JP2004332006A - METHOD OF PRODUCING ALUMINA FILM CONSISTING MAINLY OF alpha TYPE CRYSTAL STRUCTURE, MEMBER COATED WITH ALUMINA FILM CONSISTING MAINLY OF alpha TYPE CRYSTAL STRUCTURE, AND ITS PRODUCTION METHOD - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing an alumina film by which an alumina film consisting mainly of an α type crystal structure can be formed on a cBN sintered compact base material without depending on high temperatures in a CVD (Chemical Vapor Deposition) method or without specifying the composition of the cBN sintered compact. <P>SOLUTION: In the method, an alumina film consisting mainly of α type crystals is produced on a cBN sintered compact base material consisting of a bonding phase and a cubic boron nitride-dispersed phase. The surface of the cBN sintered compact base material is subjected to oxidation treatment, and subsequently, the alumina film is formed. The oxidation treatment is performed, e.g., by holding the temperature of the base material to 650 to 800°C in an oxidizing gas atmosphere. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is based on a cubic boron nitride (hereinafter sometimes abbreviated as “cBN”) sintered body having excellent wear resistance as a base material, and an α-type crystal having excellent oxidation resistance is formed on the base material. A useful method for producing an alumina coating mainly having a structure, a surface-coated member having such a coating formed thereon to have excellent wear resistance and oxidation resistance, and production of such a surface-coated member It is related to a useful method or the like for performing
[0002]
[Prior art]
Cutting tools are required to have excellent wear resistance and heat resistance. Materials used for such cutting tools include cemented carbide, high-speed steel, cBN, and the like. ) On which various hard coatings are further formed are widely used as cutting tools.
[0003]
Among the various materials described above, cBN is said to be superior in strength and abrasion resistance as compared with other materials. As such a material using cBN, for example, a technology such as Patent Document 1 is disclosed. Are known. In this technique, a ceramic binder phase composed of TiC, TiN or TiCN, and further, Al ₂ O ₃ , WC, TiB _2, etc. occupies 20 to 50% by volume, and the rest substantially consists of a cBN dispersed phase. By applying physical vapor deposition (PVD) or chemical vapor deposition (CVD) to the surface of a cBN sintered body substrate having Ti, carbides, nitrides, carbon nitrides, carbonates, and carbonitrides of Ti And a surface-coated cBN-based ceramic cutting tool in which a hard coating layer composed of a single layer or two or more layers of aluminum oxide is formed with an average layer thickness of 5 to 20 μm. This tool is used for cutting hardened steel and cast iron.
[0004]
It can be said that the properties of a cutting tool are determined by an appropriate combination of a tool base material and a hard coating formed on the surface thereof. From this viewpoint, the most attractive coating material when a cBN sintered body is used as a base material. Is an aluminum oxide (Al ₂ O ₃ : alumina) film. This is because a cBN sintered body excellent in plastic deformation resistance at high temperature is used as a base material, and an Al ₂ O ₃ film excellent in chemical stability is coated with good adhesion, so that under high temperature and high load. This is because a coating member having excellent wear resistance, particularly excellent crater resistance, can be formed and is considered to be suitable for application to a cutting tool or the like that requires such characteristics.
[0005]
From such a viewpoint, various techniques relating to the formation of an alumina film on a cBN sintered body substrate have been proposed. For example, Patent Document 2 discloses a cBN sintered body base material for the purpose of providing a cutting tool having excellent wear resistance, particularly crater wear resistance, in cutting hard-to-hard materials and high-speed and high-efficiency cutting of iron-based materials. There has been proposed a tool in which one or more Al ₂ O ₃ layers are formed on at least a part of a surface involved in cutting in the above. The sintered body base material contains 20 to 99% by volume of the cBN dispersed phase and 1.0 to less than 10% by volume of Al ₂ O ₃ having an average particle size of 1 μm or less as a binder phase, and an alumina film is formed on the base material. It is formed with a thickness of about 0.5 to 50 μm. The Al ₂ O ₃ film has an average crystal grain size of 0.01 to 4 μm when the thickness is 0.5 to 25 μm, and has an average crystal grain size when the thickness is more than 25 to 50 μm. It is also disclosed that it is effective to control the thickness to 0.01 to 10 μm.
