Slide member and internal combustion engine equipped with said slide member

Abstract

This sliding member is provided with a coating film which is formed from a particle assembly and disposed on a substrate surface.　In addition, the particle assembly includes copper-based alloy particles containing copper (Cu) as a main component, 3.5 mass% or more of nickel (Ni), and 0.001 mass% or more of silicon (Si), wherein the component ratio (Ni / Si) between Ni and Si is 5 to 50,000; and the copper-based alloy particles include nickel silicide deposits in a parent phase containing at least copper and nickel. As a result, both a solid-solution strengthening effect and a precipitation strengthening effect can be achieved such that a sliding member having high hardness and improved abrasion resistance under high temperatures and an internal combustion engine equipped with the sliding member can be provided.

Description

[Technical Field]

[0001] The present invention relates to a slide member, and more particularly to a slide member that can be suitably used in a high-temperature environment such as an internal combustion engine, and an internal combustion engine equipped with the slide member. [Background technology]

[0002] It is known that metal particles are sprayed onto the surface of a substrate, and the kinetic energy of the metal particles causes the metal particles to bond to the surface of the substrate, coating the surface with an aggregate of the metal particles, thereby improving the wear resistance of the sliding member.

[0003] Patent Document 1 discloses a sliding member having a coating film formed of a particle aggregate containing precipitation-hardened copper alloy particles, which are formed by spraying supersaturated solid solution particles onto a substrate by a cold spray method, and precipitating components exceeding the solid solubility limit due to stress and local heat generated by the impact when the particles collide with the substrate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent No. 6519962 Summary of the Invention [Problem to be solved by the invention]

[0005] The coating film of Patent Document 1 is formed by spraying soft, supersaturated solid solution particles in a solid phase state. This means that the solid solution particles before spraying are easily deformed, forming a dense coating film that is strongly bonded to the substrate. Furthermore, the particles bonded to the substrate become hard, precipitation-hardened copper alloy particles, which have high wear resistance.

[0006] However, in the precipitation-hardened copper alloy particles of Patent Document 1, while the solid solution components precipitate and the particles as a whole are precipitation-hardened, the solid solution components in the matrix itself decrease, making the composition closer to that of pure copper, and thus reducing the effect of solid solution strengthening, and therefore the wear resistance at high temperatures is insufficient.

[0007] The present invention has been made in view of the problems associated with the conventional art, and an object of the present invention is to provide a slide member that has high hardness and excellent wear resistance at high temperatures, and an internal combustion engine equipped with the slide member. [Means for solving the problem]

[0008] As a result of extensive research into achieving the above object, the present inventors have discovered that by precipitating nickel silicide in a matrix containing copper and nickel, it is possible to obtain the strengthening effects of both solid solution strengthening and precipitation strengthening, and have thus completed the present invention.

[0009] That is, the sliding member of the present invention has a coating film made of particle aggregates on the surface of a substrate. The particle aggregate includes copper-based alloy particles containing copper (Cu) as a main component, 3.5 mass % or more of nickel (Ni), and 0.001 mass % or more of silicon (Si), and the component ratio of Ni to Si (Ni / Si) is 7 or more and 100 or less, the copper-based alloy particles contain precipitates of nickel silicide in a matrix phase containing at least copper and nickel, The nickel silicide precipitate contains nanocrystals with an average grain size of 5 to 50 nm. A sliding member characterized by:

[0010] The internal combustion engine of the present invention is characterized by including the above-described sliding member. [Effects of the Invention]

[0011] According to the present invention, since a precipitate made of nickel silicide is formed in a matrix containing copper and nickel, the strengthening effects of both solid solution strengthening and precipitation strengthening can be obtained, and a slide member having high hardness and improved wear resistance at high temperatures can be provided. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic cross-sectional view showing an example of a cross section of a sliding member of the present invention. [Figure 2]FIG. 2 is a schematic enlarged cross-sectional view showing an example of a coating film structure. DETAILED DESCRIPTION OF THE INVENTION

[0013] The sliding member of the present invention will now be described in detail. The sliding member has a coating film made of a particle aggregate on the surface of a substrate. The particle aggregate contains at least copper-based alloy particles, and may contain other hard particles as needed.

