JP2005154224A - Super hard material having metal oxycarbide single crystal coating and its producing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a single crystal of a metal oxycarbide and to provide a super hard material coated with the single crystal of the metal oxycarbide. <P>SOLUTION: The super hard material consists of: a magnesium oxide single crystal or a silicon single crystal; and a single crystal coating of an oxycarbide of a metal selected from molybdenum, chromium and tungsten which is formed on the single crystal. The super hard material is produced by subjecting a metal selected from molybdenum, chromium and tungsten and a carbon oxide or a carbon oxide and a hydrocarbon to a plasma reaction in the presence of the magnesium oxide single crystal substrate or the silicon single crystal substrate kept at 350 to 450°C so as to epitaxially grow the metal oxycarbide single crystal on the surface of the substrate. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a cemented carbide material having an oxycarbide single crystal coating of a metal selected from molybdenum, chromium and tungsten useful as an abrasive, a machine part and the like, and a method for producing the same.

  To improve the abrasion resistance of abrasives and machine parts, and improve the cutting performance of tools and the life of molds, the surface of the base material is coated with excellent wear resistance and corrosion resistance, high hardness and good adhesion. The super hard material provided is used.

  As these coating materials, oxycarbides of metals such as chromium, molybdenum, and tungsten are known. In particular, chromium oxycarbide has a micro Vickers hardness of about 28 Gpa, which is larger than 22 Gpa of titanium nitride, and hydrochloric acid. In addition to having excellent corrosion resistance and anticorrosion properties against sulfuric acid, coating on high-speed steel throwaway inserts has been recognized as an improved hard coating material for tool steel because of its improved turning performance. .

Conventionally, this metal oxycarbide is obtained by incompletely decomposing metal hexacarbonyl such as Cr (CO) ₆ , W (CO) ₆ , and Mo (CO) ₆ by a plasma CVD method or a thermal CVD method. Although formed on a substrate, all formed are polycrystalline, and no single crystal has been known so far.

As a method for forming a metal oxycarbide coating without using metal hexacarbonyl, the present inventor previously reacted at least one metal selected from chromium, molybdenum and tungsten in the presence of carbon dioxide. A method of plasma treatment and forming a metal oxycarbide coating on the surface was proposed (see Patent Document 1).
However, since these films are also formed on a polycrystalline or amorphous substrate such as stainless steel, aluminum alloy, or glass, they are all polycrystalline.

  By the way, since such a polycrystal is composed of a large number of crystals having different orientation directions, the physical properties fluctuate depending on the production conditions, and the quality control of the product is difficult. Because it is composed only of oriented crystals, there is no change in physical properties depending on the generation conditions, and there is an advantage that the hardness is increased compared to the polycrystalline body. Therefore, the single crystal body of metal oxycarbide must be formed. Was requested.

JP 2001-279426 A (Claims and others)

  Under the circumstances, the present invention has been made for the purpose of providing a cemented carbide material formed by coating a single crystal of metal oxycarbide.

  As a result of extensive research on a method for forming metal oxycarbide, the present inventors have found that a metal and carbon oxide selected from molybdenum, chromium and tungsten in the presence of a magnesium oxide single crystal substrate or a silicon single crystal substrate. In some cases, it is found that a single crystal of metal oxycarbide can be obtained by plasma-reacting with hydrocarbon and epitaxially growing metal oxycarbide on a single crystal substrate, and the present invention is made based on this finding. It came to.

  That is, the present invention provides a cemented carbide material comprising a magnesium oxide single crystal or a silicon single crystal and a single crystal coating of a metal oxycarbide selected from molybdenum, chromium and tungsten formed thereon, and 350- In the presence of a magnesium oxide single crystal substrate or a silicon single crystal substrate maintained at 450 ° C., a plasma reaction is performed with a metal selected from molybdenum, chromium and tungsten and carbon oxide or carbon oxide and hydrocarbon. Thus, the present invention provides a method for producing a cemented carbide material, characterized in that a metal oxycarbide single crystal is epitaxially grown on a substrate surface.

Next, the present invention will be described in more detail.
The superhard material of the present invention is composed of a substrate made of magnesium oxide single crystal or silicon single crystal and a single crystal coating of oxycarbide of a metal selected from molybdenum, chromium and tungsten provided thereon. Yes.

