​​or any numerical values ​​between end values.

[0027] Unless otherwise specified, all raw materials used in this application can be obtained through commercial purchase, and the equipment used in this invention can be conventional equipment in the relevant field or refer to the prior art in the relevant field.

[0028] Compared with the prior art, the above-described solutions of this application have at least the following beneficial effects:

[0029] The low-friction coating provided in this application consists of two parts: a surface functional layer and a bonding layer. The surface functional layer is composed of materials such as Fe314 alloy and FeAlCr. The bonding layer enhances the bonding force between the surface functional layer and the aluminum alloy substrate. When the low-friction coating provided in this application is used to prepare an aluminum alloy cylinder block, the cast iron cylinder liner structure can be eliminated. While achieving weight reduction, the coefficient of friction and wear between the coating and the piston ring are lower than those of the cast iron cylinder liner, thus improving the engine's fuel economy. The bonding strength of the low-friction coating described in this application is greater than or equal to 35 MPa, and the microhardness is greater than or equal to 400 HV. Attached Figure Description

[0030] Figure 1 The TEM morphology of the surface functional layer prepared according to the preparation method provided in Example 1 of this application is shown.

[0031] Figure 2 The TEM morphology image of the bonding layer prepared according to the preparation method provided in Example 1 of this application is shown.

[0032] Figure 3 A graph showing the coefficient of friction of a low-friction coating prepared according to the preparation method provided in Example 1 of this application is shown.

[0033] Figure 4 A graph showing the coefficient of friction of a low-friction coating prepared according to the preparation method provided in Example 2 of this application is shown.

[0034] Figure 5 The friction coefficient curve of the cast iron cylinder liner prepared according to the preparation method provided in the comparative example of this application is shown. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0036] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the application. The singular forms “a,” “said,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms, and “multiple” generally includes at least two unless the context clearly indicates otherwise.

[0037] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0038] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device that includes said element.

[0039] It should be noted that any symbols and / or numbers present in the specification that are not marked in the accompanying drawings are not reference numerals.

[0040] To achieve the aforementioned first inventive objective, this application adopts the following specific technical solution:

[0041] A low-friction coating for aluminum alloy cylinder blocks, comprising a surface functional layer and a bonding layer;

[0042] The surface functional layer includes Fe314, Fe316L, Cr3C2, MoS2, Dy2O3, Gd2O3, WC, TiC, TiN, BN, ZrO and FeAlCr.

[0043] The bonding layer is FeNiCoCrAlY.

[0044] The low-friction coating provided in this application consists of two parts: a surface functional layer and a bonding layer. The surface functional layer is composed of materials such as Fe314 and FeAlCr. The bonding layer enhances the bonding force between the surface functional layer and the aluminum alloy substrate. By applying the low-friction coating provided in this application to the aluminum alloy cylinder block, the cast iron cylinder liner structure can be eliminated. While achieving weight reduction, the coefficient of friction and wear between the coating and the piston ring are lower than those of the cast iron cylinder liner, thus improving the engine's fuel economy. The bonding strength of the low-friction coating described in this application is greater than or equal to 35 MPa, and the microhardness is greater than or equal to 400 HV.

[0045] In some embodiments of this application, with the surface functional layer comprising 100% by mass, the surface functional layer includes the following components by mass fraction:

[0046]

[0047] The mass fraction of Fe314 can be 3.0 wt%, 3.1 wt%, 3.2 wt%, 3.3 wt%, 3.4 wt%, 3.5 wt%, 3.6 wt%, 3.7 wt%, 3.8 wt%, 3.9 wt%, or 4.0 wt%, etc.

