JPH07292454A - Surface treated aluminum material - Google Patents

Abstract

PURPOSE:To provide a surface treated aluminum material on which a surface treated layer that is more effective against friction wear is formed. CONSTITUTION:A surface treated aluminum material consists of a parent material of aluminum, a diffusion layer which nitrogen is diffused into an aluminum matrix formed on the surface part of the parent material of aluminum and a sintered layer which aluminum powder formed on the upper surface of the diffusion layer and mainly nitrided is sintered to form the object aluminum material. In the sintered layer, at least one of ceramic powder and metal powder is dispersedly held, or held made into compounds. In the diffusion layer, nitrogen and elements except nitrogen enter and diffuse into in the aluminum matrix, and exist, made into compounds. This aluminum material excels in surface friction wear resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-treated aluminum material, and more particularly to an aluminum material which can be adapted to sliding parts.

[0002]

2. Description of the Related Art As is well known, an aluminum material has a lower hardness than steel or the like, and when it slides on steel or the like, it is extremely easily seized and worn. Therefore, various surface treatments using plating, thermal spraying, and anodic oxidation have been studied and used for aluminum materials. Most of these form an oxide layer on the surface of an aluminum material, and although nitriding treatment has been attempted, a nitride layer formed on the surface is thin and a satisfactory surface-treated aluminum base material has not been obtained. In addition, there are few examples in which the above-mentioned nitriding method has been put to practical use because it requires an expensive device such as a high vacuum. Recently, a method of forming a nitride layer on the surface of an aluminum material by an ion nitriding method of performing pre-sputtering with an argon gas containing a small amount of nitrogen or oxygen gas before nitriding treatment and performing glow discharge in a nitrogen gas atmosphere has been reported. (Japanese Patent Laid-Open No. 60-211061). Further, in Japanese Patent Laid-Open No. 63-290255,
There is a disclosure of a surface treatment method for an aluminum material by implanting nitrogen ions. Further, as the direct nitriding method using an aluminum material and nitrogen gas, examples of nitriding powdery aluminum are disclosed in JP-A-62-153107 and JP-A-62-278202, but as a surface treatment method. There is no description.

[0003]

The melting point of aluminum is 650 ° C., which is about 1/3 of the melting point of steel (about 1600 ° C.).
Therefore, it has been considered unavoidable that the surface treatment method below the melting point, whether the aluminum oxide layer or the aluminum nitride layer is formed, has a very low film formation rate. Further, since the aluminum material is a metal that is very active and easily oxidized, there is always a slight natural oxide layer on the surface, which hinders the formation of the nitride layer.
Even if the natural oxide layer is removed by pre-sputtering or the like before the treatment, it is commercially available at 10 ^-5 Torr.
It is said that the material is extremely hard to nitride because the degree of vacuum gives priority to oxidation.

The present invention has been made in view of the above circumstances, and by examining and improving the characteristics of the nitriding layer, a surface-treated aluminum material having a surface treatment layer more effective against friction and wear is provided. The purpose is to get.

[0005]

The inventors of the present invention previously formed a relatively thick nitride layer on the surface of an aluminum material by heat treating the surface of the aluminum material with the aluminum powder in a nitrogen gas atmosphere. Applied for an invention based on that (Japanese Patent Application No. 5-274878). By this method, the aluminum material can be deeply nitrided from the surface, but it has been found that the nitriding auxiliary agent used must be removed before use. In addition, the nitrided layer of the prior application is basically a mixed phase of aluminum-aluminum nitride, and the hardness can be adjusted only in the range of MHv (micro Vickers hardness) 250 to 1200, and therefore, depending on the mating material, wear characteristics The adjustment range is narrow, and self-wear and / or aggression against the opponent may deteriorate. Further, it has been found that it is difficult to further improve and adjust the wear characteristics only by controlling the nitriding ratio of the nitride layer when the wear characteristics are further adjusted and adjusted. The present invention relates to the improvement of the above-mentioned prior application, and has completed the finding that the friction characteristics of the surface layer can be improved by applying a wear-resistant substance or the like to the nitriding auxiliary agent and performing surface treatment. .

