JPH04292497A - Method and device for forming diamond film - Google Patents

Abstract

PURPOSE:To provide a method and a device capable of forming a diamond coating film at high rate by a gas phase synthetic method having high purity and quality and having good adhesiveness to a substrate without the contamination of impurities. CONSTITUTION:In a method for forming a diamond coating film by burning a fuel gas 112 with oxygen gas 113, applying the generated combustion flame 115 to a substrate 118 to form the diamond film 116 on the substrate 118, the method is characterized by feeding a powder gas 114 containing a flame-coating material into the combustion flame 115 and changing the feeding amount of the powder gas 114 to form a layer of the mixture of diamond with the flame- coating material between the substrate 118 and the diamond film 116.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for forming a diamond coating using vapor phase synthesis.

0002

[Prior art] Diamond has a Vickers hardness of 10.
000, making it the hardest material on earth. It also has a high Young's modulus and is excellent in abrasion resistance and chemical stability. Diamond, which has these excellent properties, is an excellent material for tools used in so-called high-tech industries.
It is an essential existence. Furthermore, as a diamond film produced by vapor phase synthesis, it is expected to be applied to wear-resistant coatings, speaker diaphragms, transparent coatings for optical components, etc.

[0003] However, diamond films formed by vapor phase synthesis have a problem in that their adhesion is extremely weak, so that they cannot be sufficiently applied to products in the above application fields. Attempts have been made to improve adhesion by increasing the nucleation density of diamond or by providing an intermediate layer such as carbide, but no satisfactory results have been obtained.

The inventors of the present application have developed the DC plasma jet CVD method (Japanese Unexamined Patent Application Publication No. 1983-1993), which is a high-speed vapor phase synthesis method for diamond.
4-33096), and invented a method to form a sprayed film containing diamond by supplying metal or ceramic powder into the plasma during diamond synthesis using the DC plasma jet CVD method (Japanese Patent Application Laid-Open No. −
No. 22741), this method has succeeded in obtaining high adhesion by forming an intermediate layer made of a thermal spray material and diamond between the thermal spray coating and the diamond coating.

FIG. 5 shows a conventional diamond film forming apparatus. Cathode 102 connected to the cathode of DC power supply 104
An anode 101 connected to the anode of a DC power source 104 is formed around the cathode 102 and an anode 101.
A flow path through which diamond synthesis gas 103 flows is formed between them. A powder supply nozzle 105 is formed around the outer periphery of the anode 101, and a flow path is formed between the anode 101 and the powder supply nozzle 105 through which a carrier gas 106 containing metal or ceramic powder flows.

In this apparatus, a diamond synthesis gas 103 and a carrier gas 106 containing powder are mixed at the outlet of a powder supply nozzle 105, and a plasma jet 110
As a result, the substrate 107 is irradiated at high speed. In the initial stage of irradiation, the sprayed film 1 is formed by increasing the mixing ratio of the diamond synthesis gas 103 and the carrier gas 106 containing powder.
A diamond film 109 is formed by gradually lowering the mixing ratio and increasing the ratio of the diamond synthesis gas 103.

[0007]

[Problems to be Solved by the Invention] This method is based on the thermal spray coating 1
An intermediate layer made of thermal spray material and diamond is formed between the diamond film 109 and the diamond film 109, and it is an excellent method that can form a diamond film with high adhesion continuously and at high speed, but it uses DC arc discharge. Therefore, anode 1
There is a problem in that the electrode materials of 01 and the cathode 102 are mixed into the diamond film 109 as impurities.

[0008] An object of the present invention is to provide a method and apparatus for forming a diamond film that can form a diamond film of high purity, high quality, and good adhesion at high speed without contamination with impurities. .

[0009]

[Means for Solving the Problems] The principle of the present invention will be explained. The present invention basically utilizes a diamond synthesis method using combustion flame. Diamond synthesis using combustion
It was developed by Hirose et al. (NEW DIAMON
D.No. 10, p. 34 (1988)), is a method of growing a diamond film on the upper surface of a substrate by placing a water-cooled substrate in the inner flame of a combustion flame of acetylene and oxygen.

