JP2012096304A - Cutting tool made of surface-coated cubic boron nitride-based ultra-high pressure sintered material having high peeling resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cutting tool formed of a surface-coated cubic boron nitride-based ultra-high pressure sintered material having high peeling resistance during the high-speed cutting of high hard steel.SOLUTION: The cutting tool which is configured by forming a hard cover layer on the surface of the cBN-based ultra-high pressure sintered body having a content of cubit boron nitride of 50 to 85 vol.% is characterized in that: (a) the hard cover layer includes a lower layer and an upper layer each having an average layer thickness of 1.5 to 3 μm; (b) the lower layer is composed of a composite nitride layer of Ti and Al which satisfies a composition formula: [TiA1]N (X is 0.30 to 0.60 at atom ratio); (c) the upper layer has the alternate laminate structure of a thin layer A and a thin layer B each having one layer average thickness of 0.03 to 0.3 μm, the thin layer A is formed of a composite nitride layer of Ti and Al which satisfies a composition formula: [TiA1]N, and the thin layer B is formed of a Ti nitride (TiN) layer; and (d) the surface roughness, residual stress, and nano indentation hardness of a cover surface are set to predetermined values.

Description

  The present invention has a hard coating layer with excellent high-temperature hardness, high-temperature strength, and heat resistance, as well as excellent adhesion. Therefore, it is used for high-speed cutting of high-hardness steel such as alloy steel and hardened material of bearing steel. Cutting made of cubic boron nitride-based ultra-high pressure sintered material that provides excellent peel resistance and maintains excellent surface finish accuracy over long-term cutting The present 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 tool substrate.

  Generally, a throw-away tip or a throw-away tip that can be detachably attached to the tip of a cutting tool when turning various work materials such as steel and cast iron is attached to a coated cBN-based sintered tool. In addition, there is known a slow-away end mill that performs cutting in the same manner as a solid type end mill 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 coated cBN-based sintered tool, for example, inserts the cutting tool base into an arc ion plating apparatus which is one type of physical vapor deposition apparatus schematically shown in FIG. For example, a current of 90 A is applied between a cathode electrode (evaporation source) made of metal Ti or a Ti—Al alloy having a predetermined composition and an anode electrode while being heated to 500 ° C. At the same time, an arc discharge is generated and nitrogen gas is introduced into the apparatus as a reaction gas to form a reaction atmosphere of 2 Pa, for example. On the other hand, for example, a bias voltage of −100 V is applied to the cutting tool base. In addition, it is also known that it is manufactured by vapor-depositing a layer having a desired component composition such as a TiN layer or a [Ti, Al] N layer on the surface of the cutting tool base (for example, a patent) Document reference 1). Furthermore, a surface-coated cutting tool is also known in which the wear resistance and fracture resistance are improved by adjusting the surface roughness and residual stress of the hard coating layer formed on the surface of the cutting tool base (for example, Patent Documents). 2).

JP 2007-190668 A JP 2006-263857 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. However, the conventional coated tool does not cause any particular problems 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 interrupted cutting of high-hardness steel having a high hardness of 50 or more Vickers hardness (C scale) such as a hardened material of alloy steel or bearing steel, Since the adhesion strength between the sintered material and the hard coating layer is not sufficient, there is a problem that the cutting edge is peeled off and the cutting life is shortened.

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 in which the hard coating layer exhibits excellent peeling resistance,
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, the 0.30 to 0.60 It has the prescribed heat resistance, high temperature hardness and high temperature strength within the range, 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 the high-speed cutting of high-hardness steel according intermittent and impact to high mechanical loads on the cutting edge, the composite nitride of Ti and _{Al ([Ti 1-X Al} X] N) rigid consisting layer Because the coating layer lacks high-temperature strength, abnormal boundary damage occurs at the boundary of the cutting edge, and this makes it impossible to maintain the finished surface accuracy of the work material, and the service life is relatively short. To reach.

(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 30-60 atomic% of the heat resistance of Al _{(a), [Ti 1-} X Al X] having a high-temperature hardness and predetermined high-temperature strength N (where, in terms of atomic ratio, X 0.30-0.60) 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 resistance strength. Ti nitride (TiN) layers (hereinafter referred to as “thin layer B”) are alternately laminated in a state where each layer has a thin average layer thickness of 0.03 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 peel resistance is improved.
(D) Furthermore, surface treatment techniques such as wet blasting and shot peening treatment are performed on the surface of the hard coating layer, so that the surface roughness, residual stress, The indentation hardness can be set to a predetermined value, thereby suppressing the occurrence of chipping, and as a result, the wear resistance is improved.
The research results shown in (a) to (d) above were obtained.

