JP7244387B2 - Manufacturing method of vanadium siliconitride film-coated member and vanadium siliconitride film-coated member - Google Patents

Description

The present invention relates to a vanadium silicon nitride film-coated member in which a steel material is coated with a vanadium silicon nitride film.

BACKGROUND ART Conventionally, it is known to form a vanadium-based film with high film hardness and high lubricity on the surfaces of press molding dies, cutting tools, gear cutting tools, forging tools, automobile parts, and the like. Examples of vanadium-based films include vanadium nitride films (VN films), vanadium carbide films (VC films), vanadium carbonitride films (VCN films), vanadium siliconitride films (VSiN films), and the like. A vanadium siliconitride film-coated member is disclosed in which a vanadium siliconitride film is formed on the surface of a steel material.

JP 2018-145461 A

When manufacturing the vanadium siliconitride film-coated member of Patent Document 1, the steel material is plasma-nitrided before forming the vanadium siliconitride film on the surface of the steel material. Plasma nitriding of steel can improve the adhesion between the steel and the vanadium siliconitride film. It was found that the surface of the steel material became rough. When a vanadium siliconitride film is formed on a steel material with such a rough surface, the surface of the vanadium siliconitride film also becomes rough. When a vanadium siliconitride film coated member with a rough surface is used as a mold, for example, the mold surface and the material to be molded may adhere to each other due to the large frictional force between the material to be molded and the surface of the mold. It was found that the vanadium nitride film partly peeled off, which shortened the life of the mold. For this reason, when manufacturing a vanadium siliconitride film-coated member, the plasma nitriding treatment of the steel material is performed to improve the adhesion between the steel material and the vanadium siliconitride film, and the surface roughness of the steel material is reduced to prevent the vanadium siliconitride film from forming. It is preferable to reduce the surface roughness.

The present invention has been made in view of the above circumstances, and an object of the present invention is to achieve both high adhesion between a steel material and a vanadium silicon nitride film and low surface roughness of the vanadium silicon nitride film.

One aspect of the present invention for solving the above problems is a method for manufacturing a vanadium siliconitride film-coated member, wherein the partial pressure ratio of nitrogen gas and hydrogen gas (nitrogen partial pressure/hydrogen partial pressure) is 1.0 or more, and the following ( 1) Plasma nitriding is performed on the steel material under the condition that the total energy density obtained by the formula is 50000 to 140000 [kJ/m ² ] to form a nitrided layer on the steel material, and silicon is deposited on the nitrided layer formed on the steel material. It is characterized by forming a vanadium nitride film.
Voltage [V] x current [A] x plasma nitriding time [s]/(cathode surface area [m ² ] x 1000) (1)
Voltage: the voltage applied between the anode-side electrode member and the cathode-side electrode member Current: the current generated by said voltage Cathode surface area: the surface area of the cathode-side electrode member and the area electrically connected to said cathode-side electrode member the sum of the surface areas of the members in the chamber

In addition, the plasma nitriding treatment in the present invention is a treatment in which nitrogen gas and hydrogen gas are turned into plasma to form a nitrided layer on the surface of the steel material.

Another aspect of the present invention provides a member coated with a vanadium siliconitride film, comprising a steel material having a nitrided layer on the surface thereof, and a vanadium siliconitride film formed on the nitrided layer; It is characterized by having a thickness Rzjis of 1.0 μm or less and a critical load of 70 N or more in a scratch test.

The "vanadium siliconitride film-coated member" in the present invention is a member having the surface of the steel material covered with the vanadium siliconitride film by forming the vanadium siliconitride film on the surface of the steel material.

According to the present invention, it is possible to achieve both high adhesion between the steel material and the vanadium silicon nitride film and low surface roughness of the vanadium silicon nitride film.

1 is a diagram showing a schematic configuration of a vanadium siliconitride film-coated member according to an embodiment of the present invention; FIG. It is a figure which shows an example of a plasma processing apparatus. It is a figure for demonstrating the definition of duty ratio.

An embodiment of the present invention will be described below with reference to the drawings. In the present specification and drawings, elements having substantially the same functional configuration are denoted by the same reference numerals, thereby omitting redundant description.

FIG. 1 is a diagram showing a schematic configuration of a vanadium siliconitride film-coated member 1 of this embodiment. The vanadium siliconitride film-coated member 1 of this embodiment comprises a steel material 2, a nitride layer 2a formed on the surface of the steel material 2, and a vanadium silicon nitride film 3 formed on the nitride layer 2a.

