JP3103884B1 - Low defect surface coating layer composed of stainless steel with low defects or stainless steel formed on a substrate - Google Patents

Abstract

An object of the present invention is to provide a stainless steel or a surface coating layer made of stainless steel and a method for repairing minute defects on the surface thereof. SOLUTION: An electrochemical method removes dirt and an oxide film covering a microdefect and its surrounding surface while applying vibration to the liquid and cleans the surface. Passivation or at a potential within the range of ± 100 mV around this potential,
After that, the oxide particles are kept in the atmosphere to grow an oxide particle-like or band-like structure, and repair minute defects in the process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for repairing minute surface defects on the nanometer scale existing in stainless steel used as a general structural material to improve pitting corrosion resistance and crack resistance. .

[0002] This surface treatment method relates to a surface treatment method intended to extend the life of a material by delaying the onset of pitting and the initiation of cracks.

[0003]

2. Description of the Related Art Defect repair methods include a plating method (JP-A-6-49613) and a brazing method (JP-A-11-4370).
6), metals (JP-A-8-29580) and resins (JP-A-8-29580).
-145275) and the like,
Welding (Japanese Unexamined Patent Publication No. 6-289184)
6079). All of them are intended for large defects of a micrometer or more, and it is difficult to say that these methods can repair nanometer-scale minute defects targeted by the present invention.

[0004] The importance of removing stains on defective portions by pickling (JP-A-6-315779), cutting or electric discharge machining (JP-A-6-289183) is implied, but the subsequent processing is as described in the preceding section. The repair of a large defect is a target, and a small defect is often newly generated in the repair part described in the preceding paragraph. Therefore, the effect of repairing a minute defect targeted by the present invention can be improved even if a conventional repair method such as welding is applied and applied repeatedly.

[0005]

SUMMARY OF THE INVENTION The present invention is not intended for repairing large defects larger than micrometers.
It is intended for the repair of nanometer-scale minute defects that stainless steel naturally has after production, which has not come as a repair target in the past. One way to prolong the life of a material is to repair large defects after they occur, but before the large defects occur, repair nanometer-scale minute defects that cause large defects. Is more effective, and is important in extending the life. Repair of a minute defect has a remarkable effect of suppressing the occurrence of a large defect or delaying the time until the initiation of a large defect. According to the present invention, nanometer-scale minute defects are repaired, the surface is repaired to have a defect density smaller than that of an untreated one, and pitting and cracking resistance is improved and the material has a longer life.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on the electrochemical treatment method, and as a result, the dirt or amorphous oxide film covering the inside of the minute defect of stainless steel is usually removed by a liquid. Is immediately passivated in a stationary liquid, and then kept in the atmosphere, whereby a particulate or band-shaped surface structure gradually grows,
It has been found that it is possible to repair minute defects smaller than 00 nm, and to solve the above-mentioned problems.

Based on this finding, the present invention provides: 1) a stainless steel characterized in that the density of minute defects having a surface opening diameter of 0.6 nm or more and less than 1000 nm is 60 / μm 2 or less, and the density of minute defects on the surface is extremely low. Formed on steel or substrate
2) A stainless steel formed on a substrate having a low surface defect density according to 1) above, wherein the stainless steel is a coating layer made of a stainless steel and 2) a coating layer coated by sputtering.
Surface coating layer made of steel, 3) while applying vibrations to the liquid stainless steel in dilute sulfuric acid, and cathodic reduction, and characterized in that cleaning the surface to remove the minute defects in and surrounding the coating and dirt Table consisting of stainless steel having a low surface defect density or stainless steel formed on a substrate as described in 1) above.
Surface coating layer , 4) as an electrochemical treatment after surface cleaning,
The surface defect density according to the above 1), wherein the passivation treatment is performed by maintaining a passivation maintaining current density in a static liquid at a minimum potential or a potential within a range of ± 100 mV for at least 10 minutes with respect to this potential. Formed on low-strength stainless steel or substrate
Surface coating layer made of stainless steel that is, 5) after the passivation treatment, and held in the air, to grow particulate or band structure of the surface, and wherein the covering in the process of minute defects in the oxide film Surface coating made of stainless steel having a low surface defect density or stainless steel formed on a substrate as described in 1) above
6) stainless steel or stainless steel having a low surface defect density according to 1) above;
To the surface coating layer made of stainless steel on the base
Defect repairing method, there is provided a.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The defect repairing method of the present invention comprises the following steps. (1) Mechanical polishing step (2) Defect surface cleaning treatment step (3) Passivation treatment step (4) Oxide film growth step By these steps, the contents of claims 3 to 5 are concretely described.
It can be implemented in a practical manner .

Next, each of the above steps will be described in detail.
In the mechanical polishing step (1), for example, # 250
After polishing using several water-resistant abrasive papers up to # 3000, buffing is performed using a diamond paste of 1 μm or less, preferably 0.25 μm. Thereafter, degrease cleaning is performed in ethyl alcohol, propyl alcohol or acetone using an ultrasonic cleaner. In the case of a material having a coating layer formed by sputtering or the like, the coating layer itself has a smooth surface equal to or higher than the polished surface. Therefore, this mechanical polishing step is unnecessary, and is mainly used for a bulk material such as a plate material.