The present invention has been made based on the above research results,
Surface-coated cubic boron nitride-based ultra-high pressure firing with a hard coating layer deposited on the surface of a cutting tool comprising a cubic boron nitride-based high-pressure sintered body having a cubic boron nitride content of 50 to 85% by volume In the cutting tool made of binder material,
The hard coating layer is
(A) Ti satisfying the composition formula having an average layer thickness of 1.5 to 3 μm: [Ti _1-X Al _X ] N (wherein X is 0.30 to 0.60 in atomic ratio) A lower layer composed of a composite nitride layer of Al;
(B) Composition formula: [Ti _1-X Al _X ] N (wherein X is 0.30 to 0.60 in atomic ratio) and a Ti / Al composite nitride layer and Ti nitride ( TiN) layers are alternately laminated with an average layer thickness of 0.03 to 0.3 μm, and the outermost layer has an average film thickness of 0.3 to 2 μm: [Ti _1-X The total average film thickness formed by forming a composite nitride layer of Ti and Al satisfying Al _X ] N (wherein X represents 0.30 to 0.60 in atomic ratio) is 0.5 to 3 μm. With the upper layer,
(C) The surface roughness Ra of the hard coating layer surface is 0.08 to 0.20 μm on the flank and rake face, and 0.07 to 0.10 μm on the honing face,
(D) The residual stress of TiAlN of the hard coating layer is −1 to −2 GPa at the flank and rake face, and −1.5 to −3.0 GPa at the honing part, and the residual stress (flank, rake face) )> Residual stress (honing part),
(E) The nanoindentation hardness when measured with a load of 100 mg of the outermost layer TiAlN is 30 to 38 GPa in the flank and rake face, 33 to 50 GPa in the honing part, and the nanoindentation hardness (flank, Rake face) <Nano-indentation hardness (honing part) Characteristic of cutting tools made of surface-coated cubic boron nitride-based ultra-high pressure sintered material that exhibits long-term peeling resistance and wear resistance It is what has.

Next, in the coated cBN-based sintered tool of the present invention, the reason why the blending 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 will be described.
(A) Composition of the cBN-based sintered material of the cutting tip body When the content of cubic boron nitride exceeds 85% by volume, the sinterability of the boron nitride group itself decreases, and as a result, chipping occurs on the cutting edge. Is likely to occur. On the other hand, when it is less than 50% by volume, desired excellent wear resistance cannot be ensured. Therefore, the content of cubic boron nitride is set to 50 to 85% by volume.

(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 30 atomic%, the high temperature hardness and heat resistance decrease, and as a result, the wear resistance decreases. 30 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 average layer thickness exceeds 3 μm, chipping is likely to occur. Therefore, the average layer thickness was set to 1.5 to 3 μm.

(C) Upper layer of hard coating layer (a) 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 0.30 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 the Ti nitride (TiN) layer has the characteristics (high temperature strength, impact 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. The main purpose is to supplement.
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 cannot be said to be sufficient, and as a result, boundary abnormal damage occurs at the boundary portion 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 resistance strength is alternately arranged 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) Upper layer thin layer A and thin layer B one layer average layer thickness Upper layer thin layer A and thin layer B, each layer average layer thickness is less than 0.03 μm, excellent characteristics of each thin layer As a result, it is impossible to ensure excellent high temperature hardness, high temperature strength and heat resistance in the upper layer, and even better high temperature strength and impact resistance. If the average layer thickness exceeds 0.3 μm, the disadvantages of each thin layer, that is, if it is thin layer A, it is insufficient in high-temperature strength and impact resistance, and if it is thin layer B, it has heat resistance and high-temperature hardness. Insufficient deficiency appears locally in the layer, which causes peeling of the cutting edge and rapid progress of wear. It was determined to be 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 0.03 to 0.03. 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 determined to be 0.03 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 0.03 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.
(D) The outermost layer of the upper layer and its average layer thickness In the coated cBN-based sintered tool of the present invention, the desired wear resistance cannot be obtained when the thickness of the outermost layer TiAlN is less than 0.3 μm. Further, depending on the thickness of the coating layer on the outermost surface, slightly different interference colors may be generated, resulting in uneven tool appearance. In such a case, unevenness of the appearance of the tool can be prevented by thickly depositing a Ti and Al composite nitride (TiAlN) layer as the outermost layer of the upper layer. Further, since it is possible to sufficiently prevent the appearance irregularity if the average layer thickness is up to 2 μm, the average layer thickness of the composite nitride (TiAlN) layer of Ti and Al is determined to be 0.3 to 2 μm.
(E) Total average layer thickness of the upper layer Further, the total average layer thickness of the upper layer (that is, the total thickness of the average layers of the thin layers A and B constituting the alternate laminated structure and the outermost layer) If the average layer thickness is less than 0.5 μm, sufficient heat resistance, high temperature hardness, high temperature strength and impact strength required for high speed cutting of hardened steel such as hardened steel Can not be applied to the upper layer, causing a short tool life, while if the average layer thickness exceeds 3 μm, chipping tends to occur, so the total average layer thickness is 0.5 to 3 μm. It is preferable to do.

