JP2008018508A - Cutting tool made of surface coated cubic boron nitride-base very high pressure sintered material exhibiting excellent chipping resistance in high-speed intermittently cutting high-hardness steel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cutting tool made of surface coated cubic boron nitride-base very high pressure sintered material exhibiting excellent chipping resistance in high-speed intermittently cutting high-hardness steel. <P>SOLUTION: In the cutting tool made of surface coated cubic boron nitride-base very high pressure sintered material, a hard coated layer is deposited on the surface of an insert body having texture in which a very high pressure sintered reaction product is interposed in the interface between a cubic boron nitride boron phase forming a dispersed phase and a titanium nitride phase forming a continuous phase. (a) A hard coating layer includes: a lower layer having an average layer thickness ranging from 1-3 μm; and an upper layer having an average layer thickness ranging from 0.3-3 μm, (b) the lower layer is formed of a compound nitride layer of Cr, Al and Si satisfying a specified composition formula, and (c) the upper layer has an alternately stacking layer structure of a thin layer A and a thin layer B which respectively have an average layer thickness ranging from 0.05-0.3 μm, the thin layer A is formed of a compound nitride layer of Cr, Al and Si satisfying a specified composition formula, and the thin layer B is formed of a Ti nitride (TiN) layer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  Even when high hardness steel such as alloy steel, chrome steel, etc. is subjected to high-speed intermittent cutting, this invention has excellent fracture resistance with a hard coating layer and can exhibit stable cutting performance over a long period of time. A cutting tool made of a surface-coated cubic boron nitride-based super-high pressure sintered material (hereinafter referred to as a coated cBN group) in which a hard coating layer is formed on the surface of a cutting tool base composed of a cubic boron nitride-based ultra-high pressure sintered material. (Referred to as a sintered tool).

  In general, a coated cBN-based sintered tool has an insert that can be attached to the tip of a cutting tool for turning of a work material such as various types of steel and cast iron, An insert-type end mill that performs cutting work in the same manner as a solid type end mill used for machining, grooving, and shoulder machining is known.

  Further, as a coated cBN-based sintered tool, a hard coating layer is formed on the surface of a tool body composed of various cubic boron nitride-based ultrahigh pressure sintered materials (hereinafter referred to as cBN-based sintered materials). However, it is known to form a composite nitride ((Cr, Al, Si) N) layer of Cr, Al, and Si as one of the hard coating layers.

The coated cBN-based sintered tool coated with the hard coating layer made of the (Cr, Al, Si) N layer is, for example, arc ion plating which is a kind of physical vapor deposition apparatus shown in a schematic explanatory view in FIG. The above tool base is inserted into the apparatus, and the inside of the apparatus is heated to, for example, 500 ° C. with a heater, for example, between a cathode electrode (evaporation source) made of a Cr—Al—Si alloy and an anode electrode, for example A 90 A current was applied to generate an arc discharge, and at the same time, nitrogen gas was introduced into the apparatus as a reaction gas to form a reaction atmosphere of 2 Pa, for example, while a bias voltage of, for example, −100 V was applied to the tool base. It is also known that a (Cr, Al, Si) N layer is deposited on the surface of the tool base under conditions.
Japanese Patent Laid-Open No. 2003-321764 JP 2004-106183 A

  In recent years, FA has been remarkable for cutting devices, but on the other hand, there is a strong demand for labor saving and energy saving and further cost reduction for cutting, and accordingly, cutting is performed at higher speed conditions in addition to normal cutting conditions. Although there is a tendency to require lower cutting, the above-described conventional coated tool does not cause any particular problem when various types of steel and cast iron are cut under normal conditions. However, when this is used for high-speed intermittent cutting of high-hardness steel, due to the high heat generated at the cutting edge and the intermittent and impact load applied to the cutting edge, the boundary of the cutting edge of the cutting edge In the present situation, abnormal damage (hereinafter referred to as abnormal boundary damage) and loss occur, and this causes the service life in a relatively short time.