[0006]
On the other hand, as a technique related to a coated cBN cutting tool for metal working, for example, Patent Document 3 discloses a tool formed of one or more cBN sintered bodies with or without a sintered carbide support, Is composed of one or more layers of a heat-resistant compound, and at least one of the layers is composed of fine-grained crystalline γ-phase alumina having a particle size of less than 0.1 μm. . The alumina layer is deposited at a substrate temperature of 450 to 700 ° C. by a bipolar pulse DMS (dual magnetron sputtering) technique.
[0007]
Alternatively, as a technique related to a similar cBN cutting tool, for example, Patent Document 4 discloses a tool having a similar configuration, but a gamma-phase alumina as a film is deposited by plasma-activated chemical vapor deposition (PACVD). Are disclosed. In this technique, a plasma is produced by applying a bipolar pulse DC voltage between two electrodes which are fixed and electrically connected to a tool substrate to be coated.
[0008]
[Patent Document 1]
JP-A-59-8679 Patent claims etc. [Patent Document 2]
Japanese Patent Application Laid-Open No. 2000-44370 Patents [Patent Document 3]
JP-T-2002-543993 Patent claims etc. [Patent Document 4]
JP, 2002-543997, A A claim etc.
[Problems to be solved by the invention]
Regarding the formation of an alumina film, there are the following problems in various techniques proposed so far. That is, the alumina film formed by the techniques of Patent Documents 3 and 4 is alumina having a γ-type crystal structure (γ-alumina), which is metastable among aluminas having various crystal forms. When the film is exposed to a high temperature environment, it may be transformed into an alumina having an essentially stable α-type crystal structure (α-alumina). Peeling may occur. For these reasons, it is not possible to sufficiently cope with recent cutting work which tends to perform high-speed cutting.
[0010]
On the other hand, in the technique disclosed in Patent Document 2, alumina having an α-type crystal structure is also included as an alumina film to be formed, and the above-described problem does not occur in this crystal form. However, in this technique, the composition of the binder phase in the cBN sintered body that forms the film is limited. Further, as a method for forming an α-alumina film by this technique, a CVD method is described. In such a method, a substrate temperature during film formation becomes a high-temperature atmosphere exceeding 1000 ° C. The cBN sintered body may be overheated and transformed into the hBN phase, which causes an undesirable situation.
[0011]
The present invention has been made under such a circumstance, and an object of the present invention is to provide an alumina film mainly composed of an α-type crystal structure on a cBN sintered body base without using a high temperature such as a CVD method, and An object of the present invention is to provide a method for producing an alumina film that can be formed without specifying the composition of a cBN sintered body, a member coated with such an alumina film, and a useful method for producing the alumina-coated member. .
[0012]
[Means for solving the problem]
The method for producing an alumina film mainly composed of an α-type crystal structure according to the present invention is to produce an alumina film mainly composed of α-type crystals on a cBN sintered body base material comprising a binder phase and a cubic boron nitride dispersed phase. This method has a gist in that an oxidation treatment is performed on the surface of the cBN sintered body base material and then an alumina film is formed. In this method, the binder phase in the cBN sintered body includes one containing at least one selected from the group consisting of TiC, TiN, TiCN, AlN, TiB ₂ and Al ₂ O ₃ .
[0013]
Preferably, the oxidation treatment is performed in an oxidizing gas oxidizing atmosphere while maintaining the substrate temperature at 650 to 800 ° C., and the formation of the alumina film mainly composed of the α-type crystal structure is performed at a substrate temperature of 650 to 800 It is preferable to carry out by applying the PVD method at 800 ° C.
[0014]
On the other hand, the coated member of the present invention that can achieve the above object is a coated member in which an alumina coating mainly composed of an α-type crystal is coated on a cBN sintered body base material comprising a binder phase and a cubic boron nitride dispersed phase. A gist of the present invention is that the oxide-containing layer is interposed at the interface between the cBN sintered body and the alumina coating. In such a covering member, the binder phase preferably includes at least one selected from the group consisting of TiC, TiN, TiCN, AlN, TiB ₂ and Al ₂ O ₃ , and the binder phase is a sintered body. It is preferable to contain 1 to 50% by volume based on the whole.
[0015]
The alumina film mainly composed of the α-type crystal structure formed on the surface of such a covering member has a compressive residual stress.
