JP3015890B1 - Manufacturing method of coated steel with high hardness and high corrosion resistance - Google Patents

Abstract

The present invention provides a method for efficiently producing a high hardness, high corrosion resistance coated steel having a chromium oxycarbide coating on the surface of a high-speed steel base material. SOLUTION: After high-speed steel substrate surface is subjected to argon bombardment treatment at a temperature of 350 to 450 ° C, chromium oxycarbide coating is formed by chemical vapor deposition to produce high hardness, high corrosion resistant coated steel. I do.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for efficiently producing a high-hardness, high-corrosion-resistant coated steel having a chromium oxycarbide coating on a high-speed steel substrate, particularly suitable as a cutting tool.

[0002]

2. Description of the Related Art Tool steel is a special steel for tools and jigs used in forming metal and non-metallic materials. Hardness and wear resistance are particularly important, and moderate toughness and corrosion resistance are required. Depending on the application, impact resistance, heat fatigue resistance (heat check) resistance, etc. are required. In order to obtain such tool steel, the so-called hard coating technology of coating a highly tough material having high hardness, abrasion resistance, welding resistance and corrosion resistance on the surface of a highly tough steel material has been used in the industry. Widely used. As materials used for such hard coating, TiN and Al ₂ O ₃ have been awarded so far, but in recent years, with the advancement and diversification of cutting technology, TiC, W ₂ C, TiCN and the like have been used. Various hard materials have been used.

Meanwhile, chromium oxycarbide (Cr)
₂ CO) has a micro Vickers hardness of 2800 kg /
mm ² or more, greater than 2200 kg / mm ^{2 of} titanium nitride and extremely high corrosion and corrosion resistance to hydrochloric acid, sulfuric acid, etc., making it a promising material for hard coatings. In addition, it is not used as a hard coating material for tool steel, because it decomposes into chromium carbide and chromium oxide at around 600 ° C. and the coating structure becomes unstable. .

[0004]

SUMMARY OF THE INVENTION Under the above circumstances, the present invention provides a method for efficiently producing a high-hardness, high-corrosion-resistant coated steel having a chromium oxycarbide coating on a surface, which is suitable as a cutting tool or the like. The purpose of this is to provide.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies on a method for producing a high hardness, high corrosion resistance coated steel having a chromium oxycarbide coating on the surface, and as a result, have previously specified a high speed steel substrate surface. After performing an argon bombardment treatment at a temperature of, a chromium oxycarbide is chemically vapor-deposited, thereby forming a chromium oxycarbide coating having good adhesion to a substrate, and finding that the object can be achieved. The present invention has been completed based on the findings.

That is, according to the present invention, in forming a chromium oxycarbide coating on a surface of a high-speed steel substrate by chemical vapor deposition, the substrate surface is previously subjected to an argon bombardment treatment at a temperature in the range of 350 to 450 ° C. It is intended to provide a method for producing a high hardness, high corrosion resistance coated steel characterized by the following.

[0007]

DETAILED DESCRIPTION OF THE INVENTION In the method of the present invention, a substrate made of high-speed steel is used. This high-speed steel is an excellent tool steel for strong cutting that can be cut at a high speed, and is roughly classified into W-based and Mo-based, but any of them can be used in the present invention. In the present invention,
A chromium oxycarbide coating is formed on the surface of the high-speed steel substrate by plasma-enhanced chemical vapor deposition.In order to improve the adhesion between the chromium oxycarbide coating and the substrate, the surface of the substrate is previously heated to 350 to 450 ° C. It is necessary to perform argon bombardment at a temperature in the range. When the bombardment treatment temperature is out of the above range, the effect of improving the adhesion between the chromium oxycarbide coating and the substrate is not sufficiently exhibited, and the object of the present invention cannot be achieved. This bombardment treatment is performed, for example, in a vacuum chamber pressure of 0.2 to 1.0 Torr and an RF power of 50 to 4.
00 W, argon flow rate: 20 to 150 sccm, substrate bias: -50 to -400 V, substrate temperature: 350 to 45
It is preferable to carry out the reaction at 0 ° C. for 5 minutes or more. On this occasion,
As the atmosphere gas, argon alone may be used,
A mixed gas of argon and hydrogen may be used. One example of the optimum conditions is as follows: vacuum chamber pressure: 0.8 Torr, RF power: 150 W, argon flow rate: 80 sccm, substrate bias: -150 V, substrate temperature: 450 ° C., processing time:
About 30 minutes.

After the substrate surface is subjected to the argon bombardment treatment in this manner, a chromium oxycarbide coating is formed by chemical vapor deposition. The chromium oxycarbide coating is formed by a chemical vapor deposition method using, for example, hexacarbonylchromium as a raw material. As the chemical vapor deposition method, for example, a plasma chemical vapor deposition method,
A thermal chemical vapor deposition method, a photochemical vapor deposition method using laser light or ultraviolet light, and the like can be mentioned. Among them, a plasma chemical vapor deposition method is particularly preferable.