The surface aluminum nitride material of the present invention comprises a base material aluminum, a diffusion layer formed by diffusing nitrogen into an aluminum matrix formed on the surface of the base material aluminum, and an upper surface of the diffusion layer. And a sintered layer formed of mainly nitrided aluminum powder. The surface-treated layer of the surface-treated aluminum material is formed by integrally forming a sintered layer on the surface side and a diffusion layer on the base material side.

In this sintered layer, at least one of ceramic powder and metal powder is sintered together with aluminum nitride powder, dispersed and held, compounded and held in close contact with the aluminum base material. On the other hand, the diffusion layer is formed on the surface of the aluminum base material by holding the sintered layer inside the sintered layer and nitrogen, or nitrogen and an element other than nitrogen invading or diffusing into the aluminum matrix.

The ceramic powder present in this sintered layer includes oxides (Al ₂ O ₃ etc.) and carbides (Si
One or more of C, TiC, etc., boride (TiB _2, etc.), nitride (TiN, etc.) are added. Further, as the metal powder, iron (Fe), molybdenum (Mo), titanium (Ti), etc., or titanium (TiAl, Ti ₃ Al, TiAl ₃ ) which is hardened (around the powder) by compounding with aluminum , Nickel (N
iAl ₃ , Ni ₂ Al ₃ ), copper (CuAl ₂ , Al ₄ C)
u ₉ ) etc. can be used. Further, other metals may be used depending on the other material for friction. Also lead,
Addition of a soft metal powder such as tin or antimony is advantageous from the viewpoint of imparting seizure resistance to the aluminum base material, and a mixing effect can be expected. It is also possible to reduce the friction coefficient of the sintered layer and improve the wear characteristics by adding a material exhibiting self-lubricating properties such as graphite and molybdenum disulfide.

The sintered layer of the present invention is a composite layer in which an appropriate amount of aluminum nitride, ceramic powder, metal powder and the like are dispersed as described above, and is stable and inexpensive on the surface of the aluminum base material. Self-lubricant, etc. can be dispersed and fixed, surface characteristics can be improved, wear resistance,
It is possible to dramatically improve opponent attack and seizure resistance.

The diffusion layer is formed by nitrogen or nitrogen and an element other than nitrogen penetrating into the aluminum matrix to diffuse or compound. This is because when the sintered layer is formed, nitrogen penetrates into the aluminum matrix and diffuses to form aluminum nitride.
It is formed by the diffusion and penetration of some of the elements such as metals with nitrogen into the aluminum matrix.

The diffusion and permeation of elements other than nitrogen is caused by light elements such as boron and carbon, Ni, Ti,
It is formed together with a sintered layer by mixing and nitriding a metal element powder such as Cu. It is known that the above light elements such as boron and carbon have small atomic radii and cause interstitial diffusion in the substance, and in iron-based materials, they are known as surface treatments such as boriding and carburizing. In the present invention, these light elements are diffused into the aluminum matrix simultaneously with nitrogen. In particular, boron and carbon are considered to be a driving force for diffusion and penetration into the aluminum matrix because they easily form a compound with nitrogen.

On the other hand, metal elements such as Ni, Ti and Cu have large atomic radii, but are considered to easily form an intermetallic compound with aluminum and diffuse into the aluminum matrix together with nitrogen during the nitriding treatment. In addition, the surface of the sintered layer of the aluminum base material having the diffusion layer in which an element other than nitrogen is diffused as described above is polished to expose the diffusion layer, and the diffusion layer is used as the surface layer of the aluminum material. You can also

The surface treatment layer may be formed on the entire surface of the aluminum material or may be formed on a part of a specific surface portion. The aluminum material may be a plate-shaped or rod-shaped aluminum base material, or may be formed into a predetermined shape. The surface-treated aluminum material of the present invention is obtained by mixing at least a part of the surface of the aluminum material with a nitriding auxiliary agent made of aluminum powder, and mixing ceramic powder, metal powder or the like into contact with the surface of the aluminum material. The surface of an aluminum material is subjected to a nitriding treatment with an atmospheric gas which is substantially composed of nitrogen gas at a temperature.

