阅读说明：本技术 滑动部件和内燃机用部件 (Sliding member and member for internal combustion engine ) 是由 伊泽佳典 荒井淳一 乙部胜则 西村信一 于 2019-06-19 设计创作，主要内容包括：本发明的滑动部件具备基材和形成在该基材上的被膜层。并且,所述被膜层包含含有析出硬化型铜合金粒子的粒子集合体,所述析出硬化型铜合金粒子包含钴(Co)和硅(Si),本发明可提供被膜强度较高并且具有优异的耐磨性的滑动部件。(The sliding member of the present invention includes a base material and a coating layer formed on the base material. Further, the coating layer contains a particle aggregate containing precipitation hardening copper alloy particles containing cobalt (Co) and silicon (Si), and the present invention can provide a sliding member having a high coating strength and excellent wear resistance.)

1. A sliding member comprising a base material and a coating layer formed on the base material, wherein,

the coating layer contains a particle aggregate containing precipitation hardening copper alloy particles,

the precipitation hardening copper alloy particles contain cobalt (Co) and silicon (Si).

2. The sliding member according to claim 1,

the cobalt content of the precipitation hardening copper alloy particles is 0.8 to 4 mass%.

3. The sliding member according to claim 1 or 2,

the precipitation hardening copper alloy particles comprise cobalt silicide (Co)₂Si) precipitated phase.

4. The sliding member according to any one of claims 1 to 3,

the precipitation hardening copper alloy particles contain at least 1 kind selected from nickel (Ni), iron (Fe) and manganese (Mn), and the total content of the precipitation hardening copper alloy particles and cobalt is 2-4 mass%.

5. The sliding member according to any one of claims 1 to 4,

at least one of the base material and the film layer has a plastic deformation portion.

6. The sliding member according to any one of claims 1 to 5,

at least one of amorphous and nanocrystalline is present at the interface between the particles constituting the coating layer.

7. The sliding member according to any one of claims 1 to 6,

the porosity in the cross section of the coating layer is 3 area% or less.

8. The sliding member according to any one of claims 1 to 7, which is provided with an intermediate layer at least at a part between the base material and the coating layer,

the intermediate layer includes at least one of a diffusion layer and an intermetallic layer.

9. A component for an internal combustion engine, which has a sliding portion, wherein,

the component for an internal combustion engine is provided with the sliding component according to any one of claims 1 to 8 at the sliding portion.

Technical Field

The present invention relates to a sliding member, and more particularly, to a sliding member having improved wear resistance.

Background

Aluminum and aluminum alloys are lightweight and high-strength materials, and therefore are suitable for weight reduction of vehicles and the like. However, since aluminum and aluminum alloys have low wear resistance, when used in an internal combustion engine having a sliding portion, the surface of a base material containing aluminum is coated to improve wear resistance.

Patent document 1 discloses that metal particles of titanium, nickel, iron, aluminum, cobalt, copper, or the like, or alloy particles containing these metals, are sprayed onto the surface of a base material containing aluminum by a low-temperature gas, and the particles are plastically deformed by kinetic energy to be bonded to the surface of the base material, thereby coating the surface of the base material with the particles.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2008-519157

Disclosure of Invention

Technical problem to be solved by the invention

However, in the method described in patent document 1, the coating layer cannot be formed unless the material particles sprayed on the base material include soft metal particles that are plastically deformed by spraying, and therefore, even if hard particles such as tungsten carbide and silicon nitride are further added, it is difficult to improve the strength of the entire coating layer, and the wear resistance is insufficient.

The present invention has been made in view of the problems of the prior art, and an object of the present invention is to provide a sliding member having a high film strength and excellent wear resistance.

Means for solving the problems

The present inventors have conducted extensive studies to achieve the above object, and as a result, have found that the above object can be achieved by using, as material particles, high-strength particles which have high deformability when sprayed on a base material and are sufficiently plastically deformed and are hardened after being bonded to the base material, and have completed the present invention.

That is, the sliding member of the present invention includes a base material and a coating layer formed on the base material.

Also, the following features are provided: the coating layer contains a particle aggregate containing precipitation hardening copper alloy particles containing cobalt (Co) and silicon (Si).

Further, the component for an internal combustion engine of the present invention has a sliding portion.

Also, the following features are provided: the component for an internal combustion engine is provided with the sliding member at the sliding portion.

Effects of the invention

According to the present invention, a sliding member having high film strength and excellent wear resistance can be provided because the sliding member is coated with a particle assembly containing precipitation-hardened copper alloy particles containing cobalt (Co) and silicon (Si).

Drawings

FIG. 1 is a schematic cross-sectional view of a sliding member according to the present invention.