[0016]
In manufacturing the above member, the step of oxidizing the surface of the cBN sintered body base and the step of forming an alumina coating mainly composed of an α-type crystal structure are sequentially performed in the same film forming apparatus. Is preferred.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
The present inventors have found that when coating an alumina film mainly composed of an α-type crystal structure on a cBN sintered body base material, without using a high temperature such as CVD, and without specifying the composition of the cBN sintered body. The technology which can also be realized was examined from various angles. As a result, after exposing the surface of the cBN sintered body to an oxidizing gas atmosphere and oxidizing the film, the substrate temperature is set to 650 to 800 ° C. and the film is formed by the PVD method. The inventors have found that an alumina film mainly composed of an α-type crystal structure can be formed, and completed the present invention.
[0018]
Further, according to the present invention, an alumina film mainly composed of an α-type crystal structure having excellent oxidation resistance can be effectively formed on a cBN sintered body substrate having excellent wear resistance. A surface covering member having excellent oxidation resistance can be realized. In addition, when manufacturing the surface coating member, it is not exposed to a high-temperature atmosphere as in the case of applying the CVD method, and there is no restriction on the composition of the cBN sintered body.
[0019]
Although not all of the reasons for the above effects have been elucidated, it can be considered as follows. That is, the cBN sintered body contains TiC, TiN, TiCN, AlN, TiB ₂ , Al ₂ O _{3, and the} like as a binder phase, and a part of the cBN sintered body is also exposed to the surface layer forming the film. However, when such a sintered body is exposed to an oxidizing atmosphere at a high temperature and oxidized, a non-oxide bonded phase of the bonded phase is oxidized from a portion exposed on the surface. Further, even in the case of an oxide bonding phase such as Al ₂ O ₃ , the surface thereof is microscopically contaminated with hydrocarbons or other contaminants. It is believed that this removes these contaminants and exposes the surface of the pure oxide. After passing through the oxidation treatment step in this way, the surface of the cBN sintered body is an oxide in which the binder phase is oxidized, or the surface is in a pure oxide state in the case of the oxide originally. Thus, it is considered that the portion where the oxide-containing phase exists was dispersed over the entire surface of the substrate. Also, there is a possibility that cBN itself in the sintered body also forms an oxide on the surface. For this reason, an oxide layer that is a region suitable for crystal growth of α-alumina is formed over the entire surface of the cBN sintered body substrate, and crystal growth of α-alumina starts from such a region. It is considered that the alumina film mainly composed of the type crystal structure can be formed at a relatively low film formation temperature.
[0020]
The binder phase contained in the cBN sintered body used as the base material in the present invention is not limited to a specific type, and may be selected from the group consisting of TiC, TiN, TiCN, AlN, TiB ₂ and Al ₂ O _3. Those containing at least one or more selected ones can be employed, but other than these, nitrides, carbides, borides and the like of metals of the periodic table 4a, 5a, and 6a or metals such as Al and Si Those containing a mutual solid solution or a metal (for example, Al, Ti, Cr, Fe or an alloy containing them) can also be used. In consideration of the effect of the oxidation treatment according to the present invention, the compound as the binder phase preferably contains at least a non-oxide compound.
[0021]
The content of the binder phase in the cBN sintered body is preferably 1 to 50% by volume based on the whole sintered body. If the content of the binder phase is less than 1% by volume, the desired strength cannot be ensured, and if the content exceeds 50% by volume, the abrasion resistance of the base material decreases.
[0022]
In the present invention, the surface of the cBN sintered body substrate is oxidized to form an oxide-containing layer on the surface (that is, the portion that becomes the interface between the cBN sintered body and the alumina film). This oxidation treatment step is desirably performed in a film forming apparatus for forming an alumina film to be formed in the next step from the viewpoint of efficiently manufacturing a coating member. Enhanced thermal oxidation is the preferred method. The oxidizing gas atmosphere at this time includes, for example, an atmosphere containing an oxidizing gas such as oxygen, ozone, and H ₂ O ₂ , and of course, includes an air atmosphere.
[0023]
It is preferable that the oxidation is performed while maintaining the substrate temperature at 650 to 800 ° C. If the temperature of the base material is too low, the oxidation is not sufficiently performed, and the temperature is preferably increased to 700 ° C. or more. Oxidation is promoted as the substrate temperature is raised, but the upper limit of the substrate temperature must be kept below 1000 ° C. for the purpose of the present invention. In the present invention, an oxide-containing layer useful for forming an alumina film mainly composed of an α-type crystal structure can be formed even at 800 ° C. or lower.
[0024]
In the present invention, there is no particular limitation on the other conditions of the oxidation treatment. As a specific oxidation method, in addition to the thermal oxidation, for example, an oxidizing gas such as oxygen, ozone, or H ₂ O ₂ is turned into plasma and irradiated. It is, of course, also effective to adopt a method of performing the above.
