JP2022072110A - Surface coating member and nozzle body for injector - Google Patents

Abstract

To provide a surface coating member capable of securing adhesion between an iron base material and a coating material even in a case of lengthening a storage time from modification of an iron base material surface to film formation of the coating material, and a nozzle body for an injector using the surface coating member.SOLUTION: A surface coating member 1 has an iron base material 2 composed of iron or an iron alloy, a coating material 4 that coats the surface of the iron base material 2, and a mixed layer 3 interposed between the iron base material 2 and the coating material 4. The mixed layer 3 contains Fe and Fe2O3, and the Fe2O3 ratio is 52.6% or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to a surface covering member and a nozzle body for an injector.

Conventionally, in various technical fields, an iron base material made of iron or an iron alloy, a coating material covering the surface of the iron base material, and a mixed layer interposed between the iron base material and the coating material are provided. Surface covering members are used.

For example, Patent Document 1 discloses a technique of using a surface coating member having a mixed layer containing Fe atoms and O atoms between an iron base material and a coating material for a nozzle body of an injector. This document describes a technique for forming a mixed layer by alkaline-treating the surface of an iron base material with an aqueous solution of tetramethylammonium hydroxide, an aqueous solution of sodium hydroxide, or the like.

Japanese Unexamined Patent Publication No. 2019-206740

The prior art still has room for improvement in the following points regarding ensuring the adhesion between the iron base material and the covering material. That is, in the prior art, when the storage time from the modification of the surface of the iron base material to the film formation of the coating material is relatively short, the adhesion between the iron base material and the coating material can be ensured. However, in the prior art, when the storage time from the modification of the surface of the iron base material to the film formation of the coating material becomes relatively long, the adhesive force between the iron base material and the coating material decreases. Therefore, it is difficult to extend the storage time of the prior art, and the productivity is poor.

The present invention has been made in view of the above problems, and secures the adhesion between the iron base material and the coating material even when the storage time from the modification of the surface of the iron base material to the formation of the coating material is lengthened. It is an object of the present invention to provide a surface covering member capable of being used, and a nozzle body for an injector using the surface covering member.

One aspect of the present invention is an iron base material (2) made of iron or an iron alloy.
The covering material (4) that covers the surface of the iron base material and
It has a mixed layer (3) interposed between the iron base material and the covering material, and has.
The above mixed layer
Including Fe and Fe ₂ O ₃
Fe ₂ O ₃ ratio is 52.6% or less,
It is on the surface covering member (1).

Another aspect of the present invention is composed of the above-mentioned surface covering member.
The iron base material has a through hole (111) for injecting fuel, and has a through hole (111).
The injector nozzle body (5) has the mixed layer and the covering material formed at least on the inner surface (112) of the through hole.

The surface covering member has the above configuration. Therefore, according to the surface covering member, the adhesion between the iron base material and the coating material can be ensured even when the storage time from the modification of the surface of the iron base material to the film formation of the coating material is lengthened.

The injector nozzle body has the above configuration. Therefore, according to the injector nozzle body, the adhesion between the iron base material and the coating material can be ensured even when the storage time from the modification of the surface of the iron base material to the film formation of the coating material is lengthened.