In view of the above, the present inventors have conducted research to develop a coated cBN-based sintered tool that exhibits high fracture resistance with a hard coating layer in high-speed intermittent cutting of high-hardness steel from the above viewpoint. As a result,
(a) The composite nitride of Cr, Al, and Si (hereinafter referred to as (Cr _1-XY Al _X Si _Y ) N) constituting the hard coating layer has an Al content ratio X (atomic ratio). Abrasion resistance required under normal cutting conditions, with specified high-temperature hardness, heat resistance, high-temperature oxidation resistance, and heat-resistant plastic deformation within a range of 0.4 to 0.7 While comprises, in the high-speed intermittent cutting work of hardened steels, with high heat is generated in the cutting edge, applied intermittently and shocking loads the cutting edge portion, whereas, (Cr _{1- X-Y Al X} Si _Y) consisting of _N layer hard coating layer in order high-temperature strength is insufficient, edge notching occurs at the boundary portion of the cutting edge, and this may cause a defect.

(B) On the other hand, the Ti nitride (hereinafter referred to as TiN) layer is not sufficient in high temperature hardness, heat resistance, high temperature oxidation resistance, and heat plastic deformation, but has excellent high temperature strength. In addition, it is possible to prevent abnormal boundary damage from occurring at the boundary portion of the cutting edge even in high-speed intermittent cutting of high hardness steel with large heat generation.

(C) Al content ratio X in the above (a) having a predetermined high temperature hardness, heat resistance, high temperature oxidation resistance, and heat plastic deformation resistance of 40 to 70 atomic% (Cr _1-XY Al _X Si _Y ) N (however, in terms of atomic ratio, X is 0.4 to 0.7, Y is 0.02 to 0.10) layer (hereinafter referred to as thin layer A) and the thin layer A While high-temperature hardness, heat resistance, high-temperature oxidation resistance, and heat-resistant plastic deformability are inferior, on the other hand, a Ti nitride (TiN) layer (hereinafter referred to as a thin layer B) having excellent high-temperature strength is formed in each layer. When the upper layer of the hard coating layer is formed by alternately laminating with the average layer thickness being a thin layer of 0.05 to 0.3 μm, the hard coating layer of this alternate laminar structure has the excellent high temperature of the thin layer A. Combines hardness, heat resistance, high temperature oxidation resistance, and heat plastic deformation with excellent high temperature strength of thin layer B Uninari a result, even in high-speed intermittent cutting work of hardened steels, the border abnormal damage is prevented, the chipping resistance is improved.
The research results shown in (a) to (c) above were obtained.

This invention was made based on the above research results,
Ultra-high pressure sintered material of green compact having a compounding composition comprising titanium nitride 13 to 30%, aluminum and / or aluminum oxide 6 to 18%, and remaining boron nitride (wherein,% indicates mass%) And a structure in which an ultrahigh pressure sintered reaction product is interposed at the interface between a cubic boron nitride phase forming a dispersed phase and a titanium nitride phase forming a continuous phase, as observed by a scanning electron microscope. In a cutting tool made of a surface-coated cubic boron nitride-based ultra-high pressure sintered material in which a hard coating layer is vapor-deposited on the surface of the insert body having
(A) The hard coating layer is composed of a lower layer having an average layer thickness of 1 to 3 μm and an upper layer having an average layer thickness of 0.3 to 3 μm,
(B) The lower layer of the hard coating layer was formed by vapor deposition.
Cr satisfying the composition formula: (Cr _1-XY Al _X Si _Y ) N (wherein X is 0.4 to 0.7 and Y is 0.02 to 0.10 in atomic ratio) A composite nitride layer of Al and Si;
(C) The upper layer of the hard coating layer is formed by vapor deposition on the surface of the lower layer, and each has an alternately laminated structure of thin layers A and B each having an average layer thickness of 0.05 to 0.3 μm. And
The thin layer A is
Cr satisfying the composition formula: (Cr _1-XY Al _X Si _Y ) N (wherein X is 0.4 to 0.7 and Y is 0.02 to 0.10 in atomic ratio) A composite nitride layer of Al and Si;
The thin layer B is a Ti nitride (TiN) layer,
Cutting tool made of surface-coated cubic boron nitride-based ultra-high pressure sintered material that exhibits excellent fracture resistance in high-speed intermittent cutting of high-hardness steel such as alloy steel and chromium steel with a hard coating layer made of (Coated cBN-based sintered tool).