[0048] The mass fraction of Fe316L alloy can be 2.0wt%, 2.1wt%, 2.2wt%, 2.3wt%, 2.4wt%, 2.5wt%, 2.6wt%, 2.7wt%, 2.8wt%, 2.9wt%, or 3.0wt%, etc.;

[0049] The mass fraction of Cr3C2 can be 2.0wt%, 2.2wt%, 2.4wt%, 2.6wt%, 2.8wt%, 3.0wt%, 3.2wt%, 3.4wt%, 3.6wt%, 3.8wt%, or 4.0wt%, etc.;

[0050] The mass fraction of MoS2 can be 1.5wt%, 1.7wt%, 1.9wt%, 2.0wt%, 2.2wt%, 2.4wt%, 2.6wt%, 2.8wt%, 3.0wt%, 3.2wt%, 3.4wt%, or 3.5wt%, etc.;

[0051] The mass fraction of Dy2O3 can be 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1.0wt%, 1.1wt%, 1.2wt%, 1.3wt%, 1.4wt%, or 1.5wt%, etc.;

[0052] The mass fraction of Gd2O3 can be 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1.0wt%, 1.1wt%, 1.2wt%, 1.3wt%, 1.4wt%, 1.5wt%, 1.6wt%, 1.7wt%, 1.8wt%, 1.9wt%, or 2.0wt%, etc.

[0053] The mass fraction of WC can be 1.0wt%, 1.1wt%, 1.2wt%, 1.3wt%, 1.4wt%, 1.5wt%, 1.6wt%, 1.7wt%, 1.8wt%, 1.9wt%, or 2.0wt%, etc.;

[0054] The mass fraction of TiC can be 0.2wt%, 0.25wt%, 0.3wt%, 0.35wt%, 0.4wt%, 0.45wt%, or 0.5wt%, etc.;

[0055] The mass fraction of TiN can be 0.2wt%, 0.25wt%, 0.3wt%, 0.35wt%, 0.4wt%, 0.45wt%, or 0.5wt%, etc.;

[0056] The mass fraction of BN can be 0.2wt%, 0.25wt%, 0.3wt%, 0.35wt%, 0.4wt%, 0.45wt%, or 0.5wt%, etc.;

[0057] The mass fraction of ZrO can be 0.3wt%, 0.35wt%, 0.4wt%, 0.45wt%, 0.5wt%, 0.55wt%, 0.6wt%, 0.65wt%, 0.7wt%, 0.75wt%, or 0.8wt%, etc.

[0058] In some embodiments of this application, all components of the low-friction coating are present in powder form.

[0059] In some embodiments of this application, the thickness of the surface functional layer is 0.2-0.3 mm, for example, it can be 0.2 mm, 0.21 mm, 0.22 mm, 0.23 mm, 0.24 mm, 0.25 mm, 0.26 mm, 0.27 mm, 0.28 mm, 0.29 mm or 0.3 mm, etc.

[0060] In some embodiments of this application, the thickness of the bonding layer is 0.08-0.15 mm, for example, it can be 0.08 mm, 0.09 mm, 0.10 mm, 0.11 mm, 0.12 mm, 0.13 mm, 0.14 mm or 0.15 mm, etc.

[0061] The low-friction coating applied to the inner circumference of the cylinder block in this application can effectively improve the wear resistance of the components.

[0062] Surface functional layer

[0063] In the surface functional layer, the wear resistance of the matrix material can be effectively improved by adding hard particles with high wear resistance to the flexible metal matrix (FeAlCr). During the wear process, the presence of hard particles prevents the removal of the matrix material, thereby improving the wear resistance of the material. At the same time, the good toughness of the flexible metal matrix prevents the propagation of cracks.

[0064] This application uses FeAlCr as a flexible metal matrix, and adds carbides, oxides, nitrides, and sulfides as hard particles to the matrix material to achieve dispersion reinforcement, thereby improving the hardness and wear resistance of the surface functional layer. Considering the different coefficients of thermal expansion of different hard particles, this application preferably uses Cr3C2, MoS2, Dy2O3, Gd2O3, WC, TiC, TiN, BN, and ZrO as hard particles added to the matrix material. The good matching of the coefficients of thermal expansion between different compounds is beneficial to improving the interfacial compatibility between different phases within the surface functional layer, thereby improving the toughness and cohesive strength of the surface functional layer.