The type of the steel material 2 is not particularly limited, and a suitable steel type is used according to the application of the vanadium siliconitride film-coated member 1 . For example, so-called cold work tool steel such as SKD11, DC53, or SKH51, cold work mold steel (cold work die steel) or high speed tool steel (high speed steel) may be employed.

The nitrided layer 2a is a layer composed of at least one of a compound layer and a diffusion layer, and is formed by subjecting the steel material 2 to a nitriding treatment. The thickness (nitriding depth) of the nitrided layer 2a is not particularly limited as long as the nitriding of the steel material 2 progresses. The thickness of the nitride layer 2a is, for example, 0.5 μm or more. Further, in order to increase the thickness of the nitride layer 2a, it is necessary to lengthen the processing time in the plasma nitridation process, so the thickness of the nitride layer 2a is, for example, 300 μm or less in consideration of productivity. The "thickness of the nitride layer 2a" means the thickness of the compound layer when the nitride layer 2a is composed only of a compound layer. If the nitride layer 2a is composed of a compound layer and a diffusion layer, it means the sum of the thickness of the compound layer and the diffusion layer. is. In addition, the thickness of the nitrided layer 2a can be determined by a hardness test on a cut surface of the steel material 2 or by corroding the cut surface of the steel material 2 and observing the cut surface with a metallurgical microscope in accordance with the provisions of JIS G 0562. measured.

The vanadium siliconitride film 3 is a film in which the sum of the vanadium element concentration, the silicon element concentration and the nitrogen element concentration is 90 at % or more and the nitrogen element concentration is 25 to 60 at %. The composition ratio of the vanadium element concentration, the silicon element concentration and the nitrogen element concentration and the film thickness are appropriately changed according to the characteristics required of the vanadium siliconitride film-coated member 1 . The composition ratio of the vanadium siliconitride film 3 is as follows: a=vanadium element concentration [at %]/(vanadium element concentration [at %]+silicon element concentration [at %]+nitrogen element concentration [at %]), b =silicon element concentration [at %]/(vanadium element concentration [at %] + silicon element concentration [at %] + nitrogen element concentration [at %]), 0.30 ≤ a/b ≤ 1.7 preferably fulfilled. When 0.30≦a/b≦1.7 is satisfied, the hardness of the vanadium silicon nitride film 3 can be improved. A preferred lower limit of a/b is 0.4. A preferred upper limit of a/b is 1.5, and a more preferred upper limit is 1.3. c=nitrogen element concentration [at %]/(vanadium element concentration [at %]+silicon element concentration [at %]+nitrogen element concentration [at %]) is preferably 0.25 to 0.60. Moreover, the film thickness of the vanadium silicon nitride film 3 is preferably 0.5 to 4 μm. Moreover, the vanadium silicon nitride film 3 has a hardness of, for example, 2300 HV or more.

(Surface roughness Rzjis)
The vanadium siliconitride film-coated member 1 is a member having a surface roughness Rzjis of 1.0 μm or less measured according to JIS B 0601-2001. When such a vanadium siliconitride film-coated member 1 having a surface roughness Rzjis of 1.0 μm or less is used as, for example, a mold, the frictional force between the mold and the material to be molded is reduced, and the mold and the material to be molded are reduced. It is possible to suppress the occurrence of adhesion of the molding material.

(Critical load in scratch test)
The vanadium silicitride film-coated member 1 is a member having a critical load of 70 N or more in a scratch test. The vanadium siliconitride film-coated member 1 having a critical load of 70 N or more has high adhesion between the steel material and the vanadium siliconitride film, and the vanadium siliconitride film is less likely to separate from the steel material. A method for measuring the critical load in the scratch test will be described in Examples below.

As described above, the vanadium siliconitride film-coated member 1 having a surface roughness Rzjis of 1.0 μm or less and a critical load of 70 N or more in a scratch test has excellent adhesion between the steel material 2 and the vanadium siliconitride film 3, and vanadium siliconitride It is a member in which the low surface roughness of the film 3 is compatible. Such a vanadium siliconitride film-coated member 1 has a small frictional force with a mating member (a material to be molded when the vanadium siliconitride film-coated member 1 is a mold), and problems caused by the large frictional force are reduced. occurrence can be suppressed.

Next, a method for manufacturing the vanadium siliconitride film-coated member 1 will be described.

