JP2005068516A - Magnesium alloy having excellent corrosion resistance and wear resistance, and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide magnesium alloy, i.e., a magnesium alloy working stock and a magnesium alloy molded part having improved corrosion resistance, and to provide its production method. <P>SOLUTION: The surface of a magnesium alloy is provided with a first metallic layer formed by using a physical vapor deposition method. The surface of the obtained first metallic layer is provided with a second metallic layer consisting of a metal different from the metal composing the first metallic layer by using an electrolytic deposition, electroless deposition or physical vapor deposition method. Then, the obtained multilayer film is heated to a temperature at which the metals composing the first metallic layer and the second metallic layer are mutually diffused so as to be alloyed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a magnesium alloy having excellent corrosion resistance and wear resistance and a method for producing the same. More specifically, the present invention relates to magnesium having excellent corrosion resistance and wear resistance provided with a tin-nickel alloy coating layer, a tin-cobalt alloy coating layer, a zinc-nickel alloy coating layer, or a zinc-tin alloy coating layer. The present invention relates to an alloy and a manufacturing method thereof.

  Since the magnesium alloy according to the present invention is provided with an alloy coating layer having excellent corrosion resistance and wear resistance on the surface thereof, it can be suitably used for various applications requiring wear resistance and corrosion resistance.

  Despite being lightweight, magnesium alloys have high strength, and as such, have been used in structural members for high-speed moving objects such as automobiles and aircraft, and structural members such as exterior parts (housings) such as personal computers and mobile phones. Yes. Conventionally, magnesium alloys have been pointed out to be difficult to mold and have poor corrosion resistance, and the above-mentioned recent market expansion has been relatively slow, but today, various molding methods are industrially used. Once established, the market is gradually expanding.

  However, inferior corrosion resistance remains a problem, and improvement of corrosion resistance has become a major point for further expansion of the magnesium alloy market.

  Here, in order to improve the corrosion resistance of the magnesium alloy, it can be considered to improve the alloy composition, but it is not preferable to change the alloy composition so much from the viewpoint of workability. In order to improve the corrosion resistance, there is no other way to devise the surface treatment technology, and the importance of the surface treatment is more demanding than before.

As the conventional surface treatment technology for magnesium molded products, the coating technology has been most widely used. This makes it possible to impart corrosion resistance and color tone, but such treatment cannot avoid changes over time, and therefore, frequent maintenance is required, resulting in an inevitable increase in cost. Moreover, there is a problem that it is difficult to impart mechanical functionality such as wear resistance in the surface treatment by painting.
JP 2001-207255 A Japanese Patent Laid-Open No. 2001-181773

  An object of the present invention is to provide a magnesium alloy with improved corrosion resistance, that is, a magnesium alloy processed material, a magnesium alloy molded article, and a method for producing the same.

  Furthermore, another object of the present invention is to provide a magnesium alloy and a method for producing the same which are further improved not only in corrosion resistance but also in wear resistance by a cheaper means.

  The inventors of the present invention have made various studies on means for achieving the object, and have obtained the following knowledge. In the following, in order to simplify the explanation, the object to be treated is “magnesium alloy”, which is a general term for “magnesium alloy processed material” and “magnesium alloy molded product”.

  First, there are various methods other than the above-mentioned coating as the metal surface treatment, and the relationship with the magnesium alloy molded product was examined for each method.

  In the case of a magnesium alloy, it is difficult to perform so-called electrolytic plating by cathode deposition from an aqueous solution. Therefore, first, painting using a paint can be considered, but this has the problems described above, and further improvement is required.

  By the way, even in the case of a magnesium alloy, anodization using an anodic reaction from an aqueous solution can be performed in the same manner as aluminum, and it has been industrialized, but unlike anodization of an aluminum alloy, a porous layer made of hexagonal columnar cells. As a result, in order to ensure the required corrosion resistance, it is necessary to perform another coating, and the above-mentioned problems cannot be solved at all.

  In addition, the formation of an anticorrosion film by chemical conversion film treatment is also conceivable, but in many cases, the adhesion between the magnesium alloy surface and the anticorrosion film is insufficient, so that not only the corrosion resistance but also the wear resistance is sufficient. I can't say that.

  Here, the present inventors paid attention to depositing a different metal on a magnesium alloy by so-called physical vapor deposition such as vacuum vapor deposition, sputtering, or ion plating.

  Such physical vapor deposition itself has already been attempted even in the past. Thus, it has been known that various metal films including a chromium metal film and a cadmium metal film are formed on the surface of the magnesium alloy, but it has not been put into practical use. Metal coatings such as chromium and cadmium have excellent corrosion resistance and wear resistance, and can be said to be suitable for plating on magnesium alloys, but chromium and cadmium are harmful to the human body, and the former is a carcinogenic substance, hexavalent chromium. Since the latter is a harmful substance, it has a problem of high environmental impact. In addition, although other single metal films have an effect of improving corrosion resistance, the wear resistance is not sufficient, and physical vapor deposition has not been used industrially as a surface treatment technology for magnesium alloys. One reason is considered.

