JP4883480B2 - Cutting tool made of surface-coated cubic boron nitride-based ultra-high pressure sintered material that exhibits excellent fracture resistance in high-speed continuous cutting of hard difficult-to-cut materials - Google Patents

Description

  This invention has excellent fracture resistance even when a hard hard material with high hardness that easily welds to the tool surface, such as die steel, bearing steel, and manganese steel, is subjected to high-speed continuous cutting. In addition, a surface-coated cubic boron nitride group in which a hard coating layer is formed on the surface of a cutting tool base made of a cubic boron nitride group ultra-high pressure sintered material that can exhibit stable cutting performance over a long period of time. The present invention relates to a cutting tool made of an ultra-high pressure sintered material (hereinafter referred to as a coated cBN-based sintered tool).

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

  In addition, as a coated cBN-based sintered tool, a hard coating layer 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). However, it is known that a composite nitride ((Cr, Al, Si) N) layer of Cr, Al, and Si is deposited as one of the hard coating layers.

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

  In recent years, FA has been remarkable for cutting devices, but on the other hand, there is a strong demand for labor saving and energy saving and further cost reduction for cutting, and accordingly, cutting is performed at higher speed conditions in addition to normal cutting conditions. Although there is a tendency to require lower cutting, the above-described conventional coated tool does not cause any particular problem when various types of steel and cast iron are cut under normal conditions. However, when this is used for high-speed continuous cutting of hard hard materials with high hardness and high weldability such as die steel, bearing steel, manganese steel, etc. Due to the high heat generated, the work material and the chips are heated to a high temperature, and as a result, the weldability and reactivity to the surface of the hard coating layer further increase, resulting in abnormal damage to the boundary portion of the cutting edge ( Hereinafter, the boundary damage is caused), and this causes the defect resistance to deteriorate and the service life is reached in a relatively short time.

In view of the above, the present inventors have performed high-speed continuous cutting of hard, highly weldable hard difficult-to-cut materials such as die steel, bearing steel, and manganese steel that are easily welded to the tool surface. As a result of conducting research to develop a coated cBN-based sintered tool that exhibits excellent fracture resistance with a hard coating layer,
(a) The composite nitride of Cr, Al, and Si (hereinafter referred to as (Cr _1-XY Al _X Si _Y ) N) constituting the hard coating layer has an Al content ratio X (atomic ratio). When the value is 0.4 to 0.7 and the Si content ratio Y (atomic ratio) is within the range of 0.02 to 0.10, excellent high temperature hardness, heat resistance, high temperature oxidation resistance, Although it has heat-resistant plastic deformation and high-temperature strength, it has the wear resistance required under normal cutting conditions, but in high-speed continuous cutting of hard difficult-to-cut materials with high hardness and high weldability. The work material and the chips are heated to a high temperature by the high heat generated at the cutting edge, and the weldability and reactivity to the surface of the hard coating layer are further increased, while (Cr _1-XY Al _X Si _Y) hard coating layer consisting of N layers lubricity, for adhesion resistance is insufficient, the boundary portion of the cutting edge Edge notching occurs in, and this may cause a defect.

(B) On the other hand, Cr nitride (hereinafter referred to as CrN) layer is not sufficient in high temperature hardness, heat resistance, high temperature oxidation resistance, heat plastic deformation and high temperature strength, but has excellent lubricity and welding resistance. Therefore, it is possible to prevent the work material and chips from welding to the hard coating layer in high-speed continuous cutting of hard, highly weldable hard difficult-to-cut materials with large heat generation. thing.