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 diagram schematically showing a part of a cross section perpendicular to the surface of the surface covering member of the first embodiment. FIG. 2 is a diagram schematically showing another example of a part of a cross section perpendicular to the surface of the surface covering member of the first embodiment. FIG. 3 is a view showing a cross section of the injector nozzle body of the second embodiment. FIG. 4 is an enlarged view of the tip of the injector nozzle body shown in FIG. FIG. 5 is a diagram showing a determination table (based on VDI3198 standard) of the adhesive force of the coating material in the test piece prepared in Experimental Example 1. FIG. 6A is a diagram showing an example of a cross section of a through hole as an injection hole in the injector nozzle body of the test piece produced in Experimental Example 1, and FIG. 6B is a diagram showing an example of a cross section of the through hole formed in the through hole cross section. It is a figure which showed an example of the indentation. FIG. 7 is a diagram showing a peeling state of the coating material in the test piece A1 obtained in Experimental Example 1. FIG. 8 is a diagram showing a peeling state of the coating material in the test body A12 obtained in Experimental Example 1. FIG. 9 is a diagram showing a peeling state of the coating material in the test body A14 obtained in Experimental Example 1. FIG. 10 is a diagram showing the relationship between the thickness [nm] of the mixed layer and the adhesion force [Lv] obtained in Experimental Example 1. FIG. 11 is a TEM-EELS component mapping diagram of the mixed layer in the test body A4 obtained in Experimental Example 2 by a transmission electron microscope (TEM) -electron energy loss spectroscopy (EELS). FIG. 12 is a component intensity distribution diagram of the mixed layer in the test body A4 obtained in Experimental Example 2, (a) is the Fe component intensity distribution of the mixed layer, and (b) is Fe ₂ of the mixed layer. O ₃ component intensity distribution. FIG. 13 is a TEM-EELS analysis result of the mixed layer in the test body A1 obtained in Experimental Example 3, (a) is a TEM photograph, and (b) is a TEM-EELS component mapping diagram. 14A and 14B are TEM-EELS analysis results of the mixed layer in the test body A12 obtained in Experimental Example 3, where FIG. 14A is a TEM photograph and FIG. 14B is a TEM-EELS component mapping diagram. FIG. 15 is a TEM-EELS analysis result of the mixed layer in the test body A4 obtained in Experimental Example 3, (a) is a TEM photograph, and (b) is a TEM-EELS component mapping diagram. 16A and 16B are TEM-EELS analysis results of the mixed layer in the test body A14 obtained in Experimental Example 3, where FIG. 16A is a TEM photograph and FIG. 16B is a TEM-EELS component mapping diagram.

The surface covering member of the present embodiment includes an iron base material made of iron or an iron alloy, a covering material covering the surface of the iron base material, and a mixed layer interposed between the iron base material and the covering material. Have. The mixed layer contains Fe and Fe ₂ O ₃ , and the Fe ₂ O ₃ ratio is 52.6% or less.

According to the research results of the present inventors, it is possible to secure the adhesion between the iron base material and the coating material when the storage time from the modification of the surface of the iron base material to the film formation of the coating material is relatively short. Even if it was possible, it was found that when the storage time from the modification of the surface of the iron base material to the formation of the coating material was relatively long, the adhesion between the iron base material and the coating material was lowered. As a result of further investigation into the cause, the present inventors have found that the adhesion between the iron substrate and the mixed layer changes depending on the amount of Fe ₂ O ₃ contained in the mixed layer in relation to the storage time. I found it. The surface covering member of the present embodiment is made based on such knowledge. Since the surface covering member of the present embodiment has the above configuration, the adhesion between the iron base material and the mixed layer is ensured even when the storage time from the modification of the surface of the iron base material to the formation of the coating material is lengthened. It is possible to secure the adhesion between the iron base material and the covering material.

The injector nozzle body of the present embodiment is composed of the surface covering member of the present embodiment, and the iron base material has a through hole as a injection hole for injecting fuel, and at least inside the through hole. A mixed layer and a covering material are formed on the surface.

Since the injector nozzle body of the present embodiment has the above configuration, the adhesion between the iron substrate and the mixed layer is ensured even when the storage time from the modification of the iron substrate surface to the film formation of the coating material is lengthened. It is possible to secure the adhesion between the iron base material and the covering material.

Hereinafter, the surface covering member and the nozzle body for the injector of the present embodiment will be described in detail with reference to the drawings. The surface covering member and the injector nozzle body of the present embodiment are not limited by the following examples.

(Embodiment 1)
The surface covering member of the first embodiment will be described with reference to FIGS. 1 and 2. As illustrated in FIGS. 1 and 2, the surface covering member 1 of the present embodiment includes an iron base material 2, a covering material 4 that covers the surface of the iron base material 2, and an iron base material 2 and a covering material 4. It has a mixed layer 3 interposed between the two.

The layer structure of the surface covering member 1 can be basically grasped by observing a cross section perpendicular to the surface of the surface covering member 1 using a transmission electron microscope (TEM). Further, the boundary between the iron 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 FIGS. 1 and 2, the boundary between the iron 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. If the boundaries between the iron substrate 2 and the mixed layer 3 and the boundaries between the mixed layer 3 and the coating material 4 are unclear, each boundary is a transmission electron microscope (TEM) -energy dispersive X-ray analysis (EDX). It can be determined from the result of element mapping by (analysis).

The iron base material 2 is made of iron or an iron alloy. As the iron alloy, for example, carbon steel, chromium molybdenum steel and the like can be used.

