JP7047600B2 - Surface covering member and its manufacturing method - Google Patents

Description

The present invention relates to a surface covering member and a method for manufacturing the same.

Conventionally, in various technical fields, a surface covering member including a metal base material and a coating material containing a metal different from the metal base material and covering the surface of the metal base material has been used. Depending on the material of the covering material, the surface covering member can be provided with functions such as, for example, heat, a corrosive substance, an increase in durability against sliding, and a reduction in friction.

For example, Patent Document 1 has an iron-based metal material and an oxide layer formed on the surface of the iron-based metal material, and the oxide layer is selected from the group consisting of Zr, Ti, and Hf. A metal material containing at least one kind of metal (A) and Fe as an oxide is described. The oxide layer is formed by forming a film of the oxide of the metal (A) or a precursor thereof on the surface of the iron-based metal material by coating or electrodeposition, and then heating the film. The oxide layer thus formed has a two-layer structure of an upper layer containing an oxide of the metal (A) and a lower layer containing an iron oxide.

Japanese Unexamined Patent Publication No. 2009-2035119

However, since the metal material of Patent Document 1 forms a film of a metal (A) oxide or a precursor thereof by a wet method, the thickness of the film tends to vary widely. Further, the increase in the thickness variation of the metal (A) oxide or its precursor may lead to an increase in the variation in the thickness of the oxide layer.

Further, in Patent Document 1, the iron-based metal material and the oxide layer are formed by heating the film of the metal (A) oxide or its precursor to diffuse Fe in the iron-based metal material over the entire oxide layer. We are trying to improve the adhesion with. However, when Fe diffuses from the iron-based metal material, the volume of the iron-based metal material decreases. Therefore, if the diffusion amount of Fe becomes excessively large, voids may be formed between the oxide layer and the iron-based metal material, and the oxide layer may be easily peeled off from the iron-based metal material.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a surface covering member having a small variation in the thickness of the covering material and having excellent adhesion between the covering material and a metal base material, and a method for manufacturing the same. Is.

One aspect of the present invention is a metal substrate ( 203 ) made of iron and provided with one or more openings (11) of through holes, bottomed holes and grooves .
A coating material (4) containing aluminum as a second metal atom different from the first metal atom constituting the metal base material and covering the surface of the metal base material, and
It has a mixed layer (3) interposed between the metal base material and the covering material, and has.
The mixed layer is
The first metal atom, the second metal atom, and the oxygen atom are included.
The ratio of the first metal atom to the total of the first metal atom, the second metal atom, and the oxygen atom is 30 to 55 atom%, and the ratio of the second metal atom is 0.2 to 10.0 atomic%,
It has a thickness of 10 to 50 nm and has a thickness of 10 to 50 nm.
The mixed layer and the covering material are formed on the inner surface (112) of the opening.
The inner diameter at the opening end (113) of the through hole, the inner diameter at the opening end of the bottomed hole, and the width at the opening end of the groove are expressed as the opening diameter D [μm] of the opening, and the depth of the opening is defined as. The surface covering member ( 103 ) has D ≦ 200 μm and 2 ≦ L / D ≦ 50 when expressed as L [μm] .

Another aspect of the present invention is the method for manufacturing a surface covering member according to the above aspect.
A reduction step of heating a metal base material in a reducing gas atmosphere to reduce the surface of the metal base material,
An oxidation step of forming an oxide film on the surface of the metal substrate by heating the metal substrate in an oxidizing gas atmosphere.
The ALD step of forming the coating material on the oxide film layer by the atomic layer deposition method, and
It is in the manufacturing method of the surface covering member which has.

The surface covering member has a mixed layer having the specific composition and thickness between the metal base material and the covering material. By interposing the mixed layer between the metal base material and the covering material in this way, the adhesion between the metal base material and the covering material can be improved as compared with the case where the mixed layer is not provided. Further, by setting the thickness of the mixed layer within the above-mentioned specific range, the amount of the first metal atom diffused from the metal base material to the dressing is reduced, and voids are formed between the metal base material and the mixed layer. Can be suppressed.

As a result, the surface covering member can suppress the peeling of the covering material from the metal base material.

The surface covering member can be manufactured by the manufacturing method of the above-described embodiment. In the production method of the above aspect, the natural oxide film existing on the surface of the metal base material is once reduced in the reduction step, and then the surface of the metal base material is oxidized again in the oxidation step. Then, in the ALD step, a coating material is formed on the oxide film.

In the above-mentioned manufacturing method, the reduction step, the oxidation step, and the ALD step are sequentially performed on the metal base material, so that in the ALD step, the first metal atom constituting the metal base material is diffused into the coating material and coated. The second metal atom contained in the material can be diffused to the metal base material. Then, by diffusing the first metal atom and the second metal atom in this way, a mixed layer having the specific composition and thickness is formed between the metal base material and the coating material, and the surface coating is performed. Members can be obtained.

Further, in the above-mentioned manufacturing method, since the coating material is formed by a dry method, that is, a treatment that does not use a liquid, it is possible to reduce the variation in the thickness of the coating material as compared with the conventional method using a wet method.

As described above, according to the above aspect, it is possible to provide a surface covering member having a small variation in the thickness of the covering material and having excellent adhesion between the covering material and the metal base material, and a method for manufacturing the same.
The reference numerals in parentheses described in the scope of claims and the means for solving the problem indicate the correspondence with the specific means described in the embodiments described later, and limit the technical scope of the present invention. It's not a thing.