[0065] This application introduces Fe314 and Fe316L into a matrix material, forming a steel-bonded cemented carbide with its hard particles, especially carbide particles. Fe314 and Fe316L act as binders, and the hard particles are uniformly dispersed throughout the matrix material, resulting in a steel-bonded cemented carbide material with high hardness, high wear resistance, and high toughness. This steel-bonded cemented carbide material exhibits excellent resistance to thermal cracking under alternating thermal shock, demonstrating good overall performance and suitability for use under high impact loads. It has been successfully applied in various wear-resistant parts, offering a long service life and significant economic benefits.

[0066] In addition to forming steel-bonded hard alloys with iron-based alloy materials, carbides can also improve other mechanical properties of coatings. For example, adding WC particles as nucleation sites for FeAlCr matrix materials can form a dual hard phase to improve material properties. The material properties are optimal when the amount of WC added is in the range of 1-2 wt%.

[0067] In addition, by adding TiC to the raw materials, TiC and WC have a synergistic effect, forming a dual hard phase and a binder phase in the FeAlCr matrix material. The hard phase is uniformly distributed in the binder phase, resulting in a dense structure with fewer defects, which improves the toughness of the material.

[0068] In addition, Cr3C2 is added to the raw materials in this application. Its function is as follows: (1) It increases the density of the surface functional layer. Cr3C2 can act as a non-spontaneous nucleation core, which hinders the growth of columnar crystals and makes the alloy structure more refined and uniform. The carbides generated by adding Cr3C2, whether the grains precipitate along the grain boundaries or are dispersed in the matrix material, will hinder the migration of grain boundaries during the grain growth process, thereby hindering the grain growth. Therefore, the addition of Cr3C2 effectively inhibits the growth of grains during the spraying process, thereby refining the grains, making the porosity of the surface functional layer per unit volume smaller and increasing the material density. (2) During the spraying process, Fe and Cr are oxidized to form a continuous and dense composite oxide film on the surface of the material particles, which protects the internal metal and reduces the degree of oxidation of the coating during the spraying process.

[0069] This application incorporates TiN into the raw materials. TiN is a high-hardness, corrosion-resistant coating material. However, TiN has a columnar crystal structure formed by island growth, which differs from the crystal structure of the matrix material. Therefore, the resulting coating exhibits higher internal stress, and the boundaries of the columnar crystals are prone to cracking and crack propagation. To address this, this application incorporates BN into the raw materials. BN can interrupt and inhibit the growth of the columnar crystal structure of TiN, dissipate the crack stress at the crystal tips, reduce the grain size of BN, eliminate coating porosity, increase the hardness and toughness of the coating, and the relatively low residual compressive stress is beneficial for improving the adhesion of the coating, thus improving the overall performance of the coating.

[0070] The purpose of adding ZrO to the raw materials in this application is to improve the thermal insulation performance of the coating. On the one hand, ZrO has a high melting point and good thermal stability in terms of chemical composition and structure; on the other hand, ZrO has a low thermal conductivity and a coefficient of thermal expansion that is closest to that of the matrix material. ZrO exists in three crystal forms: monoclinic, tetragonal, and cubic. The transformation between monoclinic and tetragonal crystal forms is reversible, and the volume increases by 4-6% during the transformation. The transformation does not involve atomic diffusion or compositional changes, only changes in volume and shape. This will cause the coating to crack or peel off due to internal stress caused by the volume effect during use. Therefore, in order to avoid the crystal transformation of ZrO, this application adds Dy2O3 and Gd2O3 to the raw materials as crystal stabilizers to control the ZrO crystal form to remain in the tetragonal phase.

[0071] bonding layer

[0072] In this application, the bonding layer is FeNiCoCrAlY, an alloy powder produced by melting and mixing different elements. It is a commercially available product, and the bonding layer raw material used in this embodiment was purchased from Beikuang Company. Its main function is to reduce the tendency of cracking between the cylinder block and the surface functional layer due to the difference in thermal expansion coefficients, and to avoid the decrease in interfacial bonding strength between the surface functional layer and the cylinder block due to chemical incompatibility, thereby improving the interfacial bonding force between the surface functional layer and the cylinder block.

