JP2012101358A - Cutting tool made of surface-coated cubic boron nitride-based ultrahigh pressure sintered material exhibiting excellent finished surface accuracy in high-speed machining of high hardness steel over long period of time - Google Patents

Abstract

The present invention provides a cutting tool made of a surface-coated cubic boron nitride-based ultra-high pressure sintered material that exhibits excellent finished surface accuracy of Ra of 0.5 to 1.3 μm for a long period of time in high-speed cutting of high hardness steel. .
SOLUTION: It is composed of an ultra-high pressure sintered material of a green compact consisting of titanium nitride 13 to 30%, aluminum and / or aluminum oxide 6.5 to 18%, and the remainder boron nitride (all are mass%). A hard coating layer is deposited on the surface of a cutting tip body having a structure in which an ultrahigh pressure sintering 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. In the surface-coated cubic boron nitride-based ultrahigh pressure sintered material cutting tool, (a) the hard coating layer has a lower layer having an average layer thickness of 1.5 to 3 μm and an average layer thickness of 0.3 to 3 μm (B) The lower layer is composed of Ti and Al satisfying the composition formula: [Ti _1-X Al _X ] N (wherein X is 0.40 to 0.60 in atomic ratio). (C) The upper layer is a single layer average The thickness has an alternate stacked structure of the thin layer A and the thin layer B of 0.05~0.3μm respectively, the thin layer A, _{formula: [Ti 1-X Al X} ] N ( where atomic ratio, The composite nitride layer of Ti and Al satisfying X is 0.40 to 0.60), and the thin layer B is composed of a Ti nitride (TiN) layer.
[Selection figure] None

Description

  This invention has a hard coating layer with excellent high-temperature hardness, high-temperature strength, and heat resistance, as well as excellent boundary abnormal damage resistance. Therefore, high-speed cutting of high-hardness steel such as alloy steel and hardened material of bearing steel. Cubic boron nitride-based ultra-high pressure sintered material that exhibits excellent boundary abnormal damage resistance and can maintain excellent finished surface accuracy over long-term cutting even when used in machining This invention relates to a cutting tool made of a surface-coated cubic boron nitride-based ultrahigh-pressure sintered material (hereinafter referred to as a coated cBN-based sintered tool) in which a hard coating layer is formed on the surface of a cutting tool base composed of

  In general, a coated cBN-based sintered tool can be attached to a throwaway tip that is detachably attached to the tip of a cutting tool for turning various work materials such as steel and cast iron, and the throwaway tip can be detachably attached. There are known slow-away end mills that are attached and cut in the same manner as solid type end mills used for chamfering, grooving, and shoulder machining.

  In addition, as a coated cBN-based sintered tool, Ti nitride (TiN) is formed on the surface of a tool body made of various cubic boron nitride-based ultrahigh pressure sintered materials (hereinafter referred to as cBN-based sintered materials). Coated cBN-based sintered tools are known, which are formed by vapor-depositing a surface coating layer such as a layer, a composite nitride of Ti and Al ([Ti, Al] N) layer, and these include, for example, various steels and cast iron It is also known that it is used for cutting.

Further, the above-mentioned coated cBN-based sintered tool is loaded with the above-mentioned tool base in an arc ion plating apparatus which is one type of physical vapor deposition apparatus schematically shown in FIG. For example, an arc of 90 A is applied between the anode electrode and the cathode electrode (evaporation source) made of metal Ti or a Ti—Al alloy having a predetermined composition while being heated to 500 ° C., for example. At the same time, a discharge gas is generated and nitrogen gas is introduced as a reaction gas into the apparatus to form a reaction atmosphere of, for example, 2 Pa. On the other hand, a surface of the tool base is applied to the tool base under a bias voltage of, for example, −100 V In addition, it is also known that it is produced by vapor-depositing a layer having a desired component composition such as a TiN layer or a [Ti, Al] N layer.