[0010] In the surface cleaning treatment step (2), in a sulfuric acid aqueous solution of dilute sulfuric acid, preferably 0.1 M / L, at several potentials of -800 mV to -2000 mV (based on a saturated calomel electrode), the liquid By applying a vibration, preferably an ultrasonic vibration, to the cathode region for at least 10 minutes, an amorphous air oxide film and dirt in and around the defect are removed, and the defect surface is cleaned.

In the passivation treatment step (3), after the cleaning treatment, the potential at which the passive state maintaining current density is the lowest or the range of ± 100 mV around this potential immediately without passing through another potential. It is kept at the internal potential for 10 minutes or more. Further, in order to promote the growth of the oxide, the vibration of the liquid performed in the cleaning treatment (2) is stopped, and the passivation treatment is performed in the stationary liquid.

In the oxide film growth step (4), after the passivation treatment, the surface is rinsed with distilled water or ion-exchanged water, and the water is blown off. Then, a gas containing at least 20% oxygen Hold in. In this step, a particulate or band-like structure of the oxide formed by the passivation grows, and covers and repairs the minute defects in the process. Changes in the surface structure of the oxide can be confirmed by observation with a scanning tunneling microscope. At this time, a minute defect smaller than the particle diameter or the width of the band can be repaired.

[0013]

According to the present invention, the surface of the stainless steel base material or the surface of the surface coating layer made of stainless steel is remarkably excellent in that the density of minute defects is small. Such a surface can improve pitting corrosion resistance or crack resistance as compared with an untreated surface, and has an excellent effect of extending the life of stainless steel. In addition, since the present invention can be applied to a surface coating layer such as sputtering, a surface coating layer made of stainless steel is formed using a material such as a stainless steel plate or other metal or ceramics as a substrate, and the same effect as described above can be obtained. Has features.

Although the following examples are described using specific stainless steels, the present invention is naturally applicable to stainless steels other than these examples, and has the same functions and effects. The stainless steel that can be used in the present invention is not only a bulk material such as a stainless steel plate, but also a stainless steel plate (plated with a film having the same composition as the stainless steel, a physical vapor deposition method such as sputtering, and a chemical vapor deposition method). The present invention can also be applied to a material in which a coating layer is formed on a bulk material) or another metal or ceramic. For example, for the structure or material of equipment or instruments that cannot be mechanically polished,
A coating layer having the same composition as that of stainless steel is formed by sputtering or the like, and a surface treatment according to the present invention is performed on the coating layer to improve the properties of the air oxide film and repair defects. In any case, it is a problem of the surface having stainless steel or an equivalent surface coating layer, and if the conditions of the present invention can be achieved, the same operation and effect can be obtained.

FIGS. 1 and 2 show a conceptual diagram of the structural change on the surface of the stainless steel treated by the present invention and an example observed by a scanning tunneling microscope. FIG. 1 shows a schematic diagram of the changes that occur after subjecting a stainless steel to the treatment of the present invention. After the stainless steel is manufactured, the air oxide film and dirt cover the surface of the micro defect and its surroundings. When it is subjected to electrochemical surface treatment, the air oxide film and dirt are removed, and the passivation film grows in the form of particles on the clean surface, and covers and repairs minute defects.
FIG. 2 shows the changes that occur after stainless steel (SUS304) is sputtered on a substrate to form a thin film layer and subjected to the treatment of the present invention. Electrochemical surface treatment and removal into the air revealed a small particulate structure after 14 minutes, which grew to larger particles after 25 hours. During this time, minute defects are covered with an oxide film and repaired.

[0016]

Examples and Comparative Examples Next, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. That is,
Naturally, other examples, modes, modifications, and the like within the scope of the technical idea of the present invention are included.

(Example 1) Stainless steel (JIS standard S)
US430) was processed as a test material. this#
It was mechanically polished using 400, # 600, # 1000, and # 1500 water-resistant abrasive paper and a 0.25 μm diamond paste, and ultrasonically washed in ethyl alcohol, isopropyl alcohol, and acetone for 3 minutes each. Thereafter, while applying ultrasonic vibration in a 0.1 M / L sulfuric acid aqueous solution, the sample was held at -1000 mV for 5 minutes, -1500 mV for 3 seconds, -1000 mV for 2 minutes, and -800 mV for 1 minute based on a saturated calomel electrode. Immediately after that, it was kept at +400 mV for 15 minutes in a stationary liquid, washed with water, and kept in the atmosphere. After that, when the change in the surface structure was observed with a scanning tunneling microscope, the polishing scratch disappeared, and
It grew to a particle structure of 100 nm. At this time, the oxide covered and repaired minute defects of 60 nm or less, and the defect density was reduced.

