JPH0696765B2 - Surface hardening method of aluminum alloy material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for surface hardening an aluminum alloy material.

Conventional technology and its problems Aluminum alloy materials are widely used in various machine parts by taking advantage of their features such as light weight. However, aluminum alloy materials are inferior to other metals in hardness, so aluminum alloy materials In order to impart wear resistance and scratch resistance to various machine parts made of steel, a hard layer has been conventionally formed on the surface thereof. As a conventional hard layer, a hard anodic oxide film, a hard chrome plating layer, a hard nickel plating layer, etc. have been mainly used. However, in the case of a hard anodic oxide film, there are problems that the cost for forming the film is high and that the heat conductivity and electric conductivity of aluminum are impaired. Further, in the case of a hard chrome plated layer and a hard nickel plated layer, since there is no metallurgical continuity with the parent phase aluminum, the plated layer peels off or the thermal conductivity and electrical conductivity of aluminum are impaired. There was a problem.

Therefore, in order to solve the above problems, the present inventors have
A method for surface hardening an aluminum material or an aluminum alloy material as filed on the same day as the present application was proposed. This surface hardening method, after forming a coating layer of a metal that reacts with aluminum to form an intermetallic compound that is harder than aluminum on the surface of an aluminum material or an aluminum alloy material, and then performs a heat diffusion treatment, the aluminum material or An intermetallic compound layer of the metal forming the coating layer and aluminum is formed on the surface of the aluminum alloy material. The surface of the aluminum material or aluminum alloy material surface-hardened by this method becomes hard and wear resistance and scratch resistance are improved, but when strain is applied to the aluminum material or aluminum alloy material after the surface hardening treatment, an intermetallic compound is used. Cracks may occur in the layer. The reason is,
This is because the intermetallic compound is very hard, but it is brittle and poor in ductility, so that it may be broken at the grain boundary.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a surface hardening method in which cracks do not occur in the formed intermetallic compound layer even if strain occurs after the surface hardening treatment. To do.

Means for Solving the Problems The method for surface hardening an aluminum alloy material according to the present invention is
Form a coating layer with a thickness of 5 to 20 μm on the surface of an aluminum alloy material containing 0.01 to 5 wt% boron that reacts with aluminum to form an intermetallic compound that is harder than aluminum, and then apply heat diffusion treatment. According to this, an intermetallic compound layer of the metal forming the coating layer and aluminum is formed on the surface of the aluminum alloy material.

In the above, the aluminum alloy material containing 0.01 to 5 wt% of boron includes 0.01 to 5 wt% of boron, and a binary alloy consisting of balance aluminum and unavoidable impurities and 0.01 to 5 wt% of boron, and various alloy elements. , The balance of aluminum and ternary or higher alloys containing inevitable impurities.

In the above description, the intermetallic compound is very hard, but it is brittle and poor in ductility. Therefore, when strain occurs in the aluminum alloy after the surface hardening treatment, cracks may occur in the intermetallic compound layer. Boron is contained in the aluminum alloy, thereby improving the grain boundary embrittlement of the intermetallic compound to improve the ductility of the intermetallic compound layer, as a result of the strain in the aluminum alloy material after the surface hardening treatment. Even if it occurs, it has the property of preventing the intermetallic compound layer from cracking. However, the content of boron is 0.
If it is less than 01% by weight, the above effect cannot be obtained, and if it exceeds 5% by weight, coarse crystallized substances are generated and the toughness of the aluminum alloy material is remarkably lowered, and the ductility improving effect of the intermetallic compound layer is not further increased. Therefore, the content of boron is 0.01 ~
It should be selected within the range of 5 wt%.