JP-A-7-300649 JP-A-8-119774

  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 continuous cutting or high-speed intermittent cutting of high-hardness steel having a hardness of 50 or more, such as hardened material of alloy steel or bearing steel, the cutting edge Due to the high heat generated in the part or the large mechanical load that is intermittently and impactively applied to the cutting edge part, abnormal damage (hereinafter referred to as abnormal boundary damage) occurs at the boundary of the cutting edge of the cutting edge. However, it is difficult to maintain the finished surface accuracy over a long period of cutting, and the service life is reached in a relatively short time.

Therefore, the present inventors, in particular, in high-speed continuous cutting or high-speed intermittent cutting (hereinafter simply referred to as "high-speed cutting") of high hardness steel such as a hardened material of alloy steel and bearing steel from the above viewpoint, As a result of research to develop a coated cBN-based sintered tool that exhibits excellent resistance to abnormal boundary resistance with a hard coating layer,
(a) a composite nitride of Ti and Al constituting the hard layer _{([Ti 1-X Al X} ] N) layer, the value of the content X (atomic ratio) of Al, 0.40 to 0.60 In the range of the above, it has a predetermined heat resistance, high temperature hardness and high temperature strength and has the wear resistance required under normal cutting conditions, but with extremely large heat generation at the cutting edge, Or at the same time, in high-speed cutting of high-hardness steel in which a large mechanical load is intermittently and impactively applied to the cutting edge portion, it is composed of a composite nitride ([Ti _1-X Al _X ] N) layer of Ti and Al. The hard coating layer lacks high-temperature strength, resulting in abnormal boundary damage at the boundary of the cutting edge, and due to this, the finished surface accuracy of the work material cannot be maintained and used in a relatively short time. The end of life.

(B) On the other hand, the Ti nitride (TiN) layer has excellent high temperature strength and impact strength, but heat resistance and high temperature hardness are not sufficient. In high-speed cutting of high-hardness steel subject to a heavy load, even if the hard coating layer is composed of only a Ti nitride (TiN) layer, it cannot be said to have sufficient wear resistance.

(C) the content X is 40 to 60 atomic% of the heat resistance of Al (a), high-temperature hardness and a predetermined high-temperature strength _{[Ti 1-X Al X]} N ( where atomic ratio, X 0.45 to 0.60) layer (hereinafter referred to as thin layer A) and heat resistance and high temperature hardness are inferior to those of the thin layer A, but on the other hand, excellent high temperature strength and impact strength. Ti nitride (TiN) layers (hereinafter referred to as “thin layer B”) are alternately laminated in a state where each layer has an average layer thickness of 0.05 to 0.3 μm to form an upper layer of the hard coating layer. When configured, the hard coating layer of this alternately laminated structure has the excellent heat resistance and high temperature hardness of the thin layer A, and also combines the high temperature strength and impact strength superior to those of the thin layer B. As a result, the occurrence of abnormal boundary damage can be prevented.
The research results shown in (a) to (c) above were obtained.

This invention was made based on the above research results,
(1) of a green compact having a blended composition comprising titanium nitride 13 to 30%, aluminum and / or aluminum oxide 6.5 to 18%, and the remainder boron nitride (wherein,% indicates mass%) Constructed from ultra-high-pressure sintered material, and observed by microstructure using a scanning electron microscope, produced ultra-high-pressure sintering reaction at the interface between cubic boron nitride phase forming dispersed phase and titanium nitride phase forming continuous phase 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 a cutting tip body having a structure in which an object is interposed,
(A) The hard coating layer is composed of a lower layer having an average layer thickness of 1.5 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.
A composite nitride layer of Ti and Al satisfying the composition formula: [Ti _1-X Al _X ] N (wherein X is 0.40 to 0.60 in atomic ratio),
(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
A composite nitride layer of Ti and Al satisfying the composition formula: [Ti _1-X Al _X ] N (wherein X is 0.40 to 0.60 in atomic ratio),
The thin layer B is a Ti nitride (TiN) layer,
Surface-coated cubic boron nitride that exhibits excellent finished surface accuracy of Ra of 0.5 to 1.3 μm over a long period of time by high-speed cutting of hardened steel such as hardened steel, which is formed by vapor-depositing a hard coating layer comprising Cutting tool made of super-high pressure sintered material (coated cBN-based sintered tool),
(2) The surface-coated cubic boron nitride-based ultrahigh-pressure sintered material according to (1), wherein the surface roughness of the cutting tip body is 0.05 μm or more and 1.0 μm or less in terms of Ra. Cutting tools,
(3) The above (1) or (1), wherein a Ti nitride (TiN) layer having a thickness of 0.01 μm or more and 0.5 μm or less is interposed between the cutting tip body and the lower layer. 2) the surface-coated cubic boron nitride-based ultrahigh pressure sintered material cutting tool,
(4) Any one of (1) to (3) above, wherein a composite nitride layer of Ti and Al having an average layer thickness of 0.2 to 2 μm is deposited on the outermost surface of the upper layer. Cutting tool made of surface coated cubic boron nitride based ultra high pressure sintered material as described in
It has the characteristics.