The surface of the iron base material 2 is covered with a covering material 4. Depending on the material of the covering material 4, for example, the covering material 4 can exert an action effect such as improving the corrosion resistance of the surface covering member 1, improving the lubricity, and improving the electrical insulation. FIG. 1 shows an example in which the covering material 4 is composed of one layer. Further, FIG. 2 shows an example in which the covering material 4 is composed of two layers, a first layer 41 in contact with the mixed layer 3 and a second layer 42 in contact with the first layer 41. That is, the covering material 4 can be composed of one layer or a plurality of layers of two or more layers. The dressing 4 can be formed, for example, by an atomic layer deposition (ALD) method or the like. The covering material 4 can be made of, for example, a metal oxide such as Ta ₂ O ₅ , HfO ₂ , Nb ₂ O ₅ , TiO ₂ , Al ₂ O ₃ , and SiO ₂ .

Here, the mixed layer 3 contains Fe and Fe ₂ O ₃ . Further, the mixed layer 3 may further contain an atom other than Fe derived from the iron base material 2 (metal atom other than Fe, etc.) and an atom derived from the coating material 4 (metal atom, etc.). The Fe ₂ O ₃ ratio in the mixed layer 3 is 52.6% or less. The Fe ₂ O ₃ ratio is preferably set from the viewpoint of ensuring the adhesion between the iron base material 2 and the covering material 4 by ensuring the adhesion between the iron base material 2 and the mixed layer 3. 28% or less, more preferably 25% or less, still more preferably 20% or less, even more preferably 15% or less, even more preferably 10.3% or less, even more preferably 10% or less, further. It is more preferably 5% or less, still more preferably 3.6% or less, even more preferably 3% or less, even more preferably 2% or less, still more preferably 1.3% or less. Can be done. From the viewpoint of ensuring the adhesion between the iron base material 2 and the mixed layer 3, the smaller the Fe ₂ O ₃ ratio is, the better, but it is possible to completely eliminate Fe ₂ O ₃ contained in the mixed layer 3. It's difficult. Therefore, the lower limit of the Fe ₂ O ₃ ratio in the mixed layer 3 is not particularly limited. The mixed layer 3 may contain FeO and / or Fe ₃ O ₄ or the like as iron oxide other than Fe ₂ O ₃ .

The Fe ₂ O ₃ ratio in the mixed layer 3 can be measured by element analysis and chemical bond state analysis by transmission electron microscopy (TEM) -electron energy loss spectroscopy (EELS). Specifically, a measurement sample having a cross section perpendicular to the surface of the surface covering member 1 is prepared, and the spectral image region is defined so as to include a part of the mixed layer 3. At this time, the spectral image region can have a size of, for example, 100 nm to 1000 nm in the vertical direction and 100 nm to 1000 nm in the horizontal direction. Next, the component mapping of Fe and iron oxide is obtained for the spectral image region. Next, a line of the same length is drawn at the same location in the Fe component mapping, Fe ₂ O ₃ component mapping, Fe O component mapping, and Fe ₃ O ₄ component mapping, and the Fe component intensity and Fe ₂ O ₃ component intensity in the line range are used. The FeO component strength and the Fe ₃ O ₄ component strength are obtained, respectively. At this time, the line range can be in the range of 100 nm to 1000 nm. Next, the area value of the Fe component intensity in the above line range is obtained from the obtained Fe component intensity distribution. Further, the area value of the Fe ₂ O ₃ component intensity in the above line range is obtained from the obtained Fe ₂ O ₃ component intensity distribution. Further, the area value of the FeO component intensity in the above line range is obtained from the obtained FeO component intensity distribution. Further, the area value of the Fe ₃ O ₄ component intensity in the above line range is obtained from the obtained Fe ₃ O ₄ component intensity distribution. Next, 100 × (area value of Fe ₂ O ₃ component strength) / (area value of Fe component strength, area value of Fe ₂ O ₃ component strength, area value of Fe O component strength, and area value of Fe ₃ O ₄ component strength). The Fe ₂ O ₃ ratio is calculated from the formula (total value of). The FeO ratio or the Fe ₃ O ₄ ratio can be calculated by replacing the numerator in the above formula with (area value of FeO component intensity) or (area value of Fe ₃ O ₄ component intensity), respectively.

