JPH07300665A - Method for forming boron cementation layer and boron film on metallic base material - Google Patents

Abstract

PURPOSE:To form a hard boron film on a metallic base material by gradually lowering the temp. and bias voltage to the set values and continuously forming the hard boron film. CONSTITUTION:An HCD gun 14 is provided on the upper wall of a chamber 12 and a hearth 16 at the lower part in an ion plating device as the vacuum plating device (PVD). A substrate holder 20 is furnished beside the plasma producing region 18 between the gun and hearth, and a gaseous reactant introducing nozzle 22 at the lower part. A boron cementation layer and a boron film are formed on the surface of a substrate held by the holder 20, the boron or boron compd. is ionized, and a variable bias voltage is impressed on the substrate. The boron cementation layer is formed on the surface part of the base material by controlling the temperature of the substrate and the bias voltage. Meanwhile, the substrate temp. and bias voltage are gradually lowered to the set values to continuously form a hard boron film having a gradient structure. As a result, the highly adhesive boron cementation layer and hard boron film are formed on the metallic base material with good productivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a boron diffusion / penetration layer / boron film on a metal substrate. In particular, the present invention relates to a method for forming a boron diffusion / penetration layer / boron film, which is suitable for a jig / tool required to have no processing strain and a surface treatment of a mold required to have dimensional accuracy.

[0002]

BACKGROUND OF THE INVENTION Borides are generally (hexagonal boron nitride (h-BN) is soft and rich in self-lubricating property), extremely hard, and excellent in wear resistance, corrosion resistance and oxidation resistance, A so-called boride treatment, which is a surface treatment for diffusing and permeating boron on a metal surface, has been studied. For example, Japanese Patent Publication Sho 55
JP-A-51510 proposes a boring treatment method (boron diffusion permeation layer forming method) for a steel material having the following constitution.

"A method for boriding a steel material, which comprises preliminarily diffusing and permeating nitrogen into the surface of the steel material, and then diffusing and permeating boron into the portion to form a boron diffusion and permeation layer." Then, as a method for forming the above-mentioned boron diffusion / permeation layer, a gas method such as bringing a material to be treated (metal base material) into contact with a mixed gas of boron chloride (BCl ₃ ) and hydrogen or argon, boron carbide (B ₄ C) It is possible to apply the powder method in which the material to be treated is embedded in a powder containing potassium or potassium borofluoride (KBF ₄ ), the immersion method in which the material to be treated is immersed in a molten salt bath, the electrolytic method in which electrolysis is performed in the molten salt bath, etc. It is described (the same publication, column 2, line 34 to column 3, line 3).

[0004]

However, in the case of the above boride treatment method (method of forming a boron diffusion / permeation layer), there are the following problems.

(1) Each of the methods used for the boration treatment has a problem in working environment. That is, in the case of the "powder method", there is a risk of dust explosion, in the case of the "gas method", the toxicity and ignitability of the gas used, and in the case of the "molten salt method" and the "electrolysis method", the scattering of molten salt during water absorption , Etc. have their problems. Further, in the "gas method", the raw material gas used is often corrosive, and therefore sufficient attention must be paid to measures against corrosion of the exhaust system.

(2) The boron diffusion / permeation layer is sufficiently hard, but in order to obtain its surface hardness, for example, the treatment temperature is 60
When the temperature is around 0 ° C., 16 hours (Examples 1.2 and 2
(See 3) and it took a long time.

(3) Further, although crystalline boron itself is as hard as Vickers hardness (H _V ) of 1800 kg / mm ² , a technique for forming a hard boron film on the surface of a metal substrate with good adhesion has been established. Not not.

In view of the above, the present invention forms a boron diffusion / penetration layer as an intermediate layer without adversely affecting the working environment and with good productivity, and a hard boron film having good adhesion on it. Is intended to be formed.

Another object of the present invention is to provide a method for forming a highly functional boride film having good adhesion on the above hard boron film with good productivity.

[0010]

[Means for Solving the Problems]

(1) The present invention according to claim 1 achieves the first object by the following configuration.