(F) Surface roughness Ra of the hard coating layer surface
If the surface roughness Ra of the hard coating layer surface is less than 0.08 μm on the flank and rake surface, it is not preferable because it leads to an increase in manufacturing cost. If the surface roughness Ra exceeds 0.20 μm, the cutting resistance on the coating surface is large. Therefore, the thickness is set to 0.08 to 0.20 μm. Further, in the honing portion, it is not preferable that the thickness is less than 0.07 μm because it leads to an increase in manufacturing cost. If the thickness exceeds 0.10 μm, the cutting resistance of the coating surface increases and chipping is likely to occur. ˜0.10 μm.
(G) Residual stress of TiAlN of hard coating layer The residual stress of TiAlN of the hard coating layer is preferably less than -1 GPa on the flank and rake surface because desired hardness cannot be obtained and wear resistance is reduced. On the other hand, if it exceeds -2 GPa, cracking is likely to occur inside the film or at the interface between the film and the substrate during high-load cutting, and chipping is likely to occur. Therefore, it was set to −1 to −2 GPa. Further, in the honing portion, if it is less than -1.5 GPa, the desired hardness cannot be obtained and the wear resistance is lowered, so that it is not preferable. Cracks occur at the interface and chipping is likely to occur. Therefore, it was set to -1.5 to -3.0 GPa. Further, when the residual stress of the flank and the rake face is smaller than the residual stress of the honing portion, the honing portion is likely to be chipped. Therefore, it was determined that the residual stress (flank, rake face)> residual stress (honing part). By making the residual stress of the flank, rake face and honing part the above relationship, the stress in the honing part generated during cutting can be relieved, and peeling at the honing part where cutting resistance is greatest during cutting can be achieved. Can be suppressed.

(H) Nanoindentation hardness when measured with a load of 100 mg of the outermost layer TiAlN The nanoindentation hardness when measured with a load of 100 mg of the outermost layer of TiAlN is wear-resistant if it is less than 30 GPa on the flank and rake face. It is not preferable because the effect of improving the property cannot be obtained. If it exceeds 38 GPa, the wear resistance is improved, but chipping is likely to occur. Therefore, it was determined as 30 to 38 GPa. Further, in the honing portion, if it is less than 33 GPa, the effect of improving wear resistance is not obtained, which is not preferable. If it exceeds 50 GPa, wear resistance is improved but chipping is likely to occur. Therefore, it was determined as 33 to 50 GPa. Furthermore, since it is 30 to 38 GPa and 33 to 50 GPa, and the nanoindentation hardness of the flank and rake face is larger than the nanoindentation hardness of the honing part, chipping of the honing part is likely to occur. Indentation hardness (flank, rake face) <nanoindentation hardness (honing part). By making the flank, rake face, and nanoindentation hardness of the honing part the above relationship, the impact at the honing part during cutting can be mitigated, and at the honing part where cutting resistance is greatest during cutting. Peeling can be suppressed.

  Here, the nanoindentation method for obtaining the nanoindentation hardness will be described. The nanoindentation method is a kind of hardness test described in detail in the document “Tribologist, Vol. 47, No. 3, (2002) p177-183”. Conventional Knoop hardness measurement method and Vickers hardness measurement method obtain hardness from indentation shape after indentation, but nanoindentation method obtains hardness and Young's modulus from the relationship between load and depth when indenter is indented. Is the method.

  These test methods are shown in FIG. In the conventional hardness measurement methods such as Vickers hardness and Knoop hardness, since measurement is performed by a person using an optical microscope, measurement cannot be performed unless the indentation shape is large. Therefore, as shown in FIG. 3B, the indentation load of the indenter 30 is increased, and the width W of the indentation is increased, so that measurement is unavoidable. However, at this time, since both the coating film 20 and the base material 10 are indented, hardness affected by the base material has been obtained.

  On the other hand, in the present invention, the hardness of only the coating film without the influence of the substrate was determined by the nanoindentation method. Specifically, as shown in FIG. 3A, the indenter 30 is pushed in with a load of 100 mg so as to have a depth of about 1/10 or less of the film thickness of the coating film 20 to remove the influence of the base material 10. To measure the hardness. For example, when measuring the hardness of the outermost layer of 1 μm, the indentation depth is desirably 100 nm or less. In the nanoindentation method, the depth is obtained mechanically, so that high-precision measurement can be performed even at such a small depth. The indenter 30 is pushed in by the maximum pushing depth hmax, and the hardness is calculated from hmax and the load. When the load is removed, the original amount is restored by the amount of elastic deformation, so that the depth of the indentation is shallower than hmax.

  The hardness by the nanoindentation method is affected by the unevenness of the coating film surface, the average particle diameter, the residual stress, and the thickness of the coating film, and therefore varies considerably depending on the situation, unlike the conventional hardness. However, the hardness of the outermost layer of the coated cutting tool by the indentation method is one of the factors affecting the cutting performance.

In the case of a surface treatment technique such as wet blasting, the following conditions may be used.
The blast injection pressure is 0.1 to 0.15 MPa, the injection time is 1 to 5 sec, and this is repeated 3 to 10 times. If the pressure is less than 0.1 MPa, the time is less than 1 sec, or the number of repetitions is 2 times or less, the effect of blasting is weak, and the effect of improving the peel resistance on the flank, rake face and honing part of the hard coating layer cannot be obtained. In addition, when the pressure is greater than 0.15 MPa, the time is longer than 5 sec, and the number of repetitions exceeds 10, the surface roughness, residual stress, nanoindentation hardness on the flank, rake face and honing part of the hard coating layer Therefore, the effect of improving the peel resistance cannot be obtained. In addition, the slurry used for the blasting uses alumina particles, the particle diameter is 220 to 1500, and the slurry concentration is 15 to 60 wt%.

  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 alternately laminated structure of thin layers A and B, and the surface of the hard coating layer. By specifying roughness, residual stress, and nanoindentation hardness for each of the flank, rake face, and honing part, it has excellent heat resistance, high temperature hardness, high temperature strength, and impact resistance strength. High-hardness steel such as hardened steel and bearing steel, etc. under severe conditions such as high-speed continuous cutting or high-speed interrupted cutting that generates high heat and causes intermittent and impact mechanical loads on the cutting edge. Even in the cutting process, the hard coating layer is not peeled off, exhibits excellent wear resistance over a long period of time, and maintains the finished surface accuracy of the work material.

