JP3100342B2 - Low carbon steel or stainless steel with corrosion resistant nitride film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a corrosion-resistant nitride film .
Low carbon steel or stearyl imparted with abrasion resistance and corrosion resistance Ri
Stainless steel .

[0002]

2. Description of the Related Art Conventionally, for mechanical parts and structural materials that require wear resistance and impact resistance, stainless steel and other iron-based materials are surface-modified by nitriding treatment to impart necessary characteristics. That is being done.

[0003]

However, simply subjecting the iron-based material to a nitriding treatment results in insufficient corrosion resistance, so that it becomes necessary to apply a rust-preventive oil. In this case, if the rust preventive oil runs out during use, rust will be generated from the cut portion. Also, it is difficult to use oil-free applications such as vacuum equipment, semiconductor manufacturing processes, and food manufacturing processes.

It is known that a nitride film having good corrosion resistance is formed by performing a nitridation process at a low processing temperature by plasma nitridation. However, such a nitride film has low toughness and is brittle. It cannot be used for devices that are subject to impact, such as the core of a device. It is also conceivable to provide corrosion resistance by plating with chromium or the like after nitriding, but there are difficulties in terms of the thickness of the plated portion and wear resistance, and the advantages of the nitride film cannot be utilized.

[0005] The present invention has been made to solve the problems of the prior art, low-carbon steel or stainless imparted with more excellent wear resistance and corrosion resistance and corrosion resistance nitride film
It aims to provide less steel .

[0006]

Means for Solving the Problems] The present invention has been made in an attempt to solve this problem, the corrosion resistance nitride film that by the nitriding
A low carbon steel or stainless steel having its resistance
The corrosion-resistant nitride film has a thickness of 5 μm or more and 500 μm or less, contains iron nitride, has a hardness of 400 HV (Vickers hardness) or more and 1200 HV or less, and further, 1.
Takashidea than In the invention NaNO 3% ₃ solution (35 ° C.) natural potential during immersion -100 mV (vs SCE (standard calomel electrode)) of is, In the invention of claim 2 1% N
Natural potential at the time of immersion in aCl aqueous solution (35 ° C) is -200m
Ri Takashidea than V (vs SCE), wherein there are the 3.5% NaCl aqueous solution (30 ° C.) to the invention of claim 3 during immersion of pitting potential V'c ₁₀₀ (JIS G 0577) is -200 mV (v
SSCE) Takashidea Ri than, in the invention of claim 4 2
Γ-Fe ₄ N in axial X-ray diffraction measurement (Cu-Kα ray)
Α-Fe (plane index 110) peak (2θ = about 4) having an integrated intensity of (plane index 111) peak (2θ = about 41.0 °)
Those specific to the integral intensity of 4.6 °) is 0.1 or more
Der Ru. In addition, the low carbon steel referred to in the present invention is described in Table 1 below.
Limited to those shown as grade D.

That is, the low carbon steel or stainless steel of the present invention
The stainless steel is obtained by nitriding the material to be treated in a nitrogen-hydrogen mixed gas at a pressure in the range of 1.5 to 5.0 Torr (more preferably, in the range of 4.0 to 4.75 Torr). . That is, a voltage of about 350 to 450 V is applied with the material to be processed being negative, and the processing is performed for about 4 hours at a processing temperature in the range of 500 to 750 ° C. (more preferably, in the range of 500 to 650). Thus, a nitride film having a thickness of about 5 to 500 μm is formed.

The formation mechanism of this nitride film is considered as follows. That is, the nitrogen ions ionized in the atmosphere gas are accelerated by the voltage drop of the material to be processed, collide with the material to be processed, and sputter iron atoms. This is because the sputtered iron atoms are bonded to nitrogen in the atmosphere gas and then adsorbed on the surface of the material to be treated, a part of which is dissociated by ion bombardment and nitrogen enters and diffuses into the material to be treated.