The formation of the boron diffusion / permeation layer / boron film on the surface of the metal base material (base material) has the ability to ionize boron or a boron compound, and a mechanism capable of applying a variable bias voltage to the substrate. Vacuum plating (PV) having a mechanism in which a bias voltage can be applied to the substrate
D) When using an apparatus or a plasma CVD apparatus, the temperature and bias voltage of the substrate are controlled to form a boron diffusion / permeation layer on the surface layer of the base material, and then the temperature and bias voltage are gradually reduced to set values to have an inclined structure. It is characterized in that a hard boron film is continuously formed.

(2) The present invention according to claim 2 achieves the above second object by the following configuration.

In claim 1, on the hard boron film,
A method for forming a high-performance boride film on a metal substrate, which comprises gradually increasing the amount of reactive gas introduced to form a high-performance boride film having a graded structure.

[0014]

[Detailed description of means]

(1) The present invention is a vacuum plating with a mechanism capable of ionizing boron or a boron compound, and a mechanism capable of applying a variable bias voltage to a substrate for forming a boron diffusion permeation layer / boron film on a metal substrate surface. It is a superordinate concept that the process is performed by a (PVD) device or a plasma CVD device.

Here, as the metal base material, carbon tool steel,
Examples include iron-based materials such as high speed tool steel, alloy tool steel, and stainless steel, and copper-based materials such as beryllium-copper alloy and chromium-copper alloy.

The above-mentioned vacuum plating (PVD: Physical Vapor)
Examples of the Deposition) device include an ion plating device, a sputtering device, an activated reactive vapor deposition device, and the like, and are not particularly limited as long as boron can be sufficiently evaporated and reactive plating can be performed. For example, in the ion plating device, HCD method, RF excitation method,
Devices such as a multi-cathode method and a high vacuum arc discharge method can be preferably used.

Plasma CVD (Chemical Vapor)
In the case of using the Deposition apparatus, the gas is used as a boron source and ionized by plasma. BC as gas
_{l 3, B 2 H 6,} B-OR: can be used and the like (R hydrocarbon group such as a methyl group).

Of the above devices, the HCD shown in FIG.
A system type ion plating apparatus can be preferably used.

A pressure gradient type HCD gun 14 is arranged at the center of the upper wall of the chamber 12, and a hearth (crucible) 16 is arranged at a position corresponding to the lower side of the HCD gun 14. A substrate holder 20 is provided at a substantially central portion of a side of the plasma generation site 18 formed between the HCD gun 14 and the hearth 16, and a reactive gas introduction nozzle 22 is provided below the substrate holder 20.

The HCD gun 14 is of a pressure gradient type, and it is possible to introduce a carrier gas (Ar) from the center of the upper portion thereof, and to change the current and adjust the ionization and evaporation. Compared to the chamber internal type, this pressure gradient type has less chemical and physical damage (oxidation and sputter etching) to the gun part (nozzle) due to reaction gas, reactive ions, etc. It has the advantages of being usable and having a long life.

Further, the hearth 16 can control the amount of evaporation by circulating cooling water.

Further, a negative bias voltage can be applied to the substrate holder 20 by a high frequency on the substrate. In the illustrated example, 24 is a high-frequency supply device, and 26 is a high-frequency controller.

A positive voltage can be applied to the reaction gas. (2) In the present invention, the temperature of the substrate, that is, the metal base material (base material) and the bias voltage are controlled to form the boron diffusion / permeation layer on the surface layer of the base material, and then the substrate temperature and the substrate bias voltage are gradually set. The first feature is to continuously form a hard boron film having a graded structure (from the boride of the boron diffusion and permeation layer to the hard boron) by reducing the value to a value.

First, metallic boron is irradiated with a plasma electron beam (E = 30 to 80 V, I = 20 to 100 A) or the like.
The vaporized boron is further vaporized, and the vaporized boron is supplied with a high current plasma and a high frequency plasma (usually, a power density W _d = 5 to 20).
W / cm ² ) for ionization.

Then, a negative bias (-130 to -200 V) is applied to the base material by a high frequency or a DC power source (in the case of a high frequency, a negative bias is generated by self-bias), and the base material has boron ions and argon ions. Are made to collide with each other to form a boron diffusion and penetration layer on the surface layer of the base material by the same principle as the vacuum ion nitriding method. At this time, the substrate (base material) is heated to a temperature of 700 ° C to 800 ° C.