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. (A) is explanatory drawing of the nanoindentation method, (B) is explanatory drawing of the conventional altitude measuring method.

  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 the component compositions corresponding to the target compositions shown in Table 3 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 allowed 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 3 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 alternate lamination of the thin layer A and the thin layer B having the target composition shown in Table 3 along with the layer thickness direction along the layer thickness direction is also shown in Table 3. Vapor deposition is performed with a layer thickness (average layer thickness).
(E) Further, blasting pressure: 0.1 to 0.15 MPa, blasting time: 2 to 5 seconds, number of repetitions: 5 to 10 times, incident angle: 40 to 50 ° with respect to the rake face, particle size: 220 to The present invention coated cBN-based sintered tools 1 to 10 were manufactured by intermittently blasting under No. 1500, slurry concentration: 15 to 60% by mass, and grain type: Al ₂ O ₃ blasting conditions. The blasting conditions are shown in Table 2. By performing such an intermittent blasting process, fatigue does not accumulate inside the film and between each layer of the laminated part, and as a result, the film surface has high smoothness and a hard film in the absence of cracks. By increasing the residual stress of TiAlN, a film with improved hardness can be created. Table 3 shows the surface roughness Ra of the coating surface, the residual stress of TiAlN of the coating, and the nanoindentation hardness when measured with a load of 100 mg of the outermost layer TiAlN for each of the flank, rake face and honing part.

In addition, for comparison purposes, each of the tool bases A to J is ultrasonically cleaned in acetone and dried, and the tool bases A to J are separated from the central axis on the rotary table in the arc ion plating apparatus shown in FIG. It is mounted along the outer periphery at a predetermined distance in the radial direction, 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. ), Each of the upper layer thin layer A and the lower layer forming Ti—Al alloy having a component composition corresponding to the target composition shown in Table 4 is disposed 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 passed 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 4 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 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 along the layer thickness direction is also shown in Table 4 Conventionally coated cBN-based sintered tools 1 to 10 were produced by vapor deposition with a layer thickness (average layer thickness). The hard coating layer of the conventional coated cBN-based sintered tool has a laminated structure of [Ti, Al] N layer and TiN layer. Unlike the present invention product, the surface roughness, residual stress and hardness are controlled. It has not been.

  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 present 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. A high-speed continuous cutting test was performed on the cBN-based sintered tools 1 to 10 under the cutting conditions A to C.
[Cutting conditions A]
Work material: JIS SCM415 carburized quenching material (hardness: HRC61) round bar,
Cutting speed: 295 m / min. ,
Cutting depth: 0.23mm,
Feed: 0.13 mm / rev. ,
Cutting time: 6 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: 270 m / min. ,
Cutting depth: 0.23mm,
Feed: 0.13 m / rev. ,
Cutting time: 6 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: 240 m / min. ,
Cutting depth: 0.23mm,
Feed: 0.13 mm / rev. ,
Cutting time: 6 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 (Raμm) according to JIS B0601-2001) were measured. It was shown to.

  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 alternates between a thin layer A and a thin layer B each having an average layer thickness of 0.03 to 0.3 μm. An upper layer having an average layer thickness (total layer thickness) of 0.5 to 3 μm and an outer layer composed of a [Ti, Al] N layer having a laminated structure and an average layer thickness of 0.3 to 2 μm, and 1.5 to 3 μm The lower layer has an average layer thickness, and the lower layer has excellent heat resistance, high temperature strength and excellent high temperature hardness, and the upper layer has excellent heat resistance, high temperature hardness and higher temperature. Because it has strength and impact strength, it exhibits excellent wear resistance without causing abnormal boundary damage and chipping even in high-speed cutting of hardened steel such as alloy steel and hardened steel of bearing steel, It is possible to ensure excellent finished surface accuracy of the work material. In the conventional coated cBN-based sintered tool, the hard coating layer has a laminated structure of a [Ti, Al] N layer and a TiN layer. Unlike the present invention product, surface roughness, residual stress, hardness As a result, boundary damage and chipping may occur at the cutting edge due to insufficient high-temperature strength and impact strength of the hard coating layer, and maintain the finished surface accuracy of the work material. It is obvious that not only can it be done, but it will reach its service life in a relatively short time.

  As described above, the coated cBN-based sintered tool of the present invention can be used not only for cutting under normal cutting conditions such as various steels and cast iron, but particularly for high-strength materials such as hardened materials of 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.

  The present invention has a hard coating layer with excellent high-temperature hardness, high-temperature strength, and heat resistance, as well as excellent adhesion. Therefore, it is used for high-speed cutting of high-hardness steel such as alloy steel and hardened material of bearing steel. Cutting made of cubic boron nitride-based ultra-high pressure sintered material that provides excellent peel resistance and maintains excellent surface finish accuracy over long-term cutting The present 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 tool substrate.