[0014] In the particle aggregate, the surfaces of the particles locally melt and solidify, so that adjacent particles do not become one unit but form interfaces and bond together, as shown in Figure 1, and the entire particle aggregate becomes integrated to form a coating film layer.

[0015] The copper-based alloy particles contain copper (Cu) as the main component, 3.5 mass % or more of nickel (Ni), and 0.001 mass % or more of silicon (Si), and the component ratio of Ni to Si (Ni / Si) is 5 or more and 50,000 or less. In the present invention, the term "main component" refers to a component contained in an amount of 50% by mass or more.

[0016] Here, the alloy of copper and nickel is a complete solid solution type alloy and can be solid-solved at any composition ratio, but if this alloy contains silicon, the nickel in the alloy will bond with the silicon and be more likely to precipitate.

[0017] When the mass ratio of nickel to silicon (Ni / Si) of the copper-based alloy particles is 5 or more and 50,000 or less, some of the nickel precipitates as nickel silicide, but not all of the nickel in the alloy precipitates.

[0018] In other words, the nickel in the alloy is likely to precipitate as nickel silicide (e.g., NiSi), and the mass ratio of this nickel silicide (Ni / Si) is approximately 10 / 28. Therefore, by containing five times more nickel than silicon in the copper-based alloy particles, nickel will always remain in the matrix even if it precipitates as nickel silicide.

[0019] As described above, the copper-based alloy particles contain copper and nickel in the matrix, and are solid-solution strengthened alloys in which atoms of different sizes are dissolved and the atomic arrangement is distorted. This not only improves strength at the atomic level, but also improves strength at high temperatures due to a higher melting point than pure copper.

[0020] In addition, the copper-based alloy particles are also precipitation-strengthened alloys that have strain at the crystallite level due to the nickel silicide precipitated in the matrix. In combination with the strain at the atomic level, the copper-based alloy particles as a whole have strain, so there are no areas with low strength.

[0021] Therefore, the copper-based alloy particles can obtain the strengthening effects of both solid solution strengthening and precipitation strengthening, and therefore have improved strength at high temperatures and improved wear resistance.

[0022] The mass ratio of Ni to Si (Ni / Si) in the copper-based alloy particles is preferably 7 or more and 100 or less. By containing nickel at least 7 times the amount of silicon, the nickel content in the matrix increases, the effect of the solid solution strengthening is enhanced, and the strength of the matrix is ​​improved.

[0023] The copper-based alloy particles preferably contain 0.002 mass % or more of silicon, and more preferably 0.5 mass % or more and 1.3 mass % or less of silicon.

[0024] When the silicon content is 0.002 mass% or more, the amount of nickel silicide precipitated increases, thereby enhancing the precipitation strengthening effect. If the silicon content exceeds 1.3 mass%, the raw material particles may become too hard when forming a coating film by the cold spray method described below, making the film formation conditions difficult.

[0025] The copper-based alloy particles preferably have a nickel content of 10% by mass or more and 35% by mass or less. As the nickel content increases, the strength of the copper-based alloy particles improves, but the hardness of the matrix increases due to solid solution strengthening. When a coating film is formed by a cold spray method, the raw material particles may become too hard, making the film formation conditions strict.

[0026] Furthermore, for example, when the sliding member of the present invention is applied to a valve seat of an internal combustion engine and the mating material is a nickel-containing steel or nickel-based alloy, such as an exhaust valve, the nickel content is preferably 25 mass % or less. It should be noted that the valve / valve seat and its components are sliding mechanisms and sliding members, and are also valve operating mechanisms and valve operating members. However, in this application, the valve operating mechanisms and valve operating members are all referred to as sliding mechanisms and sliding members.

[0027] When sliding against a counter material containing nickel, if the nickel content exceeds 25 mass %, the affinity between the coating film and the counter material increases, making adhesion more likely and reducing wear resistance.

[0028] The particle aggregate preferably contains hard particles in addition to the copper-based alloy particles. By including hard particles, displacement between the copper-based alloy particles due to stress is suppressed, and the overall strength of the coating film is improved, resulting in improved wear resistance.