Detailed Description

< sliding Member >

The sliding member of the present invention will be described in detail.

As shown in fig. 1, the sliding member includes a base material 3 and a coating layer 2 formed on the base material, the coating layer 2 includes a particle aggregate including precipitation-hardened copper alloy particles 21, and the precipitation-hardened copper alloy particles 21 include cobalt (Co) and silicon (Si).

The precipitation hardening copper alloy particles may be formed by: particles in a supersaturated solid solution state containing copper as a main component are sprayed on the surface of the base material by a cold spray method described later.

When the particles in the supersaturated solid solution state collide with the base material in the solid phase state by the cold spray method, the solid-dissolved components are precipitated and hardened by heat, stress, or the like generated by the impact, exceeding the solid solution limit, and become precipitation-hardened copper alloy particles.

Therefore, the particles in a supersaturated solid solution state, which are soft and have a high deformability, are ejected in a solid phase and collide with the surface of the base material, whereby the particles in a supersaturated solid solution state and the base material are sufficiently plastically deformed, and are melted by local heat generation or are strongly bonded to the base material and other particles by atomic diffusion, whereby the film strength is improved.

Further, the particles in the supersaturated solid solution state are bonded to the base material, and then precipitation hardening occurs to increase the hardness, and a coating layer of a particle aggregate in which precipitation hardening copper alloy particles are firmly bonded to each other is formed, whereby a sliding member having excellent wear resistance can be formed.

Further, since the particles in the supersaturated solid solution state have a high deformability, most of the particles are bonded to the base material when being ejected onto the base material, and the number of particles which are flicked and wasted is small, so that the production efficiency is high and the cost can be reduced.

The cobalt (Co) and silicon (Si) have a small solid solution limit with respect to copper, and the precipitation-hardened copper alloy particles containing cobalt (Co) and silicon (Si) precipitate a large amount of particles containing cobalt silicide (Co)₂Si) to form precipitated phases. Therefore, the precipitation hardening copper alloy particles containing cobalt (Co) and silicon (Si) have high hardness and excellent wear resistance.

In addition, in the precipitation hardening copper alloy particles, cobalt silicide is precipitated, and the solid-dissolved cobalt component and silicon component are small, so that a heat conduction path having a high copper concentration is formed, the thermal conductivity of the coating layer is improved, the cooling performance is improved, and as a result, the heat resistance is improved.

Further, cobalt and silicon contained in the precipitation-hardened copper alloy particles or the particles in a supersaturated solid solution diffuse on the surface to form a stable cobalt oxide film or SiO₂The corrosion resistance of the coating film is improved in the same manner as that of a passivation film (Passivating film).

The particles in the supersaturated solid solution state may be those containing copper as a main component and cobalt (Co) and silicon (Si) as additive elements, and examples thereof include Cu — Co — Si alloy particles, Cu — Ni — Co — Si alloy particles, and the like.

In the present invention, the main component means a component containing 80 mass% or more.

The content of cobalt is preferably 0.8 to 4 mass%, more preferably 1.0 to 3.0 mass%, and further preferably the total content of cobalt and nickel is 2.5 to 3.5 mass%, depending on the composition of the precipitation hardening copper alloy particles constituting the coating layer.

When the content of cobalt is less than 0.8 mass%, precipitated crystal particles are reduced, and it is difficult to obtain sufficient hardness, and even in a supersaturated solid solution state, if the content of cobalt is more than 4 mass% and it is solid-solved, the deformability of the particles is reduced and it is difficult to form a coating layer by the cold spray method.

Preferably, the precipitation hardening copper alloy particles contain at least 1 kind selected from nickel (Ni), iron (Fe), and manganese (Mn), and the total content of the precipitation hardening copper alloy particles and cobalt is 2 to 4 mass%.

The hardness of the particles in the supersaturated solid solution state depends on the composition thereof, and is preferably 200HV or less at normal temperature.

If the amount of added elements in solid solution is small and the crystal grains are hard copper alloy grains precipitated in advance, the precipitated crystal grains inhibit the deformation of the copper alloy grains, and therefore the stress at the time of collision cannot be absorbed, so that the copper alloy grains are broken and the coating layer is difficult to form.

Preferably, the crystal particles in the precipitation hardening copper alloy particles are nanocrystals having an average particle diameter of less than 1 μm. Since the crystal grains in the precipitation hardening copper alloy grains are fine, the strength of the coating layer is improved.

The particles in the supersaturated solid solution state can be prepared by a water atomization method.

Specifically, it can be prepared by the following manner: the molten metal is made to flow down and water is sprayed at high pressure to atomize and rapidly condense the molten metal to be granulated.

The average diameter (D50) of the particles in the supersaturated solid solution state is preferably 20 to 40 μm.