In this embodiment, a nitride layer 2a is formed on the surface of the steel material 2 by plasma nitriding treatment of the steel material 2, and then a vanadium siliconitride film 3 is formed on the nitride layer 2a by a plasma chemical vapor deposition method (so-called plasma CVD method). Form. The method of forming the vanadium siliconitride film 3 is not limited to the plasma CVD method, but when the steel material 2 is nitrided by the plasma nitriding treatment, the vanadium siliconitride film 3 can be formed by the plasma CVD method. preferable. As a result, the nitridation of the steel material 2 and the formation of the vanadium siliconitride film 3 can be performed in the same plasma processing apparatus, and the vanadium siliconitride film-coated member 1 can be efficiently compared with the case of using separate apparatuses. can be manufactured.

FIG. 2 is a diagram showing an example of a plasma processing apparatus. The plasma processing apparatus 10 includes a chamber 11 into which the steel material 2 is loaded, an anode-side electrode member 12 , a cathode-side electrode member 13 , and a pulse power source 14 . A gas supply pipe 15 for supplying source gas is connected to the upper portion of the chamber 11 , and a gas exhaust pipe 16 for discharging the gas inside the chamber 11 is connected to the lower portion of the chamber 11 . A vacuum pump (not shown) is provided in the gas exhaust pipe 16 . The cathode-side electrode member 13 also serves as a support base for supporting the steel material 2 , and the steel material 2 carried into the chamber 11 is placed on the cathode-side electrode member 13 . A heater (not shown) is provided inside the chamber 11, and the temperature of the steel material 2 is adjusted by adjusting the atmospheric temperature in the chamber 11 with the heater.

The configuration of the plasma processing apparatus 10 is not limited to that described in this embodiment. For example, a high-frequency power source may be used instead of the pulse power source 14, or a shower head for supplying raw material gas may be provided and used as an anode. Alternatively, the steel material 2 may be heated only by a glow current without providing a heater. That is, the plasma processing apparatus 10 may have any structure as long as it is capable of plasmatizing the raw material gas supplied into the chamber 11 .

<Preparation for film formation>
First, the steel material 2 is carried into the chamber 11 and set at a predetermined position. After that, the chamber 11 is evacuated so that the pressure inside the chamber 11 becomes, for example, 10 Pa or less. At this time, the temperature inside the chamber 11 is about room temperature. Subsequently, a heater (not shown) is operated to bake the steel material 2 . After that, the heater is turned off once, and the plasma processing apparatus 10 is left alone.

<Heating process>
Next, a small amount of hydrogen gas is supplied into the chamber 11 and the heater is operated again. In this heating step, the temperature of the steel material 2 is raised to near the plasma treatment temperature. The pressure inside the chamber 11 is maintained at about 100 Pa, for example.

<Plasma treatment process>
(Hydrogen plasma process)
In this embodiment, prior to the plasma nitriding treatment of the steel material 2, the hydrogen gas is converted to plasma. Specifically, the pulse power source 14 is operated while the hydrogen gas supplied in the heating step is continuously supplied. As a result, the hydrogen gas is turned into plasma between the electrodes. The hydrogen radicals thus generated reduce the oxide film on the surface of the steel material, cleaning the surface of the steel material. The voltage, frequency, duty ratio, etc. of the pulse power source 14 are appropriately set so that the gas supplied into the chamber 11 becomes plasma. The duty ratio is defined by the voltage application time per cycle as shown in FIG. )}.

(Plasma nitriding process)
After plasmatizing the hydrogen gas, nitrogen gas and argon gas are further supplied into the chamber 11 to which the hydrogen gas is being supplied. As a result, plasma of hydrogen gas, nitrogen gas and argon gas is generated, and the steel material 2 is plasma-nitrided. Thereby, nitrogen penetrates from the surface of the steel material 2 and a nitride layer 2 a is formed on the surface of the steel material 2 . Since the vanadium siliconitride film 3 contains nitrogen in the same manner as the nitride formed by the plasma nitriding treatment, the presence of the nitride layer 2a on the surface of the steel material 2 causes the steel material 2 and the vanadium siliconitride film 3 to be separated. Chemical compatibility is improved and lattice mismatch is eliminated. This improves the adhesion between the steel material 2 and the vanadium silicon nitride film 3 . Although the supply of argon gas is not essential, it is preferable to supply argon gas as necessary because argon ions ionize other molecules and thereby contribute to stabilization of plasma and improvement of ion density. When argon gas is supplied, it is preferably 1/10 or less of the total flow rate of hydrogen gas and nitrogen gas.

