JP4653789B2 - Surface coated cubic boron nitride sintered body tool - Google Patents

Description

  The present invention relates to improvement of a cutting tool material based on a sintered body mainly composed of cubic boron nitride (cBN) (hereinafter referred to as a cBN sintered body), and is excellent in both wear resistance and toughness. The present invention relates to a surface-coated cBN sintered body tool.

  Conventional cBN sintered tools have been used under severe cutting conditions due to their high hardness and high thermal conductivity after diamond. However, due to thermal and mechanical wear and chipping of the tool edge, the current situation is that a sufficient life is not achieved in the field of high speed and high efficiency.

In order to further improve wear resistance and fracture resistance in cutting with a cBN sintered body, for example, disclosed in Japanese Patent Laid-Open Nos. 8-119774, 1-96083, 1-96084 and the like. As described above, a method of coating a cBN sintered body with TiN, TiAlN or the like has been proposed.
JP-A-8-119774 JP-A-1-96083 JP-A-1-96084

  However, if high wear resistance is required for the coating film, the toughness is reduced, and if toughness is required, the wear resistance is reduced. Yes.

  Therefore, an object of the present invention is to provide a surface-coated cBN sintered body tool that has good wear resistance and toughness and can suppress peeling and chipping of the coating film even during intermittent cutting.

  The inventors of the present application have studied internal stress in the coating film in order to realize both improvement in wear resistance and improvement in toughness of the coating film. Generally, compressive stress is generated in a coating film formed by an ion plating method. Although it is a problem that such residual compressive stress adversely affects the wear resistance of the coating film, it has been found that reducing the residual compressive stress reduces toughness. Furthermore, as a result of various studies, it was found that both wear resistance and toughness are improved by changing the compressive stress in the coating film within the film.

  In particular, when toughness is required, it is effective to increase the compressive stress in the coating film continuously or stepwise from the base material side to the surface side, and wear resistance is required. In some cases, it has been found effective to reduce the compressive stress in the coating film continuously or stepwise from the base material side to the surface side.

  Further, it has been found that as the compressive stress in the coating film increases, the toughness becomes better, and as the compressive stress decreases, the wear resistance becomes better.

Therefore, one surface-coated cBN sintered body tool of the present invention includes a base material having a portion made of a cBN sintered body having 20% by volume or more of cBN, and a substrate formed on the cBN sintered body of the base material. A covering film, and the covering film includes at least one nitride, carbide, charcoal selected from the group consisting of IVa, Va, VIa group elements, Al (aluminum), B (boron), and Ge (germanium) It has a material containing any of nitride and oxide, has an internal stress of -10 GPa or more and 0 GPa or less, and has a stress difference of 1 GPa or more between the surface side and the back side of the base material side , The internal stress of the coating film changes so that the compressive stress increases from the surface side toward the base material side . In the internal stress, the symbol “−” indicates a compressive stress.
Another surface-coated cBN sintered body tool of the present invention is a surface-coated cBN sintered body tool for cutting hardened steel, and a base material having a portion made of a cBN sintered body having 20% by volume or more of cBN, A coating film formed on the base material cBN sintered body, and the coating film is one or more nitrides selected from the group consisting of IVa, Va, VIa group elements, Al, B and Ge , Having a material containing any of carbide, carbonitride, and oxide, having an internal stress of −10 GPa to 0 GPa, and having a stress difference of 1 GPa or more between the front side and the back side of the base material The internal stress of the coating film changes so that the compressive stress increases from the base material side to the surface side.

  Thus, by changing the internal stress so as to have a stress difference of 1 GPa or more between the surface side of the coating film and the base material side, a surface-coated cBN sintered body tool excellent in both wear resistance and toughness is obtained. Obtainable. If the stress difference is less than 1 GPa, the effect of changing the internal stress in the coating film cannot be obtained sufficiently. The reason why the content of cBN is set to 20% by volume or more is that defects are likely to occur when the content is less than 20% by volume.