Next, in the coated cBN-based sintered tool of the present invention, the reason why the composition of the cBN-based sintered material of the insert main body, the composition of the hard coating layer, and the layer thickness are limited will be described.
(A) Composition of the cBN-based sintered material of the insert body (A) TiN
The TiN component in the sintered material has the effect of improving the sinterability and improving the strength by forming a continuous phase in the sintered body, but if the blending ratio is less than 13% by mass, the desired strength is ensured. On the other hand, if the blending ratio exceeds 30% by mass, the content of cBN is relatively reduced, and rake face wear is likely to occur. Therefore, the blending ratio is set to 13 to 30% by mass. It was.

(B) Aluminum and / or aluminum oxide These components aggregate preferentially on the surface of the cBN powder during the sintering and react to form a reaction product. In the sintered cBN-based material, a continuous phase is formed. The reaction product is tightly adhered to both the TiN phase forming the continuous phase and the cBN phase forming the hard dispersed phase, and is interposed between the TiN phase forming and the cBN phase forming the hard dispersed phase. Since it has the property of bonding, the adhesion of the cBN phase to the TiN phase, which is a continuous bonding phase, is remarkably improved. As a result, the chipping resistance of the cutting blade is improved. When the blending ratio is out of the range of 6 to 18% by mass, it is not possible to ensure strong adhesion between the hard dispersed phase and the continuous phase as an intermediate adhesion layer. The mixing ratio of um and / or aluminum oxide was determined to be 6 to 18% by mass.

(C) Boron nitride (cBN)
Boron nitride (cBN) in the tool base made of ultra-high pressure sintered material is extremely hard and forms a dispersed phase in the sintered material, and this dispersed phase can improve wear resistance. If the amount is too small, the desired excellent wear resistance cannot be ensured. On the other hand, if the blending ratio is too large, the sinterability of the boron nitride (cBN) base material itself decreases, resulting in a cutting edge. Deficiency is likely to occur. The mixing ratio of boron nitride (cBN) is the balance of TiN, aluminum, and aluminum oxide, which are constituents of the sintered material, that is, 52 to 81 mass%.

(B) Lower layer of hard coating layer (Cr _1-XY Al _X Si _Y ) N (wherein atomic ratio, X is 0.4 to 0.7, Y is the lower layer of the hard coating layer) 0.02 to 0.10) Cr component in the layer maintains a predetermined high temperature strength, Al component improves high temperature hardness, heat resistance, high temperature oxidation resistance, and Si component contributes to heat plastic deformation since the, constituting the lower layer of the hard coating layer _{(Cr 1-X-Y Al} X Si Y) N layer, a predetermined high-temperature strength and excellent high-temperature hardness, heat resistance, high-temperature oxidation resistance and heat plastic It is a layer having deformability and basically plays a role of ensuring the wear resistance of the cutting edge portion during high-speed intermittent cutting of high hardness steel such as alloy steel and chromium steel. However, if the Al content ratio X exceeds 70 atomic%, the heat resistance and high-temperature oxidation resistance of the lower layer will improve, but it will be difficult to maintain the B1 crystal structure due to the relative decrease in the Cr content ratio, resulting in wear resistance. On the other hand, when the Al content ratio X is less than 40 atomic%, the high-temperature hardness and heat resistance are lowered, and as a result, wear resistance is lowered. When the content ratio Y exceeds 10 atomic%, the content ratio of Cr and the content ratio of Al are relatively decreased, so that the fracture resistance and wear resistance are lowered. On the other hand, the Si content ratio Y is 2 atoms. Since the improvement of the heat-resistant plastic deformability cannot be expected if it is less than 0.5%, the value of the Al content ratio X is 0.4 to 0.7, and the value of the Si content ratio Y is 0.02 to 0.00. 10 was determined.
Moreover, if the average layer thickness of the lower layer is less than 1 μm, the high temperature hardness, heat resistance, high temperature oxidation resistance and heat plastic deformation that it has cannot be imparted to the hard coating layer over a long period of time, resulting in short tool life. On the other hand, if the average layer thickness exceeds 3 μm, defects tend to occur, so the average layer thickness was set to 1 to 3 μm.

