JP2746505B2 - Ceramic coated member and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a ceramic coated member using bearing steel and having excellent wear resistance and corrosion resistance, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Coating of a ceramic film by PVD or CVD has high hardness and excellent abrasion resistance, corrosion resistance and the like, so that its industrial use has been rapidly developed (Joytec (1989)). August issue, p. 12).

[0003] In recent years, the use conditions of members have become increasingly severe, but it is not always easy to achieve high functionality.

[0004] Members made of tool steel such as SKD11 and SKH51 coated with a titanium nitride film or a titanium carbonitride film are wear-resistant members (special steel (1990) Vol. 39, No. 9, p. 25), a corrosion-resistant member (Altopia (1989) 12, p. 4) which is in contact with a low melting point metal such as aluminum or zinc, or an alkaline solution.
It is also applied as 1).

[0005] Although the effect of the ceramic coating is recognized on these members, in the case of a coated member whose life has expired, peeling of the coating due to wear and erosion of the coating itself and corrosion and erosion often occur at the interface as a starting point ( Surface technology (199
1) vol. 42, No. 5, p. 102).

In order to cope with a change in the use environment of a severer member, there has been a demand for a member having more excellent wear resistance and corrosion resistance.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a ceramic coated member which is excellent in abrasion resistance and corrosion resistance in which the deterioration from the interface between the base material and the film and the deterioration of the film itself are reduced, and a method for producing the same. is there.

[0008]

SUMMARY OF THE INVENTION In order to reduce the deterioration from the interface between the base material and the film and the inside of the film and to improve the wear resistance and corrosion resistance, the present invention provides a tool steel, When a titanium nitride, titanium carbide or titanium carbonitride film is formed on the surface of the bearing steel and the film is represented by TiC _x N _{1 -x} , the film thickness is 0 ≦ X ≦ 0.1 and 0 .5
μm to 2.0 μm interface layer, 0.6 ≦ X ≦ 1.0
And an intermediate layer having a film thickness of 0.5 μm or more and 5.0 μm or less, and a film comprising an outermost layer having a film thickness of 1.0 μm or more and 5.0 μm or less with 0 ≦ X ≦ 0.6. Ceramic coatings have been developed.

The base material must have sufficient strength and toughness as a structural material, and a ceramic coating is applied to improve the surface characteristics.

As the tool steel used as the base material in the present invention, there are SKD11 and SKH51 and the like.
Contains 0.3% or more and 2.0% or less, plus 7%
The following V, Mo, and W are included, and Cr is also contained in 3.
Tool steels containing 0% or more and 13.0% or less can be exemplified, and these are preferable because they have high strength and excellent abrasion resistance.

As a bearing steel used as a base material, SUJ2 containing 0.8% or more and 1.2% or less by weight of carbon and 1.0% or more and 2.0% or less of Cr is used. In addition, it has excellent workability and hardenability, and is suitable as a structural material.

Most of the causes of wear of mechanical parts are corrosion, wear and fatigue failure. Fatigue failure, as well as the former two, is also a phenomenon of cracking from the surface, and both are strongly affected by the surface condition.

[0013] Corrosion is a chemical phenomenon, which can be improved by inhibiting the reaction of the surface. To improve the characteristics against wear, the surface is hardened. It is effective to improve abrasion and leave compressive residual stress on the surface.

For this purpose, it is effective to coat a ceramic having high hardness and chemically stable on a substrate by a PVD method or the like.

Titanium carbonitride is a solid solution of titanium nitride and titanium carbide. If the composition is selected, properties such as adhesion to a substrate, film hardness, and surface corrosion resistance can be obtained according to the intended use. It is preferable for the purpose.

In the present invention, when the composition of the film is expressed as TiC _x N _{1 -x} , in order to obtain sufficient adhesion to the substrate, 0 ≦ X
It is necessary to form a layer having a thickness of 0.5 μm or more and 2.0 μm or less on the substrate surface with ≦ 0.1.

If the carbon content in the coating is so high that X exceeds 0.1, the adhesion to the steel-based substrate is poor.

The adhesion between the ceramic film and the substrate must be high enough to be used as a wear-resistant member.
For example, a critical peeling load value of a film by a LEVESTEST scratch tester may be 10 N or more, preferably 20 N or more.

If the film thickness is less than 0.5 μm, there is no effect of improving the adhesion, and if it exceeds 2.0 μm, the effect remains unchanged.

Next, in order to increase the hardness of the film, a film having a thickness of 0.5 μm or more and 5.0 μm or more with 0.6 ≦ X ≦ 1.0 is formed on the layer.
It is effective to form an intermediate layer having a thickness of m or less.

When the carbon content in the coating increases, such as when X is 0.6 or more, the coating becomes harder, and the Vickers hardness (load: 50 g) becomes about 3,000 to 5,000.