When a chromium oxycarbide coating is formed by plasma enhanced chemical vapor deposition, for example, a high-speed steel substrate subjected to the above-described argon bombardment treatment is mounted in a plasma enhanced chemical vapor deposition apparatus, and hexacarbonylchromium is converted into hydrogen. Then, it was introduced into the apparatus, and the pressure in the vacuum chamber: 0.2 to 1.0 Torr, RF power: 10 to 3
0 W, hydrogen flow rate: 20 to 150 sccm, substrate bias: −50 to −400 V, substrate temperature: 350 to 400 ° C.
The thickness of the chromium oxycarbide coating is 0.5
It is preferable to perform plasma chemical vapor deposition for a time of about 5 μm (for example, a film having a thickness of about 1 to 2 μm is formed by chemical vapor deposition for 90 minutes). At this time, if the hydrogen flow rate is increased, the film forming speed is improved. The substrate electrode needs to be not grounded in order to apply a negative DC bias to the substrate. An example of the optimum conditions in this plasma chemical vapor deposition is as follows: vacuum chamber pressure: 0.6 Torr, RF
Power: 10 W, hydrogen flow rate: 50 sccm, substrate bias: -250 V, and substrate temperature: 380 ° C. In this way, a chromium oxycarbide coating having excellent adhesion to the substrate is formed, and a high hardness, high corrosion resistance coated steel is obtained. This high hardness, high corrosion resistance coated steel is particularly suitable as a cutting tool.

[0010]

According to the method of the present invention, a high hardness, high corrosion resistant coated steel having high hardness, excellent wear resistance, good corrosion resistance and appropriate toughness can be easily obtained. When turning a steel pipe using a high-speed steel tool having a chromium oxycarbide coating on the surface obtained by the method of the present invention, the maximum wear on the flank of the tool is smaller than that of a commercially available TiN-coated high-speed steel tool. It shows a lower value. Further, in the method of the present invention, the bombardment treatment of the base material surface and the formation of the chromium oxycarbide coating by chemical vapor deposition are all performed at a temperature of 450 ° C. or less, so that the performance of the tool base material is impaired or the No change occurs. Therefore,
The coated steel with high hardness and high corrosion resistance obtained by the method of the present invention is suitable for precision molds as well as cutting tools. Further, it can be used for valves of internal combustion engines, chemical plants, and the like, utilizing its excellent corrosion resistance.

[0011]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Example 1 A high-speed steel substrate having a size of 12.5 mm square and a thickness of 5
mm SH42 (manufactured by Japan High Frequency Industry Co., Ltd.) was used. First, the chip was mounted in a plasma chemical vapor deposition apparatus at a distance of 3 mm from the electrode surface such that chromium oxycarbide also wrapped around and covered the back surface of the chip. Then, under the conditions of vacuum chamber pressure: 0.8 Torr, RF power: 150 W, argon flow rate: 80 sccm, substrate bias: -150 V, substrate temperature: 450 ° C., 3
Argon bombardment treatment was performed for 0 minutes. Then, the pressure in the vacuum chamber was set to 0.6 Torr for the chips thus subjected to the argon bombardment treatment.
Plasma chemical vapor deposition was performed for 90 minutes under the conditions of RF power: 10 W, substrate bias: -250 V, and substrate temperature: 380 ° C. to form a chromium oxycarbide coating. The chromium oxycarbide coating thus formed exhibited a black luster and was formed so as to extend to the back surface of the throw-away chip. By pressing the tip of the cutter knife strongly against this film with a certain force and damaging the film,
A screening test of the adhesion of the coating was performed, but no peeling was observed under a microscope. Next, using this chromium oxycarbide coated SH42 chip, a turning test was performed by the following method, and the wear amount of the chip after turning was measured.
For comparison, uncoated SH42 chip and TiN
A turning test was similarly performed using the coated SH42 chip (commercially available).

[Turning test] As the material to be turned, a diameter of 60 m
m, 4 mm thick steel pipe (JIS G3452)
Cutting speed: 30m / min, depth of cut: 0.2mm, feed:
Under the conditions of 0.1 mm / rev and dry conditions, the black scale was removed by turning, and then turning was performed until the thickness reached 1.5 mm. This turning test was performed three times for each chip, and the average value of the maximum wear amount of the chip flank was determined. Table 1 shows the results.

[0014]

[Table 1]

As can be seen from Table 1, the maximum wear of the flank of the SH42 chip coated with chromium oxycarbide is as follows:
The value is lower than that of a commercially available TiN-coated SH42 chip. In addition, the coating could easily go around to the back side, and in this example, the back side showed higher turning properties than the front side. From these, it was confirmed that the performance of the throw-away tip was improved as an effect of the chromium oxycarbide coating.

Example 2 Under the same conditions as in Example 1, chromium oxycarbide-coated S
An H42 indexable tip was prepared. Using this chromium oxycarbide-coated SH42 chip, turning was repeated every minute under the same turning conditions as in Example 1, and the relationship between the maximum wear amount of the chip flank and the turning time was examined. The result is shown as a graph in FIG. For comparison, a similar turning test was performed using an uncoated SH42 chip and a TiN-coated SH42 chip (commercially available), and the results are shown as a graph in FIG. As can be seen from FIG. 1, similarly to the results in Table 1 of Example 1, the chromium oxycarbide coated SH42 chip exhibited a low value of the maximum flank wear. Also in this test, it was confirmed that the performance of the throw-away tip was improved by the chromium oxycarbide coating.

[Brief description of the drawings]

FIG. 1 is a graph showing an example of a relationship between a turning time and a maximum wear amount of a tool (chip) flank in each SH42 insert.

────────────────────────────────────────────────── ─── Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C23C 16/00-16/56 B23P 15/28 CA (STN) INSPEC (DIALOG) JICST file (JOIS)

Claims (3)

(57) [Claims] 1. A method of forming a chromium oxycarbide coating on a surface of a high-speed steel substrate by chemical vapor deposition, wherein the surface of the substrate is previously subjected to an argon bombardment treatment at a temperature in the range of 350 to 450 ° C. Manufacturing method of high hardness, high corrosion resistance coated steel. 2. The method according to claim 1, wherein the chromium oxycarbide coating is formed by plasma enhanced chemical vapor deposition. 3. The production method according to claim 1, wherein the high hardness, high corrosion resistance coated steel is a cutting tool.