JP7335553B2 - Hydrogen barrier functional film and metal parts - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Law 2nd International Conference on Materials Science & Engineering (ICMSE-EGYPT 2019) March 12, 2019

TECHNICAL FIELD The present invention relates to a hydrogen barrier function film formed on the surface of a metal substrate, and a metal member provided with the hydrogen barrier function film.

In recent years, the development of hydrogen energy systems using high-pressure hydrogen as fuel instead of fossil fuels is underway. Conventionally, among the members for hydrogen stations that supply high-pressure hydrogen, members such as pipes and heat exchangers that are used in a high-pressure hydrogen environment are specified to use metals that are less prone to hydrogen embrittlement. For example, as general-purpose stainless steel, the use of SUS316 and SUS316L (which satisfies specified conditions such as nickel equivalent) is permitted, but the parts cost is high. Therefore, it is required to reduce the cost of parts while ensuring resistance to hydrogen embrittlement.

Patent Literature 1 discloses a technique for improving hydrogen embrittlement resistance by forming a film (hydrogen barrier function film) on a metal substrate. In Patent Document 1, a chromium oxynitride film is formed as a first film on the surface of stainless steel for the purpose of improving the adhesion of the film to a metal substrate, and a ceramic film is further formed as a second film. Form. Although the method of forming the chromium oxynitride film and the ceramic film is not particularly limited, physical vapor deposition methods such as ion plating can be used.

Further, Patent Literatures 2 and 3 disclose techniques for forming a multilayer film on the surface of a metal substrate in order to improve the surface protection function of the metal substrate. Patent Literature 2 describes that a multi-layered film with excellent wear resistance is formed by alternately laminating two types of films composed of compounds of Ti, Al, and N on the surface of a cutting tip. there is The multilayer film described in Patent Document 2 has a total film thickness of 0.5 to 2 μm, and a thickness of one cycle in which two kinds of films are laminated one by one is 0.5 to 20 nm.

In Patent Document 3, a first super-multilayer film and a second super-multilayer film made of a predetermined compound are alternately laminated on the surface of a metal substrate by AIP (arc ion plating) to achieve excellent durability. The formation of super multilayer films is described. In the super multilayer film described in Patent Document 3, the total number of layers of the first super multilayer film and the second super multilayer film is 100 or more. Also, the film thickness of each of the first super multilayer film and the second super multilayer film is nanometer size. Such a super multilayer film can be used as a film with high wear resistance.

JP 2014-214336 A JP-A-7-97679 JP 2019-199647 A

Patent Literature 1 discloses that the hydrogen permeability of SUS316L with a first film formed on the surface and a second film laminated thereon is lower than the hydrogen permeability of SUS316L without a film. . However, further improvement in resistance to hydrogen embrittlement is required for members used in a high-pressure hydrogen environment.

On the other hand, Patent Literatures 2 and 3 describe that excellent wear resistance can be obtained by a multilayer film, but the hydrogen barrier function of the multilayer film has not been studied, and the hydrogen permeability of the multilayer film has not been investigated. No data available.

SUMMARY OF THE INVENTION An object of the present invention is to propose a hydrogen barrier function film having high resistance to hydrogen embrittlement.

In order to solve the above problems, the present invention provides a hydrogen barrier function film in which a first layer and a second layer are alternately laminated, wherein the first layer is TiSiNbN, TiMoN, TiAlN, or AlCrN. and the second layer is made of an alloy nitrogen compound different from that of the first layer among TiSiNbN, TiMoN, TiAlN, and AlCrN, and each of the first layer and the second layer constituting the Among the alloy nitrogen compounds, TiSiNbN is a nitride of an alloy in which the composition ratio of Ti, Si, and Nb is 1 at% or more, respectively, and TiMoN is a nitride of an alloy in which the composition ratio of Ti and Mo is 1 at% or more, respectively. TiAlN is a nitride of an alloy in which the composition ratio of Ti and Al is 1 at% or more, and AlCrN is a nitride of an alloy in which the composition ratio of Al and Cr is 1 at% or more. , the total number of layers of the first layer and the second layer is 10 or more and 1000 or less, and the total thickness is 0.5 μm or more and 2 μm or less.