The Vickers hardness of the tool steel and bearing steel of the base material is less than 800, and the Vickers hardness of the titanium nitride or the composition close to titanium nitride of 0 ≦ X ≦ 0.1 is about 2,000 to 2,500. Increasing the carbon content in the intermediate layer is effective for increasing the hardness.

X is less than 0.6 or the film thickness is 0.5 μm
If less, the effect of increasing the hardness is small. A single-phase film having a thickness exceeding 5.0 μm is not suitable because it tends to peel off.

The outermost layer needs to have chemically stable properties such as corrosion resistance and oxidation resistance. Titanium carbonitride has different reactivity depending on the composition. A high nitrogen content increases oxidation resistance, while a low nitrogen content increases hardness and abrasion resistance and increases corrosion resistance with molten aluminum.

Therefore, considering the oxidation resistance in the atmosphere and the corrosion resistance with the molten metal such as molten aluminum, the outermost layer should be 0 ≦
It was a layer having a film thickness of 1.0 μm or more and 5.0 μm or less when X ≦ 0.6.

When the carbon content in the film is large, such as when X exceeds 0.6, the surface is oxidized even in the air at about 400 ° C., and titanium oxide is generated, whereby the hardness becomes 1000 or less in Vickers hardness. This is not preferable because the wear resistance is significantly impaired.

If the film thickness is less than 1.0 μm, there is no corrosion resistance effect.
Coatings whose outermost layer exceeds 5.0 μm are unsuitable because they tend to peel off as described above.

In addition to making the outermost layer a chemically stable film, forming a multilayer film further contributes to the improvement of corrosion resistance.

In the case of a single layer of titanium nitride, defects such as pinholes and minute cracks reach from the film surface to the substrate surface, and corrosion often starts there.

For molten aluminum, base materials such as tool steel and bearing steel easily generate intermetallic compounds such as FeAl ₃ .

In the case of such corrosion, the reaction may be accelerated when the surroundings of the defect are chemically stable ceramics such as titanium nitride.

Therefore, by forming a multilayer structure, it is possible to reduce the starting point of corrosion without causing defects in the coating such as pinholes to reach the substrate.

Next, a method for manufacturing the ceramic coated member of the present invention will be described.

In order to obtain a titanium carbonitride film with high purity and a desired composition with high accuracy, the evaporation source is made of titanium metal, the content% of nitrogen gas in the reaction gas is A, and the content% of acetylene is B If A + B> 90%, and the titanium carbonitride film is represented by TiC _x N _1-x , a reactive gas where x = B / (A + B) is used to obtain the film, and as described above, It is necessary to form a film.

The composition of the reaction gas can be conveniently determined by setting the gas flow ratio to be equal to the above value, and is particularly accurate in a high vacuum.

That is, assuming that the nitrogen gas flow rate is a and the acetylene gas flow rate is b, x = B / (A + B) = b / (a +
What is necessary is just to set as b).

For film formation, for example, a pressure of 0.001 Torr
An ion plating method in which a film is formed using an electron gun evaporation source below r is effective.

Particularly when arc discharge plasma is used,
When metal titanium is used as the evaporation source, ionization is easy in a high vacuum, and it is not necessary to use an inert gas such as argon which is usually used, and a highly pure and adhesive film can be formed.

Further, it has been found that when the content mol% of the nitrogen gas and the acetylene gas in the reaction gas is more than 90%, the composition of the titanium carbonitride film can be controlled accurately.

When the titanium carbonitride film is represented by TiC _x N _{1 -x} , a reaction gas satisfying x = B / (A + B) may be used to obtain the film.

When forming a film by the ion plating method, in order not to soften the substrate, the substrate is treated at a temperature lower than the tempering temperature of the substrate.

In the film formation, for example, metal titanium is melted by an electron gun evaporation source, the metal titanium is ionized by a positive electrode applied between the electron gun evaporation source and the substrate, and the reaction gas To form a film on a substrate to which a negative bias is applied.

Prior to film formation by ion plating, treatment such as ion bombardment or ion carbonitriding may be performed as a pretreatment of the substrate.

In ion bombardment, ions such as an inert gas are bombarded against the surface of a base material to remove weakly adherent atoms or molecules adsorbed on the surface before coating. There is.

For example, the substrate is processed by applying a negative bias of 1 KV or less using argon at a pressure of 0.5 Torr or less.

In the ion carbonitriding, the surface of the base material is carbonitrided to form a hardened layer, so that the gap between the mechanical properties or the chemical properties of the coating and the base material is filled, and peeling, stress concentration or corrosion at the interface is avoided. It is effective for

In the carbonitriding treatment using ions, the ion density on the substrate surface is high, the treatment temperature is high, and the longer the treatment, the better the efficiency. However, the treatment temperature is 600 ° C. in order not to soften the substrate.
It is desirable to perform the heating at a temperature equal to or lower than the following substrate tempering temperature, for example, in a short time such as within 2 hours.