  In the above surface-coated cBN sintered body tool, the thickness of the coating film is preferably 0.5 μm or more and 10 μm or less. This is because when the thickness of the coating film is less than 0.5 μm, the coating effect is small, and when it exceeds 10 μm, the coating film tends to peel off.

  In the above surface-coated cBN sintered body tool, the internal stress of the coating film preferably changes so that the compressive stress increases continuously or stepwise from the base material side to the surface side. Thereby, toughness improves notably. This is presumably because chipping and other chipping can be prevented because the introduction of higher internal compressive stress toward the surface side suppresses the progress of microcracks that enter the surface.

  In the above surface-coated cBN sintered body tool, the internal stress of the coating film preferably changes so that the compressive stress increases continuously or stepwise from the surface side toward the base material side. Thereby, abrasion resistance improves notably. This is because the surface of the film becomes softer by introducing lower internal compressive stress on the surface side, and the entire film cannot be peeled off when the welding at the time of cutting is peeled off (only the vicinity of the surface of the film is peeled off), thereby improving the wear resistance. It is considered a thing.

  Preferably, in the above surface-coated cBN sintered body tool, the first thin film having a material of any of the group IVa element nitride, carbide, carbonitride, and oxide between the base material and the coating film Is further provided. Thereby, since the adhesion strength between the coating film and the base material is improved, higher performance is expected.

  In the above-mentioned surface-coated cBN sintered body tool, preferably, a second thin film having a material of any of group IVa element nitride, carbide, carbonitride and oxide is further provided on the surface of the coating film. It has been. As a result, higher performance is expected.

  Preferably in the above-mentioned surface-coated cBN sintered body tool, the cBN sintered body includes 35% by volume to 85% by volume of cBN, and includes a binder for bonding the cBN particles. 1 or more types chosen from the group which consists of a, b, c, d, and e, Al compound, and an unavoidable impurity are included.

a: group IVa, Va, VIa element b: nitride of group IVa, Va, VIa element c: boride of group IVa, Va, VIa element d: carbide of group IVa, Va, VIa element e: IVa, Va, Solid solution consisting of two or more kinds selected from the group consisting of nitrides, borides and carbides of group VIa elements, IVa, Va, and group VIa elements. Improvements can be made. When the content of cBN exceeds 85% by volume, the wear resistance of the base material is deteriorated, which affects the wear resistance of the coating film, so that the improvement of the wear resistance is hindered. Further, when the content of cBN is less than 35% by volume, the hardness of the cBN sintered body is reduced despite the fact that the hardness is high. For example, a high hardness work material such as hardened steel is used. Insufficient strength to cut at high speed.

  In the above surface-coated cBN sintered body tool, the average particle size of the cBN particles is preferably 4 μm or less.

  Thereby, the remarkable improvement of cutting performance can be aimed at. When the average particle size of the cBN particles exceeds 4 μm, the contact area between the cBN particles and the binder is reduced, and the bonding force between the cBN particles and the binder is weakened. Insufficient strength to cut material at high speed.

  As described above, in the surface-coated cBN sintered body tool of the present invention, internal stress is applied so that the surface side of the coating film and the base material side have a stress difference of 1 GPa or more within a range of −10 GPa to 0 GPa. By changing it, a surface-coated cBN sintered body tool excellent in both wear resistance and toughness can be obtained. As a result, the surface-coated cBN sintered body tool of the present invention is well applied to cutting tools such as drills, end mills, milling throwaway inserts, cutting edge replaceable inserts, metal saws, cutting tools, reamers, taps, and the like. Is possible.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a partial cross-sectional view of a surface-coated cBN sintered body tool according to an embodiment of the present invention. Referring to FIG. 1, base material 2 is formed of a cBN sintered body having 20% by volume or more of cBN in at least a part of the tool blade edge that is involved in cutting. A coating film 1 is formed on the surface of the cBN sintered body portion of the base material 2. This coating film 1 is a compound containing at least one selected from nitrides, carbides, carbonitrides and oxides of alloys of IVa, Va, VIa group elements, Al, B and Ge and any combination thereof. And has an internal stress of -10 GPa or more and 0 GPa or less, and a stress difference of 1 GPa or more between the front surface side and the base material side which is the back surface side.