  A thin layer of titanium nitride (TiN) can be interposed between the base and the lower layer in order to ensure sufficient adhesion between the cutting tool base made of the ultra-high pressure sintered material and the lower layer. The thin layer of TiN has little effect of improving the adhesion when the layer thickness is less than 0.01 μm, and on the other hand, even if the layer thickness exceeds 0.5 μm, further improvement in adhesion cannot be expected. The thickness of the TiN layer interposed between the substrate and the lower layer is preferably 0.01 μm or more and 0.5 μm or less.

(C) Upper layer of hard coating layer (b) Thin layer A of upper layer
(Cr _1-XY Al _X Si _Y ) N layer (however, in atomic ratio, X is 0.4 to 0.7, Y is 0.02 to 0.10) constituting the thin layer A of the upper layer Is a layer substantially similar to the lower layer, having a predetermined high-temperature strength, excellent high-temperature hardness, heat resistance, high-temperature oxidation resistance, and heat-resistant plastic deformation, and high-speed intermittent cutting of high-hardness steel. It has the effect | action which ensures the abrasion resistance of the cutting blade part at the time of a process.

(B) Thin layer B of the upper layer
The thin layer B composed of the TiN layer is mainly intended to supplement the characteristics (high temperature strength) that the thin layer A lacks in the upper layer composed of the alternately laminated structure of the thin layer A and the thin layer B. is there.
As described above, the thin layer A of the upper layer is a layer having excellent high-temperature hardness, heat resistance, high-temperature oxidation resistance, and heat-resistant plastic deformation, but is accompanied by high heat generation and the cutting edge portion. In high-speed intermittent cutting of high-hardness steel, which is subjected to intermittent and impact mechanical loads, the high-temperature strength cannot be said to be sufficient, leading to abnormal boundary damage and defects due to insufficient high-temperature strength. become.
Therefore, the thin layer B composed of the TiN layer having excellent high temperature strength is arranged alternately with the thin layer A to constitute an alternate laminated structure, thereby compensating for the lack of high temperature strength of the adjacent thin layer A, and as a whole upper layer. The upper layer having the excellent high-temperature strength of the thin layer B is formed without impairing the excellent high-temperature hardness, heat resistance, high-temperature oxidation resistance, and heat-resistant plastic deformation property of the thin layer A.
The TiN layer has excellent high-temperature strength, high heat generation, and high-speed intermittent cutting of high-hardness steel with intermittent and impact mechanical loads on the cutting edge. Has the effect of preventing the occurrence of abnormal boundary damage and defects.