In the nitride film, the nitrogen that has entered and diffused is combined with the iron of the material to be processed, and the iron nitride (γ-Fe ₄ N
) Is present. If the material to be treated contains chromium, such as stainless steel, chromium nitride (CrN) is also present. In addition to these, it is considered that there is also an interstitial solid solution nitrogen atom in the crystal lattice of α-Fe. Preferably, as shown in the embodiments and examples of the invention described below, an upper layer portion of the surface containing a relatively large amount of iron nitride,
It is preferable to form a two-layer film structure with a lower layer portion that does not contain much iron nitride but contains solute nitrogen. As a result, a hardness of about 400 to 1200 HV can be obtained, and excellent wear resistance and impact resistance can be obtained. Also, excellent corrosion resistance is obtained.

The thickness of the nitride film is preferably at least 5 μm from the viewpoint of corrosion resistance. Further, in consideration of the toughness of the film, the thickness is more preferably 20 μm or more. Further, as for the upper limit of the thickness, 500 μm is sufficient, and even if a thickness exceeding 500 μm is formed, it is not possible to expect an improvement in the characteristics corresponding to the cost. 300 for realistic usage
μm is almost enough.

[0011]

Embodiments of the present invention will be described below.

First, the nitriding treatment applied to the material to be processed will be described. The nitriding treatment is performed using the nitriding device 10 shown in FIG. The nitriding apparatus 10 includes a vacuum chamber 11 and a stage 13 provided inside the vacuum chamber 11 for mounting the workpiece 1. The vacuum chamber 11 and the stage 13 are insulated from each other by an insulator 23. The vacuum chamber 11 is provided with an exhaust pipe 15 and a valve 17, and the exhaust pipe 15 is connected to a vacuum pump. Therefore, if the valve 17 is opened, the inside of the vacuum chamber 11 can be evacuated by the vacuum pump. The vacuum chamber 11 has a gas introduction pipe 19 and a valve 2.
The gas introduction pipe 19 is connected to a gas source of a mixed gas of nitrogen and hydrogen. Therefore, the vacuum chamber 1
If the valve 21 is opened while the inside of 1 is evacuated, a mixed gas of nitrogen and hydrogen can be introduced into the vacuum chamber 11. The stage 13 is provided with a thermocouple 27,
The temperature of the material to be processed 1 can be measured. The thermocouple 27 is covered with an insulating tube 29 so that the vacuum chamber 11 and the stage 13 are insulated. Then, a DC voltage can be applied between the vacuum chamber 11 and the stage 13 by the power supply 25.

When performing the nitriding treatment, the workpiece 1 is placed on the stage 13, the valve 17 is opened, and the inside of the vacuum chamber 11 is evacuated by a vacuum pump. Then, the valve 21 is opened, and a mixed gas of nitrogen and hydrogen is introduced into the vacuum chamber 11. At this time, the gas pressure in the vacuum chamber 11 is 4 Torr in absolute pressure.
Maintain around r (total pressure). Then, a DC voltage of about 350 to 450 V is applied between the stage 13 and the vacuum chamber 11 using the power supply 25. At this time, the stage 13 is set to be negative and the vacuum chamber 11 is set to be positive. Then, a part of the nitrogen molecules in the mixed gas is ionized to become cations (N ₂ ⁺ ), which are accelerated toward the material 1 to be processed by a voltage drop between the stage 13 and the vacuum chamber 11, and are iron atoms Is sputtered. The sputtered iron atoms are combined with nitrogen in the atmosphere gas and then adsorbed on the surface of the workpiece 1. Then, a part thereof is dissociated while receiving ion bombardment, and nitrogen enters and diffuses inside. The nitrogen that has entered and diffused is distributed within a range of about 5 to 500 μm from the surface, depending on the type of the material to be processed, the processing time, and the processing temperature, and combines with a metal element such as iron to form a nitride. The workpiece 1 during this nitriding treatment is heated by the energy of ion bombardment to reach a temperature of about 500 to 750 ° C. This temperature is monitored by thermocouple 27.

As the material 1 to be treated, ordinary steel, stainless steel, or other iron-based material is used in a shape that can be easily mounted on the stage 13.