When the gas contains hydrogen in addition to nitrogen and carbon, diffusion of nitrogen and carbon into the base material is promoted.

Therefore, it is effective to use hydrocarbon such as acetylene or ammonia in addition to nitrogen gas.

An inert gas such as argon may be added in order to promote ionization, but it is desirable that the amount of a gas other than nitrogen, carbon, and hydrogen be less than 40% by mol%.

The ceramic-coated member of the present invention can be used as a wear-resistant member such as a tool, a cutting tool, a mold, a low-melting metal such as aluminum or zinc, or a corrosion-resistant member in contact with an alkaline solution. Can be applied.

[0052]

EXAMPLES Table 1 shows film forming conditions and film properties of the films obtained by the ion plating method. The measurement of the coating surface hardness shows the measured value of Vickers hardness under a load of 50 g.

For the measurement of the film composition and the film thickness, a calibration curve was prepared from a sample whose composition was known in advance, and RSV AN
The analysis was performed using an ALYMAT2504 glow discharge optical emission spectrometer.

The base material is 0.85% by weight of carbon,
4.4%, V 1.8%, Mo 5.1%, W 5.5%.
Alloy tool steel SKH51 containing 7% and having a Vickers hardness of 700 after quenching and tempering (tempering temperature 57
0 ° C.).

In the ion plating, titanium was used as a metal evaporation source, and this was dissolved by an electron gun. The gas used was nitrogen or acetylene gas in addition to nitrogen.

The film thickness of the interface layer is x = 0.1 = B / (A +
B = 10% (acetylene gas partial pressure 0.
4 Torr), A = 90% (nitrogen gas partial pressure 3.6 Torr)
r), and the film formation of the intermediate layer is x = 0.8 = B / (A +
B = 80% (partial pressure of acetylene gas 3.
2 Torr), A = 20% (nitrogen gas partial pressure 0.8 Torr)
r), and the composition was changed for each sample only for the outermost layer.

After the film formation, the above analysis method revealed that the interface layer had x = 0.1 and the intermediate layer had x = 0.8.

The thicknesses of the interface layer, the intermediate layer and the outermost layer were changed by changing the film forming time. The deposition rate is 0.1μ
m / min. The substrate temperature was kept at 500 ° C.

During the coating, the bias was -5 in each case.
A direct current of 00 V was applied at a pressure of ⁴ × 10 ⁻⁴ torr. Abrasion resistance was measured by a pin-on-disk test.

Attach an S45C pin (0.2r tip)
Load 29N, speed 100 on ceramic coated specimen
The comparison was made based on the pin wear weight when a 500 m wear test was performed at 500 mm / s.

There is a correlation between the pin wear weight and the coating member wear weight. In Table 1, the wear weight of 2 mg or less is reduced to 10 mg.
The above was defined as large and the others as medium. The amount of erosion was immersed for 4 hours in a test piece coated with ceramic in 700 ° C
After the test, aluminum was removed with a NaOH solution, and the weight loss at that time was measured.

The amount of erosion serves as an index of corrosion resistance. 1.0
mg / cm ² or less is a practical level. The film critical peeling load Lc is measured by a LEVESTEST scratch tester, and is an index of the adhesion between the substrate and the film.

The practical level is 10 N or more. Sample numbers 1 to 5 are examples, and sample numbers 6 to 10 are comparative examples. When the conditions are optimized as shown in Table 1, both wear resistance and corrosion resistance can be obtained.

[0064]

[Table 1]

[0065]

[Table 2]

[0066]

As described above, a ceramic coated member having excellent abrasion resistance and corrosion resistance is obtained by utilizing the mechanical characteristics of the substrate and the surface characteristics of the ceramic film to reduce the deterioration at the interface between the substrate and the film and the deterioration inside the film. Obtainable.

Claims (2)

(57) [Claims] When a titanium nitride, titanium carbide or titanium carbonitride film is represented by TiC _x N _{1 -x} , the surface of the substrate is 0 ≦ X ≦
An interface layer having a film thickness of 0.5 μm or more and 2.0 μm or less at 0.1;
An intermediate layer having a film thickness of 0.5 μm or more and 5.0 μm or less when 0.6 ≦ X ≦ 1.0, and a coating film consisting of an outermost layer having a film thickness of 1.0 μm or more and 5.0 μm or less where 0 ≦ X ≦ 0.6. A ceramic coated member characterized by being formed into a film. 2. If the evaporation source is metal titanium, the content mol% of nitrogen gas in the reaction gas is A, and the content mol% of acetylene is B, A + B> 90%, and the titanium carbonitride film is TiC _x N When expressed as _1-x , to obtain the film, x = B /
(A + B), the composition is controlled by an ion plating method using arc discharge,
A method for manufacturing a ceramic coated member, comprising forming a film as described in claim 1 on a surface of a base material made of tool steel and bearing steel.