(C) The average layer thickness of the upper layer, the thin layer A and the thin layer B, the average layer thickness of the upper layer. The excellent properties of the thin layer cannot be demonstrated, and as a result, it is impossible to ensure the high temperature hardness, heat resistance, high temperature oxidation resistance, heat plastic deformation and high temperature strength of the upper layer, In addition, if the average layer thickness of each layer exceeds 0.3 μm, the disadvantages of each thin layer, that is, if the thin layer A is insufficient in high temperature strength, if the thin layer B is high temperature hardness, heat resistance, high temperature oxidation resistance Insufficiency appears locally in the layer, which causes abnormal cutting edge boundary damage, chipping, and rapid wear. The thickness was determined to be 0.05 to 0.3 μm.
That is, the thin layer B is provided for imparting high temperature strength to the upper layer, but the average layer thickness of each of the thin layer A and the thin layer B is in the range of 0.05 to 0.3 μm. For example, the upper layer composed of the alternately laminated structure of the thin layer A and the thin layer B is a single layer having excellent high temperature hardness, heat resistance, high temperature oxidation resistance, heat plastic deformation, and excellent high temperature strength. However, if the average layer thickness of each of the thin layer A and the thin layer B exceeds 0.3 μm, the high temperature strength of the thin layer A is insufficient, or the high temperature hardness of the thin layer B, Insufficient heat resistance, high temperature oxidation resistance, and heat plastic deformation properties appear locally in the layer, and the upper layer cannot exhibit good characteristics as a single layer as a whole. The average layer thickness of each thin layer B was determined to be 0.05 to 0.3 μm.
Excellent high temperature hardness and heat resistance by forming on the lower layer surface an upper layer composed of an alternating laminate structure in which the average layer thickness of the thin layers A and B is in the range of 0.05 to 0.3 μm. In addition to high-temperature oxidation resistance and heat-resistant plastic deformation, a hard coating layer with excellent high-temperature strength is obtained. As a result, in high-speed intermittent cutting of high-hardness steel such as alloy steel and chromium steel, the cutting edge Occurrence of abnormal damage occurring at the boundary portion of the blade edge can be prevented.
In addition, when the total average layer thickness of the upper layer (that is, the total layer thickness of the thin layers A and B constituting the alternate laminated structure) is less than 0.3 μm, the high-speed steel has a high speed. Sufficient high-temperature hardness, heat resistance, high-temperature oxidation resistance, high-temperature plastic deformation and high-temperature strength required for interrupted cutting cannot be imparted to the upper layer, causing short tool life, while the average When the layer thickness exceeds 3 μm, defects are likely to occur. Therefore, the average layer thickness was determined to be 0.3 to 3 μm.

In the coated cBN-based sintered tool of the present invention, a slightly different interference color may be generated depending on the thickness of the coating layer on the outermost surface, and the tool appearance may be uneven. In such a case, unevenness of the tool appearance can be prevented by forming a thick (Cr, Al, Si) N layer or TiN layer on the outermost surface. At that time, if the average layer thickness of the (Cr, Al, Si) N layer or TiN layer is less than 0.2 μm, the appearance irregularity cannot be prevented, and if the average layer thickness is up to 2 μm, the appearance irregularity is not achieved. Therefore, the average layer thickness of the (Cr, Al, Si) N layer or TiN layer may be 0.2 to 2 μm.
In addition, the surface roughness of the coated cBN-based sintered tool base of the present invention is desirably 0.05 to 1.0 in terms of Ra. If the surface roughness Ra is 0.05 or more, an improvement in adhesion strength between the substrate and the hard coating layer due to the anchor effect can be expected. On the other hand, if Ra exceeds 1.0, the finished surface of the work material This is because the accuracy is adversely affected.

  In the coated cBN-based sintered tool of the present invention, the hard coating layer is composed of an upper layer and a lower layer, and the upper layer of the hard coating layer has an excellent laminated structure of thin layers A and thin layers B. Because it combines heat resistance, high-temperature oxidation resistance, heat-resistant plastic deformation and excellent high-temperature strength, high-hardness steels such as alloy steels and chrome steels are accompanied by high heat generation. Even under severe conditions such as high-speed interrupted cutting with impact mechanical load, the hard coating layer will not cause abnormal boundary damage or chipping and will have excellent wear resistance over a long period of time. It can be demonstrated.

  Next, the coated cBN-based sintered tool of the present invention will be specifically described with reference to examples.