The principle of the aluminum material nitriding method of the present invention is still unclear. When nitriding is carried out while flowing a nitrogen gas, a nitride layer is formed not only in the part coated with the aluminum powder used as a nitriding treatment aid, but also in the part of the part just downstream of the nitrogen gas. It is speculated that nascent nitrogen contributes to nitriding. That is, when the aluminum powder used as the nitriding auxiliary agent comes into contact with nitrogen gas at a predetermined temperature, the aluminum powder itself is nitrided, and at that time, a part of the nitrogen gas is excited to become nascent nitrogen. Seem. It is presumed that nitrogen at this nascent stage is absorbed by the aluminum material to form a nitride layer.

It is presumed that aluminum existing on the surface of the aluminum material to be nitrided is also nitrided like the aluminum powder to generate nitrogen in the nascent stage. However, a nitride layer is not substantially formed on the aluminum surface not covered with the aluminum powder. The aluminum powder used in the nitriding method of the present invention can be used as a nitriding auxiliary agent as long as the aluminum powder itself is nitrided.
However, as aluminum powder with high nitriding capacity,
The rapidly solidified aluminum powder, especially the rapidly solidified aluminum powder at a cooling rate of 10 ² ° C / sec or more, is preferable. Furthermore, a powder composed of an aluminum alloy containing magnesium is excellent as a nitriding treatment aid.
In particular, aluminum powder containing 0.5% by weight or more of magnesium is preferable.

As the aluminum powder used as the nitriding auxiliary agent, not only powder obtained by the atomizing method but also foil-like, granular or a mixture of foil and granular can be used. That is, it may be formed from foil, ribbon, or cutting waste by stamping, crushing with a ball mill, or the like. The particle size of aluminum powder is 5-200μ
About m is preferable. The powder may be granular or foil-like. Alternatively, a mixture of foil and particles may be used, the surface area of which is 0.4 m ² / g.
It is preferable from the viewpoint of reactivity.

As a method of contacting the surface of the aluminum material with the nitriding auxiliary agent, the aluminum material may be embedded in the aluminum powder constituting the nitriding auxiliary agent. Further, the surface of the aluminum material may be coated with aluminum powder.
For this coating, a suitable adhesive material may be mixed with aluminum powder and used in the form of a paste. The adhesive is preferably an organic substance that decomposes at the nitriding temperature. The coating preferably has a thickness in the range of 5 to 1000 μm.

Nitrogen gas is used as an atmosphere gas for nitriding. The nitrogen gas preferably has a low content of water or oxygen gas. It does not matter if an inert gas such as argon gas is mixed. The water content is 0.
It is preferably 1% by volume or less and oxygen is 0.08% by volume or less. The nitriding temperature is preferably high from the viewpoint of reactivity. However, the aluminum material needs to be treated in a substantially solid state. Further, when it is not desired to form a deep nitrided layer, or when heat treatment strain is desired to be reduced, it is preferable to perform at a low temperature. Usually 400
Treatment at a temperature of about 600 ° C. for 2 to 10 hours is standard.

[0019]

The surface-treated aluminum material of the present invention has a diffusion layer and a sintered layer formed on the surface. In the sintered layer, ceramic powder, metal powder, etc. are dispersed in aluminum nitride to improve the friction and wear characteristics of the aluminum material. Further, the diffusion layer holds nitrogen or nitrogen and other elements diffused into the aluminum matrix to form aluminum nitride and a compound of the diffused elements, thereby increasing the hardness of the aluminum matrix base material. With this surface treatment layer, it can be used as an aluminum material having excellent friction characteristics and high hardness.

