JP6281412B2 - Metal structure and manufacturing method thereof - Google Patents

Description

  The present invention relates to a metal structure in which an acid-resistant film is provided on the surface of a metal member so as to cover the surface, and a method for producing such a metal structure, for example, in a high-temperature, strongly acidic environment. Applied to automotive parts and the like.

  Conventionally, as metal members used for the purpose of anticorrosion, rust prevention and the like, generally, the metal itself is an iron-based metal added with Cr (chromium), Ni (nickel) or the like is known. . However, such a metal added with Cr or Ni has a problem that it is expensive and difficult to process because it is hard.

  Therefore, conventionally, for example, the surface of a metal member has been coated with a fluorine-based resin or the like, but such a resin-based coating is durable against a high-temperature environment in which automobile parts are used. Is insufficient.

  On the other hand, an organic EL using a pinholeless AlxTiyOz film (here, x, y, z is the relative number of atoms) formed by ALD (Atomic Vapor Deposition) as a gas barrier layer has been proposed. (See Patent Document 1).

JP 2007-194168 A

  The present inventor has studied the use of the AlxTiyOz film described in Patent Document 1 as an acid-resistant film for a metal member because it is a film having excellent acid resistance even in a high-temperature environment. However, in this case, according to the experiment by the present inventors, rust was generated in about several thousand hours in the acid resistance test, and no significant improvement in acid resistance was observed.

  The present invention has been made in view of the above problems, and aims to achieve a significant improvement in acid resistance by an acid resistant film in a metal structure formed by coating the surface of a metal member with an acid resistant film. To do.

  The invention described in claim 1 has been found experimentally as a result of experimental studies conducted by the inventors.

That is, according to the invention described in claim 1, the metal member (10) and the acid resistant film (20) provided on the surface (11) of the metal member so as to cover the surface are provided. In order from the surface side of the metal member, the conductive film is an amorphous thin film, and an AlxTiyOz film (21) having x, y, and z as relative atoms, and a TiO ₂ film (22) that is a crystalline thin film are alternately arranged. The AlxTiyOz film is repeatedly laminated, and when the total number of relative atoms x and y (x + y) is 100 atom% in the AlxTiyOz film, the ratio of the relative atom number y to (x + y) is 33 atom% or more and 99 atom%. A metal structure is provided that is characterized by:

  According to the inventor's experiment, when the acid-resistant film is configured as described in claim 1, the rust generation time in the acid resistance test can be tens of thousands of hours or more, and a significant improvement in acid resistance can be achieved. It has been confirmed that this can be realized.

  In addition, the code | symbol in the bracket | parenthesis of each means described in the claim and this column is an example which shows a corresponding relationship with the specific means as described in embodiment mentioned later.

It is a schematic sectional drawing of the metal structure concerning embodiment of this invention. It is process drawing which shows the manufacturing method of the metal structure shown by FIG. It is a graph which shows the relationship between 100y / (x + y) (unit: atom%) in an AlxTiyOz film | membrane, and the amount of dissolution of Ti by an acid resistance test.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, parts that are the same or equivalent to each other are given the same reference numerals in the drawings for the sake of simplicity.

  First, the metal structure according to the present embodiment will be described with reference to FIG. This metal structure is applied to, for example, automotive parts used in a high-temperature, strongly acidic environment. The metal structure of the present embodiment includes a metal member 10 and an acid-resistant film 20 provided on the surface 11 of the metal member 10 so as to cover the surface 11.

The metal member 10 is made of an iron-based metal such as stainless steel (SUS), that is, a metal mainly composed of Fe (iron). The acid resistant film 20 is configured as an alternately laminated film in which the AlxTiyOz film 21 and the TiO ₂ film 22 are alternately and repeatedly laminated in order from the surface 11 side of the metal member 10.