The thickness (thickness) of the mixed layer 3 can be 50 nm or more. When the thickness of the mixed layer is 50 nm or more, the iron base material 2 and the coating material 4 adhere to each other even when the storage time from the modification of the surface of the iron base material 2 to the film formation of the coating material 4 is relatively long. It becomes easier to secure power. The thickness of the mixed layer 3 is preferably 70 nm or more, more preferably 90 nm or more, still more preferably 100 nm or more, still more preferably 110 nm or more, and even more, from the viewpoint of ensuring the above-mentioned effect. It can be preferably 120 nm or more, and even more preferably 130 nm or more. Further, the thickness of the mixed layer 3 can be 700 nm or less. When the thickness of the mixed layer is 700 nm or less, the iron base material 2 and the mixed layer 3 adhere to each other even when the storage time from the modification of the surface of the iron base material 2 to the film formation of the coating material 4 is relatively long. It becomes easier to secure power. The thickness of the mixed layer 3 is preferably 650 nm or less, more preferably 600 nm or less, still more preferably 550 nm or less, still more preferably 500 nm or less, and further, from the viewpoint of ensuring the above effect. It can be more preferably 450 nm or less, even more preferably 400 nm or less, even more preferably 350 nm or less, and even more preferably 300 nm or less.

The thickness of the mixed layer 3 described above is an arithmetic average of the thickness measurement values of the mixed layer 3 at any 10 locations when the cross section perpendicular to the surface of the surface covering member 1 is observed with a transmission electron microscope (TEM). The value.

In the surface covering member 1, the shape of the iron base material 2 is not particularly limited, and the shape can be made according to the use of the surface covering member 1. For example, the iron substrate 2 can have at least one opening selected from through holes, bottomed holes, and grooves (not shown in FIGS. 1 and 2). The through hole means a hole that penetrates the iron base material 2, and the bottomed hole means a hole that does not penetrate the iron base material 2 and has a bottom.

The covering material 4 may cover a part of the surface of the iron base material 2 or may cover the whole surface. When the iron base material 2 has the above-mentioned opening, the mixed layer and the covering material may be formed at least on the inner surface of the opening. According to this configuration, for example, even when a high-pressure fluid is moved through the opening, the adhesion between the iron base material 2 and the mixed layer 3 is excellent, so that the shearing force of the moving high-pressure fluid causes the iron base. The covering material 4 is less likely to peel off from the material 2, and the adhesion between the iron base material 2 and the covering material 4 is excellent. Therefore, according to this configuration, the durability of the surface covering member 1 in which the iron base material 2 has an opening can be enhanced.

The surface covering member 1 can be manufactured, for example, as follows.

The method for producing the surface covering member 1 of the present embodiment includes a first step of performing an alkali treatment in which the surface of the prepared iron base material 2 is brought into contact with an alkali treatment liquid, and an atom on the surface of the iron base material 2 after the alkali treatment. It is possible to have a second step of forming the covering material 4 by the layer deposition method.

The iron base material 2 to be prepared can be subjected to pretreatment such as cleaning and degreasing treatment, if necessary.

As the alkaline treatment liquid, an alkaline liquid having a pH of 14 or higher containing an iron chelating agent capable of forming an iron chelate can be used. As a result, the above-mentioned mixed layer 3 can be formed between the iron base material 2 and the covering material 4. This is presumed to be due to the following mechanism. By using the above alkaline treatment liquid, iron is dissolved by the alkali on the surface of the iron base material 2, and the dissolved iron ions are captured by the iron chelating agent to form an iron chelate. Then, in a state where the iron chelate is separated from the surface of the iron base material 2, etching of the surface of the iron base material 2 with an alkali proceeds. As a result, the formation of FeO, Fe ₃ O ₄ and Fe ₂ O ₃ on the surface of the iron base material 2 is suppressed as compared with the case where the iron chelating agent is not used in the alkaline treatment liquid. Specifically, FeO and Fe ₃ O ₄ are hardly generated (FeO and Fe ₃ O ₄ are hardly detected), and Fe ₂ O ₃ is generated (Fe ₂ O ₃ is detected). Compared with the case where the iron chelating agent is not used in the alkaline treatment liquid, the production of Fe ₂ O ₃ is sufficiently suppressed. That is, by the alkali treatment with the alkali treatment liquid, the surface of the iron base material 2 is etched and reformed at the same time, and the iron oxide in the mixed layer 3 is reduced. Therefore, by improving the physical adhesion on the surface of the iron base material 2 and improving the adhesion by modifying the surface of the iron base material 2 with alkali, from the modification of the surface of the iron base material 2 to the film formation of the coating material. Even when the storage time of the iron base material 2 is lengthened, the adhesion between the iron base material 2 and the mixed layer 3 can be enhanced. Further, the thickness of the mixed layer 3 can also be formed to be relatively thick.