  Generally, a throw-away tip or a throw-away tip that can be detachably attached to the tip of a cutting tool when turning various work materials such as steel and cast iron is attached to a coated cBN-based sintered tool. In addition, there is known a slow-away end mill that performs cutting in the same manner as a solid type end mill 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 coated cBN-based sintered tool, for example, inserts the cutting tool base into an arc ion plating apparatus which is one type of physical vapor deposition apparatus schematically shown in FIG. For example, a current of 90 A is applied between a cathode electrode (evaporation source) made of metal Ti or a Ti—Al alloy having a predetermined composition and an anode electrode while being heated to 500 ° C. At the same time, an arc discharge is generated and nitrogen gas is introduced into the apparatus as a reaction gas to form a reaction atmosphere of 2 Pa, for example. On the other hand, for example, a bias voltage of −100 V is applied to the cutting tool base. In addition, it is also known that it is manufactured by vapor-depositing a layer having a desired component composition such as a TiN layer or a [Ti, Al] N layer on the surface of the cutting tool base (for example, a patent) Document reference 1). Furthermore, a surface-coated cutting tool is also known in which the wear resistance and fracture resistance are improved by adjusting the surface roughness and residual stress of the hard coating layer formed on the surface of the cutting tool base (for example, Patent Documents). 2).

JP 2007-190668 A JP 2006-263857 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. However, the conventional coated tool does not cause any particular problems 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 interrupted cutting of high-hardness steel having a high hardness of 50 or more Vickers hardness (C scale) such as a hardened material of alloy steel or bearing steel, Since the adhesion strength between the sintered material and the hard coating layer is not sufficient, there is a problem that the cutting edge is peeled off and the cutting life is shortened.

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 in which the hard coating layer exhibits excellent peeling resistance,
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, the 0.30 to 0.60 It has the prescribed heat resistance, high temperature hardness and high temperature strength within the range, 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 the high-speed cutting of high-hardness steel according intermittent and impact to high mechanical loads on the cutting edge, the composite nitride of Ti and _{Al ([Ti 1-X Al} X] N) rigid consisting layer Because the coating layer lacks high-temperature strength, abnormal boundary damage occurs at the boundary of the cutting edge, and this makes it impossible to maintain the finished surface accuracy of the work material, and the service life is relatively short. To reach.

(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 30-60 atomic% of the heat resistance of Al _{(a), [Ti 1-} X Al X] having a high-temperature hardness and predetermined high-temperature strength N (where, in terms of atomic ratio, X 0.30-0.60) 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 resistance strength. Ti nitride (TiN) layers (hereinafter referred to as “thin layer B”) are alternately laminated in a state where each layer has a thin average layer thickness of 0.03 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 peel resistance is improved.
(D) Furthermore, surface treatment techniques such as wet blasting and shot peening treatment are performed on the surface of the hard coating layer, so that the surface roughness, residual stress, The indentation hardness can be set to a predetermined value, thereby suppressing the occurrence of chipping, and as a result, the wear resistance is improved.
The research results shown in (a) to (d) above were obtained.

The present invention has been made based on the above research results,
Surface-coated cubic boron nitride-based ultra-high pressure firing with a hard coating layer deposited on the surface of a cutting tool comprising a cubic boron nitride-based high-pressure sintered body having a cubic boron nitride content of 50 to 85% by volume In the cutting tool made of binder material,
The hard coating layer is
(A) Ti satisfying the composition formula having an average layer thickness of 1.5 to 3 μm: [Ti _1-X Al _X ] N (wherein X is 0.30 to 0.60 in atomic ratio) A lower layer composed of a composite nitride layer of Al;
(B) Composition formula: [Ti _1-X Al _X ] N (wherein X is 0.30 to 0.60 in atomic ratio) and a Ti / Al composite nitride layer and Ti nitride ( TiN) layers are alternately stacked with an average layer thickness of 0.03 to 0.3 μm, and the outermost layer has an average layer thickness of 0.3 to 2 μm : [Ti _1-X The total average layer thickness formed by forming a composite nitride layer of Ti and Al satisfying Al _X ] N (wherein X is 0.30 to 0.60 in atomic ratio) is 0.5 to 3 μm . With the upper layer,
(C) The surface roughness Ra of the hard coating layer surface is 0.08 to 0.20 μm at the flank and rake face, and 0.07 to 0.10 μm at the honing part ,
(D) The residual stress of TiAlN of the hard coating layer is −1 to −2 GPa at the flank and rake face, and −1.5 to −3.0 GPa at the honing part, and the residual stress (flank, rake face) )> Residual stress (honing part),
(E) The nanoindentation hardness when measured with a load of 100 mg of the outermost layer TiAlN is 30 to 38 GPa in the flank and rake face, 33 to 50 GPa in the honing part, and the nanoindentation hardness (flank, Rake face) <Nano-indentation hardness (honing part) Characteristic of cutting tools made of surface-coated cubic boron nitride-based ultra-high pressure sintered material that exhibits long-term peeling resistance and wear resistance It is what has.

Next, in the coated cBN-based sintered tool of the present invention, the reason why the blending 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 will be described.
(A) Composition of the cBN-based sintered material of the cutting tip body When the content of cubic boron nitride exceeds 85% by volume, the sinterability of the boron nitride group itself decreases, and as a result, chipping occurs on the cutting edge. Is likely to occur. On the other hand, when it is less than 50% by volume, desired excellent wear resistance cannot be ensured. Therefore, the content of cubic boron nitride is set to 50 to 85% by volume.