Further, in the above, as the metal which reacts with aluminum to form an intermetallic compound harder than aluminum, Cu,
Ni, Au, Fe, Ti, Ag, etc. can be used. The metal coating layer is formed on the surface of the aluminum alloy material by various plating methods such as electroplating, hot dipping, vacuum plating and chemical plating, and PVD methods such as ion plating,
It is performed by a plasma spraying method or the like. When the aluminum alloy material is plate-shaped, the metal coating layer may be formed by the clad method. The thickness of the metal coating layer is determined in consideration of the type of metal forming the coating layer, the thickness of the intermetallic compound layer to be formed, the required hardness, etc., but the thickness is 5 to 20 μm. The reason why the coating layer thickness is less than 5 μm is that if the coating layer thickness is less than 5 μm, the thickness of the intermetallic compound layer formed by the heat diffusion treatment in the subsequent step becomes thin, and the surface hardness is affected by the base material. The reason is that it cannot be used for practical purposes because the required wear resistance and scratch resistance cannot be obtained. Further, if the thickness of the coating layer exceeds 20 μm, the time required for the heat diffusion treatment in the subsequent step becomes long, which is not suitable for actual production,
This is because it reduces the industrial value. The temperature of the heat diffusion treatment is determined in consideration of the type of metal forming the metal coating layer, the melting point of the aluminum alloy material as the base material, and the like. For example, the metal forming the metal coating layer is Cu, Ni, Au, Fe,
500 ± 20 ℃, 600 ± 20 ℃, 500 ± 2 for Ti and Ag respectively
0 ° C, 600 ± 20 ° C, 600 ± 20 ° C, 500 ± 20 ° C are preferable. At these temperatures, the above metals react with aluminum, forming intermetallic compounds that are much harder than aluminum,
This is because the intermetallic compound layer is formed on the surface of the aluminum alloy material. Further, if the temperature is higher than the above, the risk of melting due to eutectic reaction in the surface layer of the aluminum alloy material increases, and if the temperature is lower than the above, diffusion for forming the intermetallic compound layer becomes slow, and industrial Decrease the intellectual value. Further, the processing time of the diffusion process has little relation to the hardness of the intermetallic compound layer formed. Furthermore, the diffusion treatment is preferably carried out in a vacuum, in an inert gas atmosphere such as Ar, or in a gas atmosphere inert to aluminum such as N ₂ , and particularly in an industrial atmosphere in an Ar gas atmosphere. Is preferably carried out.

Example 1 An aluminum plate with a thickness of 1 mm is made from an aluminum alloy containing 0.1 wt% boron and the balance aluminum and unavoidable impurities, which is made of high-purity aluminum with a purity of 99.99 wt%, and a copper plate is electroplated on its surface. ,
A nickel coating layer was formed. Then, diffusion treatment was performed in an Ar gas atmosphere. Then, the Vickers hardness (Hv) of the surface of the aluminum alloy plate was measured. Further, the aluminum alloy plate after the surface hardening treatment was bent so that the strain was 0.47%, and it was observed whether or not cracking occurred in the intermetallic compound layer. For comparison, an aluminum plate having a thickness of 1 mm was made from high-purity aluminum having a purity of 99.99 wt%, and the aluminum plate was subjected to the surface hardening treatment as described above. Then, the hardness of Vickers on the surface of the aluminum plate was measured. Further, the aluminum plate was bent so that the strain was 0.47%, and it was examined whether or not cracks occurred in the intermetallic compound layer. The results are summarized in the table below.

As is clear from the above table, when the surface hardening treatment is performed by the method of the present invention, even if strain occurs in the aluminum alloy material after the surface hardening treatment, the metal bending compound does not crack.

Effects of the Invention As described above, according to the surface hardening method of the present invention, the intermetallic compound layer is formed on the surface of the aluminum alloy material, so that the surface hardness is harder than the surface hardness of the original aluminum alloy material. Wear resistance and scratch resistance are improved. Moreover, since the aluminum alloy material contains 0.01 to 5 wt% of boron, the ductility of the intermetallic compound layer is improved,
As a result, even if strain occurs in the aluminum alloy material after the surface hardening treatment, cracking does not occur in the intermetallic compound layer. Further, since the intermetallic compound layer has metallurgical continuity with the parent phase aluminum, there is no risk of this layer peeling from the surface of the aluminum alloy material. Further, the cost is lower than that in the case of forming a conventional hard anodized film. Moreover, unlike the hard anodic oxide film, it does not impair the thermal conductivity and electrical conductivity of the aluminum alloy material. Further, since a coating layer having a thickness of 5 to 20 μm made of a metal that reacts with aluminum to form an intermetallic compound that is harder than aluminum is formed on the surface of the aluminum alloy material, the aluminum alloy is subjected to a heat diffusion treatment in a subsequent step. It is possible to form an intermetallic compound layer with a sufficient thickness on the surface of the material, and it is possible to obtain the necessary wear resistance and scratch resistance and put it into practical use. The required time becomes suitable for actual production.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshimitsu Uchiyama 6224, Kaiyama-cho, Sakai-shi, Osaka Showa Alminium Co., Ltd. (72) Inventor Kenji Tsukamoto 6224, Kaiyama-cho, Sakai-shi, Osaka Showa Al Minium Co., Ltd. (56) Reference JP-A-51-122633 (JP, A)

Claims (1)

[Claims] 1. A thickness of 5 to 20 made of a metal which reacts with aluminum to form an intermetallic compound harder than aluminum on the surface of an aluminum alloy material containing 0.01 to 5 wt% of boron.
After forming a coating layer having a thickness of μm, a heat diffusion treatment is performed to form an intermetallic compound layer of the metal forming the coating layer and aluminum on the surface of the aluminum alloy material. Surface hardening method.