The hydrogen barrier function film of the present invention is a super-multilayer film in which the total number of layers of the first layer and the second layer is 10 to 1000 layers. Also, the first layer and the second layer are crystalline films made of two kinds of TiSiNbN, TiMoN, TiAlN, and AlCrN. By providing a large number of interfacial layers by multilayering, the hydrogen trapping function is improved. In addition, since the thickness of the entire multilayer film is within the range of 0.5 μm or more and 2 μm or less, columnar crystals are difficult to grow. Therefore, a fine crystal structure is obtained, so that a large number of crystal grain boundaries are obtained, and the hydrogen trapping function is improved. The diffusion and movement of hydrogen can be suppressed by improving the hydrogen capture function. Therefore, hydrogen permeability can be reduced, and hydrogen embrittlement resistance can be improved.

In the present invention, the film thickness of each of the first layer and the second layer is preferably 5 nm or more and 10 nm or less. With such a film thickness, a multilayer interface layer can be provided while maintaining a fine crystal structure. Therefore, the hydrogen trapping function can be enhanced, and the resistance to hydrogen embrittlement can be enhanced.

In the present invention, it is preferable that the first layer is made of TiMoN and the second layer is made of TiAlN. By adopting such a configuration, the hydrogen permeability can be significantly reduced compared to a single layer film.

In the present invention, it is preferable that the first layer is made of TiSiNbN and the second layer is made of TiMoN. By adopting such a configuration, the hydrogen permeability can be significantly reduced compared to a single layer film.

In the present invention, it is preferable that the first layer is made of TiSiNbN and the second layer is made of AlCrN. By adopting such a configuration, the hydrogen permeability can be significantly reduced compared to a single layer film.

Next, a metal member of the present invention comprises a metal substrate and a coating layer that coats the surface of the metal substrate, and the coating layer comprises the hydrogen barrier function film described above. . Thus, by forming a hydrogen barrier function film with a low hydrogen permeability on the surface of a metal substrate, hydrogen embrittlement resistance can be improved, and durability in a high-pressure hydrogen environment can be improved. In addition, since it is not necessary to use a material having high hydrogen embrittlement resistance for the metal base material, the cost of parts can be reduced.

According to the present invention, a large number of interfacial layers are provided by forming a multi-layered film, and the film thickness is set so that the growth of columnar crystals is suppressed and a fine crystal structure is obtained. do. Therefore, the hydrogen permeability of the hydrogen barrier function film can be reduced, and the resistance to hydrogen embrittlement can be enhanced.

1 is a cross-sectional view schematically showing a hydrogen barrier function film and a metal substrate of the present invention; FIG. 1 is a high-resolution transmission electron micrograph (HR-TEM image) of a cross-sectional sample of a hydrogen barrier function film. FIG. 4 is an explanatory diagram schematically showing the mechanism of the hydrogen barrier function; It is a schematic diagram of a differential pressure type hydrogen permeation test apparatus. 4 is a graph showing hydrogen permeability data of Examples and Comparative Examples. 4 is a graph showing hydrogen permeability data of Examples and Comparative Examples.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing a hydrogen barrier function film 10 and a metal substrate 20 of the present invention. The hydrogen barrier function film 10 is formed on the surface of the metal substrate 20 . FIG. 1 illustrates part of a metal member 1 such as a pipe or heat exchanger used in a high-pressure hydrogen environment. The metal member 1 of FIG. 1 includes a metal base 20 and a coating layer covering the surface of the metal base 20 . In this embodiment, the coating layer is the hydrogen barrier function film 10 . The coating layer that covers the surface of the metal substrate 20 may include other layers in addition to the hydrogen barrier function film 10 .

It is preferable that the surface of the metal substrate 20 be subjected to a predetermined pretreatment for enhancing adhesion of the hydrogen barrier function film 10 before forming the hydrogen barrier function film 10 . For example, as the metal substrate 20, one having a predetermined base layer (not shown) formed on the surface or one subjected to predetermined surface processing may be used. The metal base material 20 is a general-purpose steel material. For example, as the metal substrate 20, austenitic stainless steel such as SUS304, SUS304N2, SUS316, SUS316L can be used.