That is, the acid-resistant film 20 is formed by first forming the AlxTiyOz film 21 on the surface 11 of the metal member 10 and then forming the TiO ₂ film 22 on the AlxTiyOz film 21 and then repeating the lamination two or more times. It is a thing. Here, in the acid resistant film 20, the total film thickness and the number of stacked layers are not particularly limited because the design is appropriately changed according to the use environment, the structure of the metal structure, and the like.

The AlxTiyOz film 21 is an amorphous thin film having x, y, and z as the relative number of atoms, and is a film in which alumina (Al ₂ O ₃ ) and titania (TiO ₂ ) are mixed. On the other hand, the TiO ₂ film is a thin film in a crystalline state.

Here, although not limited thereto, it is desirable that the film thickness of one AlxTiyOz film is 7 nm or more, and the film thickness of one TiO ₂ film is 4 nm or less. The reason for this desirable film thickness will be described later. The acid resistant film 20 is formed by laminating one AlxTiyOz film 21 and one TiO ₂ film by ALD (Atomic Vapor Deposition).

  Further, in the acid resistant film 20 of the present embodiment, when the sum (x + y) of the relative number of atoms x and y in the AlxTiyOz film 21 is 100 atom%, the ratio of the relative number of atoms y to (x + y) is 33 atom% or more and 99 atom%. % Or less. That is, the ratio represented by 100y / (x + y) is 33 atom% or more and 99 atom% or less, and hereinafter this ratio is simply referred to as “y ratio”.

[Manufacturing method]
Next, the manufacturing method of the metal structure of this embodiment is described. As described above, this metal structure is manufactured by forming the AlxTiyOz film 21 and the TiO ₂ film 22 in the acid resistant film 20 by ALD. An example of this ALD manufacturing method will be described with reference to FIG.

  First, as shown in FIG. 2A, a metal member 10 is prepared. Then, the metal member 10 is installed in a reaction container (not shown) in the ALD, specifically, in a vacuum chamber. Then, heating is performed so that the temperature inside the reaction vessel and the temperature of the metal member 10 become 450 ° C. here so as to be the film formation temperature.

Next, as shown in FIG. 2B, first, an AlxTiyOz film 21 is formed on the surface of the metal member 10 by ALD (AlyTiyOz film forming step). Specifically, the first step of alternately introducing AlCl ₃ and H ₂ O into the reaction vessel and the second step of alternately introducing TiCl ₄ and H ₂ O into the reaction vessel are repeatedly performed. Thus, a single AlxTiyOz film 21 having a predetermined thickness is formed.

  At this time, the adjustment of the ratio between the relative number of atoms x and y in the AlxTiyOz film 21, that is, the ratio of y is 33 to 99 atom% is the number of cycles in the first step and the number of cycles in the second step. This can be done as appropriate by changing the ratio. For example, if the number of cycles in the first step is increased, the relative number of atoms y of Ti decreases, and if the number of cycles in the first step is decreased, the number of relative atoms y of Ti increases.

Next, as shown in FIG. 2C, a single TiO ₂ film 22 is formed on the AlxTiyOz film 21 by ALD (TiO ₂ film forming step). Specifically, by repeating the process of alternately introducing TiCl ₄ and H ₂ O into the reaction vessel, a single TiO ₂ film 22 having a predetermined thickness is formed.

After that, the AlxTiyOz film forming step and the TiO ₂ film forming step are alternately repeated, whereby the acid resistance of the present embodiment as an alternately laminated film in which the AlxTiyOz film 21 and the TiO ₂ film 22 are alternately laminated. The conductive film 20 is formed, and the metal structure of this embodiment is completed.

Note that the total film thickness of the acid-resistant film 20 is controlled by the number of repetitions of the AlxTiyOz film forming process and the TiO ₂ film forming process as in the case of normal ALD. The thickness of one layer of AlxTiyOz film 21 is controlled by the number of repetitions of the first step and the second step in the AlyTiyOz deposition step, one layer of the film thickness of the TiO ₂ film 22, the TiO ₂ It is controlled by the number of repetitions of the film forming process.
[Examination by acid resistance test]
By the way, in the acid-resistant film 20 as the alternate laminated film of the present embodiment, the configuration in which the ratio of y is 33 atom% or more and 99 atom% or less is adopted by the experimental study conducted by the present inventor as described below. It is the basis. The results of the study will be described below.