In order to manufacture the vanadium siliconitride film-coated member 1 with a small surface roughness, the partial pressure ratio (nitrogen partial pressure/hydrogen partial pressure) of the nitrogen gas and the hydrogen gas supplied into the chamber 11 during this plasma nitriding treatment is set to 1. .0 or greater. If the partial pressure ratio is less than 1.0, the amount of nitrogen diffusing into the steel material 2 per time decreases, and in order to diffuse nitrogen to the extent that sufficient adhesion can be secured, it is necessary to lengthen the nitriding treatment time. be. If the nitriding process takes a long time, the surface of the steel material 2 becomes rough, and the surface of the vanadium siliconitride film 3 formed on the steel material 2 also becomes rough. Although the upper limit of the partial pressure ratio is not particularly limited, the upper limit of the partial pressure ratio is preferably 3.0 or less because the iron nitride compound layer is preferable on the surface of the steel material 2 from the viewpoint of improving adhesion.

Also, the total energy density during the plasma nitriding treatment must be 50,000 to 140,000 [kJ/m ² ]. When the total energy density is within the above range, it becomes easier to achieve both improved adhesion between the steel material 2 and the vanadium silicon nitride film 3 and low surface roughness. The “total energy density [kJ/m ² ]” in this specification is calculated by the following formula (1).
Voltage [V] x current [A] x plasma nitriding time [s]/(cathode surface area [m ² ] x 1000) (1)

“Voltage [V]” is a set voltage of the pulse power source 14 applied between the electrode member 12 on the anode side and the electrode member 13 on the cathode side. "Current [A]" is a current generated when a voltage is applied between the electrode member 12 on the anode side and the electrode member 13 on the cathode side. It is calculated by (maximum current + minimum current)/2. “Plasma nitridation time [s]” is the time spent in plasma nitridation. is the time to start The “cathode surface area [m ² ]” is the sum of the surface area of the electrode member 13 on the cathode side and the surface area of the members present in the chamber 11 electrically connected to the electrode member 13 on the cathode side. For example, in the plasma processing apparatus 10 of the present embodiment shown in FIG. 2, the steel material 2 is placed on the electrode member 13 on the cathode side. is applied, and the electrode member 13 on the cathode side and the steel material 2 are electrically connected. Therefore, in the plasma processing apparatus 10 of the present embodiment, the steel material 2 corresponds to "a member in the chamber 11 electrically connected to the electrode member 13 on the cathode side", and the surface area of the cathode is It is the total value of the surface area of the electrode member 13 and the surface area of the steel material 2 . In addition, the area of the contact surface between the members electrically connected to each other is not included in the cathode surface area. Further, when the steel material 2 is set in a jig (not shown) and the jig is placed on the electrode member 13 on the cathode side to perform the plasma nitriding treatment, the electrode member 13 on the cathode side and the jig are , are electrically connected to the steel material. In this case, the surface area of the electrode member 13 on the cathode side, the surface area of the jig, the surface area of the steel material 2, and the area of the contact surface of the jig and the steel material 2 are excluded. is the cathode surface area.

In the plasma nitriding process, when the nitriding treatment is performed under the conditions that the partial pressure ratio of nitrogen gas and hydrogen gas is 1.0 or more and the total energy density is 50000 to 140000 [kJ/m ² ], the plasmatized nitrogen ions are converted into steel material 2. After the collision with the steel material 2, nitrogen tends to penetrate into the steel material 2, so that the surface of the steel material 2 is prevented from becoming rough while the nitriding of the steel material 2 progresses sufficiently.

The power density during plasma nitriding is preferably 6500 to 13000 [W/m ² ]. “Power density [W/m ² ]” is calculated by the following formula (2).
Voltage [V] × current [A] / cathode surface area [m ² ] (2)

When the power density is 6500 [W/m ² ] or more, nitrogen can easily diffuse into the steel material 2, and the plasma nitriding treatment time can be shortened. As a result, it becomes easier to reduce the surface roughness of the steel material 2 . When the power density is 13000 [W/m ² ] or less, it becomes difficult to form an iron nitride compound layer on the surface of the steel material 2, and the adhesion to the vanadium siliconitride film 3 tends to be improved. A power density range of 6500 W/m ² or more is a power density range that is much higher than the power density in a general plasma nitridation process.