As shown in the partially enlarged view of FIG. 1, the hydrogen barrier function film 10 is a multilayer film in which first layers 11 and second layers 12 are alternately laminated. When the number of layers of the first layer 11 is n and the number of layers of the second layer 12 is m, the total number of layers of the first layer 11 and the second layer 12, that is, n+m is 10 or more and 1000 or less.

The hydrogen barrier function film 10 has a total film thickness T of 0.5 μm or more and 2 μm or less. Moreover, the film thickness t1 of the first layer 11 and the film thickness t2 of the second layer 12 are each 5 nm or more and 10 nm or less. When the film thicknesses t1 and t2 of each layer are 5 nm or more and 10 nm or less, even if the total film thickness T is 0.5 μm or more and 2 μm or less, a super multilayer film having a total number of layers of 100 or more can be formed. The film thickness t1 of the first layer 11 and the film thickness t2 of the second layer 12 may be the same or different.

The first layer 11 and the second layer 12 consist of different alloy nitrogen compounds. Two different alloy nitrogen compounds are selected from TiSiNbN, TiMoN, TiAlN, and AlCrN for forming the first layer 11 and the second layer 12 . That is, the first layer 11 is made of any one of TiSiNbN, TiMoN, TiAlN, and AlCrN, and the second layer 12 is made of a compound other than the first layer 11 among TiSiNbN, TiMoN, TiAlN, and AlCrN. Become. It is preferable that the two selected alloy nitrogen compounds have close lattice constants.

Each of the alloy nitrogen compounds constituting the first layer and the second layer is a nitride of an alloy having a composition ratio of 1 at % or more of each component element. That is, when TiSiNbN is selected from among the above four types of alloy nitrogen compounds, nitrides of alloys having a composition ratio of Ti, a composition ratio of Si, and a composition ratio of Nb of 1 at% or more are used. When TiMoN is selected, a nitride of an alloy having a composition ratio of Ti and a composition ratio of Mo of 1 atomic % or more is used. When TiAlN is selected, a nitride of an alloy having a Ti composition ratio and an Al composition ratio of 1 atomic % or more is used. When AlCrN is selected, a nitride of an alloy having an Al composition ratio and a Cr composition ratio of 1 atomic % or more is used.

For example, the hydrogen barrier function film 10 is formed by alternately laminating a TiMoN film and a TiAlN film. Hereinafter, this combination will be referred to as a TiAlN/TiMoN super multilayer film. Alternatively, the hydrogen barrier function film 10 is formed by alternately stacking TiSiNbN films and TiMoN films. Hereinafter, this combination will be referred to as a TiSiNbN/TiMoN super multilayer film. Also, a TiSiNbN film and an AlCrN film are alternately laminated to form the hydrogen barrier function film 10 . This combination is hereinafter referred to as a TiSiNbN/AlCrN super multilayer film.

(Trial production of hydrogen barrier function film)
FIG. 2 is a high-resolution transmission electron micrograph (HR-TEM image) of a cross-sectional sample of the hydrogen barrier function film 10. FIG. FIG. 2(a) is a partial cross-sectional view of the metal substrate 20 and the hydrogen barrier function film 10, and FIG. 2(b) is an enlarged view of region A in FIG. 2(a). The hydrogen barrier function film 10 shown in FIG. 2 is a prototype example of a TiAlN/TiMoN super multilayer film. As can be seen from the scale shown in FIG. 2, in the prototype example, the film thickness t1 of the first layer 11 (TiMoN layer) is about 5 nm. The film thickness t2 of the second layer 12 (TiAlN layer) is larger than the film thickness of the first layer 11, but smaller than 10 nm. In the hydrogen barrier function film 10 of the prototype example, the first layer 11 and the second layer 12 each have a substantially constant film thickness, and are regularly and alternately laminated.