  First, as an acid resistant film 20 formed on the surface of the metal member 10, a sample A using a single film of AlxTiyOz having a film thickness of 100 nm to 200 nm was prepared. The sample A was subjected to an acid resistance test.

  In this acid resistance test, an aqueous solution (hereinafter referred to as an acidic solution) containing at least 0.1% or more of hydrochloric acid and sulfuric acid, specifically about pH 1 to 2.5, is brought into contact with the surface of the acid resistant film 20. And left in a high temperature environment of 80 ° C. And the acid-resistant film | membrane 20 reduces and the time when rust generate | occur | produced in the metal member 10 of a base | substrate is made into rust generation | occurrence | production time.

  Here, in the sample A, the ratio of y was set to 33 atom% to 99 atom%, but rust generation was confirmed within a few thousand hours. The rust generation time by this acid resistance test is a target value of, for example, about tens of thousands of hours for automobile parts. Therefore, according to Sample A in which the acid resistant film 20 is a single film of AlxTiyOz, the acid resistance is improved. Was confirmed to be insufficient.

Therefore, the present inventor first creates a sample B using a single film of TiO ₂ , which is a crystalline film having a film thickness of 100 to 200 nm, as the acid resistant film 20 and performs the acid resistance test similar to the above. It was. The reason for focusing on the TiO ₂ is TiO ₂ is to excellent acid resistance than AlxTiyOz.

However, as a result of the acid resistance test using Sample B, the occurrence of rust was confirmed within several hundred hours of rust generation time. This is presumably because the TiO ₂ film is a crystalline film, so that the acidic solution penetrates from the crystal grain boundary and easily reaches the metal member 10.

Therefore, the present inventor has further paid attention to the fact that the AlxTiyOz is an amorphous film, and therefore the alternate laminated film in which the AlxTiyOz film 21 and the TiO ₂ film 22 are alternately laminated is used as the acid resistant film 20. That is, the inventor has focused on adopting the acid resistant film 20 of the present embodiment.

According to the acid resistant film 20 of the present embodiment, the crystal grain boundary of the TiO ₂ film 22 is closed by the amorphous AlxTiyOz film 21, and the acidity from the crystal grain boundary of the TiO ₂ film 22 is determined. This is because it was thought that the penetration of the solution could be suppressed.

However, although the TiO ₂ film 22 itself does not dissolve in an acidic solution, according to the study of the present inventors, if the Al component in the AlxTiyOz film 21 is large, Al dissolves in the acidic solution, and Ti also begins to dissolve together with Al. Has been confirmed. When Ti is thus dissolves in an acidic solution in such a AlxTiyOz film 21, occlusion effect of the grain boundaries of the TiO ₂ film 22 by AlxTiyOz film 21 it will be reduced.

  Therefore, it is necessary to use the AlxTiyOz film 21 having a composition ratio with which there is no problem with the amount of dissolved Ti in the acid-resistant film 20 as the alternate laminated film of the present embodiment. Therefore, the inventor examined the relationship between the amount of Ti melted and the composition ratio in the AlxTiyOz film 21. The result is a graph shown in FIG.

  The result of FIG. 3 shows that the same acid resistance test as described above was performed by forming a single film of AlxTiyOz with a film thickness of 100 nm on the surface of the metal member 10 and changing the ratio of y in the same manner as the sample A above. It is.

  In FIG. 3, the horizontal axis represents the ratio of y, that is, 100y / (x + y) (unit: atom%), and the vertical axis represents the amount of Ti melted out. The amount of Ti melted out was determined by ordinary elemental analysis, and the amount of Ti melted out when the y ratio was 50 atom% was normalized to 1.