(C) High-temperature hardness, heat resistance, high-temperature oxidation resistance, and heat-resistant plastic deformability in which the Al content ratio X in (a) is 40 to 70 atomic% and the Si content ratio Y is 2 to 10 atomic%. (Cr _1-XY Al _X Si _Y ) N (however, in atomic ratio, X is 0.4 to 0.7, Y is 0.02 to 0.10) having a high temperature strength (hereinafter referred to as thin Layer A) and the high-temperature hardness, heat resistance, high-temperature oxidation resistance, heat-resistant plastic deformation and high-temperature strength are inferior to those of the thin layer A, but on the other hand, it has excellent lubricity and welding resistance. Cr nitride (CrN) 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. Then, the hard coating layer of this alternately laminated structure has the excellent high temperature hardness, heat resistance, high temperature oxidation resistance, and heat plastic deformation of the thin layer A. As a result, the thin layer B has excellent lubricity and welding resistance, and as a result, the weldability and reactivity of the work material and chips to the hard coating layer are reduced. Occurrence of abnormal damage is prevented and fracture resistance is improved.
The research results shown in (a) to (c) above were obtained.

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

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

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

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

(B) constituting the lower layer of the lower layer hard coating layer of the hard coating layer _{(Cr 1-X-Y Al} X Si Y) Cr component in the N layer maintains the high-temperature strength, Al component high-temperature hardness, heat resistance , improvement of high-temperature oxidation resistance, Si component because it contributes to the improvement of the heat plastic deformation resistance, constituting the lower layer of the hard coating layer _{(Cr 1-X-Y Al} X Si Y) N layer, predetermined A layer with high-temperature strength, high-temperature hardness, heat resistance, high-temperature oxidation resistance, and heat-resistant plastic deformation. Chips such as die steel, bearing steel, and high-manganese steel easily adhere to the tool surface. It basically plays the role of ensuring the wear resistance of the cutting edge during high-speed continuous cutting of hard difficult-to-cut materials. However, if the Al content ratio X exceeds 70 atomic%, the high-temperature oxidation resistance of the lower layer is improved, but the relative decrease in the Cr content ratio makes it difficult to maintain the B1 crystal structure, resulting in wear resistance. On the other hand, when the Al content ratio X is less than 40 atomic%, the high-temperature hardness and heat resistance are decreased, and as a result, the wear resistance is decreased, and the Si content ratio is further decreased. When Y exceeds 10 atomic%, the relative Cr content ratio and Al content ratio decrease, resulting in a decrease in high temperature strength, high temperature hardness, heat resistance, and high temperature oxidation resistance, and a Si content ratio Y of 2 If it is less than atomic%, improvement in heat-resistant plastic deformability due to inclusion of Si cannot be expected, so the value of Al content ratio X is 0.4 to 0.7, and the value of Si content ratio Y is It was determined to be 0.02 to 0.10.
If the average layer thickness of the lower layer is less than 1 μm, the high temperature hardness, heat resistance, high temperature oxidation resistance, high temperature plastic deformation and high temperature strength possessed by itself cannot be imparted to the hard coating layer over a long period of time, and the tool life On the other hand, if the average layer thickness exceeds 3 μm, defects are likely to occur. Therefore, the average layer thickness was set to 1 to 3 μm.

  A thin layer of chromium or titanium nitride (CrN or TiN) is 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. Can be made. The CrN or TiN thin layer is less effective in improving the adhesion when the layer thickness is less than 0.01 μm, while the layer thickness exceeding 0.5 μm cannot be expected to further improve the adhesion. Therefore, the thickness of the CrN or TiN layer interposed between the substrate and the lower layer is preferably 0.01 μm or more and 0.5 μm or less.

(C) Upper layer of hard coating layer (b) Thin layer A of upper layer
(Cr _1-XY Al _X Si _Y ) N layer (however, in atomic ratio, X is 0.4 to 0.7, Y is 0.02 to 0.10) constituting the thin layer A of the upper layer Is a layer that is substantially the same as the lower layer, and has a predetermined high-temperature hardness, heat resistance, high-temperature oxidation resistance, heat-resistant plastic deformability, and high-temperature strength, and is hard to cut easily on the tool surface. It has the effect | action which ensures the abrasion resistance of the cutting-blade part at the time of high-speed continuous cutting.