[0025]
By forming the oxide-containing layer as described above, it is possible to reliably form an alumina film mainly composed of an α-type crystal structure on the surface thereof. Incidentally, those having an α-type crystal structure of 70% or more are preferred because they exhibit excellent heat resistance, more preferably those having an α-type crystal structure of 90% or more, and most preferably those having an α-crystal structure of 100%. Things.
[0026]
The thickness of the alumina film mainly composed of the α-type crystal structure is desirably 0.1 to 20 μm. In order to maintain the excellent heat resistance of the alumina film, it is effective to secure 0.1 μm or more, and preferably 1 μm or more. However, if the thickness of the alumina film mainly composed of the α-type crystal structure is too large, internal stress is generated in the alumina film, and cracks and the like are likely to occur, which is not preferable. Therefore, the thickness is preferably 20 μm or less, more preferably 10 μm or less, and still more preferably 5 μm or less.
[0027]
In the present invention, the means for forming an alumina film mainly composed of an α-type crystal structure is not particularly limited. It is desirable to employ. Among such PVDs, a sputtering method, particularly a reactive sputtering method, is preferable because high-speed film formation can be realized using an inexpensive metal target. The temperature at which the alumina film is formed is not particularly limited. However, considering the continuity from the oxidation treatment in the previous step, the temperature is preferably the same as that in the oxidation treatment step, and 650 to 800 ° C. is suitable. . This temperature range is also preferable in that an alumina film mainly composed of an α-type crystal structure is easily formed.
[0028]
By forming the α-type alumina film on the substrate surface as described above, an alumina film-coated member in which the substrate, the intermediate layer, the oxide-containing layer and the α-type alumina film are sequentially formed can be realized. Has excellent wear resistance and heat resistance, and is useful as a material for cutting tools and the like.
[0029]
Since the alumina film mainly composed of the α-type crystal structure is formed by the PVD method, more preferably the reactive sputtering method, a compressive residual stress can be imparted by selecting a coating condition, and the strength of the entire coated member can be increased. It is preferable to secure Further, the alumina film mainly composed of the α-type crystal structure formed by the reactive sputtering method contains a small amount of Ar in addition to Al and O.
[0030]
By forming an alumina film mainly composed of an α-type crystal structure on the surface of the cBN sintered body as described above, an alumina film-coated member in which an oxide-containing layer and an α-alumina film are sequentially formed on the substrate is realized. Such a member becomes excellent in wear resistance and heat resistance, and is useful as a material for cutting tools and the like. In manufacturing such a member, it is preferable to perform the respective steps of forming the oxide-containing layer and the α-alumina film in the same apparatus from the viewpoint of improving productivity.
[0031]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples, and the present invention may be implemented with appropriate changes within a range that can be adapted to the purpose described above and below. And they are all included in the technical scope of the present invention.
[0032]
In the present invention, a commercially available cBN sintered compact cutting tool was used as the base material on which the alumina film was formed. Using a PVD apparatus (vacuum film forming apparatus) shown in FIG. 1, an alumina film was formed on the substrate. First, the sample (substrate) 2 is set on the planetary rotary jig 4 in the apparatus 1, and the inside of the apparatus 1 is evacuated to a substantially vacuum state. Heated to 750 ° C. When the temperature of the sample reached 750 ° C., oxygen gas was introduced into the apparatus 1 at a flow rate of 300 sccm and a pressure of about 0.75 Pa, and the surface was oxidized for 20 minutes.
[0033]
Next, the sputtering cathode 6 equipped with two aluminum targets is sputtered in a mixed atmosphere of argon and oxygen by applying a pulse DC power of about 2.5 kW, under the same temperature condition as the oxidation temperature ( (750 ° C.) to form an alumina film. In forming the alumina film, the discharge state was maintained in a so-called transition mode using discharge voltage control and plasma emission spectroscopy, and an alumina film of about 2 μm was formed. The formation of the alumina film was performed while rotating (revolving) the rotary table 3 shown in FIG. 1 and also rotating the planetary rotary jig provided thereon.