The method for forming the hydrogen barrier function film 10 is not particularly limited, and may be PVD (Physical Vapor Deposition) or CVD (Chemical Vapor Deposition). For example, in manufacturing the prototype shown in FIG. 2, the first layer 11 and the second layer 12 are alternately laminated on the surface of the metal substrate 20 by AIP (arc ion plating), which is a kind of PVD, and hydrogen A barrier function film 10 was formed. Specifically, the first layer 11 and the second layer 12 were formed by the following procedure.

First, the metal substrate 20 is placed and fixed on the stage in the reaction chamber of the ion plating apparatus. Targets are placed on the stage along the walls of the reaction chamber. Nitrogen gas is introduced into the reaction chamber in order to generate nitride on the metal substrate 20 . The target for the metal substrate 20 and various conditions for ion plating are appropriately set.

Although the details of ion plating are omitted, when a vacuum arc discharge is generated to initiate the process, constituent atoms of the target are vaporized and ionized, forming an atmosphere zone in front of each. As the stage rotates, the metal substrate 20 passes through this atmospheric zone and a coating is deposited on the surface of the metal substrate 20 . After forming a coating to a thickness of 5 nm to 10 nm, the metal substrate 20 is removed from the stage and removed from the reaction chamber of the ion plating apparatus.

After the first layer 11 is formed on the surface of the metal substrate 20 by the film forming process described above, the second layer 12 is formed on the surface of the first layer 11 by performing the film forming process again. 1st layer 11 and 2nd
Alternating layers 12 are repeatedly formed. As a result, n first layers 11 and m second layers 12 are alternately laminated on the surface of the metal substrate 20 . The total number of layers of the first layer 11 and the second layer 12, that is, n+m is 10 or more and 1000 or less, and the total thickness T is 0.5 μm or more and 2 μm or less. 12 to form the hydrogen barrier function film 10 on the surface of the metal substrate 20 .

(Mechanism of hydrogen barrier function)
The present inventors used a cross-sectional sample of the prototype hydrogen barrier function film 10 to analyze its microstructure. That is, HR-TEM images were analyzed as shown in FIG. Further, electron beam diffraction, EDX analysis (energy dispersive X-ray analysis), etc. were performed. As a result, the crystal structure, crystal grain size, orientation, etc. were comprehensively analyzed. Then, based on the analysis results, the mechanism of the hydrogen barrier function in the hydrogen barrier function film 10 was considered as follows.

FIG. 3 is an explanatory diagram schematically showing the mechanism of the hydrogen barrier function. As described above, the hydrogen barrier function film 10 according to the present invention is a multilayer film in which the total number of layers of the first layer 11 and the second layer 12 is 10 layers or more and 1000 layers. A number of interfacial layers 13 are provided between. Both the first layer 11 and the second layer 12 are crystalline films, but have a fine crystal structure without columnar crystals straddling the interface layer 13 . That is, by setting the total film thickness within the range of 0.5 μm or more and 2 μm or less, crystal growth is suppressed and columnar crystals are less likely to be formed. Therefore, since a large number of interface layers 13 and crystal grain boundaries 14 (boundary of crystal grains) capable of capturing hydrogen atoms H are provided, a large amount of hydrogen atoms H can be captured and the diffusion movement of hydrogen atoms H can be suppressed. It has become. Therefore, the hydrogen permeability is low, and when formed on the surface of a metal member, the resistance to hydrogen embrittlement of the member can be enhanced.

(Hydrogen permeability test)
FIG. 4 is a schematic diagram of the differential pressure type hydrogen permeation test apparatus 30. As shown in FIG. The present inventors measured the hydrogen permeability of the prototype hydrogen barrier function film 10 by the differential pressure gas measurement method using the apparatus shown in FIG. A specimen 40 used in the differential pressure gas measurement method is obtained by forming the hydrogen barrier function film 10 on the surface of a thin metal substrate 20 . FIG. 4 shows the metal substrate 20 with the hydrogen barrier function film 10 formed on one side. A functional film 10 is formed. As for the size of the specimen 40, the thickness of the metal substrate 20 is 0.1 mm, and the diameter is 35 mm.