(B) Thin layer B of the upper layer
The thin layer B made of a CrN layer is an upper layer having an alternately laminated structure in which the thin layer A and the thin layer B are alternately laminated in two to six layers . The main purpose is to supplement the welding resistance.
As already described, the upper layer thin layer A is a layer having a predetermined high-temperature hardness, heat resistance, high-temperature oxidation resistance, heat-resistant plastic deformation and high-temperature strength, but die steel with high heat generation, In high-speed continuous cutting of hard hard-to-cut materials such as bearing steel and manganese steel, the lubricity and welding resistance are insufficient, which causes abnormal boundary damage and defects.
Therefore, the thin layer B composed of the CrN layer having excellent lubricity and welding resistance is arranged alternately with the thin layer A to form an alternate laminated structure, so that the adjacent thin layer A has insufficient lubricity and is resistant to welding. The upper layer as a whole is made up of the thin layer B, and the thin layer A is tangled without any loss of high temperature hardness, heat resistance, high temperature oxidation resistance, heat plastic deformation and high temperature strength. An upper layer having excellent lubricity and welding resistance is formed.
The CrN layer has excellent lubricity and welding resistance, and prevents chip adhesion to the cutting edge in high-speed continuous cutting of hard difficult-to-cut materials with high heat generation. As a result, the cutting edge of the cutting edge It has the effect of preventing the occurrence of abnormal boundary damage and loss occurring at the boundary portion of the.

(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. As a result, the upper layer has excellent high-temperature hardness, heat resistance, high-temperature oxidation resistance, heat-resistant plastic deformation and high-temperature strength, welding resistance, and lubricity. In addition, if the average layer thickness of each layer exceeds 0.3 μm, the disadvantages of each thin layer, that is, if it is thin layer A, welding resistance, lack of lubricity, thin layer B If so, high temperature hardness, heat resistance, high temperature oxidation resistance, heat plastic deformation, and lack of high temperature strength will appear locally in the layer, which may cause abnormal damage to the edge of the cutting edge. Since the wear progresses rapidly, the average layer thickness of each layer is It was defined as .05~0.3μm.
That is, the thin layer B is provided to provide welding resistance and lubricity 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 0.3 μm. If it is within the range, the upper layer composed of an alternate laminated structure in which the thin layer A and the thin layer B are alternately laminated to each other has an excellent high temperature hardness, heat resistance, high temperature oxidation resistance, and heat plastic deformation. It acts as if it had a single layer with high properties, high-temperature strength, excellent welding resistance, and lubricity, but the average layer thickness of each of thin layer A and thin layer B exceeds 0.3 μm. Insufficient adhesion and lubricity of the thin layer A, or lack of high-temperature hardness, high-temperature strength, heat resistance, high-temperature oxidation resistance, and heat-resistant plastic deformability of the thin layer B appears locally in the layer. As a result, 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.
By forming an upper layer having an alternate laminated structure of 2 to 6 layers each having an average layer thickness of the thin layer A and the thin layer B in the range of 0.05 to 0.3 μm on the surface of the lower layer, excellent High hardness, high temperature strength, heat resistance, high temperature oxidation resistance, and heat plastic deformation resistance, as well as a hard coating layer with excellent welding resistance and lubricity, resulting in die steel, bearing steel, manganese In high-speed continuous cutting of hard difficult-to-cut materials such as steel, it is possible to prevent the occurrence of abnormal damage occurring at the boundary portion of the cutting edge of the cutting blade.
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 alternating laminated structure) is less than 0.3 μm, the hard difficult-to-cut material Sufficient high-temperature hardness, high-temperature strength, heat resistance, high-temperature oxidation resistance, heat-resistant plastic deformation and welding resistance, and lubricity required for high-speed continuous cutting cannot be imparted to the upper layer, resulting in tool life On the other hand, if the average layer thickness exceeds 3 μm, defects tend 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 CrN layer or a (Cr, Al, Si) N layer on the outermost surface. At that time, when the average layer thickness of the CrN layer or the (Cr, Al, Si) N layer is less than 0.2 μm, it is not possible to prevent the appearance irregularity, and when the average layer thickness is up to 2 μm, the appearance is uneven. Therefore, the average layer thickness of the CrN layer or the (Cr, Al, Si) N 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 is formed by alternately laminating thin layers A and thin layers B. It has excellent high-temperature hardness, high-temperature strength, heat resistance, high-temperature oxidation resistance, heat-resistant plastic deformation and welding resistance, and lubricity due to its structure, such as die steel, bearing steel, manganese steel, etc. Even hard cutting materials with high hardness that are easy to weld to the tool surface, even under severe conditions such as high-speed continuous cutting with high heat generation, there is no boundary abnormal damage or chipping in the hard coating layer, Excellent wear resistance can be exhibited over a long period of time.