As raw material powders, cubic boron nitride (cBN) powder, titanium nitride (TiN) powder, Al powder, and aluminum oxide (Al ₂ O ₃ ) powder each having an average particle size in the range of 0.5 to 4 μm are prepared. These raw material powders were blended in the composition shown in Table 1, wet mixed with a ball mill for 80 hours, dried, and then compacted with a diameter of 50 mm × thickness: 1.5 mm at a pressure of 120 MPa. The green compact is then press-molded, and then the green compact is sintered in a vacuum atmosphere at a pressure of 1 Pa at a predetermined temperature within a range of 900 to 1300 ° C. for 60 minutes and pre-sintered for a cutting edge piece. This pre-sintered body was superposed on a separately prepared support piece made of WC-based cemented carbide having Co: 8 mass%, WC: remaining composition, and diameter: 50 mm × thickness: 2 mm. Normal ultra high pressure sintering It is charged into the apparatus, and is sintered under ultra-high pressure at a predetermined temperature within the range of pressure: 5 GPa and temperature: 1200 to 1400 ° C., which is a normal condition under the condition of holding time: 0.8 hour. Polishing with a diamond grindstone, dividing into 3 mm regular triangles with a wire electric discharge machine, Co: 5% by mass, TaC: 5% by mass, WC: remaining composition and shape of CIS standard SNGA12041 (thickness) The brazing part (corner part) of the insert body made of a WC-based cemented carbide having a length of 4.76 mm and a side length of 12.7 mm is 26% by mass and Ti is 5%. , Ni: 2.5%, Ag: Brazing using a brazing material of an Ag alloy having the composition consisting of the rest, and after outer periphery processing to a predetermined dimension, the width of the cutting edge is 0.13 mm, angle: 25 ° Finished with honing The tool substrate A~J having the insert shape of ISO standard SNGA120412 by applying an abrasive was prepared, respectively.

(A) Next, each of the tool bases A to J is ultrasonically cleaned in acetone and dried, and then in a radial direction from the central axis on the rotary table in the arc ion plating apparatus shown in FIG. Are mounted along the outer periphery at a predetermined distance, and the upper layer thin layer B forming metal Ti is used as the cathode electrode (evaporation source) on one side, and the cathode electrode (evaporation source) on the other side. The upper layer thin layer A and the lower layer forming Cr—Al—Si alloy, each having a component composition corresponding to the target composition shown in Table 2, are placed opposite to each other across the rotary table,
(B) First, while the inside of the apparatus is evacuated and kept at a vacuum of 0.1 Pa or less, the inside of the apparatus is heated to 500 ° C. with a heater, and then Ar gas is introduced to create an atmosphere of 0.7 Pa. A DC bias voltage of −200 V is applied to the tool base that rotates while rotating on the table, and the tool base surface is bombarded with argon ions.
(C) Nitrogen gas is introduced as a reaction gas into the apparatus to form a reaction atmosphere of 3 Pa, a DC bias voltage of −100 V is applied to the tool base rotating while rotating on the rotary table, and the thin layer A current of 100 A is passed between A and the lower layer forming Cr—Al—Si alloy and the anode electrode to generate an arc discharge, and the target composition and target layer thickness shown in Table 2 are formed on the surface of the tool base. (Cr, Al, Si) N layer is deposited as a lower layer of the hard coating layer,
(D) Next, the flow rate of nitrogen gas as a reaction gas introduced into the apparatus is adjusted to obtain a reaction atmosphere of 2 Pa, and within a range of −10 to −100 V on the tool base that rotates while rotating on the rotary table. In a state where a predetermined DC bias voltage is applied, a predetermined current within a range of 50 to 200 A is passed between the cathode electrode and the anode electrode of the thin layer B forming metal Ti to generate arc discharge, A thin layer B having a predetermined layer thickness is formed on the surface of the tool base, and after the thin layer B is formed, arc discharge is stopped. Instead, a cathode of Cr-Al-Si alloy for forming the thin layer A and the lower layer Similarly, a predetermined current in the range of 50 to 200 A is passed between the electrode and the anode electrode to generate arc discharge to form a thin layer A having a predetermined layer thickness. Then, the arc discharge is stopped and the thin layer B is again formed. Forming metal Ti The formation of the thin layer B by arc discharge between the sword electrode and the anode electrode and the formation of the thin layer A by arc discharge between the cathode electrode and the anode electrode of the Cr-Al-Si alloy for forming the thin layer A and the lower layer are alternately performed. Table 2 shows the upper layer composed of the alternate lamination of the thin layer A and the thin layer B having the target composition and the single target layer thickness along the layer thickness direction on the surface of the tool base. The coated cBN-based sintered tools 1 to 10 of the present invention were manufactured by vapor deposition with the total layer thickness (average layer thickness) shown.