[0020]

EXAMPLES The present invention will be specifically described below with reference to examples. (Example 1) An aluminum melt containing 5% by weight of magnesium was rapidly solidified at a cooling rate of 10 ² ° C / sec or more to produce an aluminum powder having a particle size of 3 to 150 µm. 30% by weight of alumina powder (average particle size: 10 μm) was stirred and mixed with a paste-like nitriding treatment aid prepared by mixing polybutene with this aluminum-5% magnesium powder. This nitriding auxiliary agent mixture was applied by brush coating on the surface of an aluminum material of JIS 2024 to a thickness of about 200 μm.
After the aluminum material coated with the nitriding aid mixture was placed in a heat treatment furnace, the temperature inside the furnace was raised to 550 ° C. × 5.
A nitriding treatment was performed for a time. As the nitriding condition, 99.9% pure nitrogen gas was introduced into the furnace at a flow rate of 10 l / min, and the furnace dew point was kept at -20 ° C to 30 ° C.

The surface-treated aluminum obtained by the above surface treatment was confirmed by the following evaluation to have a sintered layer in which alumina was dispersed on the surface and a nitrogen-aluminum diffusion layer inside the sintered layer. An edge of the obtained surface-treated aluminum material is cut, and a micrograph of the metal structure of the cross section is shown in FIG. Further, FIG. 2 shows a main part chart of each element% by EPMA line analysis of this cross-section.

From the micrograph of the metal structure of FIG. 1, the thickness of the sintered layer of the surface-treated aluminum material is 110 μm, and the thickness of the diffusion layer is 100 μm. Vickers hardness is [M by measuring micro Vickers hardness (load weight 100 g)]
Hv] The sinter layer (black part) was MHv1097, and the diffusion layer was MHv464, which were both significantly hardened with respect to the base material MHv93.6. In particular, it is considered that the sintered layer is harder than the diffusion layer and is compounded by adding alumina particles to form a harder layer.

In the EPMA line analysis of FIG. 2, the vertical axis is the weight% of aluminum, oxygen and nitrogen, the uppermost numerical values on the vertical axis are oxygen 50, nitrogen 20, aluminum 100, and the middle numerals are oxygen 25 and nitrogen 10. , 50% by weight of aluminum. The horizontal axis shows the distance from the surface, and the left end is the outermost surface, and it moves to the inside as it progresses to the right. From FIG. 2, the surface portion is a sintered layer formed by applying a mixture of a nitriding treatment aid and alumina, and aluminum peaks of aluminum and oxygen are overlapped with each other, and aluminum nitride is dispersed and present. It is a layer. Next, a portion where the peaks of aluminum and nitrogen overlap inward from the surface of the aluminum base material is a diffusion layer, and aluminum nitride is formed. The portion after the amount of nitrogen disappeared is the aluminum base material portion. Therefore, it is understood that the diffusion layer of aluminum nitride is formed on the surface of the aluminum base material, and the sintered layer in which alumina is dispersed and present is further formed on the surface side thereof. (Example 2) As in Example 1, an aluminum melt containing 5% by weight of magnesium was rapidly solidified at a cooling rate of 10 ² ° C / sec or more to obtain an aluminum powder having a particle size of 3 to 150 µm. The aluminum powder in this example was used as a nitriding treatment aid. This aluminum-5% magnesium powder was blended with polybutene to form a paste-like nitriding auxiliary agent with 50% by weight of TiB ₂ powder (average particle size 5 μm.
m) was mixed with stirring. This nitriding auxiliary agent mixture was added to JI
The surface of the aluminum material of S5052 was applied with a brush to a thickness of about 500 μm. This coated aluminum material was charged into a heat treatment furnace, and then heated to nitriding treatment at 480 ° C. for 5 hours. The nitriding condition is 99.99.
99% highly pure nitrogen gas was introduced into the tubular furnace at a flow rate of 1 l / min, and the dew point in the furnace was kept at -60 ° C or lower. The oxygen concentration in the furnace was 100 ppm or less. As a result of this surface treatment, it was confirmed by the following evaluation that the surface-treated aluminum material had a sintered layer in which TiB ₂ was dispersed and hardened on the surface.