FIG. 1 is a partial cross-sectional view showing a main part of the surface covering member in Reference Form 1 . FIG. 2 is a partial cross-sectional view showing a main part of the surface covering member provided with the second covering material in Reference Form 2 . FIG. 3 is a cross-sectional view showing a main part of a nozzle body as a surface covering member in the first embodiment . FIG. 4 is an enlarged view of the through hole in FIG. FIG. 5 is a TEM image of the test body A2 in Experimental Example 1. FIG. 6 is an explanatory diagram showing a depth direction profile of the composition of the test body A2 in Experimental Example 1. FIG. 7 is a TEM image of the test body A3 in Experimental Example 1. FIG. 8 is a TEM image of the test body A4 in Experimental Example 1.

( Reference form 1 )
A reference form relating to the surface covering member and the manufacturing method thereof will be described with reference to FIG. As shown in FIG. 1, the surface covering member 1 of the present embodiment is a mixture of the metal base material 2, the covering material 4 covering the surface of the metal base material 2, and the metal base material 2 and the covering material 4 interposed therebetween. It has a layer 3 and. The metal base material 2 is composed of any of iron, aluminum and copper. The covering material 4 contains a second metal atom different from the first metal atom constituting the metal base material 2.

The mixed layer 3 contains a first metal atom, a second metal atom, and an oxygen atom, and has a thickness of 10 to 50 nm. Further, the ratio of the first metal atom to the total of the first metal atom, the second metal atom, and the oxygen atom in the mixed layer 3 is 30 to 55 atom%, and the second metal atom. The ratio of is 0.2 to 10.0 atomic%.

The thickness of the mixed layer 3 is a value measured in a TEM image of a cross section of the surface covering member 1, that is, a microscope image acquired by a transmission electron microscope. The boundary between the metal substrate 2 and the mixed layer 3 and the boundary between the mixed layer 3 and the covering material 4 can be determined from the result of EDX, that is, the element mapping of the TEM image by the energy dispersive spectroscopy. The boundary between the metal base material 2 and the mixed layer 3 and the boundary between the mixed layer 3 and the covering material 4 may be unclear. Therefore, in FIG. 1, the boundary between the metal base material 2 and the mixed layer 3 and the boundary between the mixed layer 3 and the covering material 4 are shown by broken lines.

The method for producing the surface covering member 1 of the present embodiment includes a reduction step, an oxidation step, and an ALD step. In the reduction step, the metal base material 2 is heated in a reducing gas atmosphere to reduce the surface of the metal base material 2. In the oxidation step, the metal base material 2 is heated in an oxidizing gas atmosphere to oxidize the surface of the metal base material 2 and form an oxide film. In the ALD step, the coating material 4 is formed on the oxide film by the atomic layer deposition method.

First, the configuration of the surface covering member 1 of the present embodiment will be described in more detail.

The metal base material 2 in the surface covering member 1 is made of any one of iron, aluminum and copper. The above-mentioned "iron" is a concept including pure iron and an iron alloy, "aluminum" is a concept including pure aluminum and an aluminum alloy, and "copper" is a concept including pure copper and a copper alloy. By selecting the material of the metal base material 2 from these materials, an oxide film can be formed on the surface of the metal base material 2 in the above-mentioned oxidation step, and further, the mixed layer 3 can be formed in the ALD step.

Of these materials, pure iron and iron alloys (excluding stainless steel) are preferably used as the metal base material 2. A relatively brittle natural oxide film is likely to be formed on the surface of these metals. Even if a film is formed on such a natural oxide film by a conventional method, there is a problem that the natural oxide film becomes a starting point of peeling and the film is easily peeled from the metal substrate 2.

On the other hand, in the present embodiment, since the natural oxide film is once reduced in the reduction step and then the oxide film is formed again, the residual amount of the relatively brittle natural oxide film can be reduced. As a result, when the above-mentioned metal is used as the metal base material 2, peeling of the covering material 4 from the metal base material 2 can be suppressed more effectively.

The shape of the metal base material 2 is not particularly limited, and can be a shape according to the use of the surface covering member 1. For example, the metal base material 2 may have one or more openings among through holes, bottomed holes, and grooves. The through hole means a hole that penetrates the metal base material 2, and the bottomed hole means a hole that does not penetrate the metal base material 2 and has a bottom.

The surface of the metal base material 2 is covered with a covering material 4. The covering material 4 may cover a part of the surface covering member 1 or may cover the entire surface covering member 1. The covering material 4 contains a second metal atom different from that of the metal base material 2. Depending on the material of the covering material 4, for example, the covering material 4 can exert an action effect such as improving the lubricity of the surface covering member 1, improving the electrical insulation property, and improving the corrosion resistance.

Further, the covering material 4 may merely have a function of improving the adhesion to the metal base material 2. In this case, by forming a film having another action on the coating material 4, the adhesion between the metal base material 2 and the film can be improved via the coating material 4.

The covering material 4 may contain, as the second metal atom, one or more metal atoms different from the first metal atom among, for example, aluminum, tantalum, titanium, niobium and hafnium. The covering material 4 may be a simple substance metal composed of one kind of metal atom among these metal atoms, or may be an alloy containing two or more kinds of metal atoms. Further, the covering material 4 may be an oxide containing these metal atoms.