The hydrogen barrier function film 10 of the prototype test piece 40 was formed so that the film thickness of each of the first layer 11 and the second layer 12 was 5 nm or more and 10 nm or less, and the total film thickness T was 1 μm or 2 μm. . The total number of layers of the first layer 11 and the second layer 12 was about several hundred layers, and was at least 100 layers.

As shown in FIG. 4, the differential pressure type hydrogen permeation test apparatus 30 includes a chamber in which a specimen 40 is placed. The chamber is sealed using a metallic sealing material 33 that has low reactivity with respect to hydrogen gas and high airtightness. A specimen 40 is held by a holding member 34 and arranged so as to partition the chamber into a pressurized space 31 and a depressurized space 32 . After setting the specimen 40, the chamber is evacuated and maintained at the test temperature under vacuum. The test temperature was set in three stages of 573K (300°C), 673K (400°C), and 773K (500°C). After the temperature of the specimen 40 is stabilized, hydrogen (99.9995% purity) is introduced into the pressurized space 31 at a filling pressure of 400 kPa. The hydrogen permeation rate of the specimen 40 was measured by measuring the amount of hydrogen permeated to the reduced pressure space 32 side by gas chromatography. Since the hydrogen concentration became constant 3 hours after the introduction of hydrogen, the measured value at this time was adopted as the measured value of the hydrogen permeability.

5 and 6 are graphs showing hydrogen permeability data of Examples and Comparative Examples. Figure 5,
The data in FIG. 6 were measured by the differential pressure gas measurement method described above. FIG. 5 shows data when SUS316L is used as the metal base material 20 . The hydrogen barrier function film 10 includes five types of Examples A1 to A5 shown below.
・Example A1: TiAlN/TiMoN super multilayer film (total film thickness 1 μm)
・Example A2: TiAlN/TiMoN super multilayer film (overall film thickness 2 μm)
・Example A3: TiSiNbN/TiMoN super multilayer film (total film thickness 1 μm)
・Example A4: TiSiNbN/TiMoN super multilayer film (overall film thickness 2 μm)
・Example A5: TiSiNbN/AlCrN super multilayer film (total film thickness 1 μm)

Among Comparative Examples B1 to B6 shown in FIG. 5, Comparative Example B1 is data of a metal substrate (SUS316L) without a film. Further, Comparative Examples B2 to B6 are the following five types of single layer films. In the same manner as in Examples A1 to A5, test specimens were used in which single-layer films were formed on both surfaces of the metal substrate 20 .
・Comparative Example B1: Metal substrate without film (SUS316L)
・Comparative example B2: TiMoN single layer film (total film thickness 1 μm)
・Comparative example B3: TiMoN single layer film (overall film thickness 2 μm)
・Comparative example B4: TiN single layer film (overall film thickness 2 μm)
・Comparative example B5: TiAlN single layer film (overall film thickness 2 μm)
・Comparative example B6: AlCrN single layer film (total film thickness 1 μm)

As shown in FIG. 5, the hydrogen permeability of the specimens having the single-layer membranes of Comparative Examples B2 to B6 is about 1/100 of the hydrogen permeability of the metal substrate without the membrane (Comparative Example B1). On the other hand, the hydrogen permeability of the specimens provided with the hydrogen barrier functional films 10 of Examples A1 to A5 is about 1/1000 of the hydrogen permeability of the metal substrate without the film (Comparative Example B1). That is, the hydrogen barrier function films 10 of Examples A1 to A4 (the TiAlN/TiMoN super multilayer film and the TiSiNbN/TiMoN super multilayer film) all have lower hydrogen permeability than the single layer film of the comparative example. Such results were obtained for all three temperature conditions. Also, the hydrogen permeability of the TiSiNbN/AlCrN super multilayer film of Example 5 is lower than that of the single layer film under the highest temperature conditions (573 K/300° C.), and is comparable to that of the single layer film under other temperature conditions. In any super multilayer film, the lower the temperature, the lower the hydrogen permeability.