[0029] Examples of the hard particles include particles of iron (Fe)-based alloys, cobalt (Co)-based alloys, molybdenum (Mo)-based alloys, chromium (Cr)-based alloys, nickel (Ni)-based alloys, and ceramics, each having a Vickers hardness of 700 Hv or more and 1500 Hv or less.

[0030] Specific examples include hard particles such as TRIBALOY (registered trademark) T-400, Stellite (registered trademark), and TRIBALOY (registered trademark) T-700.

[0031] <Method for manufacturing sliding member> The sliding member can be produced by spraying raw material particles onto the surface of a substrate by cold spraying to form a coating film of particle aggregates.

[0032] As the raw material particles for the copper-based alloy particles, solid solution particles of a copper-based alloy in which silicon is dissolved in a matrix containing copper and nickel can be used, and if necessary, the solid solution particles can be mixed with the hard particles.

[0033] Cold spraying is a method of forming a coating film by colliding raw material particles in a solid state with an inert gas in a supersonic flow against a substrate without melting or gasifying them.Unlike methods such as thermal spraying, which form a coating film by melting metal particles, cold spraying minimizes changes in the properties of the metal particles due to heat and oxidation in the coating film.

[0034] When solid-phase raw material particles collide with the substrate using the cold spray method, the raw material particles themselves undergo plastic deformation, and part of their kinetic energy is converted into thermal energy, causing the surfaces of the raw material particles to locally melt and solidify, bonding the raw material particles together and forming a particle aggregate that forms a coating film.

[0035] If the raw material particles used in cold spraying are not the above-mentioned solid solution particles but particles on which nickel silicide has already been precipitated, the raw material particles are already precipitation-strengthened, and therefore are less likely to undergo plastic deformation when colliding with the substrate or other particles, and are more likely to crack or bounce off without being able to absorb the stress of the collision, making it difficult to form a coating film.

[0036] However, if the raw material particles are the above-mentioned solid solution particles, they have not yet been precipitation strengthened and are therefore soft and plastically deformed by collision, so that a coating film of particle aggregates in which the particles are bonded together can be formed.

[0037] Even when the raw material particles contain hard particles, the solid solution particles undergo plastic deformation, allowing the hard particles to sink into the solid solution particles and deposit and bond with each other without any gaps, thereby forming a coating film of particle aggregates.The content of hard particles in the raw material particles is preferably 50 mass% or less, and the content of hard particles in the coating film is preferably 20 area% or less.

[0038] At this time, the surfaces of the raw material particles melt locally, causing diffusion and the formation of precipitates such as intermetallic compounds. However, because the temperatures of the substrate and raw material particles are below the melting point of the raw material particles, the locally melted parts are rapidly cooled, so there is no time for the precipitates to grow into crystals.

[0039] Therefore, nanocrystals and amorphous materials are formed near the bonding interfaces between the substrate and particles, and near the bonding interfaces between particles, as shown in Figure 2.

[0040] In the present invention, the silicon dissolved in the solid solution particles is precipitated as nickel silicide together with nickel due to the energy of the collision, forming crystallites with an average particle size of 5 to 50 nm.

[0041] In this way, the solid solution particles become precipitation-hardened copper-based alloy particles due to the precipitation of nickel silicide, and the inside of these copper-based alloy particles near the outer shell are refined into crystallites with an average grain size of 5 μm or less due to plastic deformation caused by collision, thereby improving strength.

[0042] The solid solution particles of the present invention are solution-strengthened due to their high nickel content, and therefore are less susceptible to plastic deformation than solid solution particles with a low nickel content. Therefore, when spraying the solid solution particles onto a substrate by cold spraying, it is necessary to sufficiently accelerate the solid solution particles and increase the kinetic energy of each solid solution particle, for example by reducing the amount of solid solution particles supplied.

[0043] The solid solution particles can be prepared by water atomization or gas atomization. Specifically, the molten metal having the above-mentioned composition is allowed to flow down, and high-pressure water or gas is sprayed onto the molten metal to atomize it, which is then rapidly cooled and solidified into particles, whereby the molten metal can be produced.

[0044] The solid solution particles preferably have an average diameter (D50) of 20 μm to 40 μm. By reducing the average particle size of the solid solution particles, a dense coating film can be formed. However, if the particle size is too small, the kinetic energy of the particles is reduced during spraying, making them less susceptible to plastic deformation, which may reduce the adhesion of the particle aggregates and make the strength of the coating film more likely to decrease.