When pure iron and an iron alloy (excluding stainless steel) are used as the metal base material 2, it is preferable that the covering material 4 contains an aluminum atom as a second metal atom, and an oxide of aluminum. It is more preferable that it is composed of (that is, alumina). In this case, when the covering material 4 is formed in the ALD step, the diffusion of iron from the metal base material 2 to the covering material 4 and the diffusion of aluminum atoms from the coating material 4 to the metal base material 2 are likely to occur. .. Therefore, after the ALD step, the mixed layer 3 can be reliably formed between the metal base material 2 and the covering material 4, and the adhesion between the metal base material 2 and the covering material 4 can be further improved.

Further, in this case, in the ALD step, the mixed layer 3 can be formed while the temperature of the metal base material 2 is kept at a relatively low temperature. As described above, by relatively lowering the temperature of the metal base material 2 in the ALD step, it is possible to suppress the deterioration of the metal base material 2 due to heat. Further, in this case, deformation of the metal base material 2 due to heating can be suppressed. As a result, the dimensional accuracy of the finally obtained surface covering member 1 can be further improved, and the desired shape can be obtained.

A mixed layer 3 is interposed between the metal base material 2 and the covering material 4. When the total of the first metal atom, the second metal atom, and the oxygen atom in the mixed layer 3 is 100 atom%, the ratio of the first metal atom is 30 to 55 atom%, and the second The ratio of the metal atoms is 0.2 to 10.0 atomic%. The thickness of the mixed layer 3 is 10 to 50 nm.

By setting the thickness of the mixed layer 3, the ratio of the first metal atom and the ratio of the second metal atom to the specific ranges, the adhesion between the metal base material 2 and the covering material 4 can be improved. .. If any of the thickness of the mixed layer 3, the ratio of the first metal atom, and the second metal atom deviates from the specific range, the adhesion between the metal base material 2 and the covering material 4 is deteriorated. There is a risk.

The mixed layer 3 may have a single-layer structure composed of a single layer having a composition in the specific range, or two or more layers having different compositions from the composition in the specific range. It may have a laminated structure composed of. Further, the composition of the mixed layer 3 may be continuously changed in the depth direction from the metal base material 2 side to the covering material 4 side within the specific range.

The surface covering member 1 of the present embodiment may further have an oxide layer containing an oxide of a first metal atom between the mixed layer 3 and the metal base material 2. The thickness of the oxide layer can be, for example, 2 to 5 nm.

Next, the method for manufacturing the surface covering member 1 of the present embodiment will be described in more detail.

In the production method of this embodiment, the metal base material 2 is subjected to pretreatment such as cleaning and degreasing treatment as necessary, and then a reduction step of heating the metal base material 2 in a reducing gas atmosphere is carried out. By this reduction step, the natural oxide film existing on the surface of the metal substrate 2 can be reduced. In the reduction step, the natural oxide film may be completely reduced or partially reduced. If at least a part of the natural oxide film is reduced, the first metal atom constituting the metal substrate 2 and the second metal atom contained in the coating material 4 are diffused in the subsequent ALD step to diffuse the metal group. A mixed layer 3 can be formed between the material 2 and the covering material 4. From the viewpoint of avoiding peeling of the coating material 4 starting from the natural oxide film, it is preferable to completely reduce the natural oxide film in the reduction step.

The temperature of the metal substrate 2 in the reduction step is preferably 300 ° C. or lower. In this case, deterioration of the metal base material 2 due to heating can be suppressed. Further, in this case, deformation of the metal base material 2 due to heating can be suppressed. Then, by suppressing the deformation of the metal base material 2 in the reduction step, the dimensional accuracy of the finally obtained surface covering member 1 can be further improved and the shape can be brought closer to a desired shape.

The pressure of the reducing gas in the reducing step may be set so that the entire surface on which the mixed layer 3 and the covering material 4 are to be formed come into contact with the reducing gas. The reducing gas used in the reduction step includes, for example, hydrogen (H ₂ ), ammonia (NH ₃ ), silane (SiH ₄ ), hydrazine (N ₂ H ₄ ), and other gases having a hydrogen atom in their molecular structure. Can be used.

When pure iron and an iron alloy (excluding stainless steel) are used as the metal base material 2, it is preferable to use ammonia as the reducing gas. Ammonia can reduce iron oxides at relatively low temperatures. Therefore, the heating temperature of the metal base material 2 in the reduction step can be kept at a relatively low temperature, and the deterioration of the metal base material 2 due to heat can be suppressed. Further, in this case, deformation of the metal base material 2 due to heating can be suppressed. Then, by lowering the heating temperature of the metal base material 2 in the reduction step, the dimensional accuracy of the finally obtained surface covering member 1 can be further improved and the shape can be brought closer to a desired shape.

After performing the reduction step, an oxidation step of heating the metal substrate 2 in an oxidizing gas atmosphere is performed. By this oxidation step, the surface of the metal substrate 2 can be oxidized again to form an oxide film.

The temperature of the metal substrate 2 in the oxidation step is preferably 300 ° C. or lower. The reason for this is the same as in the reduction step. That is, by setting the heating temperature in the oxidation step within the above-mentioned specific range, deterioration of the metal substrate 2 can be suppressed. Further, in this case, the deformation of the metal base material 2 due to heating can be suppressed, and the dimensional accuracy of the finally obtained surface covering member 1 can be further improved to bring it closer to a desired shape.