When such a nitriding treatment is performed, the material to be treated 1
A corrosion resistant nitride film is formed on the surface of the substrate. FIG. 1 shows a micrograph of an example of a cross-sectional structure of a material to be processed on which a corrosion-resistant nitride film is formed by performing a nitriding treatment for about 4 hours. In this example, about 120μ
m nitride film is formed.

The crystal structure of the material to be treated is determined by X-ray diffraction (θ-
When analyzed by the 2θ two-axis diffraction method, a pattern shown in FIG. 5 is obtained. In this pattern, 2θ = about 41.
The peaks at 0 ° and about 48.0 ° correspond to the iron nitride (γ-Fe
₄ peak of N) (plane indices are each 111 and 200), 2 [Theta] = peak at about 44.6 ° is the peak of the alpha-Fe (basic phase of iron). And γ-Fe ₄ N (11
1) The ratio of the integrated intensity of the peak to the integrated intensity of the α-Fe (110) peak is 0.1 or more (200 in FIG. 5). Since the material to be treated contains chromium, a peak of chromium nitride (CrN) appears in addition to the peak of iron nitride (γ-Fe ₄ N). Further, the reason why the peak of α-Fe appears is that not all metal atoms are combined with nitrogen even in the nitride film.

The corrosion-resistant nitride film has a high Vickers hardness of about 400 to 1200 HV. This is considered to be because the metal nitride itself such as γ-Fe ₄ N generated by the nitriding treatment is hard. This nitride film is not only hard but also excellent in toughness, and has high wear resistance and impact resistance. Also, it has excellent corrosion resistance and does not rust even if left in air for a long time.

The spontaneous potential and the polarization potential change in the electrolytic solution also show noble values. For example, the spontaneous potential in a 3% NaNO ₃ aqueous solution has a value nobler than −100 mV with respect to SCE, and the spontaneous potential in a 1% NaCl aqueous solution has a value nobler than −200 mV with respect to SCE. The pitting potential also shows a noble value. That is, according to the JIS G 0577 standard,
The most noble potential (V′c ₁₀₀ ) corresponding to a current density of 100 μA / cm ² in the anodic polarization curve when anodic polarization is performed from the spontaneous polarization potential in a state of being immersed in a 3.5% NaCl aqueous solution (30 ° C.) Is -200 mV (vsSC
E) More precious.

[0019]

EXAMPLES In the following, the formation of a nitride film was carried out for several examples, and the characteristic test was conducted. The results will be described. The first embodiment is an example in which the corrosion resistance was evaluated based on the spontaneous potential and polarization potential in an electrolytic solution.

[0020]

[Table 1]

Table 1 shows the chemical components of the material to be treated used in the first embodiment. Grades A, B, C, and D are the materials to be treated in this embodiment, and among them, grades A, B, and C are chromium-containing stainless steels. Grade D is low carbon steel. Grades E and F are used as comparative materials in a corrosion resistance test described later. Grade E is a stainless steel containing chromium, and grade F is a stainless steel containing chromium and nickel.

The materials A, B, C, and D were subjected to nitriding using the nitriding apparatus 10 shown in FIG.
At the time of nitriding, the shape of each material to be treated is 10 mm in diameter,
It was a column with a height of 10 mm. The processing conditions were as shown in Table 2 for each material type, and the processing time was 4 hours in each case.

[0023]

[Table 2]

FIGS. 1 to 4 show optical microscope photographs of the cross-sectional structure of each of the workpieces after the nitriding treatment. The magnification at the time of shooting is 160 times. About 120 μm for grade A (FIG. 1), about 160 μm for grade B (FIG. 2), and about 24 for grade C (FIG. 3).
It can be understood that a nitride film of about 50 μm is formed with 0 μm and the grade D (FIG. 4).