[0073] To achieve the second objective of this application, this application provides a method for preparing a low-friction coating for aluminum alloy cylinder blocks, comprising the following steps:

[0074] 1) Spray the raw material powder of the bonding layer onto the inner surface of the cylinder to form the bonding layer;

[0075] 2) Prepare a mixed powder according to the content of each component in the surface functional layer, and spray the mixed powder onto the surface of the bonding layer to form a surface functional layer on the bonding layer;

[0076] 3) Abrasive particles are used to grind the surface of the functional layer.

[0077] In this application, the reason for the high bonding strength between the surface functional layer and the bonding layer is that: (1) the surface functional layer is dense and uniform, without pores and cracks, and has a low oxide content; (2) since the main raw material of the surface functional layer is FeAlCr, during spraying, Fe, Cr and Al elements will react with oxygen in the air to release a large amount of heat, which will further increase the temperature of the molten alloy particles. After the high-temperature and high-speed particles collide with the surface of the bonding layer, they will not cool down quickly due to the exothermic reaction, so that the micro-area of ​​the bonding layer contacted by the high-temperature and high-speed particles will be heated to form a local metallurgical bond, which is conducive to improving the bonding strength between the surface functional layer and the bonding layer; (3) the metal elements in the raw materials are easy to react with oxidation and release heat in the air during the spraying process, which will heat the sprayed particles or deposited materials a second time, improve the fluidity and ductility of the sprayed materials, and enable the sprayed materials to better wet the bonding layer and spread on the surface of the bonding layer, improve the interface bonding state between the coatings, and thus improve the bonding force and cohesive strength between the coatings.

[0078] In some embodiments of this application, in steps 1) and 2), the spraying is atmospheric plasma thermal spraying.

[0079] In some embodiments of this application, in step 1), the thickness of the bonding layer is 0.08-0.15 mm.

[0080] In some embodiments of this application, in step 2), the thickness of the surface functional layer is 0.2-0.3 mm.

[0081] In some embodiments of this application, in steps 1) and 2), the power of the spray gun used for spraying is 19-23kW, for example, it can be 19kW, 19.5kW, 20kW, 20.5kW, 21kW, 21.5kW, 22kW, 22.5kW or 23kW, etc.

[0082] In some embodiments of this application, in steps 1) and 2), the spraying spacing is 75-85mm, for example, it can be 75mm, 76mm, 77mm, 78mm, 79mm, 80mm, 81mm, 82mm, 83mm, 84mm or 85mm, etc.

[0083] In some embodiments of this application, in steps 1) and 2), the spray gun rotation speed is 150-200 rpm, for example, it can be 150 rpm, 155 rpm, 160 rpm, 165 rpm, 170 rpm, 175 rpm, 180 rpm, 185 rpm, 190 rpm, 195 rpm or 200 rpm, etc.

[0084] In some embodiments of this application, in step 3), the grinding particles are silicon carbide particles.

[0085] In some embodiments of this application, in step 3), the grinding time is 10-30 minutes, such as, but not limited to, 10-25 minutes, 10-20 minutes, 10-15 minutes, 15-30 minutes, 15-25 minutes, 15-20 minutes, etc.

[0086] Atmospheric plasma spraying is achieved through a plasma spray gun. The nozzle (anode) and electrode (cathode) of the spray gun are connected to the positive and negative terminals of a power supply, respectively. A working gas is introduced between the nozzle and the electrode, and an electric arc is ignited by a high-frequency spark. The electric arc heats and ionizes the gas, generating a plasma arc. The gas expands thermally and is ejected from the nozzle as a high-speed plasma jet. A powder feed gas delivers powder from inside the nozzle (internal powder feed) or outside (external powder feed) into the plasma jet, where it is heated to a molten or semi-molten state and accelerated by the plasma jet, spraying it at a certain speed onto the pre-treated substrate surface to form a coating. Commonly used plasma gases include argon, hydrogen, helium, nitrogen, or mixtures thereof.