  For comparison purposes, each of the tool bases A to J described above is ultrasonically cleaned in acetone and dried, and then charged into a normal arc ion plating apparatus shown in FIG. As the (evaporation source), a Cr—Al—Si alloy having a component composition corresponding to the target composition shown in Table 3 is mounted, and first, the apparatus is evacuated and kept at a vacuum of 0.1 Pa or less. After heating the interior of the apparatus to 500 ° C. with a heater, Ar gas was introduced to create an atmosphere of 0.7 Pa, and a DC bias voltage of −200 V was applied to the tool base rotating while rotating on the table. Then, the surface of the tool base is bombarded with argon ions, and then nitrogen gas is introduced into the apparatus as a reaction gas to make a reaction atmosphere of 3 Pa and applied to the tool base. The bias voltage is lowered to −100 V to generate an arc discharge between the cathode electrode and the anode electrode of the Cr—Al—Si alloy, and the surface of each of the tool bases A to J is shown in Table 3. Conventionally coated cBN-based sintered tools 1 to 10 were respectively produced by vapor-depositing a hard coating layer composed of a (Cr, Al, Si) N layer having a target composition and a target layer thickness.

  Regarding the cBN-based sintered material constituting the insert body of various coated cBN-based sintered tools obtained as a result, the structure was observed using a scanning electron microscope, and all the insert bodies were substantially dispersed. A structure in which an ultrahigh-pressure sintered reaction product is present at the interface between the cBN phase forming the phase and the TiN phase forming the continuous phase is shown.

  Further, when the composition of the surface coating layer was measured by energy dispersive X-ray analysis using a transmission electron microscope, the composition showed substantially the same composition as the target composition, and the average layer thickness was When the cross section was measured using a transmission electron microscope, all showed the average value (average value of five places) substantially the same as the target layer thickness.

Next, according to the present invention, the coated cBN-based sintered tools 1 to 10 and the conventional coated cBN-based sintered tool, in a state where all the above-mentioned coated cBN-based sintered tools are screwed to the tip of the tool steel tool with a fixing jig. About the cBN base sintered tools 1-10, the high-speed intermittent cutting test was implemented on the cutting conditions AC shown below.
[Cutting conditions A]
Work material: JIS / SCM420 (Hardness: HRC62) lengthwise equidistant four round bars with vertical grooves,
Cutting speed: 255 m / min. ,
Cutting depth: 0.09 mm,
Feed: 0.06 mm / rev. ,
Cutting time: 8 minutes,
Dry interrupted high-speed cutting test of alloy steel under the conditions of (normal cutting speed is 150 m / min.),
[Cutting conditions B]
Work material: JIS · SCr420 (Hardness: HRC60) lengthwise equidistant four round grooved round bars,
Cutting speed: 240 m / min. ,
Cutting depth: 0.12 mm,
Feed: 0.10 mm / rev. ,
Cutting time: 8 minutes,
A dry intermittent high-speed cutting test of chromium steel under the conditions of (normal cutting speed is 120 m / min.),
[Cutting conditions C]
Work material: JIS · S45C (Hardness: HRC58) lengthwise equidistant four round grooved round bars,
Cutting speed: 270 m / min. ,
Cutting depth: 0.15 mm,
Feed: 0.11 mm / rev. ,
Cutting time: 8 minutes,
Carbon steel dry interrupted high-speed cutting test under normal conditions (normal cutting speed is 180 m / min.),
In each cutting test, the flank wear width (mm) of the cutting edge and the finished surface accuracy of the work material (arithmetic average height (Ra (μm)) according to JIS B0601-2001) were measured. Are shown in Table 4.