The results of X-ray diffraction measurement of each material to be processed are shown in FIGS. The measurement was performed using X-rays of a Cu target. Grade A (Fig. 5), B (Fig. 6), C containing chromium
(7) the peak of iron nitride (gamma-Fe ₄ N) and chromium nitride (CrN) was observed for chromium and does not contain grade D of the iron nitride for (FIG. _{8) (γ-Fe 4 N} ) A peak is seen. In addition, although peaks of α-Fe (a basic phase of iron) appear in all the materials to be processed, not all metal atoms are combined with nitrogen, and α
This is because the phase remains.

FIG. 9 is a graph showing the results of measuring the Vickers hardness of each material to be processed. It can be understood that the hardness of each material type is significantly increased in the nitride film as compared with the hardness of the base material (about 200 HV). That is, 800 to 90 for grade A
About 0HV, about 800-1100HV for grade B, about 400-900HV for grade C, 300-500 for grade D
It shows a hardness of about HV. In addition, the depth from the surface where the increase in hardness is observed here substantially matches the thickness of the nitride film read from the cross-sectional photographs of FIGS.

Next, the results of the corrosion resistance test of each sample will be described. The corrosion resistance test was performed by measuring a spontaneous potential and a polarization potential change using a test device 30 shown in FIG. The test apparatus 30 includes a water tank 31, a measurement tank 34, an auxiliary tank 33, and a reference tank 32. The water tank 31 is filled with water W at a temperature of 35 ° C., and the measuring tank 34 and the auxiliary tank 3
3. The reference tank 32 is kept at a constant temperature. The measuring tank 34 and the auxiliary tank 33 are both filled with a test solution T described later, and the sample 1 and the platinum counter electrode 39 are arranged in the measuring tank 34. The area of the measurement target surface of the sample 1 is set to 0.332 cm ² by an O-ring seal. The test solution T between the measurement tank 34 and the auxiliary tank 33 is connected by a lugine tube 38, and the end of the lugine tube 38 on the measurement tank 34 side is set at a position 1 mm above the surface of the sample 1 to be measured. The reference tank 32 is filled with a saturated aqueous KCl solution S, and a standard calomel electrode (SCE) 36 is provided. In addition, a salt bridge 37 is provided between the auxiliary tank 33 and the reference tank 32 so that the two solutions do not mix and conduct. And
Galvanostat 41 is placed between sample 1 and platinum counter electrode 39.
However, there is a high input resistance voltmeter 4 between the sample 1 and the SCE 36.
2 are provided respectively.

First, using the test solution T as a 3% NaNO ₃ aqueous solution, in addition to the treated materials of the grades A to D, the untreated materials of the grades A to D and the comparative grades E and F were measured.

The natural potential is measured by immersing the sample 1 in the measuring tank 34 and stabilizing it for 15 minutes, and then setting the high input resistance voltmeter 42
Is the reading of. At this time, the galvanostat 41 is not operated. The results are shown in the graph of FIG. From FIG. 10, it can be understood that each of the materials to be treated of the grades A to D shows a good value in the range of −100 to 0 mV. In particular, the materials to be treated of the grades A and B show excellent values close to 0 mV. In the case of the material D containing no chromium, the treated material is about -80 mV compared to -650 mV of the untreated material.

The polarization potential was changed by using a galvanostat 41 immediately after the measurement of the spontaneous potential, and applying a direct current of 1.5 μA between the sample 1 and the platinum counter electrode 39 in a direction in which the sample 1 became an anode. This is the amount of change in the read value of the high input resistance voltmeter 42 from the natural potential. The results are shown in the graph of FIG. From FIG. 11, each of the materials to be treated of the grades A to D is 1
It can be understood that a good value in the range of 00 to 250 mV is shown. In particular, in the case of grade D, which is ordinary steel, the treated material has a remarkably large polarization due to the nitriding treatment, with the treated material having a strength of about 130 mV, compared to the untreated material of about 10 mV.

Then, for the grades A and B which showed particularly excellent values in the self potential measurement shown in FIG.
Was changed to a 1% NaCl aqueous solution, and the same measurement was performed.
The graph of FIG. 12 shows the spontaneous potential in this test solution.
In both of the grades A and B, the treated material has a potential higher than the untreated material by 200 mV or more. The change in polarization potential in this test solution is shown in the graph of FIG. For grades A and B,
The treated material has about 100 mV more polarization than the untreated material.