The pressure of the oxidizing gas in the oxidizing step may be set so that the entire surface on which the mixed layer 3 and the covering material 4 are to be formed come into contact with the oxidizing gas, as in the reducing step. As the oxidizing gas used in the oxidation step, a gas containing an oxygen atom in its molecular structure, such as oxygen (O ₂ ) or water (H ₂ O), can be used.

In the oxidation step, the thickness of the oxide film is preferably 10 to 50 nm. In this case, it is possible to prevent the amount of the first metal atom diffused from the metal base material 2 to the covering material 4 from becoming excessively large in the subsequent ALD step. As a result, it is possible to suppress the formation of voids between the metal base material 2 and the mixed layer 3, and to avoid a decrease in the adhesion between the metal base material 2 and the covering material 4.

After the oxidation step, the ALD step of forming the coating material 4 on the oxide film by the atomic layer deposition method is performed. In the manufacturing method of this embodiment, when the coating material 4 is deposited on the metal base material 2 in the ALD step, the first metal atom contained in the metal base material 2 is diffused to the coating material 4 and the coating material 4 is deposited. The second metal atom contained in the metal base material 2 can be diffused to the metal base material 2. In this way, the first metal atom and the second metal atom diffuse each other, so that the first metal atom, the second metal atom, and the second metal atom are formed between the metal base material 2 and the covering material 4. The mixed layer 3 containing oxygen atoms derived from the oxide film can be naturally formed.

The first metal atom may reach the covering material 4 beyond the mixed layer 3 due to the above-mentioned diffusion. In this case, the ratio of the first metal atom to the total of the first metal atom, the second metal atom, and the oxygen atom in the covering material 4 is the ratio of the first metal atom described above in the mixed layer 3. It will be lower than the range of. Further, the second metal atom may also reach the metal base material 2 beyond the mixed layer 3 due to the above-mentioned diffusion. In this case, the ratio of the second metal atom to the total of the first metal atom, the second metal atom, and the oxygen atom in the metal substrate 2 is the ratio of the second metal atom described above in the mixed layer 3. It will be lower than the ratio.

The above-mentioned atomic layer deposition method includes a step of bringing a raw material gas containing a precursor of a coating material 4 into contact with the surface of the object to be treated to adsorb the precursor to the surface of the object to be treated, and adsorbing the precursor to the surface of the object to be treated. It is a method of alternately repeating the steps of reacting the precursors on the surface. By reacting the precursor on the surface of the object to be treated, the layered dressing 4 can be formed on the surface of the object to be treated. In the ALD step, the above steps may be repeated alternately until the thickness of the covering material 4 becomes a desired thickness.

The precursor used in the ALD step can be appropriately selected depending on the material of the covering material 4. For example, when a metal oxide such as alumina (Al ₂ O ₃ ) or tantalum pentoxide (Ta ₂ O ₅ ) is used as the coating material 4, a volatile organic metal compound containing these metal atoms is used as a precursor. can do. By adsorbing a volatile organic metal compound as a precursor on the surface of an oxide film or a coating material 4, the precursor is reacted with a reaction gas such as oxygen (O ₂ ) or water (H ₂ O). , Metal oxides can be deposited in layers.

In the ALD step, the metal base material 2 may be heated, if necessary, in order to deposit the covering material 4. The temperature of the metal substrate 2 in the ALD step is preferably 300 ° C. or lower. The reason for this is the same as in the reduction step. That is, by setting the heating temperature in the ALD step within the above-mentioned specific range, deterioration of the metal base material 2 can be suppressed. Further, in this case, the deformation of the metal base material 2 due to heating can be suppressed, and the dimensional accuracy of the finally obtained surface covering member 1 can be further improved to bring it closer to a desired shape.

The pressure of the precursor and the reaction gas in the ALD step may be set so that the entire surface on which the mixed layer 3 and the coating material 4 are to be formed come into contact with these gases, as in the reduction step.

The surface covering member 1 of the present embodiment has a mixed layer 3 having the specific composition and thickness between the metal base material 2 and the covering material 4. Therefore, the adhesion between the metal base material 2 and the covering material 4 can be improved and the formation of voids between the metal base material 2 and the mixed layer 3 can be suppressed as compared with the case where the mixed layer 3 is not provided. .. As a result, peeling of the covering material 4 from the metal base material 2 can be suppressed.

Further, in the production method of the present embodiment, the natural oxide film existing on the surface of the metal base material 2 is once reduced in the reduction step, and then the surface of the metal base material 2 is oxidized again in the oxidation step. After that, the coating material 4 is formed on the oxide film in the ALD step. In this way, by sequentially performing the reduction step, the oxidation step, and the ALD step on the metal base material 2, in the ALD step, the first metal atom constituting the metal base material 2 is diffused into the coating material 4, and the metal atom is diffused into the covering material 4. The second metal atom contained in the covering material 4 can be diffused to the metal base material 2. As a result, the mixed layer 3 having the specific composition and thickness can be formed between the metal base material 2 and the covering material 4.

Further, in the manufacturing method of this embodiment, since the covering material 4 is formed by a dry method, that is, a treatment that does not use a liquid, the variation in the thickness of the covering material 4 is reduced as compared with the conventional method using a wet method. Can be done.

( Reference form 2 )
This embodiment is an example of a surface covering member 102 provided with a second covering material 41 that covers the surface of the covering material 4. In addition, among the codes used in the present and subsequent forms, the same codes as those used in the above-mentioned forms represent the same components and the like as those in the above-mentioned forms, unless otherwise specified.