The above single crystal substrate is known and can be obtained as a commercial product. However, when a magnesium oxide single crystal is used as the substrate, the (110) plane or the (100) plane is used, and when a silicon single crystal is used. The (111) plane, (100) plane, or (110) plane is preferably used.
In particular, the use of the (110) plane of magnesium oxide single crystal is advantageous because a single crystal film of metal oxycarbide having a high hardness is formed.

  When a single crystal other than a magnesium oxide single crystal or a silicon single crystal, for example, a sapphire single crystal generally used for forming a single crystal, is used as a substrate, a polycrystalline film is formed, and a metal oxycarbide single crystal film is formed. I can't get it.

  In the superhard material of the present invention, it is necessary to use a magnesium oxide single crystal or a silicon single crystal as a substrate. This single crystal is applied to the surface of a molded body made of another metal, an alloy or a ceramic by a conventional method. A single crystal film formed in (1) may be used.

  Examples of such molded bodies include iron alloys such as carbon steel, nickel-chromium steel, nickel-molybdenum steel, silicon-manganese steel, free-cutting steel, tool steel, and stainless steel, copper, silver, gold, tin, and aluminum. Examples thereof include a molded body made of a ceramic such as a non-ferrous metal such as an alloy thereof, titanium nitride, titanium carbide, iron nitride, or chromium nitride.

  According to the method of the present invention, the superhard material of the present invention uses the above-described magnesium oxide single crystal or silicon single crystal as a substrate, and the surface thereof has a metal oxycarbide single crystal selected from molybdenum, chromium and tungsten by plasma reaction. It is obtained by forming a film.

  This plasma reaction includes, for example, a reactive sputtering method, a high frequency excitation reactive sputtering method (hereinafter referred to as an RF reactive sputtering method), a reactive ion plating method, a reactive deposition method in a plasma atmosphere, and a reactive laser ablation method. Etc. Since a negative DC bias is applied to the substrate electrode in order to improve the film quality, it is necessary to prevent grounding.

  When RF reactive sputtering is used, an apparatus equipped with a planar magnetron type target electrode is used. However, if an inductive coupling type RF electrode for plasma generation of another system is incorporated, a higher quality coating is formed. Can be made.

  This reactive plasma treatment needs to be performed at a substrate temperature of 350 to 450 ° C. When deviating from this temperature range, an epitaxial single crystal film is not formed, and even if it is formed, it becomes a single crystal film having a wide rocking curve half-width and extremely low quality.

Next, in the method of the present invention, it is necessary to use a reaction gas containing a carbon oxide such as carbon dioxide or carbon monoxide as a carbon source and an oxygen source of the metal oxycarbide to be produced.
Normally, carbon dioxide is used alone, but in this case, metal oxycarbide having a high oxygen content and a low carbon content may be formed, so that both can be mixed and used as necessary. . Moreover, in order to increase the carbon content of the produced metal oxycarbide, a lower hydrocarbon can be added to the reaction gas as desired. As the lower hydrocarbon, a hydrocarbon having 4 or less carbon atoms such as methane, ethane, propane and butane is used, and methane is particularly preferable.

  In the method of the present invention, argon is usually used as a sputtering gas. However, when tungsten oxycarbide is formed, a rare gas other than argon, that is, helium, neon, krypton, and the like is used as an auxiliary gas in order to promote ionization of carbon dioxide. At least one selected from radon can be used in combination.

  In the method of the present invention, it is preferable to apply a negative bias to the substrate during the film formation when the single crystal metal oxycarbide is formed. In general, crystal orientation greatly depends on the bias. When the bias is 0, no orientation is observed, and there is a tendency of [111] orientation at 0 to −200 V and [110] orientation at −200 V or less. In order to form a high-quality metal oxycarbide epitaxial single crystal film, the substrate bias is selected in the range of −200V or less and −500V or more, preferably −350V or less and −450V or more.

  In the method of the present invention, in order to improve the epitaxial growth property, it is preferable that the surface of the substrate material is bombarded with argon in advance. If the degree of vacuum is 1 to 10 Pa, the high frequency excitation power is 20 to 400 W, the argon flow rate is 10 to 30 sccm, the substrate bias is −100 to −200 V, and the substrate temperature is 350 to 450 ° C., a sufficiently epitaxial film is formed. Can be formed. The best single crystal film can be obtained when the vacuum is 2 Pa, the high frequency excitation power is 300 W, the argon flow rate is 20 sccm, the substrate bias is −150 V, and the substrate temperature is 400 ° C. for 15 to 30 minutes.