(Example 2) Stainless steel (JIS standard S)
US304) was treated as a test material. this#
It was mechanically polished using 400, # 600, # 1000, and # 1500 water-resistant abrasive paper and a 0.25 μm diamond paste, and ultrasonically washed in ethyl alcohol, isopropyl alcohol, and acetone for 3 minutes each. Thereafter, while applying ultrasonic vibration in a 0.1 M / L sulfuric acid aqueous solution, the sample was held at -1000 mV for 5 minutes, -1500 mV for 3 seconds, -1000 mV for 2 minutes, and -800 mV for 1 minute based on a saturated calomel electrode. Immediately after that, it was kept at +400 mV for 15 minutes in a stationary liquid, washed with water, and kept in the atmosphere. After that, when observed with a scanning tunneling microscope, some of the polishing scratches disappeared and grown into a band-like structure with a width of about 60 nm. Therefore, the oxide has a thickness of 60 nm.
The following small defects were covered and repaired to reduce the defect density on the surface.

(Example 3) Sputtering was performed using SUS304 stainless steel as a target, and 15 sputtered on a silicon substrate.
The laminated stainless steel was treated as a test material by 0 nm. In this case, no mechanical polishing was performed. Next, this was subjected to ultrasonic cleaning in acetone for 1 minute, and then subjected to vibration in a 0.1 M / L sulfuric acid aqueous solution for 5 minutes at -1000 mV and -3500 mV for 3 seconds based on a saturated calomel electrode while applying vibration.
It was held at 1000 mV for 2 minutes and at -800 mV for 1 minute. Immediately after that, it was kept at +400 mV for 15 minutes in a stationary liquid, washed with water, and kept in the atmosphere. The particulate surface structure grew rapidly until after 1 hour, and almost stopped after 5 hours. When a change in the surface structure in the atmosphere was observed with a scanning tunneling microscope, 35 nm was observed after 14 minutes.
Grew to 220 nm after 25 hours. Therefore, the oxide covered and repaired minute defects of 220 nm or less, and the defect density on the surface was reduced.

(Comparative Example 1) Sputtering was performed using SUS304 stainless steel as a target, and 15 sputtered on a silicon substrate.
The stainless steel laminated by 0 nm was processed as a test material. In this case, no mechanical polishing was performed. Next, this was ultrasonically cleaned in acetone for 1 minute, and then in a 0.1 M / L aqueous sulfuric acid solution for 5 minutes at -1000 mV, 3 seconds at -1500 mV, and 2 -1000 mV based on a saturated calomel electrode.
And held at -800 mV for 1 minute. Thereafter, in a stationary liquid, the potential was held at −420 mV for 2 minutes, then at a passive potential of +400 mV for 15 minutes, washed with water, and held in the atmosphere. By passing through −420 mV, hydroxides and the like are also generated in the defect, and even if the passivation treatment is performed, the layer becomes a layer in which the oxide and the hydroxide are mixed.
Even after a lapse of time, no particle growth was observed, and it was about 30 nm. Therefore, at this time, although a defect repaired in the liquid may exist, the defect is at most 30 nm or less, which is much smaller than the effect of the third embodiment.

[Brief description of the drawings]

FIG. 1 shows a schematic diagram of the changes that occur after subjecting a stainless steel to the treatment of the present invention. The air oxide film and dirt formed after the production of stainless steel cover the surface of the minute defect and its surroundings. When it is electrochemically surface-treated, the air oxide film and dirt are removed, and the passivation film grows in the form of particles on the clean surface, covering and repairing minute defects.

FIG. 2 illustrates the changes that occur after stainless steel (SUS304) is sputtered on a substrate to form a thin film layer and subjected to the treatment of the present invention. After being electrochemically surface-treated and taken out into the air, a small particulate structure was observed after 14 minutes, which grew into large particles after 26 hours.

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C23C 14/00-14/58 C23C 28/00 C25D 11/02 JICST file (JOIS)

Claims (5)

(57) [Claims] 1. A stainless steel formed on a substrate or a stainless steel formed on a substrate, wherein the density of minute defects having a surface opening diameter of 0.6 nm or more and less than 1000 nm is 60 / μm 2 or less and the minute defect density on the surface is extremely low. Surface coating made of steel
Covering layer . 2. A stainless steel having a low surface defect density or a stainless steel formed on a substrate according to claim 1, wherein the coating is a coating layer coated by sputtering.
Surface coating layer . 3. The surface defect density according to claim 1, wherein the stainless steel is subjected to cathodic reduction in dilute sulfuric acid to remove the coating and dirt in and around the micro defects to clean the surface. scan formed lower stainless steel or substrate
Surface coating layer made of stainless steel . 4. The electrochemical treatment after the surface cleaning according to claim 3, wherein the potential in the static liquid is a potential at which the passive state maintaining current density is the smallest or a potential within a range of ± 100 mV around this potential. The table made of stainless steel having a low surface defect density or a stainless steel formed on a substrate according to claim 1, wherein the passivation treatment is performed by holding for 10 minutes or more.
Surface coating layer . 5. After the passivation treatment according to claim 4, it is kept in the air to grow a particulate or band-like structure on the surface.
The stainless steel having a low surface defect density according to claim 1, wherein the minute defects are covered with an oxide film in the process.
A surface coating layer made of stainless steel and formed on a substrate .