Examples of the alkali used in the alkali treatment liquid include an aqueous solution of sodium hydroxide, an aqueous solution of potassium hydroxide, an aqueous solution of tetramethylammonium hydroxide, and an aqueous solution of tetramethylammonium in methanol. Further, as the iron chelating agent used in the alkali treatment liquid, one having a high iron ion blocking ability can be used, for example, sodium gluconate, potassium gluconate, triethanolamine, diethanolamine, ethylenediaminetetraacetic acid (EDTA), hydroxy. Ethylenediaminetriacetic acid (HEDTA), diethylenetriaminetetraacetic acid (DTPA), nitrilotriacetic acid (NTA), hydroxyethyliminodiacetic acid (HIDA), L-aspartic acid-N, N-diacetate (ADSA), hydroxyiminodicohaku Acid (HIDS) and the like can be exemplified. These can be used alone or in combination of two or more. Specifically, the alkaline treatment liquid can be an alkaline aqueous solution.

The treatment time by alkaline treatment can be, for example, 1 minute or more and 30 minutes or less. In this case, a relatively thick mixed layer 3 is likely to be formed, and even when the storage time from the modification of the surface of the iron base material 2 to the formation of the coating material 4 is relatively long, the iron base material 2 and the coating material 4 are coated. It is easy to improve the adhesion with the material 4. The treatment time with the alkaline treatment solution is preferably 1.5 minutes or longer, more preferably 2 minutes or longer, still more preferably 2.5 minutes or longer, from the viewpoint of ensuring the above effects. Can be done. The treatment time with the alkaline treatment liquid is preferably less than 30 minutes, more preferably from the viewpoint of suppressing a decrease in the adhesive force between the iron base material 2 and the coating material 4 due to an excessive increase in the film thickness of the mixed layer 3. , 25 minutes or less, more preferably 20 minutes or less.

The treatment temperature by the alkaline treatment can be, for example, 40 ° C. or higher and 90 ° C. or lower. In this case, a relatively thick mixed layer 3 is likely to be formed, and even when the storage time from the modification of the surface of the iron base material 2 to the formation of the coating material 4 is relatively long, the iron base material 2 and the coating material 4 are coated. It is easy to improve the adhesion with the material 4. The treatment temperature with the alkaline treatment liquid can be preferably 50 ° C. or higher, more preferably 55 ° C. or higher, still more preferably 60 ° C. or higher, from the viewpoint of ensuring the above effect. The treatment temperature with the alkaline treatment liquid is preferably 85 ° C. or lower, more preferably 85 ° C. or lower, from the viewpoint of suppressing a decrease in the adhesive force between the iron base material 2 and the coating material 4 due to an excessive increase in the film thickness of the mixed layer 3. , 80 ° C or lower, more preferably 75 ° C or lower. The alkaline treatment can be carried out in the air atmosphere.

The atomic layer deposition method in the second step includes an adsorption step in which the raw material gas containing the precursor of the coating material 4 is brought 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 the object to be treated. It can include a reaction step of reacting the precursor adsorbed on the surface on the surface. In the second step, the adsorption step and the reaction step can be alternately repeated. 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.

The precursor used in the atomic layer deposition method can be appropriately selected depending on the material of the above-mentioned dressing 4. For example, when the above-mentioned metal oxide is used as the coating material 4, a volatile organic metal compound containing a metal atom constituting the above-mentioned metal oxide can be used as a precursor. After adsorbing a volatile organic metal compound as a precursor on the surface of the object to be treated, the precursor can be reacted with a reaction gas such as oxygen gas or water vapor to deposit a metal oxide in layers. ..

At the time of forming the covering material 4, the iron base material 2 can be heated if necessary. At this time, the temperature of the iron base material 2 can be set to 300 ° C. or lower. Further, the forming atmosphere of the covering material 4 can be, for example, in a vacuum.