[0034]
The samples of each example after the completion of the treatment were analyzed by thin-film X-ray diffraction, and their crystal structures were identified. FIG. 2 is a graph showing a thin-film X-ray diffraction result of an alumina film formed on a cBN sintered body substrate. In FIG. 2, since many diffraction peaks were observed, including the diffraction peak from the cBN sintered body of the substrate, the diffraction peak from the film was compared with the result of first performing X-ray diffraction on the substrate alone. The diffraction peak from the substrate was separated. In FIG. 2, the diffraction peaks from the substrate are marked with triangles, and the diffraction peaks due to cBN are marked with “▽”, and the diffraction peaks other than cBN are marked with “▼”. The diffraction peaks from the coating were marked with circles, and the diffraction peaks from alumina having an α-type crystal structure were marked with “○”, and the other peaks were marked with “●”.
[0035]
As can be seen from FIG. 2, the cBN sintered body used as the base material has many diffraction peaks other than cBN, but this is a diffraction peak from the binder phase. Some of the diffraction peaks, which are thought to be binder phases, were observed at angles consistent with hexagonal AlN, so the binder phase is believed to contain at least AlN. As can be seen from the figure, most of the diffraction peaks from the coating are from α-alumina, and very weak peaks were observed at very low but coincident positions with diffraction from γ-alumina.
[0036]
At the same time, as a result of composition analysis of this film by XPS (X-ray photoelectron spectroscopy), the film composition contains a trace amount (about 1 atomic%) of Ar. It is contained in proportions.
[0037]
From these results, the film formed on the cBN sintered body substrate can be identified as an alumina film mainly composed of an α-type crystal structure, and the alumina film mainly composed of α-type crystal structure is formed on the cBN sintered body substrate. It could be judged that the coated member coated with the film could be manufactured.
[0038]
The coated member produced in this way is formed by forming an alumina film with excellent oxidation resistance on a cBN sintered body base material with excellent hardness, mainly based on the α-type crystal structure with particularly good thermal stability. Therefore, when applied to a cutting tool, for example, it is suitable for applications such as high-speed cutting of a high-hardness material, and excellent performance can be expected.
[0039]
【The invention's effect】
The present invention is configured as described above. An alumina film mainly composed of an α-type crystal structure is formed on a cBN sintered body base material without using a high temperature such as a CVD method, and the composition of the cBN sintered body is not changed. A method for producing an alumina film that can be formed without specifying the same was realized.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory view (top view) showing an example of an apparatus used for carrying out the present invention.
FIG. 2 is a graph showing a thin-film X-ray diffraction result of an alumina film formed on a cBN sintered body substrate.
[Explanation of symbols]
1 Apparatus 2 Sample (substrate)
3 rotating table 4 planetary rotating jig 5 heater 6 sputtering cathode

Claims (9)

A method for producing an alumina film mainly composed of α-type crystals on a cBN sintered body base material comprising a binder phase and a cubic boron nitride dispersed phase, wherein the cBN sintered body surface is oxidized, A method for producing an alumina film mainly composed of an α-type crystal structure, comprising forming an alumina film on a surface. The binder phase, TiC, TiN, TiCN, AlN , The method according to claim 1 is intended to include one or more selected from the group consisting of TiB ₂ and _Al 2 _{O 3.} The method according to claim 1, wherein the oxidation treatment is performed in an oxidizing gas oxidizing atmosphere while maintaining the substrate temperature at 650 to 800 ° C. 4. The method according to any one of claims 1 to 3, wherein the formation of the alumina film mainly composed of the α-type crystal structure is performed by applying a physical vapor deposition method at a substrate temperature of 650 to 800 ° C. A coating member comprising a cBN sintered body composed of a binder phase and a cubic boron nitride dispersed phase coated with an alumina coating mainly composed of an α-type crystal, wherein an interface between the cBN sintered body base material and the alumina coating is A member coated with an alumina coating mainly composed of an α-type crystal structure, characterized in that an oxide-containing layer is interposed. The binder phase, TiC, TiN, TiCN, AlN , member of claim 5 in which contains at least one element selected from the group consisting of TiB ₂ and _Al 2 _{O 3.} The member according to claim 5, wherein the binder phase contains 1 to 50% by volume of the entire sintered body. The member according to any one of claims 5 to 7, wherein the alumina film mainly composed of the α-type crystal structure has a compressive residual stress. A step of oxidizing the surface of the cBN sintered body to produce a coated member in which an alumina coating mainly composed of an α-type crystal is coated on a cBN sintered body composed of a binder phase and a cubic boron nitride dispersed phase; A method for producing a member coated with an alumina film mainly composed of an α-type crystal structure, wherein the step of forming an alumina film mainly composed of an α-type crystal structure is sequentially performed in the same film forming apparatus.

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