  Therefore, the present inventors conceived of providing an alloyed coating layer and further studied.

  In other words, the physical vapor deposited metal alone has insufficient mechanical strength such as wear resistance, in addition to corrosion resistance, and therefore an alloyed film is provided. However, as described above, alloy plating from an aqueous solution has practical problems. In addition, it is conceivable to deposit an alloy from the beginning by the physical vapor deposition described above, but in that case, it is difficult to form an alloy film having a uniform composition.

  Here, as a result of various trials and errors, the present inventors not only enable alloying by performing multilayer plating of a single metal on the surface of the magnesium alloy by the above-described physical vapor deposition and heat diffusing it. It has been found that an alloy alloyed by heat diffusion is uniform over the entire coating surface in composition, and further has no internal thermal stress, so that the corrosion resistance is further improved. Furthermore, it has been found that the adhesion with the magnesium alloy base is greatly improved by using an alloy film having a specific composition.

  Furthermore, the present inventors provide a tin-nickel alloy coating layer, a tin-cobalt alloy coating layer, a tin-copper alloy coating layer, and a zinc-nickel alloy coating as the alloy coating layer having the above-mentioned characteristic composition provided on the magnesium alloy. It was found that the layer and the zinc-tin alloy coating layer are excellent not only in corrosion resistance but also in adhesion to the magnesium alloy surface, and are particularly excellent in terms of corrosion resistance and wear resistance.

  That is, the inventors of the present invention have found that tin and nickel, cobalt or copper, zinc and tin or nickel are completely alloyed to obtain a uniform and stable tin alloy film of the above metal or a zinc alloy film on a magnesium alloy. As a result of intensive studies, each layer composed of any of the constituent elements of the alloy film was deposited by physical vapor deposition, and then a multilayer film was formed by the same physical vapor deposition method, electrodeposition, or electroless deposition method. The multilayer film is heated to a predetermined temperature to cause diffusion between the layers, whereby tin or zinc and various alloy elements are uniformly alloyed, and have excellent corrosion resistance, wear resistance, It was found to show decorativeness.

  That is, according to the method of the present invention, a tin alloy film or a zinc alloy film is indirectly manufactured through diffusion of the tin element constituting the tin layer or the zinc layer, or the zinc element and the various alloy elements. It is.

  Here, in the broadest sense, the present invention is a magnesium alloy or a magnesium alloy characterized in that a heat diffusion alloy coating layer is provided on the surface.

  According to a preferred embodiment of the present invention, the heating diffusion alloy coating layer derived from the multilayer metal (single) layer includes a tin-nickel alloy coating layer, a tin-cobalt alloy coating layer, a tin-copper alloy coating layer, zinc A nickel alloy coating layer and a zinc-tin alloy coating layer.

  According to the present invention, the first and second metal layers provided on the surface of the magnesium alloy are dissimilar metals and are formed by physical vapor deposition, but the second metal layer is an aqueous solution. You may provide by electroless plating which used electroplating or displacement plating.

  According to another aspect of the present invention, the metal layer of the first layer provided on the surface of the magnesium alloy is by physical vapor deposition. When the metal species at that time is, for example, zinc, tin, or nickel, The second metal layer to be provided may be provided by electrolytic plating using an aqueous solution or electroless plating. Of course, even in such a case, the second layer may be provided by physical vapor deposition.

  Here, “physical vapor deposition” in the present specification refers to a so-called PVD method such as vacuum vapor deposition, sputtering, or ion plating.

  Moreover, what is necessary is just to use normal electrolytic plating using aqueous solution as it is for "electrolytic plating." Normally, electroplating is very slow, so it is not practically suitable for thick plating, but in the case of the present invention, the thickness of the surface layer is about 1 to 10 μm, which can be achieved by short-term electroplating. Become.

  Similarly, “electroless plating” means normal chemical plating using an aqueous solution, and a reducing agent to be used may be appropriately selected and used depending on the metal type and its type. Also in this case, in the present invention, the plating film thickness is very thin, and such electroless plating can be plated in a relatively short time.

  More specifically, in the present invention, the first layer is laminated on a predetermined magnesium alloy substrate by a physical vapor deposition method, and then the second layer is laminated by the same physical vapor deposition, electrolysis, or electroless deposition. Forming a multilayer film composed of one combination of a layer, a tin layer and a cobalt layer, a tin layer and a copper layer, a zinc layer and a tin layer, a zinc layer and a nickel layer, and heating the multilayer film at a predetermined temperature, Generating a heat diffusion alloy coating layer of a tin-nickel alloy coating layer, a tin-cobalt alloy coating layer, a tin-copper alloy coating layer, a zinc-nickel alloy coating layer, or a zinc-tin alloy coating layer, This is a method for producing a magnesium alloy having excellent corrosion resistance and wear resistance.