Next, in the coated cBN-based sintered tool of the present invention, the reason why the composition of the cBN-based sintered material, the composition of the hard coating layer, and the layer thickness of the cutting tip body constituting the tool are limited will be described.
(A) Composition of cBN-based sintered material of cutting tip 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. If the blending ratio is out of the range of 6.5 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 blending ratio of minium and / or aluminum oxide was determined to be 6.5 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. Chipping is likely to occur. The blending ratio of boron nitride (cBN) is the balance of TiN, aluminum and aluminum oxide, which are constituents of the sintered material, that is, about 52 to 80% by mass.

(B) Ti component in the hard coating layer composite nitride of Ti and Al constituting the lower layer of the lower layer hard coating layer of _{([Ti 1-X Al X} ] N) layer is maintained in the high-temperature strength, Al component hot since contributing to the improvement of hardness and heat resistance, the composite nitride of Ti and Al constituting the lower layer of the hard coating layer _{([Ti 1-X Al X} ] N) layer a predetermined high-temperature strength, high-temperature hardness And a layer having heat resistance, and basically plays a role of ensuring the wear resistance of the cutting edge portion during high-speed cutting of hardened steel such as hardened steel. However, when the Al content ratio X exceeds 60 atomic%, the high temperature hardness and heat resistance of the lower layer are improved, but due to the relative decrease in the Ti content ratio, the high temperature strength is lowered and chipping is likely to occur. When the Al content ratio X is less than 40 atomic%, the high temperature hardness and heat resistance decrease, and as a result, the wear resistance decreases. 40 to 0.60.
Moreover, if the average layer thickness of the lower layer is less than 1.5 μm, the heat resistance, high temperature hardness and high temperature strength possessed by itself cannot be imparted to the hard coating layer over a long period of time, resulting in a short tool life. When the layer thickness exceeds 3 μm, chipping is likely to occur. Therefore, the average layer thickness was set to 1.5 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
Composite nitride of Ti and Al constituting the thin layer A of the upper layer _{([Ti 1-X Al X} ] N) layer (where an atomic ratio, X is shows the 0.40 to 0.60), the lower It is a layer that is substantially the same as the layer and has the prescribed heat resistance, high temperature hardness, and high temperature strength, and has the effect of ensuring the wear resistance of the cutting edge during high speed cutting of high hardness steel such as hardened steel. Have.

(B) Thin layer B of the upper layer
The thin layer B composed of a Ti nitride (TiN) layer is an upper layer composed of an alternating laminated structure of the thin layer A and the thin layer B. In other words, the thin layer B has characteristics that are insufficient for the thin layer A (high temperature strength, impact strength strength). The main purpose is to compensate.
As already described, the thin layer A as the upper layer is a layer having predetermined heat resistance, high temperature hardness and high temperature strength. However, in the high-speed cutting processing of high hardness steel with high mechanical generation as well as large mechanical addition, The high-temperature strength and impact strength are not sufficient, and as a result, abnormal boundary damage occurs at the boundary of the cutting edge of the cutting edge.
Therefore, the thin layer B composed of the Ti nitride (TiN) layer having excellent high-temperature strength and impact strength is arranged alternately with the thin layer A to form an alternate laminated structure, thereby forming the adjacent thin layer A. Compensating for lack of high-temperature strength and impact strength, the upper layer as a whole was superior to that of the thin layer B without any loss of the excellent heat resistance, high-temperature hardness, and high-temperature strength of the thin layer A. Form an upper layer with high temperature strength and impact strength.
The Ti nitride (TiN) layer has excellent high-temperature strength and impact strength, and is used for high-speed cutting of hardened steel such as hardened steel with high mechanical load and high heat generation. It has the effect of preventing the occurrence of abnormal boundary damage occurring at the boundary portion.