As shown in FIG. 2, the surface covering member 102 of the present embodiment is a mixture of the metal base material 2, the covering material 4 covering the surface of the metal base material 2, and the metal base material 2 and the covering material 4 interposed therebetween. It has a layer 3 and. Further, the surface covering member 102 contains a third metal atom different from the second metal atom contained in the covering material 4, and has a second covering material 41 that covers the surface of the covering material 4.

The thickness of the second covering material 41 can be appropriately selected from the range of, for example, 100 to 200 nm. As the third metal atom, for example, a tantalum atom, a hafnium atom, a titanium atom, a silicon atom and the like can be adopted.

The second coating material 41 may be formed by an atomic layer deposition method like the coating material 4, or may be formed by a method other than the atomic layer deposition method such as a sputtering method, a vapor deposition method, a CVD method, or a plating method. May be good. When the second covering material 41 is formed by the atomic layer deposition method, for example, the work of forming the covering material 4 and the work of forming the second covering material 41 are continuously performed by using the apparatus used in the ALD step. It can be carried out.

When the second covering material 41 is formed by a method other than the atomic layer deposition method, after the formation of the covering material 4 is completed, the metal base material 2 is once taken out from the apparatus, and the second covering material is used by another apparatus. The work of forming the 41 may be performed. Others are the same as in Reference Form 1 .

By providing the second covering material 41 on the surface of the covering material 4 as in this embodiment, the presence of the mixed layer 3 suppresses the peeling of the covering material 4 from the metal base material 2, and the second covering material 41 Functions according to the material can be added.

For example, in order to further improve the oxidation resistance of the surface covering member 1, Ta ₂ O ₅ (that is, tantalum oxide (V)) and HfO ₂ (that is, hafnium oxide) are placed on the surface of the covering material 4. (IV))), a second coating material 41 composed of TiO ₂ (that is, titanium oxide (IV)) or SiO ₂ (that is, silicon dioxide) may be provided.

When the second covering material 41 made of SiO ₂ is provided on the surface of the covering material 4, not only the oxidation resistance of the surface covering member 1 can be further improved, but also the electrical insulation property can be further improved. Further, in order to further improve the hardness of the surface covering member 1, a second covering material 41 made of TiN (that is, titanium nitride) or the like may be provided on the surface of the covering material 4.

( Embodiment 1 )
This embodiment is an example of a surface covering member 103 configured as a nozzle body 5 of an injector for injecting fuel into a combustion chamber in an internal combustion engine.

As shown in FIG. 3, the nozzle body 5 has a tubular shape and has a through hole 111 as an opening 11 at its tip. The through hole 111 penetrates the nozzle body 5 and opens at the tip of the nozzle body 5.

An injector can be configured by arranging a nozzle needle 6 that reciprocates in the longitudinal direction thereof in the in-cylinder space S of the nozzle body 5 of the present embodiment. The injector can intermittently inject fuel by reciprocating the nozzle needle 6 in the in-cylinder space S of the nozzle body 5 and switching the opening and closing of the through hole 111.

As shown in FIG. 3, the nozzle body 5 includes a tubular metal base material 203, a coating material 4 covering the metal base material 203, and a mixed layer 3 interposed between the metal base material 203 and the coating material 4. , A second covering material 41 that covers the surface of the covering material 4. Further, the entire surface of the metal base material 203, that is, the outer surface 21 facing the outer space shown in FIG. 3, the inner surface 22 facing the in-cylinder space S, and the inner surface 112 of the through hole 111 shown in FIG. 4 are mixed layers. 3. It is covered with a covering material 4 and a second covering material 41.

Specifically, the metal base material 203 of this embodiment is made of carbon steel such as chromium molybdenum steel. Further, the covering material 4 is made of Al ₂ O ₃ , and the second covering material 41 is made of Ta ₂ O ₅ or Hf O ₂ . For convenience, the description of the mixed layer 3, the covering material 4, and the second covering material 41 is omitted in FIG. Similarly, in FIG. 4, the description of the mixed layer 3 is omitted, and the description of the covering material 4 and the second covering material 41 is simplified.

In the through hole 111 of the present embodiment, as shown in FIG. 4, when the inner diameter of the opening end 113 is expressed as the opening diameter D [μm] and the depth is expressed as L [μm], D ≦ 200 μm and 2 ≦ L / D ≦ 50 is satisfied. More specifically, the open end 113 of the through hole 111 has a circular shape with an inner diameter of 100 μm. The depth of the through hole 111 is 600 μm.

When the opening 11 is a bottomed hole, the inner diameter of the bottomed hole at the opening end can be set to the opening diameter D [μm] as in the case of the through hole 111. When the opening 11 is a groove, the width of the groove, that is, the inner dimension of the groove in the direction perpendicular to the extending direction of the groove can be set to the opening diameter D [μm].

The nozzle body 5 of this embodiment can be manufactured, for example, by the following method. First, the reduction step, the oxidation step, and the ALD step similar to those in Reference Form 2 are sequentially performed on the metal base material 203 provided with the through holes 111 to form the mixed layer 3 and the covering material 4 on the metal base material 203. After that, while the metal base material 203 is placed in the apparatus used in the ALD step, the second coating material 41 is formed by the atomic layer deposition method using the apparatus.

Further, in the present embodiment, the pressures of the reducing gas in the reducing step, the oxidizing gas in the oxidizing step, the precursor and the reaction gas in the forming work of the ALD step and the second coating material 41 are set to 1 or more Knudsen numbers. It should be set so as to be. Here, the Knudsen number Kn can be calculated by the following mathematical formula (1).