In the plasma nitridation process, the ambient temperature in the chamber 11 is preferably 350-650.degree. C., more preferably 400-550.degree. The ambient temperature in the chamber 11 is changed by adjusting the heater set temperature according to the plasma conditions. The voltage of the pulse power source 14 in the plasma nitridation process is preferably 1000-2500V. More preferably, the voltage of the pulse power supply 14 is 1400V or higher. Moreover, it is more preferable that the voltage of the pulse power supply 14 is 2000 V or less. The pressure inside the chamber 11 is set at 50-200 Pa, for example. Also, when the pulse power source 14 is used, the duty ratio is preferably 5 to 95%. The plasma nitriding treatment time is, for example, 5400 to 14400 seconds.

(Vanadium silicitride film forming step)
After the nitride layer 2a is formed on the surface of the steel material 2, a vanadium chloride gas and a silane source gas are further supplied into the chamber 11 as a vanadium source gas. As a result, the chamber 11 is supplied with hydrogen gas, nitrogen gas, argon gas, vanadium chloride gas, and silane source gas. The pressure inside the chamber 11 is set at 50-200 Pa, for example.

As the vanadium chloride gas, for example, vanadium tetrachloride (VCl ₄ ) gas and vanadium trichloride oxide (VOCl ₃ ) gas are used. It is preferable to use vanadium tetrachloride gas from the viewpoint that the number of elements constituting the gas is small and the impurities in the vanadium silicon nitride film 3 can be easily removed. Vanadium tetrachloride gas is also preferable because it is readily available, is liquid at room temperature, and can be easily supplied as a gas.

Silane-based gases such as silicon tetrachloride gas, silane trichloride gas, silane dichloride gas, silane chloride gas, silane, and silicon tetrafluoride are used as the silane source gas. The gases exemplified here may be supplied singly, or may be supplied as a mixture of one or more gases. Among these gases, it is preferable to use silicon tetrachloride (SiCl ₄ ) gas, which can easily remove chlorine atoms by hydrogen plasma, is thermally stable, and decomposes only in plasma.

Since the partial pressure of the vanadium chloride gas and the partial pressure of the hydrogen gas affect the amount of vanadium contained in the vanadium siliconitride film 3, at least one of the partial pressure of the vanadium chloride gas and the partial pressure of the hydrogen gas can be adjusted to change the amount of vanadium in the vanadium silicon nitride film 3 . Since the partial pressure of the silane source gas affects the amount of silicon contained in the vanadium siliconitride film 3, the amount of silicon in the vanadium siliconitride film 3 can be changed by adjusting the partial pressure of the silane source gas. . Since the partial pressure of nitrogen gas affects the amount of nitrogen contained in vanadium silicon nitride film 3, the amount of nitrogen in vanadium silicon nitride film 3 can be changed by adjusting the partial pressure of nitrogen gas.

The voltage in the step of forming the vanadium silicon nitride film 3 is preferably 700-2000V. Also, the ambient temperature in the chamber 11 in the step of forming the vanadium silicon nitride film 3 is preferably 450 to 550.degree. The amount of vanadium in the vanadium silicon nitride film 3 can be increased by raising the ambient temperature in the chamber 11 .

By supplying the vanadium chloride gas and the silane source gas into the chamber 11, the vanadium chloride gas and the silane source gas are turned into plasma between the electrodes, and the vanadium and silicon together with the already plasmatized nitrogen are formed on the surface of the steel material 2. will be absorbed by As a result, the vanadium siliconitride film 3 is formed on the nitride layer 2a of the steel material 2, and the vanadium siliconitride film-coated member 1 is manufactured.

If a vanadium chloride gas is used as the vanadium source gas when forming the vanadium siliconitride film 3, the vanadium siliconitride film 3 inevitably contains chlorine as the remainder excluding nitrogen, vanadium and silicon. On the other hand, since hydrogen gas contained in the raw material gas easily bonds with chlorine, when hydrogen gas is contained in the raw material gas as in the present embodiment, chlorine generated from the vanadium chloride gas combines with hydrogen. It becomes easy to be discharged out of the system. This can prevent chlorine from entering the vanadium silicon nitride film 3 . The flow rate of hydrogen gas during plasma processing is preferably at least 25 times the flow rate of vanadium chloride gas. The remainder of the vanadium silicitride film 3 may contain unavoidable impurities other than chlorine.