After the first step and before the second step, in order to remove the alkaline treatment liquid adhering to the surface of the iron base material 2, the surface of the iron base material 2 may be washed with water or the like as necessary. can. Further, the iron chelate that could not be completely removed from the surface of the iron base material 2 can be removed from the surface of the iron base material 2 when the covering material 4 is formed by the atomic layer deposition method. Further, a step of storing (leaving) the iron base material 2 after the alkali treatment can be inserted between the first step and the second step. In this case, storage can be carried out, for example, in the atmosphere. The storage time can be, for example, preferably 168 hours or less, more preferably 120 hours or less, still more preferably 96 hours or less, and the iron base material and the covering material by reducing the Fe ₂ O ₃ ratio. From the viewpoint of improving the adhesion with the material, the time is even more preferably 72 hours or less.

(Embodiment 2)
The injector nozzle body of the second embodiment (hereinafter, simply referred to as a nozzle body) will be described with reference to FIGS. 3 and 4. As illustrated in FIGS. 3 and 4, the nozzle body 5 of the present embodiment is used as an injector for injecting fuel into a combustion chamber in an internal combustion engine, and is based on the surface covering member of the first embodiment described above. Can be configured. This will be described in detail below.

The iron base material 2 of the surface covering member 1 constituting the nozzle body 5 has a through hole 111 for injecting fuel, and the mixed layer 3 and the covering material 4 are formed on the inner surface of the through hole 111. There is. The through hole 111 may also be referred to as a jet hole.

In the present embodiment, the nozzle body 5 is specifically a mixture of the iron base material 2 having a cylindrical shape, the covering material 4 covering the iron base material 2, and the iron base material 2 and the covering material 4 interposed therebetween. It has a layer 3 and. The covering material 4 is composed of two layers, a first layer 41 in contact with the mixed layer 3 and a second layer 42 in contact with the first layer 41. A through hole 111 is formed at the tip of the tubular iron base material 2. The through hole 111 penetrates the iron base material 2. The inner diameter D of the through hole 111 can be, for example, 1 mm or less. In the present embodiment, the entire surface of the iron base material 2, 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 of the through hole 111 shown in FIG. 112 is covered with a mixed layer 3 and a covering material 4.

Specifically, the iron base material 2 can be made of, for example, carbon steel, chromium molybdenum steel, or the like. Further, among the covering materials 4, the first layer 41 may be composed of, for example, Al ₂ O ₃ , and the second layer 42 may be composed of, for example, Ta ₂ O ₅ or Hf O ₂ . For convenience, the description of the mixed layer 3 and the covering material 4 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 is simplified.

The nozzle body 5 can form an injector by arranging a nozzle needle 6 that reciprocates in the longitudinal direction thereof in the in-cylinder space S thereof. 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.

According to the nozzle body 5 of the present embodiment, the adhesion between the iron base material 2 and the mixed layer 3 is ensured even when the storage time from the modification of the surface of the iron base material 2 to the film formation of the covering material 4 is lengthened. Therefore, the adhesion between the iron base material 2 and the covering material 4 can be ensured. Therefore, according to the nozzle body 5 of the present embodiment, it is possible to improve the peeling resistance of the covering material 4 by the high-pressure fuel when it is incorporated into the injector and used, and it is possible to form an injector having high corrosion resistance. It will be possible.

(Experimental Example 1)
A cylindrical iron base material (material: chrome molybdenum steel) used for the injector nozzle body was prepared. A through hole as a jet hole is formed at the tip of the iron base material. The prepared iron substrate was washed and degreased by immersing it in acetone for 15 minutes. Next, the iron base material was immersed in an alkaline treatment liquid to perform alkaline treatment. As the alkaline treatment liquid, a sodium hydroxide (NaOH) aqueous solution containing sodium gluconate as an iron chelating agent or a sodium hydroxide (NaOH) aqueous solution containing no iron chelating agent was used. The details of the alkaline treatment conditions are as shown in Table 1.

Next, the alkali-treated iron base material is stored (leaved) in the atmosphere (65 ° C., humidity 60 RH%) for the storage time (standing time) shown in Table 1 below, and then placed on the surface of the iron base material. A coating material was formed by forming an Al ₂ O ₃ layer (thickness 100 nm) and a Ta ₂ O ₅ (thickness 200 nm) in this order by an atomic layer deposition method. As a result, the test bodies A1 to A14 shown in Table 1 were prepared.

Next, a cross section perpendicular to the surface of each prepared test piece (a cross section along the thickness direction of the iron substrate) was observed by TEM. As a result, as shown in FIGS. 13 (a) to 16 (a) described later, each test piece has an iron base material, a covering material covering the surface of the iron base material, and an iron base material and a covering material. It had a mixed layer intervening between and. In addition, the thickness of the mixed layer was measured by the method described above.