The inventors of the present invention have improved this conventional method, and have developed a method (Japanese Patent Application No. 2003-20002) of synthesizing diamond by irradiating a substrate with a high-speed gas flame generated by pressurized combustion.
-1367), and a method of synthesizing diamond by causing a combustion reaction in the combustion chamber in the torch, ejecting the generated high-temperature, high-pressure combustion gas from a nozzle and irradiating it onto the substrate (
Japanese Patent Application No. 2-402541; filed on December 15, 1990).

[0011] The present invention is capable of forming a mixed layer of diamond and thermal spraying material by supplying metal or ceramic powder or wire to the frame and thermally spraying them while synthesizing diamond using these methods. Features. FIG. 1 shows an apparatus that performs diamond synthesis and thermal spraying using combustion flame, which is the basic principle of the present invention.

[0012] A flow path is formed in the torch 111 for flowing a fuel gas 112, an oxygen gas 113, and a carrier gas (powder gas) 114 containing metal or ceramic powder. The above gases are mixed at the tip of the torch 111, accelerated, and irradiated onto the substrate 118 as a frame 115.

At this time, by gradually lowering the mixing ratio of the powder gas 114, the sprayed film 11 is formed on the substrate 118.
7 is formed, then an intermediate layer of thermal spray material and diamond is formed, and a diamond film 116 is formed thereon. To obtain a diamond film with extremely high adhesion,
The thermal spraying material is made of the same material as the substrate 118, and the film structure is such that the composition changes continuously from the thermal spraying material to diamond from the substrate 118 side toward the surface of the diamond film 116.
Functionally graded materials).

As the fuel gas 112, a gas whose main component is a carbon compound gas or a mixed gas of a carbon compound gas and hydrogen is used. However, in order to synthesize a diamond film at a high film formation rate, it is necessary to use a gas that can obtain a high combustion temperature, such as acetylene, propane (C
3 H8 ), propylene (C3 H6 ), map (
C3 H4), a mixed gas of hydrogen and hydrocarbon gas, etc. are most suitable.

[0015] To synthesize a diamond film using this method, the frame 115 needs to be reducible and carbon-rich. In other words, the compositions of the fuel gas 112 and the oxygen gas 113 must have more carbon atoms than oxygen atoms. The surface temperature of the substrate 118 during diamond film synthesis is 500~
Must be 1200℃. This is because if the temperature is higher than this range, graphite tends to form, and if it is lower than this range, it tends to become amorphous.

[0016]Although it is possible to synthesize a diamond film under atmospheric pressure, if it is synthesized under reduced pressure, mixing of nitrogen can be prevented, a high film forming rate can be obtained, and furthermore, the thermal sprayed film 1
17 can be increased in density.

[0017]

[Operation] According to the present invention, without contamination with impurities,
A diamond film of high purity, high quality, and good adhesion can be formed at high speed.

[0018]

Embodiment A method and apparatus for forming a diamond film according to a first embodiment of the present invention will be explained with reference to FIG. A diamond film forming apparatus according to this embodiment will be explained. Cemented carbide (WC-12%) with dimensions 20 x 20 x 5 mm
A substrate 124 made of Co., Ltd.) is fixed on a water-cooled substrate holder 125A. Above the substrate 124, the manipulator 1
A movable torch 119 is supported at the end of the torch 119. Inside the torch 119, acetylene fuel gas 1
20, a flow path for flowing oxygen gas 121, and powder gas 122 is formed. These gases combusted within the torch 119 form a flame 123 from a jet nozzle at the tip of the torch 119, and can irradiate the surface of the substrate 124.

Next, a method for forming a diamond film according to this embodiment will be explained. In the gas flow path in the torch 119,
The fuel gas 120 is ignited while flowing acetylene at a rate of 20 l/min and oxygen gas 121 at a rate of 20 l/min, and the flame 123 is irradiated onto the surface of the substrate 124. Board 1
The torch 119 is brought close to the substrate 124 until the surface temperature of the torch 24 reaches 1000°C.