The smaller the amount of Ti melted out, the better. When the amount of Ti melted is 1, the amount of Ti melted is almost undissolved, which affects the effect of blocking the crystal grain boundaries of the TiO ₂ film 22 by the AlxTiyOz film 21. It is something that does not. Here, the data indicated by the black rhombus plot in FIG. 3 is data in which the ratio of y is 25 atom%, 33 atom%, 50 atom%, 75 atom%, 83 atom%, and 87.5 atom% in order from the left side of FIG. It is.

  As shown in FIG. 3, it can be seen that when the y ratio is 33 atom% or more, the amount of Ti melted is substantially 1, and a problem-free level is realized. Here, in order to secure the configuration of the AlxTiyOz film, the upper limit of y is 99% or less. In FIG. 3, it is confirmed that the amount of dissolution of Ti is substantially 1 until the y ratio is 87.5 atom%.

  On the other hand, as shown in FIG. 3, when the ratio of y is less than 33 atom%, specifically, 25 atom%, the amount of Ti melted is greatly increased to 6, and such a large value is obtained. Then, the effect of closing the crystal grain boundary by the AlxTiyOz film 21 is affected. In other words, it was confirmed that when the y ratio was 33 atom% to 99 atom%, the amount of Ti melted out could be dramatically reduced to a problem-free level.

Therefore, from the results shown in FIG. 3, the AlxTiyOz film 21 having a y ratio of 33 atom% or more and 99 atom% or less is used together with the TiO ₂ film 22 and the acid-resistant film 20 of the present embodiment as the above-described alternate laminated film. did. And the sample C whose total film thickness of the acid-resistant film | membrane 20 is 100-200 nm was created, and the acid resistance test similar to the above was done.

Here, in the sample C, the film thickness of the single AlxTiyOz film 21 was 7 nm, and the film thickness of the single TiO ₂ film 22 was 4 nm. As a result of the acid resistance test, it was confirmed that the rust generation time was tens of thousands of hours or more when the y ratio in the AlxTiyOz film 21 was in the range of 33 atom% to 99 atom%.

More specifically, in the acid-resistant film 20 of this embodiment, even if the thickness of the single AlxTiyOz film 21 is reduced to 7 nm, the above-described effect of blocking the crystal grain boundaries of the TiO ₂ film 22 is obtained. It can be said that it is demonstrated. The above is the reason why the acid resistant film 20 of the present embodiment adopts a configuration in which the ratio of y is 33 atom% or more and 99 atom% or less.

  Note that, as described above, when the acid resistance test was performed by preparing the sample A using a single film of AlxTiyOz having a thickness of 100 nm to 200 nm as the acid resistant film 20, the ratio of y was 33 atom% or more and 99 atom%. The reason for the occurrence of rust in several thousand hours is estimated as follows.

  Since the AlxTiyOz film is a mixed film in which alumina and titania are mixed, when the film is formed on the surface of the metal member 10, film defects are likely to occur due to impurities present at the crystal grain boundaries of the metal member 10. Then, it is considered that the acidic solution permeates from the film defect in the AlxTiyOz film and causes the metal member 10 to generate rust.

On the other hand, according to the acid resistant film 20 of the alternate laminated film of the present embodiment, since the TiO ₂ film 22 having a larger lattice constant than the AlxTiyOz film 21 is interposed, the film defects in the AlxTiyOz film 21 are suppressed. It is estimated that. Therefore, according to the present embodiment, it is considered that a significant improvement in rust occurrence time has been realized.

[Effects]
As described above, according to this embodiment, the acid resistance film 20, the alternate lamination film of a AlxTiyOz film 21 and the TiO ₂ film 22, and the following 99 atom% or more 33Atom% ratio of y in AlxTiyOz film 21 By doing so, a significant improvement in acid resistance can be realized.