A dense coating film can be formed by reducing the average particle diameter of the particles in the supersaturated solid solution state, but when the particle diameter is too small, there are cases where: at the time of spraying, kinetic energy of the particles becomes small, so that plastic deformation becomes difficult, and adhesion between the particles is reduced, so that film strength is reduced.

The porosity of the cross section of the coating layer is preferably 3 area% or less, and preferably 1 area% or less. Since the pores are small and dense, the film strength is improved and the wear resistance is improved.

The porosity in the cross section of the coating layer and the average particle diameter (equivalent circle diameter: diameter of a circle having the same area as the projected area of the particle image) of the precipitation-hardened copper alloy particles were calculated by binarizing a scanning electron microscope image (SEM image) by image processing and analyzing the image.

The thickness of the coating layer depends on the temperature of the position where the sliding member is used and the sliding environment, and is preferably 0.05 to 5.0mm, and more preferably 0.1 to 0.5mm, for example.

When less than 0.05mm, there are the following cases: the coating layer itself has insufficient strength, and plastic deformation occurs when the strength of the base material is low. Further, when it is larger than 5.0mm, there are cases where: the coating layer is likely to be peeled off due to the relationship between residual stress generated during film formation and interfacial adhesion.

The base material is not particularly limited, and a metal conventionally used as a sliding member of an internal combustion engine can be used, but an aluminum alloy is preferably used because it has high thermal conductivity.

Examples of the aluminum alloy include AC2A, AC8A, ADC12, and the like defined in japanese industrial standards.

The sliding member has excellent wear resistance and is suitably used for members for internal combustion engines having sliding portions, such as pistons, piston rings, piston pins, cylinders, crankshafts, camshafts, and valve lifters.

< method for producing sliding Member >

The sliding member may be manufactured by: particles in a supersaturated solid solution state containing cobalt (Co) and silicon (Si) and having copper as a main component are sprayed on the surface of the base material by a cold spray method.

The cold spray method is a method of forming an coating layer by causing particles in a supersaturated solid solution state to collide with a base material as they are in a solid phase state by a supersonic flow together with an inert gas without melting or vaporizing, and can minimize oxidation of the coating layer due to heat, unlike a method of forming a coating layer by melting metal particles of a material by a thermal spray method or the like.

When the particles in the solid phase supersaturated solid solution state collide with the base material by the cold spray method, the particles themselves and the base material 3 are plastically deformed to form the plastic deformation portions 22, and components exceeding the solid solution limit are precipitated and hardened to become precipitation-hardened copper alloy particles 21.

Then, a part of the kinetic energy is converted into thermal energy to melt and solidify the surfaces of the precipitation-hardening copper alloy particles 21 by local heat generation, or atomic diffusion occurs to bond the precipitation-hardening copper alloy particles to each other to form the coating layer 2.

At this time, since the temperature of the substrate 3 and the particles in the supersaturated solid solution state is equal to or lower than the melting point of the particles, the surfaces of the partially melted particles in the supersaturated solid solution state are rapidly cooled, and amorphous and nanocrystals are formed at the interface 23 between the particles in the supersaturated solid solution state.

The particle assembly of the precipitation hardening copper alloy particles 21 thus formed is such that the surfaces of the precipitation hardening copper alloy particles 21 are locally melted and solidified, and the particle assembly of the entire coating layer is joined and integrated, and the precipitation hardening copper alloy particles 21 are not uniform with each other to form an interface 23, and a plastic deformation portion 22 including amorphous and nano-crystals is provided in the vicinity of the interface 23.

In this respect, it differs from the following coating layers: the metal particles of the material are completely melted or dissolved and solidified by thermal spraying or the like, and become a uniform coating layer without forming the plastic deformation portion.

Further, the intermediate layer 4 including a diffusion layer and an intermetallic compound layer is formed between the base material 3 and the coating layer 2, but the surface of the molten particles in a supersaturated solid solution state is rapidly cooled, and therefore, the thickness of the intermediate layer is thinner than that of the intermediate layer formed by thermal spraying or sintering, and the film thickness is 2 μm or less.

Crystal grains in the amorphous and precipitation-hardened copper alloy grains at the interface of the precipitation-hardened copper alloy grains can be confirmed by: the diffraction pattern is projected onto the detector surface by Electron Back Scattering Diffraction (EBSD) with a Scanning Electron Microscope (SEM), and the crystal orientation is analyzed from its projected pattern.

The velocity of spraying the particles in the supersaturated solid solution state is preferably 300 to 1200m/s, and preferably 500 to 1000 m/s. When the amount is less than 300m/s, the stress for plastically deforming the particles in the supersaturated solid solution is small, precipitation hardening may be insufficient, and the porosity may be increased.