Next, the adhesion of the covering material was determined in accordance with the VDI3198 standard. Specifically, using a Rockwell hardness tester (D scale), the peeling condition of the covering material around the indentation that occurs when the indenter (diamond indenter) is pushed under a load of 980.7 N is measured at a magnification of 500 to 700 times. They were observed and ranked according to the judgment table shown in FIG. A scanning electron microscope was used to observe the peeling state of the coating material. Further, FIG. 6 shows an example of a cross section of a through hole as a injection hole in a nozzle body for an injector of a test piece, and an example of an indentation formed on the cross section of the through hole.

In FIG. 5 described above, it was determined that HF1 to HF4 are acceptable defects and have adhesion. In HF1, only microcracks can be seen. In HF2, peeling of the film around the indentation surrounded by microcracks is observed. In HF3, continuous film peeling is seen around the indentation surrounded by microcracks. In HF4, continuous film peeling around the indentation surrounded by microcracks spreads outward within the microcrack region. Therefore, the adhesion increases in the order of HF4 <HF3 <HF2 <HF1. Further, it was determined that HF5 and H6 were unacceptable peeling and had no adhesion. In HF5, the continuous film peeling around the indentation partially extends outward from the microcracked region. In HF6, a wide range of exfoliation is observed around the indentation with no residual microcracks. Table 1 shows the measurement results of the adhesion force. Further, FIG. 7 shows the peeling state of the covering material in the test piece A1. FIG. 8 shows the peeling state of the covering material in the test piece A12. FIG. 9 shows the peeling state of the covering material in the test piece A14. Further, FIG. 10 shows the relationship between the thickness [nm] (horizontal axis) of the mixed layer and the adhesion force [Lv] (vertical axis).

According to Table 1 and FIGS. 5 to 9, the following can be seen. That is, when the test bodies A12 to the test body 14 using the alkaline treatment liquid containing no iron chelating agent have a relatively short storage time from the modification of the iron substrate surface by the alkaline treatment to the formation of the coating material, the storage time is relatively short. The adhesion between the iron base material and the covering material can be ensured. However, in the test bodies A12 to 14, when the storage time from the modification of the iron base material surface by alkaline treatment to the film formation of the coating material was relatively long, the adhesion between the iron base material and the coating material decreased. .. Moreover, although the treatment time of the alkali treatment was relatively long, the thickness of the formed mixed layer was relatively thin.

On the other hand, in the test bodies A1 to A4 using the alkaline treatment liquid containing an iron chelating agent, the storage time from the modification of the iron substrate surface by the alkaline treatment to the film formation of the coating material is relatively long. However, no decrease in the adhesion between the iron base material and the covering material was observed. The storage time for which the determination result of the adhesion was HF4 was 168 hours for the test piece A5 using the alkaline treatment solution containing the iron chelating agent. On the other hand, in the test body A14 using the alkaline treatment liquid containing no iron chelating agent, the determination result of the adhesion was H5 after the storage period of 72 hours. From these results, it can be seen that the storage period can be extended by alkali-treating the surface of the iron substrate with an alkali-treated solution containing an iron chelating agent. It can also be seen that a relatively thick mixed layer can be formed.

Further, when the test body A1 and the test body A6 to the test body A11 using the alkaline treatment liquid containing the iron chelating agent are compared, the following can be found. As shown in FIG. 10, when the thickness of the mixed layer is 50 nm or more and 700 nm or less, the iron base material 2 is used even when the storage time from the modification of the surface of the iron base material to the film formation of the coating material is relatively long. It can be seen that it becomes easier to secure the adhesion between the surface and the covering material 4. This is because the adhesion between the iron base material and the mixed layer is improved.