The meanings of the symbols in the above mathematical formula (1) are as follows.
Kn: Knudsen number k _B [J / K]: Boltzmann constant T [K]: Gas temperature σ [m]: Gas molecule diameter P [Pa]: Gas pressure D [μm]: Opening diameter

In this case, the gas described above can be introduced into the through hole 111 by Knudsen diffusion. As a result, these gases can be brought into contact with the entire inner surface of the through hole 111 to form the mixed layer 3, the coating material 4, and the second coating material 41.

As described above, according to the manufacturing method of the present embodiment, the mixed layer 3 and the covering material are formed on the inner surface 112 of the opening 11 in the metal substrate 203 having the opening 11 having a narrow opening diameter D and a deep depth L. 4 and the second covering material 41 can be formed.

Further, according to the manufacturing method of the present embodiment, the temperature of the metal base material 2 can be set to 300 ° C. or lower in each of the reduction step, the oxidation step, the ALD step, and the forming work of the second coating material 41. Therefore, it is possible to reduce the deformation of the metal base material 2 due to heat in the manufacturing process of the surface covering member 103. Further, since the manufacturing method of this embodiment employs a dry method in each of the reduction step, the oxidation step and the ALD step, it is possible to reduce the variation in the thickness of the mixed layer 3 and the covering material 4. As a result, according to the manufacturing method of the present embodiment, it is possible to reduce the change in the dimensions of the opening 11 in the manufacturing process of the surface covering member 103.

The manufacturing method of this embodiment is suitable as a manufacturing method of the nozzle body 5 of the injector. In the injector, it is required to precisely control the injection amount and injection range of the fuel for the purpose of improving the fuel efficiency of the internal combustion engine and purifying the exhaust gas. In order to precisely control the fuel injection amount, injection range, etc., it is necessary to improve the dimensional accuracy of the through hole 111 as the opening 11. Further, since the nozzle body 5 of the injector is exposed to a highly corrosive combustion gas, high corrosion resistance is required.

According to the manufacturing method of this embodiment, as described above, it is possible to reduce the change in the dimensions of the through hole 111 in each of the reduction step, the oxidation step and the ALD step. Further, according to the manufacturing method of the present embodiment, the mixed layer 3, the covering material 4 and the second covering material 41 can be formed on the inner surface 112 of the through hole 111 to improve the corrosion resistance. Therefore, by using the surface covering member 103 manufactured by the manufacturing method of this embodiment as the nozzle body 5 of the injector, the corrosion resistance of the nozzle body 5 is improved, the dimensional accuracy of the through hole 111 is improved, and the internal combustion engine Fuel economy can be improved.

(Experimental Example 1)
This example is an example in which the adhesion between the metal base material 204 and the covering material 4 is evaluated by a scratch test using a flat plate-shaped surface covering member produced by variously changing the treatment conditions in the reduction step. In this example, a chrome molybdenum steel plate was prepared as the metal base material 204. After cleaning and degreasing the metal substrate 204 with acetone, the plate material was heated in ammonia as a reducing gas to perform a reduction step. The pressure of ammonia in the reduction step was 70 Pa, and the heating temperature was 300 ° C. The heating time was set to any of 4 minutes, 16 minutes, and 28 minutes as shown in Table 1. The film thickness of the natural oxide film remaining on the surface of the metal substrate 204 after the reduction step was as shown in Table 1.

Next, the metal base material 204 was heated in oxygen as an oxidizing gas to perform an oxidation step, and an oxide film was formed on the surface of the metal base material 204. The pressure of oxygen in the oxidation step was 1 Pa, the heating temperature was 300 ° C., and the heating time was 13 minutes. Then, alumina as a coating material 4 was formed on the oxide film by the atomic layer deposition method. The thickness of alumina was 0.1 μm. As a result, the test bodies A1 to A3 shown in Table 1 were obtained.

Further, in this example, for comparison with the test bodies A1 to A3, the test body A4 prepared under the same conditions as the test bodies A1 to A3 except that the reduction step was omitted was prepared.

FIG. 5 shows a TEM (that is, transmission electron microscope) image of the test piece A2. As shown in FIG. 5, the test piece A2 has a mixed layer 3 shown in an intermediate darkness between the metal substrate 204 shown in the darkest and the dressing 4 shown in the brightest. Had had. Table 2 shows the results of evaluating the compositions of the measurement points B1 to B4 shown in FIG. 5 by EDX (that is, energy dispersive spectroscopy).

As shown in Table 2, in the test piece A2, when the total of Fe as the first metal atom, Al as the second metal atom, and the oxygen atom contained in the mixed layer 3 is 100 atomic%. The ratio of Fe was 30 to 55 atomic%, and the ratio of Al was 0.2 to 10.0 atomic%.

Further, as shown in Table 2, the composition of the mixed layer 3 in the test piece A2 was different depending on the position in the depth direction. Specifically, the ratio of Fe at the measurement point B2 near the metal substrate 204 was higher than the ratio of Fe at the measurement point B3 closer to the covering material 4 than the measurement point B2. Further, the ratio of Al at the measurement point B2 close to the metal substrate 204 was lower than the ratio of Al at the measurement point B3. From these results and the contrast of the TEM image, the mixed layer 3 of the test body A2 is laminated on the metal base material 204, and is laminated on the lower layer 31 having a relatively high Fe ratio and on the lower layer 31, and is relatively Fe. It is presumed to have a two-layer structure with the upper layer 32 having a low ratio.