Further, as described above, according to the present embodiment, it is desirable that the film thickness of the single TiO ₂ film 22 is 4 nm or less. This is because if the film thickness is thicker than 4 nm, the influence of the penetration of the TiO ₂ film 22 from the crystal grain boundary becomes large, or the film stress becomes large, and peeling easily occurs.

Further, it is desirable that the thickness of the single layer AlxTiyOz film 21 be 7 nm or more. As described above, it has been experimentally confirmed that when the film thickness is 7 nm, the effect of blocking the crystal grain boundaries of the TiO ₂ film 22 by the AlxTiyOz film 21 is exhibited.

  It is obvious that the blocking effect is more effectively exhibited as the thickness of the single AlxTiyOz film 21 increases. Therefore, it is desirable that the thickness of the single AlxTiyOz film 21 be 7 nm or more.

  And although the total film thickness of the acid-resistant film | membrane 20 is not limited, For example, it shall be about 100 nm-200 nm. In addition, as described above, in the acid resistant film 20 which is an alternately laminated film, the total film thickness and the number of laminated layers are not particularly limited, and may be appropriately changed depending on the use environment, the structure of the metal structure, and the like. Good.

In the present embodiment, the AlxTiyOz film 21 and the TiO ₂ film 22 in the acid resistant film 20 are preferably formed by ALD (Atomic Vapor Deposition) as described above. This is because even if the surface 11 of the underlying metal member 10 is not a single flat surface but has a complicated shape having a concavo-convex shape or the like, it is easy to achieve pinhole-less film formation.

(Other embodiments)
The metal member 10 only needs to be capable of forming the acid-resistant film 20 on the surface 11 and may be made of a metal other than the iron-based metal described above. In addition, the application of the metal structure is not limited to the above-described automobile parts, and it is needless to say that the metal structure may be applied to other metal parts.

  Further, the present invention is not limited to the above-described embodiment, and can be appropriately changed within the scope described in the claims. The above embodiments are not irrelevant to each other, and can be combined as appropriate unless the combination is clearly impossible, and the above embodiments are not limited to the illustrated examples. Absent. In each of the above-described embodiments, it is needless to say that elements constituting the embodiment are not necessarily indispensable except for the case where it is clearly indicated that the element is essential and the case where the element is clearly considered essential in principle. Yes. Further, in each of the above embodiments, when numerical values such as the number, numerical value, quantity, range, etc. of the constituent elements of the embodiment are mentioned, it is clearly limited to a specific number when clearly indicated as essential and in principle. The number is not limited to the specific number except for the case. Further, in each of the above embodiments, when referring to the shape, positional relationship, etc. of the component, etc., the shape, unless otherwise specified and in principle limited to a specific shape, positional relationship, etc. It is not limited to the positional relationship or the like.

Surface of 10 the metal member 11 a metal member 20 acid-resistant film 21 AlxTiyOz film 22 TiO ₂ film

Claims (4)

A metal member (10);
An acid-resistant film (20) provided on the surface (11) of the metal member so as to cover the surface,
The acid-resistant film is, in order from the surface side of the metal member, an amorphous thin film, an AlxTiyOz film (21) having x, y and z as relative atoms, and a TiO ₂ film (22) which is a crystalline thin film. Are alternately laminated a plurality of times,
In the AlxTiyOz film, when the sum of relative atoms x and y (x + y) is 100 atom%, the ratio of the relative atom number y to (x + y) is 33 atom% or more and 99 atom% or less. . _2. The metal structure according to claim 1, wherein the film thickness of the one layer of the TiO ₂ film is 4 nm or less.   3. The metal structure according to claim 1, wherein a film thickness of the one layer of the AlxTiyOz film is 7 nm or more. It is a manufacturing method of the metal structure according to claim 1,
The AlxTiyOz film in the acid-resistant film, and a method for producing a metal structure, characterized in that said TiO ₂ film is deposited by ALD (atomic vapor deposition), respectively.

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