According to the measurement results shown in FIGS.
It can be understood that the corrosion resistance of the treated material is good for each material type.

Next, as a second embodiment, the above-mentioned grade A,
For B and D, an example will be described in which a processed product is manufactured by gradually changing the processing temperature during the nitriding process, and the characteristics are evaluated based on the peak integrated intensity ratio of X-ray diffraction and the pitting potential. In this example, processed products were manufactured under the conditions shown in Table 3.

[0034]

[Table 3]

Optical micrographs of the cross-sectional structure of each of the processed products after the nitriding treatment are shown in FIGS. 16 to 19, and the results of X-ray diffraction measurement are shown in FIGS. 20 to 23, respectively. For each of these processed products,
The film thickness read from the cross-sectional structure and the peak intensity ratio (γ-Fe ₄ N (111) / α) read from the X-ray diffraction pattern
Table 4 shows -Fe (110), the ratio of the integrated intensity) and the pitting corrosion potential (the measuring method will be described later). Each of these treated products had a Vickers hardness of 40 when measured.
It shows a good value of 0 HV or more.

[0036]

[Table 4]

According to the column of X-ray diffraction intensity ratio in Table 4, in the case of grade A, good values having an intensity ratio of 0.1 or more were obtained in the processed products at processing temperatures of 600 ° C. and 620 ° C. Grade B
In the case of No. 1, good values having an intensity ratio of 0.1 or more were obtained in the processed products at a processing temperature of 600 to 640 ° C. In the case of the material type D, a good value having an intensity ratio of 0.1 or more was obtained in all the processed products at a processing temperature of 500 ° C. to 600 ° C. According to the X-ray diffraction patterns of FIGS.
Chromium-containing grades A and B also have chromium nitride (CrN) peaks. Further, the relationship between the X-ray diffraction intensity ratio and the nitriding treatment temperature in Table 4 has a strong correlation as shown in the graph of FIG.
Peak of -fe ₄ N is relatively weaker tendency is read.

Further, according to the cross-sectional structures shown in FIGS. 16 to 19, in many processed products, the nitrided layer is composed of the upper layer and the lower layer.
In layers. The most remarkable is the processing temperature of grade D5.
40 ° C and 560 ° C. At 540 ° C., the upper layer that appears white in the photograph is about 9 μm, and the lower layer that appears black below it is about 14 μm. 560
In the case of ° C., the upper layer is about 13 μm and the lower layer is about 37 μm. The numerical values shown in the column of the film thickness in Table 4 are the total film thickness of the upper layer and the lower layer. This upper layer is considered to be a layer containing a relatively large amount of iron nitride (iron nitride and chromium nitride in the case of grade A and grade B). On the other hand, the lower layer is considered to be a layer that does not contain much iron nitride or chromium nitride, but has nitrogen atoms interstitial solid solution in the lattice of the metal crystal. In addition, when only the upper layer was polished and removed from these treated products, and X-ray diffraction measurement was performed, almost no peak of iron nitride or chromium nitride was observed.

The upper layer is considered to be a layer mainly responsible for the properties such as excellent hardness and corrosion resistance of the nitride film due to iron nitride and chromium nitride contained therein. It is considered that the lower layer has an intermediate property between the upper layer and the base in terms of hardness in particular, thereby preventing the hard upper layer from peeling off due to impact or the like.

Next, the pitting potential will be described. The measurement of the pitting potential here was performed according to JIS G 0577 standard. That is, in the test apparatus 30 of FIG. 15, the galvanostat 41 and the high input resistance voltmeter 42 are replaced with a potentiostat and a potential sweeping device, the test solution T is a 3.5% NaCl aqueous solution, and the temperature of the water W in the water tank 31 is reduced. 30 ° C. In this state, while the test solution T in the measuring tank 34 was degassed with nitrogen gas N ₂ or argon gas Ar, the potential sweeping device was used to sweep the sample 1 from the spontaneous immersion potential by the electrokinetic method at a sweep rate of 20 mV / min. Is 5
Anodize until reaching 00 μA / cm ² . In the anode polarization curve at this time, the anode current density 10
The most noble potential corresponding to 0 μA / cm ² is the pitting potential V ′.
c is ₁₀₀ .