The test piece A2 was further analyzed in the depth direction by X-ray photoelectron spectroscopy. FIG. 6 shows the depth direction profile of the composition of the test piece A2. The vertical axis of FIG. 6 is the concentration (atomic%) of each component, and the horizontal axis is the depth (nm) from the surface. In the depth direction analysis, the concentrations of O (oxygen), Al (aluminum), and Fe (iron) were analyzed. For Fe, the states of Fe, Fe ²⁺ , and Fe ³⁺ were distinguished based on the difference in binding energy, and the concentration of each state was analyzed.

As shown in FIG. 6, the test piece A2 had a mixed layer 3 in which Fe, Al, and O coexisted between the metal base material 204 and the covering material 4. Further, according to FIG. 6, it can be understood that the metals Fe, Fe ²⁺ , and Fe ³⁺ coexist in the mixed layer 3 of the test body A2. Since the concentration of Fe ²⁺ in the mixed layer 3 and Fe ³⁺ are about the same, it can be estimated that the mixed layer 3 contains the metal Fe and Fe ₃ O ₄ . Since the depth direction analysis by X-ray photoelectron spectroscopy is a method of acquiring a depth direction profile by repeating etching and analysis, the interface between layers is accurately defined in a laminated structure as in this embodiment. It's difficult to decide. The thickness of each layer based on the depth profile tends to be greater than the thickness of each layer measured in the TEM image.

Further, according to FIG. 6, it can be understood that in the test piece A2, the oxide layer 33 containing the oxide of Fe is formed between the mixed layer 3 and the metal base material 204. Since the concentration of Fe ²⁺ in the oxide layer 33 and Fe ³⁺ are about the same, it can be estimated that Fe ₃ O ₄ is contained in the oxide layer 33.

FIG. 7 shows a TEM (that is, transmission electron microscope) image of the test piece A3. Similar to the test piece A2, the test piece A3 has a mixed layer 3 shown in the middle of the darkness between the metal base material 204 shown in the darkest and the covering material 4 shown in the brightest. Had had. Table 3 shows the results of evaluating the compositions of the measurement points C1 to C4 shown in FIG. 7 by the energy dispersive spectroscopy.

表３に示すように、試験体Ａ３においては、混合層３に含まれる第１の金属原子としてのＦｅ、第２の金属原子としてのＡｌ、酸素原子との合計を１００原子％とした場合に、Ｆｅの比率は３０～５５原子％であり、Ａｌの比率は０．２～１０．０原子％であった。

As shown in Table 3, in the test piece A3, when the total of Fe as the first metal atom, Al as the second metal atom, and the oxygen atom contained in the mixed layer 3 is 100 atomic%. The ratio of Fe was 30 to 55 atomic%, and the ratio of Al was 0.2 to 10.0 atomic%.

The composition of the mixed layer 3 in the test body A3 was different depending on the position in the depth direction, although the change was small as compared with the test body A2. Specifically, the ratio of Fe at the measurement point C2 near the metal substrate 204 was slightly higher than the ratio of Fe at the measurement point C3. Further, the ratio of Al at the measurement point C2 was slightly lower than the ratio of Al at the measurement point C3. From these results and the contrast of the TEM image, the mixed layer 3 of the test body A3 also has two layers, that is, the lower layer 31 having a relatively high Fe ratio and the upper layer 32 having a relatively low Fe ratio, like the test body A2. It is presumed to have a structure.

FIG. 8 shows a TEM image of the test piece A4 without the reduction treatment. Specimen A4 had a layer 34 between the darkest shown metal substrate 204 and the brightest shown dressing 4 with a darkness intermediate between the two. When the composition of this layer 34 was evaluated by EDX, this layer 34 was composed of Fe and O and did not contain Al. From these results, it is presumed that the layer 34 between the metal base material 204 and the coating material 4 in the test piece A4 is a natural oxide film of the metal base material 204 or an oxide film formed in the oxidation step.

In this example, a scratch test was performed on the test pieces A1 to A4 to evaluate the presence or absence of peeling of the covering material 4. For the scratch test, a conical indenter with a tip radius of curvature of 0.2 mm and an angle of 120 degrees was used. The tip of the conical indenter was brought into contact with the covering material 4 of each test piece, and the conical indenter was moved in one direction while being pressed against the covering material 4. At this time, a load was applied to the conical indenter so as to increase in proportion to the moving distance. The rate of increase in the load was set so that the load after moving 10 mm was 100 N.

The residual ratio of the covering material 4 when the conical indenter is removed from the test piece when the moving distance becomes 10 mm and the area sliding with the conical indenter is 100%, that is, the area where the covering material 4 remains. The ratio of was calculated. Further, for the test body A2 and the test body A4, the test body was visually observed during the scratch test, and the load at the time when the covering material 4 started to peel off due to sliding with the conical indenter was recorded. The residual ratio of the covering material 4 and the load at the time when the covering material 4 started to peel off in each test piece were as shown in Table 1.

In the evaluation of the adhesion by the scratch test, when the load at the time when the covering material 4 started to peel off was 27 N or more, it was judged to be acceptable because it has sufficient adhesion for automobile parts. Further, when the load is less than 27N, it is determined to be unacceptable because it does not have the adhesion required for the automobile parts.