  In order to suitably carry out the method of the present invention, after completion of the above bombardment, at the same substrate temperature, the degree of vacuum is 0.1 to 2 Pa, preferably about 0.6 Pa, the high frequency excitation power is 10 to 150 W, preferably 20 W, sputtering. Argon flow rate 2 under conditions of power output 0.2 to 1.0 kW, preferably about 0.3 kW, substrate bias −200 to −500 V, preferably −450 V, substrate temperature 350 to 450 ° C., preferably 380 to 420 ° C. The reactive plasma treatment is performed under a mixed gas flow of ˜20 sccm, preferably 5 to 10 sccm, carbon dioxide flow rate of 1 to 4 sccm, preferably 2 to 3 sccm, and methane flow rate of 0.1 to 1 sccm, preferably 0.3 to 0.6 sccm. By treating for 30 to 60 minutes under such conditions, a metal oxycarbide single crystal film having a film thickness of 0.25 to 0.5 μm is obtained.

  Whether the film thus formed is monocrystalline or polycrystalline can be confirmed by an X-ray diffraction test of the film. That is, if a single independent plane index diffraction line is observed in the X-ray diffraction pattern by the θ-2θ scan, and the half-width of the rocking curve of the diffraction line by the ω scan is narrow, the film is recognized as a single crystal. Can do. The full width at half maximum indicates the degree of crystal quality. The narrower the width, the better the quality as a single crystal.

  With molybdenum oxycarbide formed on a magnesium oxide (110) plane substrate, a single crystal having a rocking curve half-width of 0.11 ° minimum was obtained. This is larger than the device resolution of 0.04 ° measured using a silicon single crystal, but it can be said to be a good quality single crystal.

  In addition, a silicon (100) plane substrate, a silicon (111) plane substrate, and a magnesium oxide (100) substrate can be used as the substrate, and any of them can epitaxially grow the (110) plane of metal oxycarbide, but the rocking curve The minimum half-value width is 2.5 °, 2.3 ° and 3.2 °, respectively, which is larger than 0.12 ° of the film formed on the magnesium oxide (110) surface, and the quality is not so good.

  According to the present invention, it is possible to obtain a cemented carbide material coated with a novel metal oxycarbide single crystal not described in any literature. And this super hard material, for example, chromium oxycarbide, has a micro Vickers hardness of about 28 GPa, which is larger than 22 GPa of conventional titanium nitride.

  Next, the best mode for carrying out the present invention will be described by way of examples. However, the present invention is not limited thereto.

  A planar magnetron type target electrode with metallic high-frequency excitation electrode comprising a three-turn coil and using a deposition-up type apparatus capable of generating plasma independently of a sputter electrode under the condition of a radio frequency of 13.56 MHz. Then, the magnesium oxide single crystal (110) plane was disposed about 100 mm above the target electrode as a substrate.

  First, the substrate was pretreated by performing argon bombard cleaning for 30 minutes under the conditions of a degree of vacuum of 2 Pa, a high frequency excitation power of 300 W, an argon flow rate of 20 sccm, a substrate bias of −150 V, and a substrate temperature of 400 ° C.

  Next, 45 minutes under conditions of vacuum degree 0.6 Pa, high frequency excitation power 20 W, sputtering power output 0.3 kW, substrate bias −450 V, argon flow rate 6 sccm, carbon dioxide flow rate 2 sccm, methane flow rate 0.3 sccm, substrate temperature 400 ° C. Plasma reaction was performed to form a 5 μm-thick molybdenum oxycarbide crystal film on the substrate.

The chemical composition of this crystal film was determined by Auger electron spectroscopy, and found to be Mo: 45 atomic%, C: 43 atomic%, and O: 13 atomic%.
FIG. 1 shows an X-ray diffraction pattern (a) and a rocking curve (b) of the (220) diffraction line of this crystal film. In these X-ray diffraction patterns, only very strong Mo (C, O) (220) diffraction lines are recognized, and it is recognized from the rocking curve that the half-value width is 0.12 °. From these results, it can be seen that this crystalline film is a good quality epitaxial single crystal.