  The internal stress of the coating film 1 is measured by, for example, an X-ray diffraction method. Details of this measurement method are described in, for example, “Basics and Applications of PVD / CVD Coating”, edited by Surface Technology Association, published by Tsuneo Yamamoto, pp. 156-164.

Moreover, it is preferable that the film thickness of the coating film 1 is 0.5 micrometer or more and 10 micrometers or less.
The internal stress of the coating film 1 may be changed continuously from the base material side to the surface side as shown in FIG. 2 or stepwise as shown in FIG. . Thereby, the improvement of the toughness of the surface-coated cBN sintered body tool becomes remarkable. Further, the internal stress of the coating film 1 changes continuously from the base material side to the surface side as shown in FIG. 4 or so that the compressive stress decreases stepwise as shown in FIG. Also good. Thereby, the improvement of the wear resistance of the surface-coated cBN sintered body tool becomes remarkable.

  Further, as shown in FIG. 6, an adhesion strengthening layer 3a having any one of a nitride, carbide, carbonitride, and oxide of an IVa group element is provided between the base material 2 and the coating film 1. It is preferable. Further, as shown in FIG. 7, a thin film 3 b made of any one of a group IVa element nitride, carbide, carbonitride, and oxide may be formed on the surface of the coating film 1.

  The cBN sintered body portion of the base material 2 contains 35% by volume or more and 85% by volume or less of cBN, and contains a binding material for binding the cBN particles. The binding material includes the following a, b, c It is preferable that one or more selected from the group consisting of d, e, an Al compound, and inevitable impurities are contained.

a: group IVa, Va, VIa element b: nitride of group IVa, Va, VIa element c: boride of group IVa, Va, VIa element d: carbide of group IVa, Va, VIa element e: IVa, Va, Solid solution consisting of two or more selected from the group consisting of nitrides, borides and carbides of group VIa elements, IVa, Va, and group VIa elements. The average particle size of the cBN particles is preferably 4 μm or less.

Examples of the present invention will be described in detail below.
Example 1
First, using a cemented carbide pot and balls, TiN, Ti, and Al, which are binder materials, were mixed to obtain a binder powder. Next, the binder powder and the cBN powder were mixed, filled in a Mo (molybdenum) container, and sintered at a pressure of 5 GPa and a temperature of 1400 ° C. for 20 minutes. This sintered body was processed into the shape of ISO standard SNGN120408 to obtain a cBN sintered body base material. The cBN content of the cBN sintered body base material was 65% by volume, and the average particle size of the cBN particles was 2.5 μm.

  The base material was coated with various types of TiCN having a film thickness of 3.5 μm shown in Table 3 using a known arc ion plating method. Further, the high carbon chromium bearing steel round bar was cut under the conditions shown in Table 1 using each of the coated samples, and the flank wear amount of each sample after cutting was measured.

  Next, a toughness test was performed on the samples coated under the same conditions as the above samples. The toughness test is performed by cutting the outer periphery of a work material having six V-shaped grooves with an alloy tool steel round bar under the conditions shown in Table 2, and measuring the time until the coating film peels in addition to normal wear. Therefore, it was set as evaluation of toughness.

  Table 3 shows the stress distribution of the coating film of each sample and the results of evaluating the flank wear amount (wear resistance) and the cutting time (toughness) until film peeling when a cutting test is performed.

  From the results of Table 3, samples 1-4 of the present invention in which the internal stress in the TiCN layer was changed by 1 GPa or more within a range of −10 GPa or more and 0 GPa or less were excellent in both wear resistance and toughness. Recognize. On the other hand, Samples 5 to 9 having no change in internal stress and Samples 10 and 11 in which the internal stress was changed in a range different from the stress range of the present invention may show a low value of at least one of wear resistance and toughness. Recognize.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a fragmentary sectional view of the surface covering cBN sintered compact tool in one embodiment of the present invention. It is a figure which shows the 1st form of distribution of the internal stress in a coating film. It is a figure which shows the 2nd form of distribution of the internal stress in a coating film. It is a figure which shows the 3rd form of distribution of the internal stress in a coating film. It is a figure which shows the 4th form of distribution of the internal stress in a coating film. It is a fragmentary sectional view of the structure which provided the adhesion reinforcement | strengthening layer between the coating film and the base material. It is a fragmentary sectional view which shows the structure which provided the additional thin film on the surface of the coating film.