(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 30 atomic%, the high temperature hardness and heat resistance decrease, and as a result, the wear resistance decreases. 30 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 average layer thickness exceeds 3 μm, chipping is likely to occur. Therefore, the average layer thickness was set to 1.5 to 3 μm.

(C) Upper layer of hard coating layer (a) 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 0.30 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 the Ti nitride (TiN) layer has the characteristics (high temperature strength, impact 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. The main purpose is to supplement.
As already described, the upper layer thin layer A is a layer having predetermined heat resistance, high temperature hardness and high temperature strength. However, in the high-speed cutting of high hardness steel with high mechanical load and high mechanical load , The high-temperature strength and impact strength cannot be said to be sufficient, and as a result, boundary abnormal damage occurs at the boundary portion 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 resistance strength is alternately arranged 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) Upper layer thin layer A and thin layer B one layer average layer thickness Upper layer thin layer A and thin layer B, each layer average layer thickness is less than 0.03 μm, excellent characteristics of each thin layer As a result, it is impossible to ensure excellent high temperature hardness, high temperature strength and heat resistance in the upper layer, and even better high temperature strength and impact resistance. If the average layer thickness exceeds 0.3 μm, the disadvantages of each thin layer, that is, if it is thin layer A, it is insufficient in high-temperature strength and impact resistance, and if it is thin layer B, it has heat resistance and high-temperature hardness. Insufficient deficiency appears locally in the layer, which causes peeling of the cutting edge and rapid progress of wear. It was determined to be 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 0.03 to 0.03. 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 determined to be 0.03 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 0.03 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.
(D) The outermost layer of the upper layer and its average layer thickness In the coated cBN-based sintered tool of the present invention, if the layer thickness of the outermost layer TiAlN is less than 0.3 μm, desired wear resistance cannot be obtained. Further, depending on the thickness of the coating layer on the outermost surface, slightly different interference colors may be generated, resulting in uneven tool appearance. In such a case, unevenness of the appearance of the tool can be prevented by thickly depositing a Ti and Al composite nitride (TiAlN) layer as the outermost layer of the upper layer. Further, since it is possible to sufficiently prevent the appearance irregularity if the average layer thickness is up to 2 μm, the average layer thickness of the composite nitride (TiAlN) layer of Ti and Al is determined to be 0.3 to 2 μm.
(E) Total average layer thickness of the upper layer Further, the total average layer thickness of the upper layer (that is, the total thickness of the average layers of the thin layers A and B constituting the alternate laminated structure and the outermost layer) If the average layer thickness is less than 0.5 μm, sufficient heat resistance, high temperature hardness, high temperature strength and impact strength required for high speed cutting of hardened steel such as hardened steel Can not be applied to the upper layer, causing a short tool life, while if the average layer thickness exceeds 3 μm, chipping tends to occur, so the total average layer thickness is 0.5 to 3 μm. It is preferable to do.

(F) Surface roughness Ra of the hard coating layer surface
If the surface roughness Ra of the hard coating layer surface is less than 0.08 μm on the flank and rake surface, it is not preferable because it leads to an increase in manufacturing cost. If the surface roughness Ra exceeds 0.20 μm, the cutting resistance on the coating surface is large. Therefore, the thickness is set to 0.08 to 0.20 μm. Further, in the honing portion, it is not preferable that the thickness is less than 0.07 μm because it leads to an increase in manufacturing cost. If the thickness exceeds 0.10 μm, the cutting resistance of the coating surface increases and chipping is likely to occur. ˜0.10 μm.
(G) Residual stress of TiAlN of hard coating layer The residual stress of TiAlN of the hard coating layer is preferably less than -1 GPa on the flank and rake surface because desired hardness cannot be obtained and wear resistance is reduced. On the other hand, if it exceeds -2 GPa, cracking is likely to occur inside the film or at the interface between the film and the substrate during high-load cutting, and chipping is likely to occur. Therefore, it was set to −1 to −2 GPa. Further, in the honing portion, if it is less than -1.5 GPa, the desired hardness cannot be obtained and the wear resistance is lowered, so that it is not preferable. Cracks occur at the interface and chipping is likely to occur. Therefore, it was set to -1.5 to -3.0 GPa. Further, when the residual stress of the flank and the rake face is smaller than the residual stress of the honing portion, the honing portion is likely to be chipped. Therefore, it was determined that the residual stress (flank, rake face)> residual stress (honing part). By making the residual stress of the flank, rake face and honing part the above relationship, the stress in the honing part generated during cutting can be relieved, and peeling at the honing part where cutting resistance is greatest during cutting can be achieved. Can be suppressed.

(H) Nanoindentation hardness when measured with a load of 100 mg of the outermost layer TiAlN The nanoindentation hardness when measured with a load of 100 mg of the outermost layer of TiAlN is wear-resistant if it is less than 30 GPa on the flank and rake face. It is not preferable because the effect of improving the property cannot be obtained. If it exceeds 38 GPa, the wear resistance is improved, but chipping is likely to occur. Therefore, it was determined as 30 to 38 GPa. Further, in the honing portion, if it is less than 33 GPa, the effect of improving wear resistance is not obtained, which is not preferable. If it exceeds 50 GPa, wear resistance is improved but chipping is likely to occur. Therefore, it was determined as 33 to 50 GPa. Furthermore, since it is 30 to 38 GPa and 33 to 50 GPa, and the nanoindentation hardness of the flank and rake face is larger than the nanoindentation hardness of the honing part, chipping of the honing part is likely to occur. Indentation hardness (flank, rake face) <nanoindentation hardness (honing part). By making the flank, rake face, and nanoindentation hardness of the honing part the above relationship, the impact at the honing part during cutting can be mitigated, and at the honing part where cutting resistance is greatest during cutting. Peeling can be suppressed.