[0045] The coating film preferably has a porosity of 4% by area or less, and more preferably 1% by area or less. The solid solution particles undergo sufficient plastic deformation, resulting in a dense coating with few pores, which improves the strength and wear resistance of the coating film.

[0046] The porosity of the coating film and the average particle size of the copper-based alloy particles (equivalent circle diameter: the diameter of a circle having the same area as the projected area of ​​the particle image) can be calculated by binarizing the scanning electron microscope (SEM) image through image processing and analyzing the image.

[0047] In the present invention, the cross section of the coating film was photographed using an SEM composition image of five fields of view with an image field range of 350 μm horizontal × 263 μm vertical, and the images were binarized using an image processing device to calculate the porosity. In addition, the area ratio of the hard particles was calculated using the same images, and the area ratio of the copper-based alloy was obtained as the remainder.

[0048] Additionally, the presence of amorphous or crystalline structures at the interface between copper-based alloy particles can be confirmed by projecting a diffraction pattern onto the detector surface using electron backscatter diffraction (EBSD) with a scanning electron microscope (SEM) and analyzing the crystal orientation from the projected pattern.

[0049] The speed at which the raw material particles are sprayed is preferably 300 to 1200 m / s, and more preferably 500 to 1200 m / s.

[0050] The pressure of the working gas against which the raw material particles are blown is preferably 2 to 7 MPa, more preferably 3.5 to 7 MPa. If the working gas pressure is less than 2 MPa, the particle velocity cannot be obtained, and the porosity may become large.

[0051] The temperature of the working gas is preferably 400 to 1000°C, more preferably 600 to 1000°C, although this depends on the type and particle size of the raw material particles. If the temperature of the working gas is below 400°C, the raw material particles are less likely to undergo plastic deformation, resulting in a high porosity and reduced wear resistance. If the temperature of the working gas exceeds 1000°C, the temperature becomes too close to the melting point of the raw material particles, making the throat of the injection nozzle more susceptible to clogging.

[0052] Examples of the working gas include nitrogen gas and helium gas, and these may be used alone or in combination.

[0053] The thickness of the coating film depends on the temperature and sliding environment of the location where the sliding member is used, but is preferably 0.05 to 5.0 mm, and more preferably 0.1 to 0.5 mm, for example.

[0054] If the thickness is less than 0.05 mm, the strength of the coating film itself will be insufficient, and plastic deformation may occur if the substrate strength is low. If the thickness is more than 5.0 mm, the coating film may easily peel off due to the relationship between the residual stress generated during coating film formation and the interfacial adhesion strength.

[0055] The substrate is not particularly limited, and metals conventionally used as sliding members in internal combustion engines can be used, but aluminum alloys are preferably used because of their high thermal conductivity.

[0056] Examples of the aluminum alloy include A5056, A1050, AC2A, AC8A, and ADC12, which are specified by the Japanese Industrial Standards.

[0057] The sliding member has excellent wear resistance at high temperatures and can therefore be suitably used for sliding members such as valve seats, valve lifters, pistons, piston rings, piston pins, cylinders, crankshafts, camshafts, connecting rods, and metals thereof in internal combustion engines. [Example]

[0058] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0059] [Example 1] An aluminum substrate (A5056) was mounted on a rotating table. While the rotating table was rotating, raw material particles, a 50:50 mixture of solid solution particles (Cu-3.5Ni-0.5Si, average particle diameter (D50): 31.5 μm) produced by water atomization and TRIBALOY (registered trademark) T-400, were cold sprayed under the following conditions to form a coating film layer with a thickness of 0.8 to 1.0 mm. The coating film was then finish-machined on a lathe to a thickness of 0.4 to 0.5 mm.

[0060] High-pressure cold spray device: Plasma Giken Kogyo Co., Ltd., PCS-1000 Working gas: Nitrogen Working gas temperature: 600℃ Working gas pressure: 4MPa Spray distance: 20mm Substrate rotation speed: 300 rpm Particle supply amount: approx. 7g / min Other: During application, the gun was fixed and powder was supplied until the specified film thickness was achieved. (After the temperature was raised outside the application area, the gun was driven at 100 mm / sec to the application area and powder was supplied while the gun was fixed. After the required film thickness was achieved, the powder supply was stopped and the gun was driven at 100 mm / sec outside the application area, completing the application.)