  As described above, according to the method of the present invention, since any one of the alloy elements of tin and zinc is formed by physical vapor deposition as the first layer, it is conventionally difficult to deposit a plating metal from an aqueous solution. Is possible. In addition, since the alloy film is manufactured through diffusion between alloy elements by heating, even if a thermally non-equilibrium phase exists, it is shifted to a stable equilibrium phase by heating in the heating diffusion process. End up. For this reason, even if a conventional alloy electrodeposition method can be performed from an aqueous solution, unlike an alloy film obtained by such a method, the formation of a nonequilibrium phase can be prevented by heat treatment. Changes in the characteristics of the alloy film can be extremely effectively suppressed.

  Also, by appropriately adjusting the diffusion temperature and diffusion time, tin, nickel, cobalt, copper, or zinc, and tin, nickel can be alloyed almost completely. In addition, the composition does not change when used for a long time. Therefore, also from this, various functions such as corrosion resistance and wear resistance imparted to the alloy film can be maintained for a long time.

  According to the present invention, it is possible to obtain a tin-nickel alloy film that is usually impossible by electrodeposition from an aqueous solution onto the surface of the magnesium alloy. Therefore, it is possible to suppress changes in the characteristics of the alloy film due to wear or heating when using the alloy film. For this reason, various functions such as wear resistance and corrosion resistance imparted by the alloy film can be maintained for a long time.

  The present invention can further expand the range of application of magnesium alloys, whose range of use is expanding, and its practical significance is great.

  Although the present invention has been described in detail with specific examples, the present invention is not limited to the above contents, and many modifications and changes can be made without departing from the spirit and the spirit of the present invention. And they are all within the scope of the present invention.

  Next, the present invention will be described in detail based on the embodiment.

  In the present invention, a multilayer film made of tin and cobalt, nickel, copper, zinc and tin, or nickel is formed on a magnesium substrate.

  As a method for forming a multilayer film, first, a first layer is deposited on a magnesium substrate by a physical vapor deposition method such as vacuum vapor deposition, sputtering, or ion plating. Thereafter, the other of the alloy constituent elements is laminated thereon by the same physical vapor deposition method, electrodeposition or electroless deposition method, and it is necessary to heat these multilayer films at a predetermined temperature or higher. It is preferable to be higher than the melting point of tin or zinc. As a result, the tin layer or the zinc layer dissolves into a liquid phase, and the nickel, cobalt, copper, and tin diffuse quickly into the liquid phase, so that alloying can be easily formed in a relatively short time. it can.

  The magnesium alloy in the present invention is not particularly limited, but in general, there are Mg-Al alloys, Mg-Al-Zn alloys, Mg-Zn-Zr alloys, Mg-rare earth element alloys, etc. Examples of the types of molded products include die-cast molded products, extruded products, and rolled products.

  In these multilayer films, the stacking order of these layers is not particularly limited.

  In addition, the thickness of the multilayer film is not particularly limited, but the thickness of each layer constituting the multilayer film is preferably several μm, so that the heat treatment can be performed in a short time. Can be shortened.

  The first layer of the multilayer film is formed by deposition on a predetermined substrate by physical vapor deposition because it is difficult to deposit on the magnesium substrate. However, the means for forming the second layer thereon is not particularly limited, whether it is a physical vapor deposition method or any other method. However, it is preferable to use a physical vapor deposition method, particularly a sputtering method, because a dense film with good adhesion can be formed and the apparatus is relatively inexpensive.

  According to the present invention, when zinc is physically vapor-deposited as the first layer, it is easy to provide the second metal layer by electrolytic plating or electroless plating.

  The thickness of the metal layer is not particularly limited, but usually the first metal layer and the second metal layer are substantially the same, for example, 0.5 to 5 μm, preferably about 0.5 to 2 μm. This is because alloying by thermal diffusion performed later becomes easy.

  Although heat diffusion changes with kinds of metal, generally, in this invention, what is necessary is just to carry out for 1 to 60 minutes at 200-400 degreeC. Preferably, alloying is performed more rapidly by heating to the melting point of any metal. Such alloying is referred to as “liquid phase alloying”. In this case, the magnesium alloy substrate is sufficiently wetted, so that the adhesion to the alloy film is further improved. Uniformly alloyed and stable tin with good adhesion or an alloy film of zinc can be formed, and such an effect is obtained when tin and zinc having a relatively low melting point are provided, particularly in the first layer. This is particularly noticeable when these metal layers are provided.