As shown in Table 1, the longer the treatment time in the reduction step, the thinner the film thickness of the natural oxide film remaining after the reduction step can be made, and in particular, by setting the treatment time to 16 minutes or more, it is natural. The oxide film could be completely reduced. Further, from the results in Table 1, it can be understood that the adhesion between the covering material 4 and the metal base material 204 is improved by performing the reduction step, and the peeling of the covering material 4 by the scratch test can be suppressed.

From the results in Table 1, it is understood that the test specimens A1 to A3 in which the reduction step, the oxidation step, and the ALD step are sequentially performed on the metal base material 204 have sufficient adhesion for automobile parts and for automobile parts. can. On the other hand, the test body A4 omitting the reduction step was inferior in adhesion to the test bodies A1 to A3.

(Experimental Example 2)
This example is an example in which the adhesion between the metal base material 203 and the covering material 4 is evaluated by a fuel injection test using the nozzle body 5 as the surface covering member 103 manufactured by variously changing the treatment conditions in the reduction step. .. In this example, the shape of the metal base material 203 is changed to the shape of the nozzle body 5 shown in the first embodiment , and the second covering material 41 made of Ta ₂ O ₅ is provided on the covering material 4, except that the shape is different from that of Experimental Example 1. The coating material 4 was formed on the metal base material 203 by the same method to prepare the test pieces D1 to D4.

Injectors were assembled using the test bodies D1 to D4 thus obtained, and a fuel injection test was conducted using the obtained injectors. In the fuel injection test, gasoline was intermittently injected 3.2 × 10 ⁷ times at a pressure of 285 MPa. After the fuel injection test was completed, the nozzle body 5 was cut and the inner surface 112 of the through hole 111 was visually observed to evaluate the presence or absence of the covering material 4. The presence or absence of the covering material 4 in each test piece was as shown in Table 4.

As shown in Table 4, the thinner the film thickness of the natural oxide film remaining after the reduction step, the less likely it is that the coating material 4 is peeled off after the fuel injection test. By comparing Table 1 and Table 4, the thinner the thickness of the natural oxide film remaining after the reduction step, the better the adhesion between the covering material 4 and the metal base material 203, and the peeling of the covering material 4 is achieved. It can be understood that it can be suppressed.

The present invention is not limited to the above-described embodiment and each of the above-mentioned experimental examples, and can be applied to various embodiments without departing from the gist thereof.
For example, in the first embodiment and the second experimental example, an example of the surface covering member 103 in which the second covering material 41 having excellent corrosion resistance is formed on the metal base material 203 and configured as the nozzle body 5 of the injector is shown. However, the surface covering member can be applied to other uses. Further, as the covering material 4 and the second covering material 41, for example, a material having an oxygen barrier property or a material having a water vapor barrier property can be adopted in addition to the material having a high corrosion resistance.

1, 102, 103 Surface covering member 2, 202, 203 Metal base material 3 Mixed layer 4 Coating material

Claims (8)

A metal substrate ( 203 ) made of iron and provided with one or more openings (11) of through holes, bottomed holes and grooves .
A coating material (4) containing aluminum as a second metal atom different from the first metal atom constituting the metal base material and covering the surface of the metal base material, and
It has a mixed layer (3) interposed between the metal base material and the covering material, and has.
The mixed layer is
The first metal atom, the second metal atom, and the oxygen atom are included.
The ratio of the first metal atom to the total of the first metal atom, the second metal atom, and the oxygen atom is 30 to 55 atom%, and the ratio of the second metal atom is 0.2 to 10.0 atomic%,
It has a thickness of 10 to 50 nm and has a thickness of 10 to 50 nm.
The mixed layer and the covering material are formed on the inner surface (112) of the opening.
The inner diameter at the opening end (113) of the through hole, the inner diameter at the opening end of the bottomed hole, and the width at the opening end of the groove are expressed as the opening diameter D [μm] of the opening, and the depth of the opening is defined as. When expressed as L [μm], D ≦ 200 μm and 2 ≦ L / D ≦ 50.
Surface covering member ( 103 ). The surface covering member according to claim 1 , further comprising an oxide layer (33) containing an oxide of the first metal atom between the mixed layer and the metal base material. The surface covering member ( 103 ) contains a third metal atom different from the second metal atom contained in the covering material, and has a second covering material (41) that covers the surface of the covering material. The surface covering member ( 103 ) according to claim 1 or 2 . The surface covering member according to claim 3 , wherein the third metal atom is one or more of tantalum atom, hafnium atom, titanium atom and silicon atom. The surface covering member according to claim 3 or 4 , wherein the second covering material is composed of any one of Ta ₂ O ₅ , HfO ₂ , TIO ₂ or SiO ₂ . The surface covering member according to any one of claims 1 to 5 , wherein the metal base material is made of carbon steel. The method for manufacturing a surface covering member according to any one of claims 1 to 6 .
A reduction step of heating a metal base material in a reducing gas atmosphere to reduce the surface of the metal base material,
An oxidation step of forming an oxide film on the surface of the metal substrate by heating the metal substrate in an oxidizing gas atmosphere.
The ALD step of forming the coating material on the oxide film by the atomic layer deposition method, and
A method for manufacturing a surface covering member. The method for manufacturing a surface covering member according to claim 7 , wherein the reduction step, the oxidation step, and the ALD step are performed under the condition that the temperature of the metal substrate is 300 ° C. or lower.

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