(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 superior properties of the thin layer cannot be demonstrated, and as a result, the high temperature hardness, high temperature strength and heat resistance superior to the upper layer, and even better high temperature strength and impact strength can be ensured. If the average layer thickness of each layer exceeds 0.3 μm, the defects of each thin layer, that is, if it is thin layer A, high temperature strength, insufficient impact strength, if thin layer B, heat resistance Insufficient high-temperature hardness will appear locally in the layer, causing abnormal edge damage on the cutting edge and rapid progress of wear. The layer thickness was determined to be 0.05 to 0.3 μm.
That is, the thin layer B is provided to give higher temperature strength and impact strength superior to the upper layer, but the average layer thickness of each of the thin layer A and the thin layer B is 0.05 to If it is within the range of 0.3 μm, the upper layer composed of the alternately laminated structure of the thin layer A and the thin layer B has excellent heat resistance and high temperature hardness, and further improved high temperature strength and impact resistance strength. It acts as if it is a single layer, but when the average layer thickness of each of the thin layers A and B exceeds 0.3 μm, the high temperature strength of the thin layer A, the impact strength is insufficient, or The heat resistance of the thin layer B and the lack of high-temperature hardness 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 layer B was set to 0.05 to 0.3 μm.
Excellent heat resistance and high temperature hardness by forming on the lower layer surface an upper layer composed of an alternating laminated 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, a hard coating layer with even higher high-temperature strength and impact strength is obtained. As a result, the cutting edge of the cutting edge of high-hardness steel such as hardened steel can be cut at high-speed continuous cutting or high-speed intermittent cutting. Occurrence of abnormal damage occurring at the boundary portion can be prevented.
Further, if 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 total thickness of the hardened steel or the like is high. Sufficient heat resistance, high-temperature hardness, high-temperature strength and impact strength required for high-speed cutting of hardened steel cannot be imparted to the upper layer, resulting in a short tool life, while its average layer thickness When the thickness exceeds 3 μm, chipping is likely to occur. Therefore, the average layer thickness is 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 thickly depositing a Ti and Al composite nitride (TiAlN) layer on the outermost surface. At that time, if the average thickness of the TiAlN layer is less than 0.2 μm, uneven appearance cannot be prevented, and if there is an average layer thickness of up to 2 μm, uneven appearance can be sufficiently prevented. The average layer thickness of the composite nitride (TiAlN) 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 excellent heat resistance by having an alternating laminated structure of thin layers A and thin layers B. Combined with high-temperature hardness, high-temperature strength, and impact strength, especially high-hardness steel, such as hardened steel of alloy steel and bearing steel, is accompanied by high heat generation and intermittent / impact on the cutting edge. Even under severe conditions such as high-speed continuous cutting or high-speed interrupted cutting with a heavy mechanical load, the hard coating layer does not cause abnormal boundary damage and exhibits excellent wear resistance over a long period of time. In addition, excellent finished surface accuracy of the work material can be maintained.

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.

  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, temperature: 1200 to 1400 ° C., which is a normal condition, and holding time: 0.8 hours. 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 WC-based cemented carbide chip body having a length of 4.76 mm × one side length: 12.7 mm is Cu: 26%, Ti: 5 %, Ni: 2.5%, Ag: Brazing using a brazing material of an Ag alloy having the remaining composition, and after outer peripheral processing to a predetermined dimension, the width of the cutting edge is 0.13 mm, angle: 25 ° Honing and finishing The tool substrate A~J having a tip shape of ISO standard SNGA120412 by performing grinding was produced, 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 Ti—Al alloy having component compositions corresponding to the target compositions shown in Table 2 are arranged opposite to each other with the rotary table interposed therebetween,
(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 caused to flow between A and the lower layer forming Ti—Al alloy and the anode electrode to generate an arc discharge, so that the target composition and target layer thickness shown in Table 2 are formed on the surface of the tool base. Ti, Al] 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, the arc discharge is stopped. Instead, the cathode electrode of the thin layer A and the lower layer forming Ti—Al alloy Similarly, a predetermined current in the range of 50 to 200 A is passed between the anode electrodes 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 formed again. Metal Ti Catho The thin layer B is formed by arc discharge between the electrode and the anode electrode, and the thin layer A is formed by arc discharge between the cathode electrode and the anode electrode of the Ti-Al alloy for forming the thin layer A and the lower layer alternately. Thus, on the surface of the tool base, the upper composition composed of the alternating lamination of the thin layer A and the thin layer B having the target composition shown in Table 2 along with the layer thickness direction along the layer thickness direction is also shown in Table 2. The coated cBN-based sintered tools 1 to 10 of the present invention were manufactured by vapor deposition with a layer thickness (average layer thickness).