  Therefore, as the alloy plating film for improving the corrosion resistance and wear resistance of the magnesium alloy according to the present invention, tin-nickel alloy, tin-cobalt alloy, tin-copper alloy, zinc-nickel alloy and zinc-tin alloy are particularly preferable. .

  According to the present invention, magnesium diffuses from the magnesium alloy matrix and is alloyed with the coating layer, whereby the adhesion with the coating layer is further improved. Such an effect is particularly remarkable when the above-described liquid phase alloying is observed.

  Next, the effects of the present invention will be specifically described with reference to examples.

A magnesium alloy equivalent to ASTM AZ31 with a thickness of 0.5 mm was used as the magnesium alloy substrate, and this was installed in a vacuum evaporation system and evacuated to a vacuum of 10 ^-3 Pa. Heating was performed to deposit nickel on the substrate. Thereafter, the deposition source was changed to tin, and tin was deposited on the nickel layer by the same operation to produce a multilayer film. At this time, the thickness of each layer of nickel and tin was about 1 μm. The substrate temperature during deposition was maintained at 390 ° C. during nickel deposition and 180 ° C. during tin deposition.

  After preparing the nickel-tin multilayer film, the sample was loaded into an electric furnace, heated to 350 ° C. and held for 5 minutes, and then air-cooled. The obtained sample was analyzed using SEM-EDX.

  FIG. 1 is an SEM image after the heat treatment of the multilayer film sample. FIG. 1 shows that a uniform alloy coating layer 20 is formed on the surface of the magnesium alloy base 10.

FIG. 2 shows the results of analyzing the cross section of tin, nickel, and magnesium from the material surface to the inside of the material by SEM-EDX. The analysis results shown in FIG. 2 correspond to the analysis points shown in FIG. 1, and it can be seen that tin and nickel react with each other to form an alloy phase. When this sample was identified using X-ray diffraction, it was confirmed that various tin-nickel alloy layers including Ni ₃ Sn ₄ were formed.

  Magnesium is also detected in the alloy coating layer, which shows that the adhesion of the alloy coating layer is improved.

  In this example, zinc is used instead of the above tin. In particular, since the first layer is a zinc vapor deposition layer, the nickel plating of the second layer was performed by electrolytic plating with a conventional aqueous solution.

  As an alternative method, the first zinc deposition layer was provided relatively thick, and a nickel layer was provided thereon by chemical plating (substitution plating).

It is a cross-sectional photograph which shows the SEM image of the tin-nickel alloy coating layer cross section obtained by the manufacturing method of this invention, Comprising: The analysis point of each element concentration is shown in the figure. It is a graph which shows the density | concentration change regarding a tin, nickel, and magnesium of the cross section of the tin-nickel alloy coating layer obtained by the manufacturing method of this heat treatment.

Claims (10)

  A corrosion-resistant and wear-resistant magnesium alloy characterized in that a heat diffusion alloy coating layer is provided on the surface.   The magnesium alloy according to claim 1, wherein the heat diffusion alloy coating layer is obtained by heat diffusion of the first single metal layer and the second single metal layer provided thereon to form an alloy.   The magnesium alloy according to claim 1 or 2, wherein the heat diffusion alloy coating layer is made of one alloy selected from the group consisting of a tin-nickel alloy, a tin-cobalt alloy, and a tin-copper alloy.   The magnesium alloy according to claim 1, wherein the heat diffusion alloy coating layer is made of a zinc-nickel alloy or a zinc-tin alloy.   The magnesium alloy according to any one of claims 1 to 4, wherein the magnesium alloy constitutes a molded product or a molding material.   The first metal layer is provided on the magnesium alloy by physical vapor deposition, and the first metal layer is obtained by electrolytic deposition, electroless deposition, or physical vapor deposition on the first metal layer. A second metal layer made of a metal different from the metal constituting one metal layer is provided, and the obtained multilayer film is subjected to mutual diffusion of the metal constituting the first metal layer and the second metal layer. A method for producing a magnesium alloy, characterized in that a heating diffusion alloy coating layer is provided on the surface, wherein the alloying is performed by heating to a temperature.   The method for producing a magnesium alloy according to claim 6, wherein the physical vapor deposition method for providing the first metal layer is one selected from the group consisting of vacuum vapor deposition, sputtering, and ion plating. The metal constituting the first metal layer is one selected from the group consisting of tin, nickel, cobalt, and copper, and the alloy plating layer includes a tin-nickel alloy, a tin-cobalt alloy, and a tin-copper. The method for producing a magnesium alloy according to claim 6 or 7, which is one selected from the group consisting of alloys.   The metal constituting the first metal layer is one selected from the group consisting of zinc, tin, and nickel, and the alloy plating layer is a zinc-nickel alloy or a zinc-tin alloy. 8. A method for producing a magnesium alloy according to 7.   The magnesium alloy according to any one of claims 6 to 9, wherein the magnesium alloy constitutes a molded product or a molding material.

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