FIG. 6 shows data when SUS304 is used as the metal substrate. FIG. 6 shows data when the hydrogen barrier function films 10 (TiSiNbN/TiMoN multilayer films) of Examples A3 and A4 among the above Examples A1 to A5 are formed on both surfaces of SUS304. As comparative examples, data for a metal substrate (SUS304) without a film and data for a case where the single-layer films of Comparative Example B3 were formed on both surfaces of SUS304 are shown. Even when SUS304 was used as the metal substrate, the test specimens provided with the hydrogen barrier functional films 10 of Examples A3 and A4 had lower hydrogen permeability than the specimen provided with the single layer film of Comparative Example B3. Also, the lower the temperature, the lower the hydrogen permeability.

(Effect)
As described above, the hydrogen barrier function film 10 according to the present invention was able to achieve a hydrogen permeability of about 1/1000 that of a metal substrate without a film. In other words, a hydrogen permeation rate one order of magnitude lower than that of a single-layer film could be achieved. A low hydrogen permeability means high hydrogen barrier properties and high hydrogen embrittlement resistance. The combination of alloy nitrogen compounds forming the hydrogen barrier function film 10 is not limited to the above three types, and two types of TiSiNbN, TiMoN, TiAlN, and AlCrN can be appropriately combined.

By forming the hydrogen barrier function film 10 according to the present invention on the surface of the metal substrate 20, the resistance to hydrogen embrittlement can be enhanced, and the durability of the metal member 1 in a high-pressure hydrogen environment can be enhanced. Moreover, since the metal base material 20 does not need to be made of a material having high resistance to hydrogen embrittlement, the parts cost of the metal member 1 can be reduced.

Although the present invention has been specifically described above based on the embodiments, it is needless to say that the present invention is not limited to the above embodiments and can be variously modified without departing from the gist of the invention.

REFERENCE SIGNS LIST 1 Metal member 10 Hydrogen barrier function film 11 First layer 12 Second layer 13 Interface layer 14 Crystal grain boundary 20 Metal substrate 30 Differential pressure type hydrogen permeation test device 31 Pressurized space 32 Reduced pressure Space 33 Seal material 34 Holding member 40 Specimen T Overall film thickness t1 First layer film thickness t2 Second layer film thickness

Claims (6)

A hydrogen barrier function film in which a first layer and a second layer are alternately laminated,
the first layer comprises an alloy nitrogen compound of any of TiSiNbN, TiMoN, TiAlN, and AlCrN;
wherein the second layer comprises an alloy nitrogen compound different from that of the first layer among TiSiNbN, TiMoN, TiAlN, and AlCrN;
Among the alloy nitrogen compounds constituting the first layer and the second layer, TiSiNbN is a nitride of an alloy having a composition ratio of Ti, Si, and Nb of 1 at% or more, and TiMoN is Ti and Ti. TiAlN is a nitride of an alloy in which the composition ratio of Mo is 1 at% or more, respectively, TiAlN is a nitride of an alloy in which the composition ratio of Ti and Al is 1 at% or more, and AlCrN is a composition ratio of Al and Cr. is a nitride of an alloy in which each is 1 at% or more,
The total number of layers of the first layer and the second layer is 10 or more and 1000 or less,
A hydrogen barrier function film characterized by having a total film thickness of 0.5 μm or more and 2 μm or less. 2. The hydrogen barrier function film according to claim 1, wherein each of said first layer and said second layer has a thickness of 5 nm or more and 10 nm or less. 3. The hydrogen barrier function film according to claim 1, wherein the first layer is made of TiMoN and the second layer is made of TiAlN. 3. The hydrogen barrier function film according to claim 1, wherein said first layer is made of TiSiNbN, and said second layer is made of TiMoN. 3. The hydrogen barrier function film according to claim 1, wherein said first layer is made of TiSiNbN, and said second layer is made of AlCrN. a metal substrate;
a coating layer covering the surface of the metal substrate,
A metal member, wherein the coating layer comprises the hydrogen barrier function film according to any one of claims 1 to 5.

Images