Explanation of symbols

  1 coating film, 2 base material, 3a adhesion strengthening layer, 3b thin film.

Claims (11)

A base material having a portion made of a cubic boron nitride sintered body having 20% by volume or more of cubic boron nitride;
A coating film formed on the cubic boron nitride sintered body of the base material,
The coating film has a material including any one or more of nitrides, carbides, carbonitrides and oxides selected from the group consisting of IVa, Va, VIa group elements, Al, B and Ge, And having an internal stress of -10 GPa or more and 0 GPa or less , and having a stress difference of 1 GPa or more between the surface side and the base material side which is the back surface side , and the internal stress of the coating film from the surface side A surface-coated cubic boron nitride sintered body tool that changes so that the compressive stress increases toward the base material side . The internal stress of the coating film is continuously compressive stress direction from the surface side to the base material side is changed to increase, surface-coated cubic boron nitride sintered body tool according to claim 1 . The internal stress of the coating film, stepwise compressive stress direction from the surface side to the base material side is changed to increase, surface-coated cubic boron nitride sintered body tool according to claim 1 . A surface-coated cubic boron nitride sintered tool for cutting hardened steel,
A base material having a portion made of a cubic boron nitride sintered body having 20% by volume or more of cubic boron nitride;
A coating film formed on the cubic boron nitride sintered body of the base material,
The coating film has a material including any one or more of nitrides, carbides, carbonitrides and oxides selected from the group consisting of IVa, Va, VIa group elements, Al, B and Ge, And having an internal stress of -10 GPa or more and 0 GPa or less, and having a stress difference of 1 GPa or more between the front surface side and the back surface side of the base material side, and the internal stress of the coating film from the base material side A surface-coated cubic boron nitride sintered body tool that changes so that compressive stress increases toward the surface side. The surface-coated cubic boron nitride sintered body tool according to claim 4 , wherein the internal stress of the coating film changes so that the compressive stress continuously increases from the base material side toward the surface side. . 5. The surface-coated cubic boron nitride sintered body tool according to claim 4 , wherein the internal stress of the coating film changes so that a compressive stress gradually increases from the base material side toward the surface side. . The surface-coated cubic boron nitride sintered body tool according to any one of claims 1 to 6 , wherein the coating film has a thickness of 0.5 µm to 10 µm. Between the coating film and the base material, a nitride of group IVa elements, carbides, further comprising a first thin film having any of the material of the carbonitride and oxide of claim 1-7 The surface-coated cubic boron nitride sintered body tool according to any one of the above. On the surface of the coating film, a nitride of group IVa elements, carbides, further comprising a second thin film having any of the material of the carbonitride and oxide, according to any one of claims 1-8 Surface coated cubic boron nitride sintered body tool. The cubic boron nitride sintered body contains 35% by volume to 85% by volume of the cubic boron nitride, and includes a binder for binding the cubic boron nitride particles.
In the following a, b, c, d and e:
a: IVa, Va, VIa group element,
b: nitride of group IVa, Va, VIa element,
c: boride of group IVa, Va, VIa elements,
d: Carbide of IVa, Va, VIa group element,
e: a solid solution composed of two or more selected from the group consisting of group IVa, Va, VIa group elements, nitrides, borides and carbides of group IVa, Va, VIa elements,
The surface-coated cubic nitriding according to any one of claims 1 to 9 , wherein a material of the binder includes one or more selected from the group consisting of a, b, c, d, and e, an aluminum compound, and inevitable impurities. Boron sintered tool. The surface-coated cubic boron nitride sintered body tool according to claim 10 , wherein an average particle diameter of the cubic boron nitride particles is 4 µm or less.

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