WC- made of the same material as the substrate material of the substrate 124
A 12% Co powder is supplied as powder gas 122 together with a nitrogen carrier gas from a flow path in the torch 119, and thermal spraying is performed for 10 minutes to form a thermal sprayed film. Next, for 30 minutes, the powder gas 122 is gradually reduced to zero flow rate, and the flow rate of oxygen gas 121 is decreased from 20 l/min to 1
The rate is reduced to 7 l/min to form a mixed layer.

Next, the supply of powder gas 122 is stopped, and
A diamond film is formed by irradiating the surface of the substrate 124 with the frame 123 for one hour under the condition that the flow rate of the oxygen gas 121 is 17 l/min. Diamond coating formed on the surface of the substrate 124 (sprayed coating, mixed layer, and diamond coating)
125 was analyzed by SEM, X-ray diffraction, EPMA, and SIMS, and the adhesion was examined by a tensile test.

From the SEM observation of the cross section, the thickness of the diamond coating 125 is about 150 μm, and from the EPMA analysis, the thickness of the sprayed film is about 50 μm, the mixed layer of sprayed material and diamond is about 50 μm, and the diamond film is about 50 μm. Ta. Only diamond was detected in the surface X-ray diffraction, diamond, WC, and Co were detected in the cross-sectional X-ray diffraction, and no graphite was detected at all.

SIMS analysis of the diamond film detected C, a small amount of N, and O and H at levels close to the detection limit. The adhesion strength is 15, which is the measurement limit of the tensile test.
A value exceeding 0 kg/cm2 was obtained. In the conventional DC arc plasma method, the electrode materials W and Cu are mixed into the formed diamond film, but according to the invention of the diamond film forming method and its forming apparatus of this embodiment,
A highly pure diamond film can be obtained. Further, a diamond film having excellent adhesion can be obtained.

A method and apparatus for forming a diamond film according to a second embodiment of the present invention will be explained with reference to FIG. This example is characterized in that the diamond coating is formed in a reduced pressure atmosphere in a reduced pressure chamber with an exhaust system. A diamond film forming apparatus according to this embodiment will be explained.

A molybdenum substrate 132 with dimensions of 20×20×5 mm is fixed on a water-cooled substrate holder 134. A movable torch 127 is provided above the substrate 132 and supported by the end of the manipulator 135. The torch 127, the water-cooled substrate holder 134, the substrate 132, and the manipulator 135 are installed in the chamber 136,
The atmosphere within chamber 136 can be exhausted through exhaust port 137.

Pipes for supplying propylene fuel gas 128, oxygen gas 129, and powder gas 130 are connected to the torch 127 from outside the chamber 136.
Respective channels for flowing these gases are formed within the chamber. These gases burned in the torch 127 form a flame 131 from a jet nozzle at the tip of the torch 127, and can irradiate the surface of the substrate 132.

Next, a method for forming a diamond film according to this embodiment will be explained. In the gas flow path in the torch 127,
20 liters of propylene at a pressure of 6 atmospheres as fuel gas 128
/min, 30l/m of oxygen gas 129, also at 6 atm.
The flame 131 is ignited while flowing at a rate of
32 irradiate the surface. The surface temperature of the substrate 132 is 1000
The torch 127 is brought close to the substrate 132 until the temperature reaches .

Molybdenum powder, which is the same as the substrate material of the substrate 132, is supplied together with an Ar carrier gas as the powder gas 130 from the channel in the torch 127, and thermal spraying is performed for 5 minutes to form a thermal spray film. Next, for 10 minutes, powder gas 1
30 is gradually decreased to zero flow rate, and the flow rate of oxygen gas 129 is decreased from 30 l/min to 24 l/min to form a mixed layer.

Next, the supply of powder gas 130 is stopped, and
A diamond film is formed by irradiating the surface of the substrate 132 with the frame 131 for 30 minutes at a flow rate of oxygen gas 129 of 24 l/min. The diamond coating (sprayed coating, mixed layer, and diamond coating) 133 formed on the surface of the substrate 132 was analyzed by SEM, X-ray diffraction, EPMA, and SIMS, and the adhesion was examined by a tensile test.