FIG. 2 is a high-resolution transmission electron micrograph of the cross section of the crystal film, in which the upper part is a molybdenum oxycarbide crystal film and the lower part is a magnesium oxide (110) plane substrate. This figure shows that the atoms are regularly arranged above and below the interface.
Further, the insets are electron diffraction patterns from the respective regions. According to this, both the in-plane direction is the [001] direction and the plane perpendicular direction is the [110] direction. It can be seen that this is a single crystal having an epitaxial relationship with respect to.

  A molybdenum oxycarbide crystal using a magnesium oxide single crystal (110) plane as a substrate in the same manner as in Example 1 except that the high-frequency excitation power during the pretreatment was 20 W and the substrate bias during the film formation was −350 V. A film was formed. In this X-ray diffraction pattern of the crystal film, a (220) diffraction line was recognized, and the half-width of the rocking curve of this diffraction line was 1.2 °.

  Magnesium oxide (100) obtained by performing argon bombardment cleaning treatment for 30 minutes under the conditions of a vacuum of 2 Pa, a high frequency excitation power of 100 W, an argon flow rate of 20 sccm, a substrate bias of −150 V, and a substrate temperature of 400 ° C. using the same apparatus as in Example 1. A molybdenum oxycarbide single crystal was formed on the surface of the surface substrate under the following conditions.

  Vacuum degree 0.5 Pa, high frequency excitation power 20 W, sputtering power output 0.3 kW, substrate bias −350 V, substrate temperature 400 ° C., argon flow rate 6 sccm, carbon dioxide flow rate 2 sccm, methane flow rate 0.4 sccm, treatment time 60 minutes.

FIG. 3 shows rocking curves of the X-ray diffraction pattern (a) and (200) diffraction line (b) of the crystal film thus obtained.
From this X-ray diffraction pattern, a Mo (C, O) (200) diffraction line partially overlapping with the magnesium oxide (200) plane diffraction line is observed, and the half-value width is 3.2 ° from the rocking curve. I found out.
From this, it was confirmed that an epitaxial single crystal film was formed, but it can be seen that the quality of the crystal is deteriorated by reducing the substrate bias to -350V.

  Using the silicon single crystal (111) plane as a substrate, a molybdenum oxycarbide crystal film was formed in the same manner as in Example 1. From the X-ray diffraction pattern, it was confirmed that this was composed of a single crystal.

  When the same treatment was carried out using metal chromium or metal tungsten instead of metal molybdenum in Example 1, single crystal films of chromium oxycarbide or tungsten oxycarbide were obtained, respectively.

Comparative Example Using a sapphire single crystal (001) substrate, a molybdenum oxycarbide crystal film was formed under the same conditions as in Example 1. In this X-ray diffraction pattern, diffraction lines of (111) and (220) were recognized, and it was found that the structure was polycrystalline.

  By coating with a metal oxycarbide single crystal, it is possible to obtain higher hardness than that using a polycrystal, and it can be widely used as an abrasive, a machine part, or a cutting tool.

The X-ray diffraction pattern (a) of the crystal film formed on the magnesium oxide single crystal (110) plane substrate in Example 1, and the rocking curve (b) of the molybdenum oxycarbide (220) diffraction line. FIG. 3 is a high-resolution transmission electron microscope photograph of the crystal film cross section obtained in Example 1. The rocking curve (b) of the X-ray-diffraction pattern (a) and molybdenum oxycarbide (220) diffraction line of the crystal film formed on the magnesium oxide single crystal (100) plane board | substrate in Example 3. FIG.

Claims (4)

  A cemented carbide material comprising a magnesium oxide single crystal or silicon single crystal and a single crystal coating of oxycarbide of a metal selected from molybdenum, chromium and tungsten formed thereon.   Plasma reaction between a metal selected from molybdenum, chromium and tungsten and carbon oxide or carbon oxide and hydrocarbon in the presence of a magnesium oxide single crystal substrate or a silicon single crystal substrate maintained at 350 to 450 ° C. A method for producing a super hard material, characterized in that a metal oxycarbide single crystal is epitaxially grown on a substrate surface.   The method for producing a cemented carbide material according to claim 2, wherein epitaxial growth is performed on a (110) plane or a (100) plane of a magnesium oxide single crystal or a (111) plane, a (100) plane, or a (110) plane of a silicon single crystal. . The method for manufacturing a super hard material according to claim 2 or 3, wherein a negative bias voltage of -250 to -500 V is applied to the single crystal substrate.