  Here, the nanoindentation method for obtaining the nanoindentation hardness will be described. The nanoindentation method is a kind of hardness test described in detail in the document “Tribologist, Vol. 47, No. 3, (2002) p177-183”. Conventional Knoop hardness measurement method and Vickers hardness measurement method obtain hardness from indentation shape after indentation, but nanoindentation method obtains hardness and Young's modulus from the relationship between load and depth when indenter is indented. Is the method.

  These test methods are shown in FIG. In the conventional hardness measurement methods such as Vickers hardness and Knoop hardness, since measurement is performed by a person using an optical microscope, measurement cannot be performed unless the indentation shape is large. Therefore, as shown in FIG. 3B, the indentation load of the indenter 30 is increased, and the width W of the indentation is increased, so that measurement is unavoidable. However, at this time, since both the coating film 20 and the base material 10 are indented, hardness affected by the base material has been obtained.

On the other hand, in the present invention, the hardness of only the coating film without the influence of the substrate was determined by the nanoindentation method. Specifically, as shown in FIG. 3 (A), the indenter 30 is pushed in with a load of 100 mg so as to have a depth of about 1/10 or less of the layer thickness of the coating film 20 to remove the influence of the base material 10. To measure the hardness. For example, when measuring the hardness of the outermost layer of 1 μm, the indentation depth is desirably 100 nm or less. In the nanoindentation method, the depth is obtained mechanically, so that high-precision measurement can be performed even at such a small depth. The indenter 30 is pushed in by the maximum pushing depth hmax, and the hardness is calculated from hmax and the load. When the load is removed, the original amount is restored by the amount of elastic deformation, so that the depth of the indentation is shallower than hmax.

  The hardness by the nanoindentation method is affected by the unevenness of the coating film surface, the average particle diameter, the residual stress, and the thickness of the coating film, and therefore varies considerably depending on the situation, unlike the conventional hardness. However, the hardness of the outermost layer of the coated cutting tool by the indentation method is one of the factors affecting the cutting performance.

In the case of a surface treatment technique such as wet blasting, the following conditions may be used.
The blast injection pressure is 0.1 to 0.15 MPa, the injection time is 1 to 5 sec, and this is repeated 3 to 10 times. If the pressure is less than 0.1 MPa, the time is less than 1 sec, or the number of repetitions is 2 times or less, the effect of blasting is weak, and the effect of improving the peel resistance on the flank, rake face and honing part of the hard coating layer cannot be obtained. In addition, when the pressure is greater than 0.15 MPa, the time is longer than 5 sec, and the number of repetitions exceeds 10, the surface roughness, residual stress, nanoindentation hardness on the flank, rake face and honing part of the hard coating layer Therefore, the effect of improving the peel resistance cannot be obtained. In addition, the slurry used for the blasting uses alumina particles, the particle diameter is 220 to 1500, and the slurry concentration is 15 to 60 wt%.

  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 alternately laminated structure of thin layers A and B, and the surface of the hard coating layer. By specifying roughness, residual stress, and nanoindentation hardness for each of the flank, rake face, and honing part, it has excellent heat resistance, high temperature hardness, high temperature strength, and impact resistance strength. High-hardness steel such as hardened steel and bearing steel, etc. under severe conditions such as high-speed continuous cutting or high-speed interrupted cutting that generates high heat and causes intermittent and impact mechanical loads on the cutting edge. Even in the cutting process, the hard coating layer is not peeled off, exhibits excellent wear resistance over a long period of time, and maintains the finished surface accuracy of the work material.

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. (A) is explanatory drawing of a nanoindentation method, (B) is explanatory drawing of the conventional hardness measuring method.

  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 the component compositions corresponding to the target compositions shown in Table 3 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 allowed 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 3 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 alternate lamination of the thin layer A and the thin layer B having the target composition shown in Table 3 along with the layer thickness direction along the layer thickness direction is also shown in Table 3. Vapor deposition is performed with a layer thickness (average layer thickness).
(E) Further, blasting pressure: 0.1 to 0.15 MPa, blasting time: 2 to 5 seconds, number of repetitions: 5 to 10 times, incident angle: 40 to 50 ° with respect to the rake face, particle size: 220 to The present invention coated cBN-based sintered tools 1 to 10 were manufactured by intermittently blasting under No. 1500, slurry concentration: 15 to 60% by mass, and grain type: Al ₂ O ₃ blasting conditions. The blasting conditions are shown in Table 2. By performing such an intermittent blasting process, fatigue does not accumulate inside the film and between each layer of the laminated part, and as a result, the film surface has high smoothness and a hard film in the absence of cracks. By increasing the residual stress of TiAlN, a film with improved hardness can be created. Table 3 shows the surface roughness Ra of the coating surface, the residual stress of TiAlN of the coating, and the nanoindentation hardness when measured with a load of 100 mg of the outermost layer TiAlN for each of the flank, rake face and honing part.