[0030] Analysis of the cross section by EPMA revealed that the mixed layer of thermal spray material and diamond was approximately 20 μm thick, and the diamond film was approximately 50 μm thick. Surface X-ray diffraction detects only diamond, cross-sectional X-ray diffraction reveals diamond,
Mo and MoC2 were detected, and no graphite was detected.

[0031] In the SIMS analysis of the diamond film, O, H, and N were detected at levels close to the detection limit. The adhesion strength is 150 kg/cm, which is the measurement limit of the tensile test.
Values exceeding 2 were obtained.

In this way, also in this example, a diamond film of high purity and excellent adhesion, which could not be obtained conventionally, can be obtained. Furthermore, since the diamond film is formed in a reduced pressure atmosphere in a reduced pressure chamber with an exhaust system, there is an advantage that the film forming rate can be increased. A method and apparatus for forming a diamond film according to a third embodiment of the present invention will be described with reference to FIG.

The diamond film forming apparatus according to this embodiment will be explained. A copper substrate 144 with dimensions of 20×20×5 mm is fixed on a water-cooled substrate holder 146. A movable internal combustion torch 138 is provided above the substrate 144 and supported by the end of the manipulator 147 . Internal combustion torch 138, water-cooled board holder 146, board 1
44, the manipulator 147 is installed in the vacuum chamber 148, and the atmosphere in the vacuum chamber 148 is controlled by the exhaust port 1.
49 can be exhausted.

Internal combustion torch 1 from outside the vacuum chamber 148
38, propane fuel gas 139, oxygen gas 140,
and powder gas 141 supply pipes are connected to each other to form respective flow paths for sending these gases into a combustion chamber 142 provided inside the internal combustion torch 138.

These gases combusted in the combustion chamber 142 inside the internal combustion torch 138 become a flame jet 143 from the jet nozzle at the tip of the torch 138, and can irradiate the surface of the substrate 144.

Next, a method for forming a diamond film according to this embodiment will be explained. The flame jet 143 is ignited by feeding propane as a fuel gas 139 into the combustion chamber 142 of the internal combustion torch 138 at a rate of 20 l/min at a pressure of 5 atm and oxygen gas 140 at a rate of 30 l/min at a pressure of 5 atm. The surface of the substrate 144 is irradiated. Substrate 14
Internal combustion torch 138 until the surface temperature of 4 reaches 900°C.
is brought closer to the substrate 144.

Copper powder made of the same material as the substrate material of the substrate 144 is supplied as a powder gas 141 together with an Ar carrier gas into the combustion chamber 142 of the internal combustion torch 138, and thermal spraying is performed for 5 minutes to form a thermal spray film. Next, over 10 minutes, the powder gas 141 is gradually reduced to zero flow rate, and the flow rate of oxygen gas 140 is decreased from 30 l/min to 24 l/min.
/min to form a mixed layer.

Next, the supply of powder gas 141 is stopped, and
A diamond film is formed by irradiating the surface of the substrate 144 with the flame jet 143 for one hour under the condition that the flow rate of the oxygen gas 140 is 24 l/min. The diamond coating (sprayed coating, mixed layer, and diamond coating) 145 formed on the surface of the substrate 144 is analyzed by SEM, X-ray diffraction, EPMA, and SIM.
In addition to the analysis using S, the adhesion was examined by a tensile test.

[0039] Analysis of the cross section by EPMA revealed that the mixed layer of thermal spray material and diamond was approximately 25 μm thick, and the diamond film was approximately 120 μm thick. Only diamond was detected in the surface X-ray diffraction, diamond and Cu were detected in the cross-sectional X-ray diffraction, and no graphite was detected at all.

[0040] SIMS analysis of the diamond film detected O, H, and N at levels close to the detection limit. The adhesion strength is 150 kg/cm, which is the measurement limit of the tensile test.
Values exceeding 2 were obtained.