(Experimental Example 2)
The mixed layer of the test body A4 in Experimental Example 1 was subjected to element analysis and chemical bond state analysis by a transmission electron microscope (TEM) -electron energy loss spectroscopy (EELS) by the above-mentioned method. The results are shown in FIGS. 11 and 12. As shown in FIG. 11, it can be seen by TEM-EELS analysis that the mixed layer of the test body A4 mainly contains Fe and Fe ₂ O ₃ . It can also be seen that the mixed layer also contains FeO and Fe ₃ O ₄ . The Fe ₂ O ₃ ratio in the mixed layer calculated by the above method using FIG. 12 was 28%. Further, since the test bodies A1 to A3 having a shorter storage time than the test body A4 had less oxidation of the iron substrate surface during storage, the Fe ₂ O ₃ ratio in the mixed layer was 28% or less. On the other hand, in the test body A5 having a storage time longer than that of the test body A4, the iron substrate surface was oxidized during storage, and the Fe ₂ O ₃ ratio in the mixed layer exceeded 28%. In Table 1, the symbol "-" of the Fe ₂ O ₃ ratio in the test body A6 to the test body A11 means that the measurement of the Fe ₂ O ₃ ratio has not been measured.

According to the above results, it can be said that the adhesion between the iron substrate and the mixed layer changes depending on the amount of Fe ₂ O ₃ contained in the mixed layer in relation to the storage time. By setting the Fe ₂ O ₃ ratio in the mixed layer to 52.6% or less, even when the storage time from the modification of the iron substrate surface to the film formation of the coating material is lengthened, the iron substrate and the mixed layer are formed. It can be seen that the adhesion between the iron base material and the covering material can be ensured because the adhesion with the iron base material can be secured. In particular, by setting the Fe ₂ O ₃ ratio in the mixed layer to 28% or less, even when the storage time from the modification of the surface of the iron substrate to the film formation of the coating material is lengthened, the iron substrate and the mixed layer can be kept together. It can be seen that since the adhesive force can be sufficiently secured, the adhesive force between the iron base material and the covering material can be sufficiently secured.

(Experimental Example 3)
In this experimental example, the same TEM-EELS as in Experimental Example 2 is obtained for the mixed layer in the test body A1 using the alkaline treatment liquid containing an iron chelating agent and the test body A12 using the alkaline treatment liquid containing no iron chelating agent. It is an analysis. The results are shown in FIGS. 13 and 14. The storage time of the test body A1 and the test body A12 is the same. Further, in this experimental example, the same TEM as in Experimental Example 2 is used for the mixed layer in the test body A4 using the alkaline treatment liquid containing an iron chelating agent and the test body A14 using the alkaline treatment liquid containing no iron chelating agent. -EELS analysis was performed. The results are shown in FIGS. 15 and 16. The storage time of the test body A4 and the test body A14 is the same.

According to the above results, the test body A1 and the test body A4 using the alkaline treatment liquid containing the iron chelating agent, the test body A12 and the test body A14 using the alkali treatment liquid not containing the iron chelating agent are all. The mixed layer contains Fe and Fe ₂ O ₃ . However, in the test body A1 and the test body A4 using the alkaline treatment liquid containing the iron chelating agent, Fe ₂ O ₃ was detected in a trace amount. Further, in the test body A1 and the test body A4, FeO and Fe ₃ O ₄ were hardly detected. On the other hand, in the test body A12 and the test body A14 using the alkaline treatment liquid containing no iron chelating agent, the mixed layer is as thin as 10 nm, and a large amount of iron oxide such as Fe ₂ O ₃ and Fe O ₃ O ₄ is also contained. was detected.

The present invention is not limited to each of the above embodiments and experimental examples, and various modifications can be made without departing from the gist thereof. In addition, each configuration shown in each embodiment and each experimental example can be arbitrarily combined.

1 Surface covering member 2 Iron base material 3 Mixed layer 4 Coating material 5 Injector nozzle body 111 Through hole 112 Inner surface of through hole

Claims (5)

An iron base material (2) composed of iron or an iron alloy, and
The covering material (4) that covers the surface of the iron base material and
It has a mixed layer (3) interposed between the iron base material and the covering material, and has.
The above mixed layer
Including Fe and Fe ₂ O ₃
Fe ₂ O ₃ ratio is 52.6% or less,
Surface covering member (1). The thickness of the mixed layer is 50 nm or more.
The surface covering member according to claim 1. The thickness of the mixed layer is 700 nm or less.
The surface covering member according to claim 1 or 2. The iron substrate has at least one opening selected from through holes, bottomed holes, and grooves.
The mixed layer and the covering material are formed at least on the inner surface (112) of the opening.
The surface covering member according to any one of claims 1 to 3. It is composed of the surface covering member according to any one of claims 1 to 3.
The iron base material has a through hole (111) for injecting fuel, and has a through hole (111).
An injector nozzle body (5) in which the mixed layer and the covering material are formed at least on the inner surface (112) of the through hole.

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