[0061] The coating films of Examples 2 to 8 and Comparative Examples 1 to 4 were formed under the conditions shown in Table 1 below, and the coating films of the Examples and Comparative Examples were evaluated under the following conditions. Table 1 shows the conditions for forming the coating film and the evaluation results.

[0062] (Vickers hardness test) Test piece size: 5mm x 5mm x 10mm Test temperature: 200℃, 300℃, 400℃ Number of measurement points: each temperature x 5 points Measurement load: 500gf

[0063] (High temperature wear test) Test method: Valve seat single-piece hammering wear test (Takachiho Seiki) Expected model: KR20DDET Test temperature: 300℃ Mating valve material: SUH38 (Ni content 20% by mass) Number of times seated: 540,000 times (3000cpm x 3hr) Evaluation item: Valve seat wear

[0064] (Quantitative analysis of coating film) The coating film per unit area was dissolved in acid, and the resulting solution was measured by ICP (inductively coupled plasma mass spectrometry). In all of Examples 1 to 8, the mass percentages of Si and Ni in the coating film were the same as those in the raw material particles.

[0065] [Table 1]

[0066] Comparison of Examples 2 to 6 with Comparative Example 1 reveals that the coating film of the present invention has high hardness at high temperatures and excellent wear resistance.

[0067] In Examples 2, 3, and 4, although the silicon content of the copper-based alloy particles was the same, the hardness increased as the nickel content increased, which indicates that the matrix was solid-solution strengthened.

[0068] In Examples 4, 5, and 6, although the nickel content of the copper-based alloy particles was the same, the hardness increased as the silicon content increased, which indicates that the particles were strengthened by precipitation hardening.

[0069] Furthermore, a comparison of Examples 2, 3, and 4 shows that when the mating material contains nickel, adhesive wear occurs, as the wear resistance of Example 4, in which the nickel content of the copper-based alloy particles exceeds 25 mass %, decreases. [Explanation of symbols]

[0070] 1. Sliding member 2 Coating film 21 Copper-based alloy particles 22 Hard particles 23 Amorphous nanocrystals 3 Base material

Claims

1. A sliding member having a coating film made of a particle aggregate on a substrate surface, the particle aggregate comprises copper-based alloy particles containing copper (Cu) as a main component, 3.5 mass % or more of nickel (Ni), and 0.001 mass % or more of silicon (Si), and the mass ratio of Ni to Si (Ni / Si) is 7 or more and 100 or less, the copper-based alloy particles contain precipitates of nickel silicide in a matrix phase containing at least copper and nickel, The slide member is characterized in that the precipitate made of nickel silicide contains nanocrystals with an average grain size of 5 to 50 nm.

2. 2. The sliding member according to claim 1, wherein the copper-based alloy particles have a silicon content of 0.002 mass % or more.

3. 3. The sliding member according to claim 1, wherein the copper-based alloy particles have a silicon content of 0.5% by mass or more and 1.3% by mass or less.

4. 4. The sliding member according to claim 1, wherein the copper-based alloy particles have a nickel content of 35 mass % or less.

5. The mating material is steel or nickel-based alloy containing nickel, 5. The sliding member according to claim 1, wherein the nickel content of the copper-based alloy particles is 25 mass % or less.

6. 6. The slide member according to claim 1, wherein the particle aggregate further contains one or more types of hard particles selected from the group consisting of iron (Fe)-based alloys, cobalt (Co)-based alloys, molybdenum (Mo)-based alloys, chromium (Cr)-based alloys, nickel (Ni)-based alloys, and ceramics.

7. 7. The sliding member according to claim 1, wherein at least some of the particles constituting the particle aggregate have nanocrystalline and / or amorphous structures near the interfaces with adjacent particles.

8. 8. The sliding member according to claim 1, wherein the coating film has a porosity of 4% or less.

9. The sliding member according to claim 1, wherein the copper-based alloy particles contain crystallites having an average particle size of 5 μm or less.

10. An internal combustion engine comprising the slide member according to any one of claims 1 to 9.

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