Although one embodiment of the present invention has been described above, the present invention is not limited to such an example. It is obvious that a person skilled in the art can conceive various modifications or modifications within the scope of the technical idea described in the claims, and these are also within the technical scope of the present invention. be understood to belong to

Various evaluations were performed using a test piece in which a nitrided layer was formed on a steel material and a vanadium siliconitride film was formed on the nitrided layer. Steel materials for test pieces are produced by the following procedure. First, a φ22 round bar made of SKH51 is quenched and tempered. Next, the tempered round bar is cut at intervals of 6 to 7 mm. Then, the surface of the cut round bar was mirror-polished, and this was used as the steel material for the test piece. The surface roughness Rzjis of the mirror-polished surface at this time was 0.066 μm. The vanadium siliconitride film is formed on the mirror-polished surface of the steel material. Also, a film forming apparatus having a structure shown in FIG. 2 is used, and a pulse power source is used as a power source.

<<Example 1>>
A method for producing the test piece of Example 1 will be described. The flow rates of hydrogen gas, nitrogen gas, argon gas, vanadium tetrachloride gas, and silicon tetrachloride gas in the following description are volume flow rates at 0° C. and 1 atm.

<Preparation for film formation>
First, the steel material for the test piece is set in the chamber of the film forming apparatus, the chamber is evacuated for 30 minutes, and the pressure in the chamber is reduced to 10 Pa or less. At this time, the heater is not activated. The heater is provided inside the chamber, and the ambient temperature in the chamber is measured with a sheathed thermocouple. Subsequently, the set temperature of the heater is set to 200° C., and the steel material is baked for 10 minutes. After that, the heater is turned off, and the film forming apparatus is left for 30 minutes to cool the inside of the chamber.

<Heating process>
Next, hydrogen gas is supplied into the chamber at a flow rate of 100 ml/min, and the pressure in the chamber is adjusted to 100 Pa by adjusting the exhaust amount. Then, the set temperature of the heater is set to 440° C., and the steel material is heated for 30 minutes. This heating process raises the temperature of the steel material to near the plasma treatment temperature.

<Plasma treatment process>
(Hydrogen plasma process)
Next, the pulse power supply is operated with a voltage of 800 V, a frequency of 25 kHz, a duty ratio of 30%, and a unipolar output format. As a result, the hydrogen gas is turned into plasma between the electrodes in the chamber, and the surface of the steel material is cleaned by the hydrogen radicals.

(Plasma nitriding process)
After that, the flow rate of hydrogen gas is lowered to 40 ml/min, and nitrogen gas and argon gas are supplied into the chamber. In this step, the flow rate of nitrogen gas is set at 80 ml/min and the flow rate of argon gas is set at 2 ml/min. At this time, the total pressure in the chamber is maintained at 58 Pa by adjusting the exhaust amount. The partial pressure ratio of nitrogen partial pressure and hydrogen partial pressure (nitrogen partial pressure/hydrogen partial pressure) in Example 1 was 2.0. After that, the voltage of the pulse power supply is increased to 1800V. Here, by increasing the voltage of the pulse power source, hydrogen gas, nitrogen gas and argon gas are brought into a plasma state between the electrodes. As a result, nitrogen penetrates from the surface of the steel material and a nitride layer is formed on the surface of the steel material. The nitriding time in Example 1 is 120 minutes, the current is 1.22 A, the power density is 9247 W/ ^m2 , and the total energy density is 66578 kJ/ ^m2 . Further, the frequency of the pulse power supply in this process is 25 kHz and the duty ratio is 30%, which are the same as in the hydrogen plasma process described above.

(Vanadium silicitride film forming step)
Subsequently, a vanadium siliconitride film is formed on the surface of the steel material on which the nitride layer is formed by plasma CVD. In this process, the pressure in the chamber is 58 Pa, the heater installation temperature is 540 ° C., the flow rate of hydrogen gas is 98 ml / min, the flow rate of nitrogen gas is 77 ml / min, the flow rate of argon gas is 3 ml / min, vanadium tetrachloride Plasma treatment is performed by setting the gas flow rate to 4.5 ml/min, the silicon tetrachloride gas flow rate to 5.0 ml/min, the voltage of the pulse power source to 1400 V, the frequency to 25 kHz, and the duty ratio to 5.9%. . Through this step, vanadium tetrachloride gas is decomposed into vanadium and chlorine, and silicon tetrachloride gas is decomposed into silicon and chlorine. Then, the silicon, vanadium, and nitrogen converted into plasma are adsorbed on the steel material, thereby forming a vanadium silicitride film on the nitride layer on the surface of the steel material. This state is maintained for 6 hours. Through the above steps, the test piece of Example 1 coated with the vanadium silicon nitride film was produced. Using this test piece, the following evaluations were carried out.