At this time, a large amount of electrons and argon ions are present in the high-current plasma. Boron and argon ions (both positive ions) approach the substrate by diffusion in a vacuum. Positive ions approaching to a certain distance,
Board RF self-bias (RFE _S = -130~-20
0V), it accelerates and collides. Then,
Iron atoms on the surface of the base material are knocked out by the sputtering action and combine with boron ions to form iron boride (Fe ₂ B or FeB). This compound redeposits on the substrate (base material) to form a compound layer. At this time, when the temperature of the base material is sufficiently high (700 ° C. or higher), boron in the compound formed on the surface diffuses into the base material. The thickness of the diffusion / penetration layer of boron is usually about 10 μm, and the treatment time at this time is about 60 minutes.

Next, the substrate temperature and the bias voltage are gradually lowered to a set value to form a hard boron film having a graded structure. The rate of temperature / voltage drop at this time is 20 to 30 ° C./minute and 5 to 10 V / minute, respectively. The final set temperature / voltage is, for example, about 500 ° C. and the bias voltage is −130 to −200V. Processing time is 20-60
Minutes.

(3) Further, when high functionality is required, the amount of reaction gas introduced from the reaction gas introduction nozzle to which a positive bias is applied is gradually increased to obtain a graded structure (from boron to a high-performance boron-based compound). A high-performance boride film having a) is formed on the hard boron film. At this time, the plasma amount, the substrate temperature, and the bias voltage are Wd = 5 to 30 W / cm ² , 200 to 500 ° C., −, respectively.
It is set to 80 to -200V.

Here, the high-performance boride film means hexagonal boron nitride (h-BN) and cubic boron nitride (c-B).
N), hard amorphous boron nitride (a-BN, i-B)
N), various boron nitride films, titanium boride (TiB)
_X ), chromium boride (CrB _X ), and other metal borides.

[0030]

EXAMPLES Examples carried out to confirm the effects of the present invention will be described. As the ion plating device, the one shown in FIG. 3 was used.

The scratch test, which is an adhesion test of the boron film / high-performance boride film, was carried out by using a scratch tester (a continuous load increasing method) manufactured in-house. The test conditions are: Scratch needle: Diamond indenter for Rockwell C scale (Cone angle: 120 °, Tip radius: 0.2 ±
0.02 mm), the load increasing speed was 1 N / sec, and the stage moving speed was 10 mm / min.

<Example 1> (1) A base material (die steel SKD-11) which has undergone a pre-cleaning step in the case of performing a normal surface treatment is placed on a substrate holder in an ion plating apparatus.

(2) After the inside of the chamber 12 is evacuated to the order of 10 ^-6 Torr, the substrate is heated to about 700 ° C.

(3) Argon gas (30 SCCM) is introduced from the HCD gun 14 to turn on an auxiliary discharge for heating the HCD gun (first 300 V × 1 A gradually decreases and is stable at 80 V, 5 A). Substrate to a high frequency bias (RFE _S ≒ -
400 V) is applied to expose the substrate surface to high frequency plasma and plasma beam for plasma cleaning (about 10
Minutes). Here, from the reaction gas introduction nozzle 22, argon-
A mixed gas of hydrogen (10 SCCM and 20 SCCM, respectively) was introduced.

(4) The HCD gun 14 heated by the auxiliary discharge is transferred to a high-current plasma (main discharge) (gradual increase from 30V × 20A to 80V × 40A) with a hot cathode and a hearth 16 as an anode, and boron is added. Metal boron B, which is the source, is melted and evaporated, and at the same time, plasma (power density W _d
= 15 W / cm ² ) for ionization. Then, a negative bias voltage of RFE _S = −200 V was applied to the base material, and the base material surface was heated to 700 ° C. to form a diffusion permeation layer. A boron diffusion / infiltration layer (about 10 μm) was formed in the surface layer of the base material 60 minutes after the melting of boron.

(5) After forming the diffusion / permeation layer, the temperature of the substrate is gradually lowered to a set value (500 ° C.), and the high frequency self-bias is also gradually lowered to RFES _s = −130 V to the inside of boron. Stop the spread of. Further, the temperature of the substrate was lowered to about 200 ° C., and the film formation was continued to form a hard boron film. Here, the substrate temperature is set to 50
A hard boron film having a film thickness of about 4 μm including a graded structure from the boride of the boron diffusion / permeation layer was formed 60 minutes after the temperature was lowered to around 0 ° C.