  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 insert body made of a WC-based cemented carbide having a length of 4.76 mm and a side length of 12.7 mm is 26% by mass and Ti is 5%. , Ni: 2.5%, Ag: Brazing using a brazing material of an Ag alloy having the composition consisting of the rest, and after outer periphery processing to a predetermined dimension, the width of the cutting edge is 0.13 mm, angle: 25 ° Finished with honing The tool substrate A~I having the insert shape of ISO standard SNGA120412 by applying an abrasive was prepared, respectively.

(A) Next, each of the tool bases A to I is ultrasonically cleaned in acetone and dried, and then in the 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 Cr is used as the cathode electrode (evaporation source) on one side, and the cathode electrode (evaporation source) on the other side. The upper layer thin layer A and the lower layer forming Cr—Al—Si alloy, each having a component composition corresponding to the target composition shown in Table 2, are placed opposite to each other across the rotary table,
(B) First, while the inside of the apparatus is evacuated and kept at a vacuum of 0.1 Pa or less, the inside of the apparatus is heated to 500 ° C. with a heater, and then Ar gas is introduced to create an atmosphere of 0.7 Pa. A DC bias voltage of −200 V is applied to the tool base that rotates while rotating on the table, and the tool base surface is bombarded with argon ions.
(C) Nitrogen gas is introduced as a reaction gas into the apparatus to form a reaction atmosphere of 3 Pa, a DC bias voltage of −100 V is applied to the tool base rotating while rotating on the rotary table, and the thin layer A current of 100 A is passed between A and the lower layer forming Cr—Al—Si alloy and the anode electrode to generate an arc discharge, and the target composition and target layer thickness shown in Table 2 are formed on the surface of the tool base. (Cr, Al, Si) N layer is deposited as a lower layer of the hard coating layer,
(D) Next, the flow rate of nitrogen gas as a reaction gas introduced into the apparatus is adjusted to obtain a reaction atmosphere of 2 Pa, and within a range of −10 to −100 V on the tool base that rotates while rotating on the rotary table. In a state where a predetermined DC bias voltage is applied, a predetermined current in a range of 50 to 200 A is passed between the cathode electrode and the anode electrode of the thin layer B forming metal Cr to generate an arc discharge, A thin layer B having a predetermined layer thickness is formed on the surface of the tool base, and after the thin layer B is formed, arc discharge is stopped. Instead, a cathode of Cr-Al-Si alloy for forming the thin layer A and the lower layer Similarly, a predetermined current in the range of 50 to 200 A is passed between the electrode and the anode electrode to generate arc discharge to form a thin layer A having a predetermined layer thickness. Then, the arc discharge is stopped and the thin layer B is again formed. Of forming metal Cr The formation of the thin layer B by arc discharge between the sword electrode and the anode electrode and the formation of the thin layer A by arc discharge between the cathode electrode and the anode electrode of the Cr-Al-Si alloy for forming the thin layer A and the lower layer are alternately performed. Table 2 shows the upper layer composed of the alternate lamination of the thin layer A and the thin layer B having the target composition and the single target layer thickness along the layer thickness direction on the surface of the tool base. The present invention-coated cBN-based sintered tools 1 to 9 were produced by vapor deposition with the total layer thickness (average layer thickness) shown.