  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 Ti—Al alloy having a component composition corresponding to the target composition shown in Table 3 was mounted. First, the apparatus was evacuated and kept at a vacuum of 0.1 Pa or less while heating. After heating the inside of the apparatus to 500 ° C., Ar gas is introduced to make an atmosphere of 0.7 Pa, and a DC bias voltage of −200 V is applied to the tool base that rotates while rotating on the table. The tool substrate surface is bombarded with argon ions, and then nitrogen gas is introduced into the apparatus as a reaction gas to form a reaction atmosphere of 3 Pa, and a via applied to the tool substrate. The voltage was lowered to −100 V to generate an arc discharge between the cathode electrode and the anode electrode of the Ti—Al alloy, and the target composition shown in Table 3 and the surface of each of the tool substrates A to J were Conventionally coated cBN-based sintered tools 1 to 10 were manufactured by vapor-depositing a hard coating layer composed of a [Ti, Al] N layer having a target layer thickness.

  Regarding the cBN-based sintered material constituting the cutting tip body of the various coated cBN-based sintered tools obtained as a result, the structure was observed using a scanning electron microscope. 1 shows a structure in which an ultrahigh pressure sintering reaction product is interposed at the interface between the cBN phase forming the dispersed phase and the TiN phase forming the continuous phase.