Vickers hardness of this hard boron film: Hv
_The adhesion (scratch test) was Lc (critical load): 50 N, around _0.05 1800 kg / mm ² .

<Embodiment 2> After forming a hard boron film of about 2 μm with the formation time of 20 minutes in Embodiment 1, the reaction gas introducing nozzle 6 to which a DC positive bias (150 V × 4 A) was continuously applied was used. Nitrogen gas was introduced, and treatment was performed for 60 minutes from the start of introduction to form a boron nitride (i-BN) film on the hard boron film.

At this time, the amount of reaction gas introduced is from 0 SCCM to 1
It was gradually increased to 0 SCCM over 10 minutes. Further, the high frequency power density W _d = 20 W / cm ² and the high frequency self-bias voltage RFE _S = −220 to −240 V were set.

This boron nitride (i-BN) film has a graded structure in which the amount of nitrogen gradually increases from the hard boron film, the film thickness is about 1.5 μm, and the Vickers hardness: Hv _0.05 3000.
It was kg / mm ² . The adhesion (scratch test) was Lc (critical load): 45N.

<Embodiment 3> After forming a hard boron film of about 2 μm with the formation time of 20 minutes in Embodiment 1, the reaction gas introducing nozzle 6 to which a DC positive bias (100 V × 3 A) was continuously applied was used. Nitrogen gas was introduced, and treatment was performed for 60 minutes from the start of introduction as described below to form a hexagonal boron nitride (h-BN) film on the hard boron film.

At this time, the amount of the reaction gas introduced is 0 SCCM to 2
It was gradually increased to 0 SCCM over 10 minutes. Further, the high frequency power density W _d = 10 W / cm ² and the high frequency self-bias voltage RFE _S = −140 V.

This boron nitride (h-BN) film has a graded structure in which the amount of nitrogen gradually increases from the hard boron film, the film thickness is about 2.5 μm, and the Vickers hardness: Hv _0.05 200 k.
The film had a very high self-lubricating property at g / mm ² .

[0044]

[Operation and effect of the invention]

(1) The method for forming a boron diffusion / permeation layer / boron film according to claim 1 of the present invention is such that the substrate (metal base material) temperature and the bias voltage are controlled to form a base material surface layer portion on the base material surface layer portion by the above configuration. After forming the boron diffusion / permeation layer, a hard boron film having a graded structure can be continuously formed by ion plating. For this reason, it becomes possible to form a hard boron film on a metal base material, which was obtained with insufficient adhesion by conventional ion plating. Further, it becomes possible to continuously form high-performance boride films (various boron nitride films) as described below using this hard boron film as a base.

Therefore, the conventional gas method, powder method, dipping method,
As in the electrolysis method, a boron diffusion / permeation layer and a hard boron film which do not adversely affect the working environment and have good productivity and good adhesion can be obtained on a metal substrate.

(2) In the method for forming a high-performance boride film according to the second aspect of the present invention, as described above, the reactive gas is gradually introduced onto the hard boron film obtained in the first aspect. By forming a highly functional boride film having a graded structure, it is possible to form highly functional boride films such as various boron nitride films with good adhesion on the hard boron film with good productivity. Becomes

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an ion plating device used in the method for forming a boron diffusion / permeation layer / boron film of the present invention.

[Explanation of symbols]

 12 chamber 14 HCD gun 16 hearth 18 plasma generation site 20 substrate holder

Claims (2)

[Claims] 1. A mechanism for forming a boron diffusion / permeation layer / boron film on the surface of a metal base material (base material), capable of ionizing boron or a boron compound, and a mechanism capable of applying a variable bias voltage to a substrate. When performing with a vacuum plating (PVD) apparatus or a plasma CVD apparatus, the temperature and bias voltage of the substrate are controlled to form a boron diffusion / permeation layer on the surface layer of the base material, and then the temperature and bias voltage are gradually lowered to set values. A method for forming a boron diffusion / penetration layer / boron film of a metal substrate, characterized in that a hard boron film having a graded structure is continuously formed. 2. On the boron film according to claim 1,
A method for forming a high-performance boride film on a metal substrate, which comprises gradually increasing the amount of reactive gas introduced to form a high-function boride film having a graded structure.