For comparison purposes, each of the above tool bases A to I is ultrasonically cleaned in acetone and dried, and then charged into the ordinary arc ion plating apparatus shown in FIG. As the (evaporation source), a Cr—Al—Si alloy having a component composition corresponding to the target composition shown in Table 3 is mounted, and first, the apparatus is evacuated and kept at a vacuum of 0.1 Pa or less. After heating the interior of the apparatus to 500 ° C. with a heater, Ar gas was introduced to create an atmosphere of 0.7 Pa, and a DC bias voltage of −200 V was applied to the tool base rotating while rotating on the table. Then, the surface of the tool base is bombarded with argon ions, and then nitrogen gas is introduced into the apparatus as a reaction gas to make a reaction atmosphere of 3 Pa and applied to the tool base. Lower the bias voltage to -100 V, the Cr-Al-Si to generate arc discharge between the cathode electrode and the anode electrode of the alloy, with each of the surface of the tool substrate A to I, shown in Table 3 Conventionally coated cBN-based sintered tools 1 to 9 were respectively produced by vapor-depositing a hard coating layer composed of a (Cr, Al, Si) N layer having a target composition and a target layer thickness.

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

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

Next, according to the present invention, the coated cBN-based sintered tools 1 to 9 and the conventional coated cBN-based sintered tools, in a state where all of the above-mentioned coated cBN-based sintered tools are screwed to the tip of the tool steel tool with a fixing jig. About the cBN base sintered tools 1-9 , the high-speed continuous cutting test was implemented on the cutting conditions ac shown below.
[Cutting conditions a]
Work material: JIS · SKD61 (hardness: HRC61) round bar,
Cutting speed: 260 m / min. ,
Cutting depth: 0.10mm,
Feed: 0.05 mm / rev. ,
Cutting time: 6 minutes,
Die steel dry high-speed continuous cutting test under normal conditions (normal cutting speed is 160 m / min.),
[Cutting conditions b]
Work material: JIS / SUJ2 (Hardness: HRC61) round bar,
Cutting speed: 260 m / min. ,
Cutting depth: 0.12mm,
Feed: 0.11 mm / rev. ,
Cutting time: 8 minutes,
Dry high-speed continuous cutting test of bearing steel under the conditions of (normal cutting speed is 160 m / min.),
[Cutting conditions c]
Work material: JIS · SMnC443 (hardness: HRC60) round bar,
Cutting speed: 255 m / min. ,
Cutting depth: 0.12mm,
Feed: 0.07 mm / rev. ,
Cutting time: 8 minutes,
Dry high-speed continuous cutting test of manganese chromium steel under the conditions (normal cutting speed is 160 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. It is shown in Table 4.

From the results shown in Table 2-4, the present invention coated cBN-based sintered tool are both hard coating layer, and a further thin layer A of 0.05~0.3μm average layer thickness is respectively thin layer B the average layer thickness (total layer thickness) 0.3 to 3 m upper layer with alternating multilayer structure obtained by stacking the 2-6 layers alternately, consists of a lower layer having an average layer thickness of 1 to 3 [mu] m, the lower layer It has excellent high-temperature strength and excellent high-temperature hardness, heat resistance, high-temperature oxidation resistance, and heat-resistant plastic deformation, and the upper layer has excellent high-temperature strength, high-temperature hardness, heat resistance, high-temperature oxidation resistance, In addition to heat-resistant plastic deformation, it has excellent lubricity and welding resistance, so high-speed continuous hard hard-to-cut materials that are easy to weld to the tool surface, such as die steel, bearing steel, manganese steel, etc. Even during cutting, the hard coating layer has no abnormal boundary damage or chipping, Conventionally, the hard coating layer consists of a single (Cr, Al, Si) N layer, while exhibiting excellent wear resistance and ensuring the finished surface accuracy of the work material. The coated cBN-based sintered tool not only cannot maintain the finished surface accuracy of the work material due to abnormal boundary damage and chipping at the cutting edge, especially due to the lack of lubricity and welding resistance 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 can be used not only for cutting under normal cutting conditions such as various steels and cast iron, but particularly for die steel, bearing steel, manganese steel, Even in high-speed continuous cutting of hard, hard, difficult-to-cut materials that are easily welded to the tool surface, the hard coating layer exhibits excellent boundary abnormal damage resistance and fracture resistance, and excellent work surface finish accuracy. That can maintain a high degree of wear resistance and also exhibits excellent wear resistance, so that it can sufficiently satisfy cutting equipment performance, labor saving and energy saving, and cost reduction. It is.

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

Claims (1)

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