In the column of pitting potential V'c _{100 in} Table 4, three samples are prepared for each processed product, and the measured values and their average values are described. The relationship between the average value and the peak intensity ratio of the X-ray diffraction pattern has a strong correlation as shown in the graph of FIG. 25, and the peak intensity of γ-Fe ₄ N is relatively strong (the intensity ratio in the graph is lower). It can be seen that the larger the value, the higher the pitting potential V'c ₁₀₀ (the better the corrosion resistance). From this, it is understood that the presence of γ-Fe ₄ N contributes to the high corrosion resistance of the nitride film.

As described above with reference to the embodiment and the examples, a nitride film containing a nitride such as iron nitride or chromium nitride is obtained by performing a nitriding treatment on a material to be processed, which is an iron-based material. Is formed in the order of 5 to 500 μm. This nitride film has excellent hardness, high wear resistance and high impact resistance, and also excellent corrosion resistance. Therefore, it can be suitably used for a member that repeatedly receives an impact such as an iron core of an electromagnetic solenoid, or has no frictional parts of a device that dislikes oil, such as a vacuum device, a semiconductor manufacturing process, and a food manufacturing process. It can be used for lubrication.

The above embodiments and examples do not limit the present invention in any way, and it is needless to say that various modifications and improvements can be made without departing from the gist of the invention.

[0044]

According to the present invention As apparent from the above description, it is possible to provide better abrasion resistance and low-carbon steel or stainless steel corrosion resistance imparted corrosion resistance nitride film, the low Carbon steel or stainless steel can be suitably used for a member that receives an impact or a friction portion that must be used without lubrication.

[Brief description of the drawings]

FIG. 1 is a cross-sectional micrograph of a workpiece on which a corrosion-resistant nitride film according to the present invention is formed.

FIG. 2 is a cross-sectional micrograph of a workpiece on which a corrosion-resistant nitride film according to the present invention is formed.

FIG. 3 is a cross-sectional micrograph of a material to be processed on which a corrosion-resistant nitride film according to the present invention is formed.

FIG. 4 is a cross-sectional micrograph of a material to be processed on which a corrosion-resistant nitride film according to the present invention is formed.

FIG. 5 is a graph showing the results of X-ray diffraction measurement of the material to be processed in FIG.

FIG. 6 is a graph showing an X-ray diffraction measurement result of the material to be processed in FIG. 2;

FIG. 7 is a graph showing the results of X-ray diffraction measurement of the material to be processed in FIG.

8 is a graph showing the results of X-ray diffraction measurement of the material to be processed in FIG.

FIG. 9 is a graph showing Vickers hardness measurement results of each of the workpieces shown in FIGS.

FIG. 10 is a graph showing a spontaneous potential in a 3% NaNO ₃ aqueous solution.

FIG. 11 is a graph showing the polarization potential in a 3% NaNO ₃ aqueous solution.

FIG. 12 is a graph showing a spontaneous potential in a 1% NaCl aqueous solution.

FIG. 13 is a graph showing a polarization potential in a 1% NaCl aqueous solution.

FIG. 14 is a schematic view of a nitriding apparatus used for forming a corrosion-resistant nitride film according to the present invention.

FIG. 15 is a schematic view of a test apparatus used for a corrosion resistance test of a corrosion resistant nitride film.

FIG. 16 is a cross-sectional micrograph of a material to be processed on which a corrosion-resistant nitride film according to the present invention is formed.

FIG. 17 is a cross-sectional micrograph of a material to be processed on which a corrosion-resistant nitride film according to the present invention is formed.