In this way, also in this example, a diamond film of high purity and excellent adhesion, which could not be obtained conventionally, can be obtained. This embodiment also has the advantage that the diamond coating is formed in a reduced-pressure atmosphere in a reduced-pressure vacuum chamber with an exhaust system, so that the film-forming speed can be increased.

[0042]

As described above, according to the present invention, a diamond film of high purity and excellent adhesion can be formed, and the quality and reliability of the diamond film can be improved.

[Brief explanation of drawings]

FIG. 1 is a diagram explaining the principle of the present invention.

FIG. 2 is a diagram showing a diamond film forming apparatus according to a first embodiment of the present invention.

FIG. 3 is a diagram showing a diamond film forming apparatus according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a diamond film forming apparatus according to a third embodiment of the present invention.

FIG. 5 is a diagram showing a conventional diamond film forming apparatus.

[Explanation of symbols]

101...Anode 102...Cathode 103...Diamond synthesis gas 104...DC power source 105...Powder supply nozzle 106...Carrier gas containing powder 107...Substrate 108...Sprayed film 109...Diamond film 110...Plasma jet 111...Torch 112...Fuel gas 113...Oxygen gas 114...Carrier gas (powder gas) 115 containing powder
…Frame 116…Diamond film 117…Sprayed film 118…Substrate 119…Torch 120…Fuel gas 121…Oxygen gas 122…Powder gas 123…Frame 124…Substrate 125…Diamond coating 125A…Water-cooled substrate holder 126…Manipulator 127…Torch 128… Fuel gas 129...Oxygen gas 130...Powder gas 131...Frame 132...Substrate 133...Diamond coating 134...Water-cooled substrate holder 135...Manipulator 136...Chamber 137...Exhaust port 138...Internal combustion torch 139...Fuel gas 140...Oxygen gas 141...Powder gas 142...Combustion chamber 143...Flame jet 144...Substrate 145...Diamond coating 146...Water-cooled substrate holder 147...Manipulator 148...Vacuum chamber 149...Exhaust port

Claims (8)

[Claims] 1. A method for forming a diamond film in which a diamond film is formed on the substrate by combusting oxygen gas and fuel gas and irradiating the generated combustion flame onto the substrate, wherein a thermal spray material is added to the combustion flame. between the substrate and the diamond film by supplying a powder gas containing the thermal spray material and changing the supply amount of the powder gas.
A method for forming a diamond film, comprising forming a mixed layer of diamond and the thermal spraying material. 2. The diamond film forming method according to claim 1, wherein the composition of the fuel gas and the oxygen gas is such that the number of carbon atoms is greater than the number of oxygen atoms. 3. The diamond film forming method according to claim 1, wherein the diamond film is formed in a reduced pressure atmosphere. 4. The diamond film forming method according to claim 1, wherein a wire containing the thermal spraying material is supplied into the combustion flame instead of the powder gas, and the wire is extruded to remove the thermal spraying material. A diamond film forming method characterized by mixing. 5. The method for forming a diamond film according to claim 1, wherein the proportion of the sprayed material in the mixed layer formed between the sprayed film on the substrate and the diamond film is: A method for forming a diamond film, characterized in that the mixing ratio of the thermal spraying material is adjusted so that it decreases continuously from the thermal sprayed film toward the diamond film. 6. A fuel gas supply port for supplying fuel gas for diamond formation, an oxygen gas supply port for supplying oxygen gas, and a jet nozzle for jetting combustion flame generated by combustion of the fuel gas and oxygen gas. , a torch having a thermal spraying material supply device that supplies thermal spraying material to the combustion flame; a substrate holding mechanism that holds a substrate to which the combustion flame is irradiated; and a substrate/torch that changes the distance between the substrate and the torch. A diamond film forming apparatus characterized by comprising a distance changing mechanism. 7. The diamond film forming apparatus according to claim 6, wherein the torch, the substrate holding mechanism, and the substrate-torch distance changing mechanism are provided in a reduced pressure chamber with an exhaust system. Diamond film forming equipment. 8. The diamond film forming apparatus according to claim 6, wherein the torch has a combustion chamber in which the fuel gas and the oxygen gas are combusted.