[0087] In plasma spraying, the spraying conditions directly affect the mechanical properties of the coating. Based on the spraying material used in this application, the process parameters for the spraying process are specifically defined. Combining the spraying material defined in this application with the process parameters under specific conditions results in a more uniform and denser coating structure after spraying. Specifically:

[0088] This application specifically limits the spray gun power to the range of 19-23kW. The spray gun power directly affects the melting degree of the sprayed powder and the spraying speed, which in turn directly affect the structural morphology of the coating. Higher spray power results in more complete melting of the sprayed particles, higher particle flatness, and a denser coating. However, when the spray power exceeds a certain range, it can cause the sprayed powder to melt excessively, leading to powder deposition inside the spray gun nozzle and making spraying impossible to continue.

[0089] This application specifically limits the spraying distance to within the range of 75-85 mm. During the spraying process, the powder is heated by the spray gun to form molten spherical droplets. Under the spraying action of the spray gun, these droplets impact the substrate and extend into flat sheets. After rapid cooling, they form a solid phase. As the spray gun moves back and forth, multiple solid phases accumulate to form a coating of a certain thickness. When the distance between the spray gun and the substrate is within the range of 75-85 mm, it ensures that the impact velocity and temperature of the droplets upon reaching the substrate remain at a high level, resulting in increased droplet extension on the substrate surface and thus improved wettability. Furthermore, the droplets impact the previous solid phase while maintaining a high temperature, causing the solidified solid phase to remelt upon heating, resulting in a significant increase in the porosity of the final coating. If the spraying distance is less than 75 nm, the powder cannot be sufficiently heated and accelerated in the flame, which can easily lead to a loose coating and cause excessively high local temperatures on the substrate, resulting in thermal deformation and increased stress in the coating. If the spraying spacing is greater than 85mm, the temperature and velocity of the droplets when they collide with the substrate and coating will be too low, resulting in insufficient droplet deformation, high coating porosity, and reduced bonding strength.

[0090] The optional embodiments of this application are described in detail below with reference to the accompanying drawings.

[0091] Example 1

[0092] This embodiment provides a method for preparing a low-friction coating for aluminum alloy cylinder blocks, specifically including the following steps:

[0093] (1) FeNiCoCrAlY powder was sprayed onto the inner surface of the cylinder using atmospheric plasma thermal spraying process to form a bonding layer. The spray gun parameters were set as follows: the power of the spray gun was 20kW, the spraying distance was 75mm, and the spray gun speed was 150rpm.

[0094] (2) After spraying, the coating surface is ground with silicon carbide particles for 20 minutes to obtain a bonding layer with a thickness of 0.11 mm;

[0095] (3) Mix the powder according to the following composition ratio: 3.2% Fe314, 2.4% Fe316L, 2.5% Cr3C2, 1.6% MoS2, 0.8% Dy2O3, 0.7% Gd2O3, 1.3% WC, 0.2% TiC, 0.2% TiN, 0.2% BN, 0.3% ZrO, and the remainder is FeAlCr. After mixing, a mixed powder is obtained.

[0096] (4) Atmospheric plasma thermal spraying process is used to spray mixed powder on the surface of the bonding layer to form a surface functional layer on the bonding layer. The spray gun parameters are set as follows: power 20kW, spraying spacing 75mm, spray gun speed 150rpm.

[0097] (5) After spraying, the coating surface is ground with silicon carbide particles for 20 minutes to obtain a surface functional layer with a thickness of 0.23 mm, and finally a low friction coating for aluminum alloy cylinder is obtained.

[0098] The low-friction coating prepared by the above steps has a bonding strength of 38 MPa and a hardness of 410 HV.

[0099] The TEM morphology of the prepared surface functional layer is shown in the figure. Figure 1 .

[0100] Depend on Figure 1 It can be seen that the surface functional layer exhibits a grain distribution characteristic with different particle sizes. From the surface to a depth of 500 nm, the surface functional layer shows a coexistence of amorphous and nanocrystalline particles, with nanocrystalline grains having a diameter of approximately 50-100 nm. Within a depth range of 500-2000 nm, the grain diameter increases to approximately 100-200 nm. Below a depth of 2000 nm, elongated strip-shaped grains appear, with grain lengths of 1000-2000 nm and widths of 50-100 nm. From the surface to a depth of 5000 nm, the surface functional layer exhibits three grain characteristics. Simultaneously, the precipitated phases within the coating are tightly bonded together, without obvious cracks or defects.