FIG. 18 is a cross-sectional micrograph of a material to be processed on which a corrosion-resistant nitride film according to the present invention is formed.

FIG. 19 is a cross-sectional micrograph of a workpiece on which a corrosion-resistant nitride film according to the present invention is formed.

20 is a graph showing the result of X-ray diffraction measurement of the material to be processed in FIG.

FIG. 21 is a graph showing the result of X-ray diffraction measurement of the material to be processed in FIG.

FIG. 22 is a graph showing the results of X-ray diffraction measurement of the material to be processed in FIG.

FIG. 23 is a graph showing the results of X-ray diffraction measurement of the material to be processed in FIG.

FIG. 24 is a graph showing a relationship between a processing temperature and a peak intensity ratio in each of the materials to be processed in FIGS. 16 to 19;

FIG. 25 is a graph showing a relationship between a peak intensity ratio and a pitting potential in each of the materials to be processed shown in FIGS. 16 to 19;

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshiyuki Ukai 3005 Hayasaki, Kita-gaiyama, Komaki-shi, Aichi Prefecture Inside Kakei Co., Ltd. (72) Inventor Akihiko Yanagiya 3007 Nakajima, Shima, Himeji-shi, Hyogo Sanyo Special Steel Co., Ltd (72) Inventor Yangta Takada 3007 Nakajima, Shima, Himeji City, Hyogo Prefecture Inside Sanyo Special Steel Co., Ltd. (72) Inventor Norio Sato 3007 Nakajima, Shima, Ward, Himeji City, Hyogo Prefecture Inside Sanyo Special Steel Co., Ltd. (72) Inventor Yoshikazu Tanaka 3007 Nakashima, Shima, Himeji-shi, Hyogo Sanyo Special Steel Co., Ltd. (58) Field surveyed (Int. Cl. ⁷ , DB name) C23C 8/26

Claims (4)

(57) [Claims] 1. A low-resistant to corrosion nitride film that by the nitriding
In carbon steel or stainless steel , the corrosion-resistant nitride film has a thickness of 5 μm to 500 μm, contains iron nitride, has a hardness of 400 HV to 1200 HV, and is immersed in a 3% NaNO ₃ aqueous solution (35 ° C.) When the natural potential is-
Low carbon steel or stainless steel having a corrosion resistant nitride film , which is nobler than 100 mV (vs SCE). 2. A low-resistant to corrosion nitride film that by the nitriding
In carbon steel or stainless steel , the corrosion-resistant nitride film has a thickness of 5 μm or more and 500 μm or less, contains iron nitride, has a hardness of 400 HV or more and 1200 HV or less, and is dipped in a 1% NaCl aqueous solution (35 ° C.) Has a natural potential of -2
A low carbon steel or a stainless steel having a corrosion resistant nitride film , which is nobler than 00 mV (vs SCE). 3. A low-resistant to corrosion nitride film that by the nitriding
In carbon steel or stainless steel , the corrosion-resistant nitride film has a thickness of 5 μm or more and 500 μm or less, contains iron nitride, has a hardness of 400 HV or more and 1200 HV or less, and has a 3.5% NaCl aqueous solution (30 ° C.) A low-carbon steel or stainless steel having a corrosion-resistant nitride film , characterized in that the pitting potential V'c ₁₀₀ upon immersion is more noble than -200 mV (vs SCE) .
Tenless steel . 4. A low-resistant to corrosion nitride film that by the nitriding
In carbon steel or stainless steel, the corrosion-resistant nitride layer has a thickness of at least 500μm below 5 [mu] m, and contains iron nitride, hardness of less 1200HV least 400 HV, 2-axis X-ray diffraction measurement (Cu- Γ-Fe ₄
Α-Fe (plane index 110) peak (2θ = about 4) having an integrated intensity of N (plane index 111) peak (2θ = about 41.0 °)
Low carbon steel or stainless steel having a corrosion resistant nitride film , wherein the ratio to the integrated strength (4.6 °) is 0.1 or more.
Stainless steel .