  From the results shown in Tables 2 to 4, the coated cBN-based sintered tool of the present invention has a hard coating layer and alternating layers of thin layers A and B each having an average layer thickness of 0.05 to 0.3 μm. An upper layer having an average layer thickness (total layer thickness) of 0.3 to 3 μm having a laminated structure and a lower layer having an average layer thickness of 1 to 3 μm. The lower layer has excellent high-temperature hardness, heat resistance, High-temperature oxidation resistance, heat-resistant plastic deformation and predetermined high-temperature strength, and the upper layer has excellent high-temperature strength in addition to excellent high-temperature hardness, heat resistance, high-temperature oxidation resistance, and heat-resistant plastic deformation Therefore, even in high-speed intermittent cutting of high-hardness steel such as alloy steel and chrome steel, there is no abnormal boundary damage or chipping in the hard coating layer, and excellent wear resistance over a long period of time. As well as excellent finished surface accuracy of the work material. On the other hand, the conventional coated cBN-based sintered tool in which the hard coating layer is a single (Cr, Al, Si) N layer, especially due to insufficient high-temperature strength of the hard coating layer, causes abnormal boundary damage or chipping at the cutting edge. It is obvious that the finished surface accuracy of the work material cannot be maintained and the service life is reached in a relatively short time.

  As described above, the coated cBN-based sintered tool of the present invention is not limited to cutting under normal cutting conditions such as various steels and cast irons, particularly high hardness steels such as alloy steels and chrome steels. Even in high-speed interrupted cutting, the hard coating layer exhibits excellent boundary abnormal damage resistance and fracture resistance, maintaining excellent work surface finish accuracy over a long period of time and excellent wear resistance. Therefore, it is possible to satisfactorily cope with high performance of the cutting device, labor saving and energy saving of the cutting, and cost reduction.

The arc ion plating apparatus used for forming the hard coating layer which comprises the coated cBN group sintered tool of this invention is shown, (a) is a schematic plan view, (b) is a schematic front view. It is a schematic explanatory drawing of a normal arc ion plating apparatus.

Claims (1)

Ultra-high pressure sintered material of green compact having a compounding composition comprising titanium nitride 13 to 30%, aluminum and / or aluminum oxide 6 to 18%, and remaining boron nitride (wherein,% indicates mass%) And a structure in which an ultrahigh pressure sintered reaction product is interposed at the interface between a cubic boron nitride phase forming a dispersed phase and a titanium nitride phase forming a continuous phase, as observed by a scanning electron microscope. In a cutting tool made of a surface-coated cubic boron nitride-based ultra-high pressure sintered material in which a hard coating layer is vapor-deposited on the surface of the insert body having
(A) The hard coating layer is composed of a lower layer having an average layer thickness of 1 to 3 μm and an upper layer having an average layer thickness of 0.3 to 3 μm,
(B) The lower layer of the hard coating layer was formed by vapor deposition.
Cr satisfying the composition formula: (Cr _1-XY Al _X Si _Y ) N (wherein X is 0.4 to 0.7 and Y is 0.02 to 0.10 in atomic ratio) A composite nitride layer of Al and Si;
(C) The upper layer of the hard coating layer is formed by vapor deposition on the surface of the lower layer, and each has an alternately laminated structure of thin layers A and B each having an average layer thickness of 0.05 to 0.3 μm. And
The thin layer A is
Cr satisfying the composition formula: (Cr _1-XY Al _X Si _Y ) N (wherein X is 0.4 to 0.7 and Y is 0.02 to 0.10 in atomic ratio) A composite nitride layer of Al and Si;
The thin layer B is a Ti nitride (TiN) layer,
A surface-coated cubic boron nitride-based ultra-high pressure sintered material cutting tool that exhibits excellent fracture resistance in high-speed intermittent cutting of high-hardness steel with a hard coating layer made of

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