<Film thickness measurement>
The film thickness of the vanadium siliconitride film is calculated by cutting the test piece vertically, mirror-polishing the cut surface, observing the cut surface with a metallurgical microscope at a magnification of 1000, and calculating the film thickness based on the observed image information. Measure.

<Surface roughness>
A 3D laser microscope (VK-X120 manufactured by Keyence Corporation) was used for surface roughness measurement. After obtaining a laser microscope image of 0.2 mm×1.2 mm with an objective lens magnification of 50, the surface roughness of the test piece was measured using the multi-line roughness measurement function of the multi-file analysis application attached to the microscope. Then, 15 line profiles were obtained in the longitudinal direction of the test piece, and the surface roughness Rzjis of the test piece was obtained by averaging the surface roughness obtained from each line profile. The surface roughness was measured within a region of φ10 mm from the center position of the test piece.

<Scratch test>
Adhesion between the steel material and the vanadium silicon nitride film was evaluated using a scratch tester (Revetest manufactured by csm). The scratch test was performed using a conical diamond indenter with a tip curvature of 100 μm, a minimum load of 1 N, a maximum load of 100 N, a load rate of 100 N/min, a scratch speed of 5 mm/min, and a scratch distance of 5 mm. Then, the load when the vanadium silicitride film around the contact point between the indenter and the test piece breaks, that is, the critical load, which is the load when the vanadium silicitride film peels off from the steel material, is measured. Adhesion of the vanadium silicon nitride film was evaluated. The greater the critical load in the scratch test, the more difficult it was for the vanadium siliconitride film to separate from the steel material, indicating that the adhesion between the steel material and the vanadium siliconitride film was high. If the film thickness of the vanadium siliconitride film is within the range of 0.5 to 4.0 μm, the variation in the scratch test results due to the difference in the film thickness becomes negligible. Also, the scratch test was performed within a region of φ10 mm from the center position of the test piece.

<Hardness measurement>
Hardness measurements are performed by the nanoindentation method using a FISCHER SCOPE® H100C from Fischer Instruments. Specifically, the maximum indentation load is 10 mN, and the Berkovich indenter is indented into the test piece, and the indentation depth is continuously measured. From the measurement data of the indentation depth obtained, using the software "trade name: WIN-HCU (registered trademark)" manufactured by Fisher Instruments, Martens hardness, Vickers hardness converted from Martens hardness to calculate the The calculated Vickers hardness is displayed on the screen of the measuring device, and this numerical value is treated as the hardness of the film at the measuring point. In this example, the Vickers hardness of 20 arbitrary points on the surface of each test piece is determined, and the average value of the obtained hardness is recorded as the hardness of the film. When the indenter is pushed into the test piece, the indentation load may propagate up to about 10 times the maximum indentation depth of the indenter. Therefore, if the indentation load reaches the steel material of the test piece, the hardness measurement result may be affected by the steel material. Therefore, in order to measure the hardness of a pure hard film, it is necessary to satisfy the following condition: "film thickness of hard film>maximum indentation depth of indenter×10".

<Composition Analysis of Vanadium Silicon Nitride Film>
The composition of the vanadium silicon nitride film of the specimen was analyzed. Analysis conditions are as follows.
EPMA: JXA-8530F manufactured by JEOL Ltd.
Measurement mode: Semi-quantitative analysis Acceleration voltage: 15 kV
Irradiation current: 1.0×10 ⁻⁷ A
Beam shape: Spot Beam diameter setting value: 0
Analysis crystal: LDE6H, TAP, LDE5H, PETH, LIFH, LDE1H

Further, test pieces of Example 2 and Comparative Examples 1 and 2 were prepared under the following conditions, and the same evaluation as in Example 1 was performed for each test piece.

<<Example 2>>
In the plasma nitriding process, the test piece was prepared under the same conditions as in Example 1 except that the current was 1.24 A, the power density was 9398 W/m ² , the total energy density was 101498 kJ/m ² , and the nitriding treatment time was 180 minutes. was made.