[0101] The TEM morphology of the prepared binding layer is shown in the figure. Figure 2 .

[0102] Depend on Figure 2 It can be seen that the lattice fringes of the bonding layer are clearer, and there are a large number of highly crystalline nanocrystal particles. No cracks or defects are found in the structure.

[0103] Example 2

[0104] This embodiment provides a method for preparing a low-friction coating for aluminum alloy cylinder blocks, specifically including the following steps:

[0105] (1) FeNiCoCrAlY powder was sprayed onto the inner surface of the cylinder using atmospheric plasma thermal spraying process to form a bonding layer. The spray gun parameters were set as follows: power 22kW, spraying distance 80mm, and spray gun speed 180rpm.

[0106] (2) After spraying, the coating surface is ground with silicon carbide particles for 20 minutes to obtain a bonding layer with a thickness of 0.13 mm;

[0107] (3) Mix the powder according to the following composition ratio: 3.7% Fe314 alloy, 2.8% Fe316L alloy, 3.6% Cr3C2, 3.2% MoS2, 1.2% Dy2O3, 1.6% Gd2O3, 1.6% WC, 0.4% TiC, 0.3% TiN, 0.3% BN, 0.5% ZrO, and the remainder is FeAlCr. After mixing, a mixed powder is obtained.

[0108] (4) Atmospheric plasma thermal spraying process is used to spray mixed powder on the surface of the bonding layer to form a surface functional layer on the bonding layer. The spray gun parameters are set as follows: power 22kW, spraying spacing 80mm, spray gun speed 180rpm.

[0109] (5) After spraying, the coating surface is ground with silicon carbide particles for 20 minutes to obtain a surface functional layer with a thickness of 0.28 mm, and finally a low friction coating for aluminum alloy cylinder is obtained.

[0110] The low-friction coating prepared by the above steps has a bonding strength of 45 MPa and a hardness of 435 HV.

[0111] Example 3

[0112] This embodiment provides a method for preparing a low-friction coating for aluminum alloy cylinder blocks, specifically including the following steps:

[0113] (1) FeNiCoCrAlY powder was sprayed onto the inner surface of the cylinder using atmospheric plasma thermal spraying process to form a bonding layer. The spray gun parameters were set as follows: the power of the spray gun was 19kW, the spraying distance was 78mm, and the spray gun speed was 160rpm.

[0114] (2) After spraying, the coating surface is ground with silicon carbide particles for 20 minutes to obtain a bonding layer with a thickness of 0.08 mm;

[0115] (3) Mix the powder according to the following composition ratio: 3% Fe314 alloy, 2% Fe316L alloy, 4% Cr3C2, 1.5% MoS2, 1.5% Dy2O3, 0.5% Gd2O3, 2% WC, 0.3% TiC, 0.5% TiN, 0.4% BN, 0.8% ZrO, and the remainder is FeAlCr. After mixing, a mixed powder is obtained.

[0116] (4) Atmospheric plasma thermal spraying process is used to spray mixed powder on the surface of the bonding layer to form a surface functional layer on the bonding layer. The spray gun parameters are set as follows: the power of the spray gun is 19kW, the spraying distance is 78mm, and the spray gun speed is 160rpm.

[0117] (5) After spraying, the coating surface is ground with silicon carbide particles for 20 minutes to obtain a surface functional layer with a thickness of 0.2 mm, and finally a low friction coating for aluminum alloy cylinder is obtained.

[0118] The low-friction coating prepared by the above steps has a bonding strength of 36 MPa and a hardness of 418 HV.

[0119] Example 4

[0120] This embodiment provides a method for preparing a low-friction coating for aluminum alloy cylinder blocks, specifically including the following steps:

[0121] (1) FeNiCoCrAlY powder was sprayed onto the inner surface of the cylinder using atmospheric plasma thermal spraying process to form a bonding layer. The spray gun parameters were set as follows: the power of the spray gun was 23kW, the spraying distance was 85mm, and the spray gun speed was 200rpm.