  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. Among the cBN-based sintered tools 1 to 10, the present coated cBN-based sintered tools 1 to 5 and the conventional coated cBN-based sintered tools 1 to 5 are subjected to a high-speed intermittent cutting test under the following cutting conditions A to C. Moreover, about this invention coated cBN group sintered tool 6-10 and conventional coated cBN group sintered tool 6-10, the high-speed continuous cutting test was similarly implemented on the cutting conditions ac shown below.
[Cutting conditions A]
Work material: JIS / SCM415 carburized quenching material (hardness: HRC61) in the longitudinal direction, four equally spaced round bars,
Cutting speed: 200 m / min. ,
Cutting depth: 0.2 mm,
Feed: 0.15 mm / rev. ,
Cutting time: 6 minutes,
Dry interrupted high-speed cutting test of alloy steel under the conditions (normal cutting speed is 120 m / min.),
[Cutting conditions B]
Work material: JIS · SCr420 carburized quenching material (hardness: HRC60), 4 longitudinally spaced round bars with equal intervals in the length direction,
Cutting speed: 210 m / min. ,
Cutting depth: 0.15 mm,
Feed: 0.12 mm / rev. ,
Cutting time: 6 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 / SUJ2 quenching material (hardness: HRC61), 4 longitudinally spaced round bars with equal intervals in the length direction,
Cutting speed: 240 m / min. ,
Cutting depth: 0.16 mm,
Feed: 0.10 mm / rev. ,
Cutting time: 6 minutes,
Dry interrupted high-speed cutting test of bearing steel under the conditions of (normal cutting speed is 150 m / min.),
[Cutting conditions a]
Work material: JIS SCM415 carburized quenching material (hardness: HRC61) round bar,
Cutting speed: 280 m / min. ,
Cutting depth: 0.2 mm,
Feed: 0.10 mm / rev. ,
Cutting time: 8 minutes,
Dry continuous high-speed cutting test of alloy steel under normal conditions (normal cutting speed is 200 m / min.),
[Cutting conditions b]
Work material: JIS / SCr420 carburized quenching material (hardness: HRC60) round bar,
Cutting speed: 250 m / min. ,
Cutting depth: 0.2 mm,
Feed: 0.1 mm / rev. ,
Cutting time: 8 minutes,
Dry continuous high speed cutting test of chromium steel under the conditions of (normal cutting speed is 160 m / min.),
[Cutting conditions c]
Work material: JIS / SUJ2 hardened material (hardness: HRC61) round bar,
Cutting speed: 220 m / min. ,
Cutting depth: 0.2 mm,
Feed: 0.1 mm / rev. ,
Cutting time: 8 minutes,
Dry continuous high speed cutting test of bearing steel under the conditions of (normal cutting speed is 150 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. It consists of an upper layer having an average layer thickness (total layer thickness) of 0.3 to 3 μm and a lower layer having an average layer thickness of 1.5 to 3 μm, and the lower layer has excellent heat resistance and high temperature strength. It has excellent high temperature hardness, and the upper layer has excellent heat resistance, high temperature hardness and superior high temperature strength and impact resistance, so alloy steel, hardened steel of bearing steel, etc. Even in high-speed cutting of high-hardness steel, it exhibits excellent wear resistance without occurrence of abnormal boundary damage and chipping, and it can ensure excellent finished surface accuracy of the work material, but hard coating Conventionally coated cB whose layer consists of a single [Ti, Al] N layer The base sintered tool is not only unable to maintain the finished surface accuracy of the work material due to abnormal boundary damage and chipping at the cutting edge, especially due to insufficient high temperature strength and impact strength of the hard coating layer, It is clear that 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 only used for cutting under normal cutting conditions such as various types of steel and cast iron, but particularly as high as a hardened material for alloy steel and bearing steel. Even in high-speed continuous cutting or high-speed intermittent cutting in which hard steel has high heat generation and a very large intermittent / impact mechanical load is applied to the cutting edge, the hard coating layer has excellent boundary abnormal damage resistance. Demonstrates excellent work material finish surface accuracy over a long period of time and exhibits excellent wear resistance. Furthermore, it can cope with cost reduction sufficiently satisfactorily.

Claims (4)

Ultra-high pressure firing of a green compact having a blended composition comprising titanium nitride 13-30%, aluminum and / or aluminum oxide 6.5-18%, and the remainder boron nitride (wherein,% indicates mass%). An ultra high pressure sintered reaction product is present at the interface between the cubic boron nitride phase that forms the dispersed phase and the titanium nitride phase that forms the continuous phase, which is composed of a binder material and is observed with 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 a cutting tip body having a texture,
(A) The hard coating layer is composed of a lower layer having an average layer thickness of 1.5 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.
A composite nitride layer of Ti and Al satisfying the composition formula: [Ti _1-X Al _X ] N (wherein X is 0.40 to 0.60 in atomic ratio),
(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
A composite nitride layer of Ti and Al satisfying the composition formula: [Ti _1-X Al _X ] N (wherein X is 0.40 to 0.60 in atomic ratio),
The thin layer B is a Ti nitride (TiN) layer,
Surface-coated cubic boron nitride-based ultra-high pressure sintering that exhibits excellent finished surface accuracy of Ra of 0.5 to 1.3 μm over a long period of time by high-speed cutting of high-hardness steel with a hard coating layer made of Material cutting tool.   2. The surface-coated cubic boron nitride-based ultrahigh pressure sintered material cutting tool according to claim 1, wherein the surface roughness of the cutting tip body is 0.05 μm or more and 1.0 μm or less in terms of Ra.   3. The surface according to claim 1, wherein a Ti nitride (TiN) layer having a thickness of 0.01 μm or more and 0.5 μm or less is interposed between the cutting tip body and the lower layer. Cutting tool made of coated cubic boron nitride based ultra-high pressure sintered material. The surface according to any one of claims 1 to 3, wherein a composite nitride layer of Ti and Al having an average layer thickness of 0.2 to 2 µm is formed by vapor deposition on the outermost surface of the upper layer. Cutting tool made of coated cubic boron nitride based ultra-high pressure sintered material.