<<Comparative Example 1>>
In the plasma nitriding process, the test piece was prepared under the same conditions as in Example 1 except that the current was 1.16 A, the power density was 8792 W/m ² , the total energy density was 31651 kJ/m ² , and the nitriding time was 60 minutes. was made.

<<Comparative Example 2>>
In the plasma nitriding process, the partial pressure ratio of nitrogen partial pressure and hydrogen partial pressure (nitrogen partial pressure/hydrogen partial pressure) is 0.5, the current is 0.64 A, the power density is 4851 W/m ² , and the total energy density is 87318 kJ/m. ^2. A test piece was prepared under the same conditions as in Example 1, except that the nitriding treatment time was 300 minutes.

Table 1 below shows the plasma nitriding conditions when the test pieces of Examples 1 and 2 and Comparative Examples 1 and 2 were produced. Table 1 below shows the measurement results of the surface roughness Rzjis of each test piece and the measurement results of the critical load in the scratch test.

The test pieces of Examples 1 and 2 and Comparative Example 1 had a surface roughness Rzjis of 1.0 μm or less, indicating small surface roughness. On the other hand, the test piece of Comparative Example 2 had a surface roughness Rzjis that greatly exceeded 1.0 μm. If a member having a vanadium siliconitride film with a rough surface as in Comparative Example 2 is used, for example, as a mold, there is a possibility that the mold and the material to be molded will adhere due to excessive frictional force between the mold and the material to be molded. There is

From the viewpoint of improving the adhesion between the steel material and the vanadium silicon nitride film, the critical load in the scratch test is preferably 70 N or more. As shown in Table 1 above, the test pieces of Examples 1 and 2 all had a critical load of 70 N or more in the scratch test, indicating high adhesion.

From the above results, it can be said that the test pieces of Examples 1 and 2 are members having both low surface roughness and high adhesion at high levels. According to the results in Table 1 above, in order to obtain such a member, the conditions are that the partial pressure ratio of nitrogen gas and hydrogen gas is 1.0 or more and the total energy density is 50000 to 140000 [kJ/m ² ]. It is required to perform plasma nitriding treatment at The hardness, film thickness, and composition of the vanadium silicon nitride films in Examples 1 and 2 and Comparative Examples 1 and 2 are shown in Table 2 below. Since the film forming conditions of the vanadium silicon nitride film forming step are the same in all the examples and the comparative examples, the vanadium silicon nitride films shown in Table 2 below are formed in each example.

INDUSTRIAL APPLICABILITY The present invention can be used to coat molds, tools, automobile parts such as gears, etc. with a hard film. That is, the vanadium siliconitride film-coated member according to the present invention is used, for example, as molds, tools, and automobile parts.

1 vanadium siliconitride film coated member 2 steel material 2a nitride layer 3 vanadium siliconitride film 10 plasma processing apparatus 11 chamber 12 anode-side electrode member 13 cathode-side electrode member 14 pulse power supply 15 gas supply pipe 16 gas exhaust pipe

Claims (4)

Plasma is applied to the steel material under the conditions that the partial pressure ratio of nitrogen gas and hydrogen gas (nitrogen partial pressure/hydrogen partial pressure) is 1.0 or more and the total energy density calculated by the following formula (1) is 50000 to 140000 [kJ/m ² ]. Nitriding is performed to form a nitride layer on the steel material,
A method for producing a vanadium siliconitride film-coated member, comprising forming a vanadium siliconitride film on the nitride layer formed on a steel material.
Voltage [V] x current [A] x plasma nitriding time [s]/(cathode surface area [m ² ] x 1000) (1)
Voltage: the voltage applied between the anode-side electrode member and the cathode-side electrode member Current: the current generated by said voltage Cathode surface area: the surface area of the cathode-side electrode member and the area electrically connected to said cathode-side electrode member with the surface area of the members in the chamber 2. The method for producing a vanadium silicon nitride film-coated member according to claim 1, wherein the power density during said plasma nitriding treatment determined by the following formula (2) is 6500 to 13000 [W/m ² ].
Voltage [V] × current [A] / cathode surface area [m ² ] (2) 3. The method of manufacturing a vanadium silicon nitride film-coated member according to claim 1, wherein said vanadium silicon nitride film is formed using a plasma CVD method. a steel material having a nitride layer on its surface;
a vanadium silicon nitride film formed on the nitride layer;
The surface roughness Rzjis is 1.0 μm or less,
A vanadium silicon nitride film-coated member having a critical load of 70 N or more in a scratch test.

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