FIG. 3 shows a photomicrograph of the metal structure of the surface-treated aluminum material obtained, and FIG. 4 shows a principal part chart of the EPMA line analysis result of the surface-treated layer. In FIG. 4, the vertical axis shows the weight% of aluminum, Ti, B and nitrogen, and the horizontal axis shows that the left end is the outermost surface and progresses to the inside of the aluminum material as it goes to the right. In the sintered layer shown in FIG. 4, peaks of Ti and B are overlapped with each other, indicating that TiB is dispersed. The diffusion layer has nitrogen and aluminum peaks, indicating that aluminum nitride is formed. From the structure photograph of FIG. 3, the thickness of the sintered layer is about 60 μm, the thickness of the diffusion layer is 110 μm, and the Vickers hardness is MHv3 of the sintered layer.
83, the diffusion layer is MHv285, and the base material hardness is MHv7
A hardened surface is obtained for all of 1.3. (Example 3) Same as in Example 1, an aluminum melt containing 5% by weight of magnesium was rapidly solidified at a cooling rate of 10 ² ° C / sec or more to use aluminum powder having a particle size of 3 to 150 µm as an auxiliary agent for nitriding treatment. did. This aluminum-5
% Magnesium powder mixed with polybutene into a paste-like nitriding auxiliary agent of 10 wt% B powder (average particle size 2
˜3 μm) was mixed with stirring and applied by brush coating to the aluminum material surface of JIS 2024 so as to form a coating layer having a thickness of about 700 μm. The thus prepared material was charged into a heat treatment furnace previously purged with nitrogen and then heated to 50
Nitriding was performed at 0 ° C. for 3 hours. The nitriding condition is 99.99.
It was carried out by using 99% high-purity nitrogen gas and introducing it into the tubular furnace at a flow rate of 21 / min to keep the furnace dew point at -20 ° C to -45 ° C. The oxygen concentration was 200 ppm or less.

As a result of this surface treatment, it was confirmed by the following evaluation that the surface-treated aluminum material obtained was one in which boron was dispersed in the sintered layer and boron was also diffused in the diffusion layer.
A micrograph of the metal structure of the obtained surface-treated aluminum material is shown in FIG. 5, and a principal part chart of the EPMA line analysis result of the surface-treated layer is shown in FIG. In the EPMA line analysis result of FIG. 6, the vertical axis shows the weight% of aluminum, boron, and nitrogen, and the horizontal axis shows the outermost surface at the left end, and progresses to the right inside the aluminum material. In the sintered layer of FIG. 6, peaks of aluminum, nitrogen and boron are observed, and further peaks of boron are observed in the diffusion layer, and it is confirmed that boron is present in the diffusion layer. From the structure photograph of FIG. 5, the thickness of the sintered layer is 1
00 μm, the thickness of the diffusion layer is 250 μm, and the Vickers hardness is MHv824 for the sintered layer and MHv514 for the diffusion layer, and a hardened surface is obtained with respect to the base material hardness MHv122.

In particular, according to EPMA, the diffusion layer has a nitrogen ratio of 50% in the sintered layer, and the nitrogen ratio in the diffusion layer is ⅕, which is 10%. However, the decrease in the hardness of the diffusion layer is small as shown in the above Vickers hardness. It is considered that this is because boron becomes a diffusion compound and hardens in the diffusion layer. (Example 4) As in Example 1, aluminum powder of Al-2.5Mg composition manufactured by the rapid solidification method was used as a nitriding treatment aid, and 50% by weight of Ti powder (-100
Mesh). Further, this mixed powder was stirred and mixed with polybutene to form a paste, which was applied to an aluminum material of JIS 5052 so as to form a coating layer having a thickness of about 900 μm, and a nitriding treatment was performed. 540 ° C ×
Nitriding treatment was performed for 10 hours. Nitriding condition is 9
Pure nitrogen gas of 9.9% was introduced into the furnace (at a flow rate of 20 / min), and the furnace dew point was maintained at -30 ° C to -40 ° C.