[0122] (2) After spraying, the coating surface is ground with silicon carbide particles for 20 minutes to obtain a bonding layer with a thickness of 0.15 mm;

[0123] (3) Mix the powder according to the following composition ratio: 4% Fe314 alloy, 3% Fe316L alloy, 2% Cr3C2, 3.5% MoS2, 0.5% Dy2O3, 2% Gd2O3, 1% WC, 0.5% TiC, 0.4% TiN, 0.5% BN, 0.6% ZrO, and the remainder is FeAlCr. After mixing, a mixed powder is obtained.

[0124] (4) Atmospheric plasma thermal spraying process is used to spray mixed powder on the surface of the bonding layer to form a surface functional layer on the bonding layer. The spray gun parameters are set as follows: the power of the spray gun is 23kW, the spraying distance is 85mm, and the spray gun speed is 200rpm.

[0125] (5) After spraying, the coating surface is ground with silicon carbide particles for 20 minutes to obtain a surface functional layer with a thickness of 0.3 mm, and finally a low friction coating for aluminum alloy cylinder is obtained.

[0126] The low-friction coating prepared by the above steps has a bonding strength of 35 MPa and a hardness of 405 HV.

[0127] The aluminum alloy cylinder blocks and cast iron cylinder liners with low-friction coatings prepared in Examples 1 and 2 were subjected to friction and wear tests on piston ring pairs. The test mode was linear reciprocating motion, the test load was 200 N, the speed was 0.27 m / s, the test time was 2 hours, and lean oil lubrication was used. The friction coefficient and wear rate measured after the test are shown in Table 1.

[0128] Table 1

[0129]

[0130]

[0131] The friction coefficient test curve is shown below. Figures 3-5 As can be seen from the test results provided in Table 1 and the friction coefficient test curve, After preparing a low-friction coating on the surface of the aluminum alloy cylinder block, both the coefficient of friction and wear are less than those of the cast iron cylinder liner. .

[0132] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A low-friction coating for aluminum alloy cylinder blocks, characterized in that, It consists of a surface functional layer and a bonding layer; The surface functional layer includes Fe314, Fe316L, Cr3C2, MoS2, Dy2O3, Gd2O3, WC, TiC, TiN, BN, ZrO and FeAlCr; The bonding layer is FeNiCoCrAlY; With the surface functional layer comprising 100% by mass, the surface functional layer includes the following components by mass fraction: The rest are FeAlCr.

2. The low-friction coating according to claim 1, characterized in that: The low-friction coating is applied to the inner circumference of the cylinder body, with a bonding strength greater than or equal to 35 MPa and a microhardness greater than or equal to 400 HV.

3. The low-friction coating according to claim 1, characterized in that: All components of the surface functional layers and bonding layers exist in powder form.

4. The low-friction coating according to claim 1, characterized in that: The thickness of the surface functional layer is 0.2-0.3 mm.

5. The low-friction coating according to claim 1, characterized in that: The thickness of the bonding layer is 0.08-0.15 mm.

6. The method for preparing a low-friction coating for aluminum alloy cylinder blocks as described in any one of claims 1-5, comprising the following steps: 1) Spray the raw material powder of the bonding layer onto the inner surface of the cylinder to form the bonding layer; 2) Prepare a mixed powder according to the content of each component in the surface functional layer, and spray the mixed powder onto the surface of the bonding layer to form a surface functional layer on the bonding layer; 3) The surface of the functional layer is polished using abrasive particles; In step 3), the grinding particles are silicon carbide particles; In step 3), the grinding time is 10-30 minutes.

7. The preparation method according to claim 6, characterized in that: In steps 1) and 2), the spraying is atmospheric plasma thermal spraying.

8. The preparation method according to claim 6, characterized in that: In step 1), the thickness of the bonding layer is 0.08-0.15 mm; In step 2), the thickness of the surface functional layer is 0.2-0.3 mm.

9. The preparation method according to claim 6, characterized in that: In steps 1) and 2), the power of the spray gun used for spraying is 19-23kW; In steps 1) and 2), the spraying spacing is 75-85mm; In steps 1) and 2), the spray gun rotation speed is 150-200 rpm.

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