For comparison purposes, (a) each of the tool bases A to J is ultrasonically cleaned in acetone and dried, on a rotary table in the arc ion plating apparatus shown in FIG. Attached along the outer peripheral portion at a predetermined distance in the radial direction from the central axis, the upper layer thin layer B forming metal Ti is used as one side cathode electrode (evaporation source), and the other side cathode electrode As the (evaporation source), the upper layer thin layer A and the lower layer forming Ti—Al alloy each having a component composition corresponding to the target composition shown in Table 4 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 passed 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 4 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 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 along the layer thickness direction is also shown in Table 4 Conventionally coated cBN-based sintered tools 1 to 10 were produced by vapor deposition with a layer thickness (average layer thickness). The hard coating layer of the conventional coated cBN-based sintered tool has a laminated structure of [Ti, Al] N layer and TiN layer. Unlike the present invention product, the surface roughness, residual stress and hardness are controlled. It has not been.

  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 present 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. A high-speed continuous cutting test was performed on the cBN-based sintered tools 1 to 10 under the cutting conditions A to C.
[Cutting conditions A]
Work material: JIS SCM415 carburized quenching material (hardness: HRC61) round bar,
Cutting speed: 295 m / min. ,
Cutting depth: 0.23mm,
Feed: 0.13 mm / rev. ,
Cutting time: 6 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: 270 m / min. ,
Cutting depth: 0.23mm,
Feed: 0.13 m / rev. ,
Cutting time: 6 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: 240 m / min. ,
Cutting depth: 0.23mm,
Feed: 0.13 mm / rev. ,
Cutting time: 6 minutes,
Dry continuous high speed cutting test of bearing steel under the conditions of (normal cutting speed is 150 m / min.),
In each of the cutting tests, the flank wear width (mm) of the cutting blade and the finished surface accuracy of the work material (arithmetic average roughness (Raμm) according to JIS B0601-2001) were measured. It was shown to.

  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 alternates between a thin layer A and a thin layer B each having an average layer thickness of 0.03 to 0.3 μm. An upper layer having an average layer thickness (total layer thickness) of 0.5 to 3 μm and an outer layer composed of a [Ti, Al] N layer having a laminated structure and an average layer thickness of 0.3 to 2 μm, and 1.5 to 3 μm The lower layer has an average layer thickness, and the lower layer has excellent heat resistance, high temperature strength and excellent high temperature hardness, and the upper layer has excellent heat resistance, high temperature hardness and higher temperature. Because it has strength and impact strength, it exhibits excellent wear resistance without causing abnormal boundary damage and chipping even in high-speed cutting of hardened steel such as alloy steel and hardened steel of bearing steel, It is possible to ensure excellent finished surface accuracy of the work material. In the conventional coated cBN-based sintered tool, the hard coating layer has a laminated structure of a [Ti, Al] N layer and a TiN layer. Unlike the present invention product, surface roughness, residual stress, hardness As a result, boundary damage and chipping may occur at the cutting edge due to insufficient high-temperature strength and impact strength of the hard coating layer, and maintain the finished surface accuracy of the work material. It is obvious that not only can it be done, but it will reach its service life in a relatively short time.

  As described above, the coated cBN-based sintered tool of the present invention can be used not only for cutting under normal cutting conditions such as various steels and cast iron, but particularly for high-strength materials such as hardened materials of 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 (1)

Surface-coated cubic boron nitride-based ultra-high pressure firing with a hard coating layer deposited on the surface of a cutting tool comprising a cubic boron nitride-based high-pressure sintered body having a cubic boron nitride content of 50 to 85% by volume In the cutting tool made of binder material,
The hard coating layer is
(A) Ti satisfying the composition formula having an average layer thickness of 1.5 to 3 μm: [Ti _1-X Al _X ] N (wherein X is 0.30 to 0.60 in atomic ratio) A lower layer composed of a composite nitride layer of Al;
(B) Composition formula: [Ti _1-X Al _X ] N (wherein X is 0.30 to 0.60 in atomic ratio) and a Ti / Al composite nitride layer and Ti nitride ( TiN) layers are alternately laminated with an average layer thickness of 0.03 to 0.3 μm, and the outermost layer has an average film thickness of 0.3 to 2 μm: [Ti _1-X The total average film thickness formed by forming a composite nitride layer of Ti and Al satisfying Al _X ] N (wherein X represents 0.30 to 0.60 in atomic ratio) is 0.5 to 3 μm. With the upper layer,
(C) The surface roughness Ra of the hard coating layer surface is 0.08 to 0.20 μm on the flank and rake face, and 0.07 to 0.10 μm on the honing face,
(D) The residual stress of TiAlN of the hard coating layer is −1 to −2 GPa in the flank and rake face, and −1.5 to −3.0 GPa in the honing part, and the residual stress (flank and rake face). > Residual stress (honing part),
(E) The nanoindentation hardness when measured with a load of 100 mg of the outermost layer TiAlN is 30 to 38 GPa in the flank and rake face, 33 to 50 GPa in the honing part, and the nanoindentation hardness (flank, Cutting tool made of surface-coated cubic boron nitride-based ultra-high pressure sintered material that exhibits long-term peeling resistance and wear resistance characterized by rake face) <nanoindentation hardness (honing part).