As a result of this surface treatment, it was confirmed by the following evaluation that the surface-treated aluminum material obtained had Ti dispersed in the sintered layer and further diffused in the diffusion layer. FIG. 7 shows a micrograph of the metal structure of the obtained surface-treated aluminum material, and FIG. 8 shows a main part chart of the EPMA line analysis result of the treated layer. According to the EPMA line analysis of FIG. 8, Ti is present in the sintered layer, and the surface side of the diffusion layer has a T content of about 1%.
i is detected and Ti is a layer formed into a compound compound with nitrogen diffused. A diffusion layer containing only nitrogen is present on the aluminum base material side of this diffusion layer, and Ti is not necessarily present at the same time as nitrogen. This is probably because the atomic radius of Ti is large and the diffusion is slower than that of nitrogen.

The white portion of the sintered layer in the photograph of the metal structure of FIG. 7 is Ti particles. The hardness of Ti particles is MHv147, T
The hardness of the sintered layer other than the i particles was MHv1200.
Therefore, although the nitrogen content of the sintered layer is 20% or less even in the vicinity of Ti particles in the EPMA line analysis result, it is extremely hard. (The Vickers hardness of AlN is 1200 to 1400). It is considered that this is because the compound in the form of any combination of Ti, Al and N is produced and hardened.

The Vickers hardness of the diffusion layer inside the sintered layer is M
Hv824, the Vickers hardness of the diffusion nitride layer is MHv51
It was 4. Even in the diffusion layer inside the sintered layer, Ti, A
It is considered that since the compounds of l and N were generated, they were hardened more than the simple diffusion nitride layer. The hardness of the aluminum base material is MHv50.7, and it can be seen that the sintered layer diffusion layer is also significantly hardened. It can be seen that the addition of Ti has an extremely hardening effect during nitriding.

[0030]

The surface-treated aluminum material of the present invention has a sintered layer and a diffusion layer on the surface thereof, and the sintered layer contains a substance such as ceramics that improves friction characteristics of metal, and the diffusion layer is made of aluminum nitride. It has been hardened. Therefore, this surface-treated aluminum material is most suitable for use in sliding parts and the like that require abrasion resistance.

[Brief description of drawings]

FIG. 1 is a micrograph showing a metal structure of a cross section of an aluminum material having a sintered layer and a diffusion layer formed on the surface of Example 1.

FIG. 2 is a chart showing a main part of an EPMA line analysis result of a surface layer of an aluminum base material having a sintered layer and a diffusion layer formed on the surface of Example 1.

FIG. 3 is a micrograph showing a metal structure of a cross section of an aluminum base material having a sintered layer and a diffusion layer formed on the surface of Example 2.

FIG. 4 is a chart showing a main part of an EPMA line analysis result of a surface layer of an aluminum base material having a sintered layer and a diffusion layer formed on the surface of Example 2.

FIG. 5 is a micrograph showing a metal structure of a cross section of an aluminum base material having a sintered layer and a diffusion layer formed on the surface of Example 3.

FIG. 6 is a chart showing a main part of an EPMA line analysis result of a surface layer of an aluminum base material having a sintered layer and a diffusion layer formed on the surface of Example 3.

FIG. 7 is a micrograph showing a metal structure of a cross section of an aluminum base material having a sintered layer and a diffusion layer formed on the surface of Example 4.

FIG. 8 is a chart showing a main part of an EPMA line analysis result of a surface layer of an aluminum base material having a sintered layer and a diffusion layer formed on the surface of Example 4.

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[Submission date] May 23, 1994

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Claims (4)

[Claims] 1. A base material aluminum, a diffusion layer formed by diffusing nitrogen into an aluminum matrix formed on a surface portion of the base material aluminum, and mainly nitrided formed on an upper surface of the diffusion layer. A surface-treated aluminum material comprising a sintered layer formed from aluminum powder. 2. The surface-treated aluminum material according to claim 1, wherein the sintered layer holds at least one of a ceramic powder and a metal powder dispersedly held or compounded and held. 3. The surface-treated aluminum material according to claim 1, wherein the diffusion layer has nitrogen and an element other than nitrogen infiltrated and diffused or compounded in an aluminum matrix. 4. A surface comprising a base material aluminum and a diffusion layer in which nitrogen and an element other than nitrogen are infiltrated and diffused or compounded and present in an aluminum matrix formed on a surface portion of the base material aluminum. Treated aluminum material.