The pressure of the working gas for spraying the particles in the supersaturated solid solution state is preferably 2 to 5MPa, and more preferably 3.5 to 5 MPa. When the pressure of the working gas is less than 2MPa, there are cases where it is difficult to obtain the particle velocity.

The temperature of the working gas depends on the kind of the particles in the supersaturated solid solution state, and is preferably 400 to 800 ℃, and more preferably 500 to 700 ℃.

When the temperature of the working gas is less than 400 ℃, the particles in a supersaturated solid solution state are less likely to be plastically deformed, and the porosity may increase, and the film strength may decrease. Further, when the temperature of the working gas is more than 800 ℃, there is a case where the strength is reduced by oxidation.

Examples of the working gas include nitrogen gas and helium gas, and 1 of these may be used alone or in combination.

Examples

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

[ example 1]

In a state where the machining of the engine valve seating portion in the cylinder head was completed, the aluminum material (a5056BE-H112) was prepared by preprocessing, assuming that the target coating layer thickness was 0.2 mm.

The aluminum substrate was mounted on a rotary table, and while the rotary table was rotated, particles (composition (% by mass) Cu-3Co-0.7Si, average particle diameter (d 50): 26.3 μm) in a supersaturated solid solution state prepared by a water atomization method were cold-sprayed under the following conditions to form a coating layer of 0.4 to 0.5 mm.

The adhesion rate of the particles in the supersaturated solid solution state is shown in table 1.

High pressure type cold spraying device: PCS-1000 manufactured by PLASMA technical research industries, Inc

Working gas: nitrogen is present in

The gas pressure in the cavity is as follows: 4MPa

Temperature of gas in the cavity: 600 deg.C (particle temperature at collision about 200 deg.C.)

Particle velocity: 680 to 720m/s

Amount of particles supplied: 7g/min

The coating layer was processed into the shape of the mounting portion of the engine valve in the actual cylinder head, and a sliding member having a coating layer thickness of 0.2mm was obtained.

[ example 2]

A sliding member was obtained in the same manner as in example 1, except that particles (composition (mass%) of Cu-0.8Ni-2.2Co-0.7Si, average particle diameter (d 50): 26.1 μm) in a supersaturated solid solution state were used.

[ example 3]

A sliding member was obtained in the same manner as in example 1, except that particles (composition (mass%) of Cu-1.5Ni-1.5Co-0.7Si, average particle diameter (d 50): 26.2 μm) in a supersaturated solid solution state were used.

[ example 4]

A sliding member was obtained in the same manner as in example 1, except that particles (composition (mass%) of Cu-2.2Ni-0.8Co-0.7Si, average particle diameter (d 50): 26.3 μm) in a supersaturated solid solution state were used.

Comparative example 1

A sliding member was obtained in the same manner as in example 1, except that particles (composition (mass%) of Cu-3.0Ni-0.7Si, and an average particle diameter (d 50): 27.7 μm) in a supersaturated solid solution state were used.

Comparative example 2

A sliding member was obtained in the same manner as in example 1, except that particles (composition (mass%) of Cu-14Ni-3Si-2V-2.2Cr-1.4Fe-1.2Al, average particle diameter (d 50): 33.2. mu.m) in a supersaturated solid solution state were used.

< evaluation >

The sliding member was evaluated by the following method. The evaluation results are shown in table 1.

(Observation of capsular tissue)

Electron Back Scattering Diffraction (EBSD) by a Scanning Electron Microscope (SEM) was performed to observe the structure of the coating layer, and the following was confirmed: the composition and porosity of precipitated crystal particles in the precipitation-hardening copper alloy particles, the particle size of the precipitated crystal particles, whether or not the particles have an amorphous state and whether or not the particles have a plastically deformed portion, and the intermediate layer.

(abrasion resistance)

The wear amount of the sliding member after the corrosion resistance test was measured under the following conditions using a valve seat wear tester manufactured by seiko co.

Specifically, the shapes of the engine valve seating portions in the cylinder head before and after the test were obtained using a shape measuring device, and the wear ratio with respect to comparative example 1 was calculated from the average value of the wear amounts at 4 positions obtained by the measurement.

Target valve material: SUH35

Test temperature: 325 deg.C

Upper and lower speeds: 3000 times/min

Valve rotating speed: 5rpm

The installation times are as follows: 540000 times

[ Table 1]

From the results of table 1, it can be found that the wear resistance of the clad layer of the example containing cobalt and silicon is superior to that of the clad layer of the comparative example.

Description of the symbols

1 sliding member

2 coating layer

21 precipitation hardening copper alloy particles

22 plastic deformation part

23 interface (I)

3 base material

4 intermediate layer