JP5418833B2 - Cutting tool made of surface coated cubic boron nitride based ultra high pressure sintered material - Google Patents

Description

  This invention has excellent welding resistance, chipping resistance, and abrasion resistance even when high-hardness materials such as hardened materials of alloy tool steel and bearing steel are subjected to high-speed intermittent cutting. Surface-coated cubic boron nitride-based ultra-high-pressure sintering with a hard coating layer formed on the surface of a cutting tool base made of cubic boron nitride-based ultra-high-pressure sintered material that can exhibit stable cutting performance The present invention relates to a material cutting tool (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.

  Further, as a coated cBN-based sintered tool, for example, as shown in Patent Document 1, a tool body made of a cubic boron nitride-based ultrahigh pressure sintered material (hereinafter referred to as a cBN-based sintered material) is used. A coated cBN-based sintered tool is known which is formed by vapor-depositing a surface coating layer such as a TiN layer or a Ti / Al composite nitride (hereinafter referred to as TiAlN) layer on the surface. It is known that it is used for cutting of cast iron and the like.

In these coated cBN-based sintered tools, various improvements have been made in order to enhance the cutting performance.
For example, in Patent Document 2, a cutting blade having a honing surface is formed between a rake surface and a flank surface of a tool base, and a hard coating layer is formed on the rake surface, the honing surface, and the flank surface. In the coated cBN-based sintered tool, the layer thickness of the hard coating layer on the honing surface is set on the other honing surface at the ridge line portion between the honing surface and at least one of the rake surface and the flank surface. It is known that by making it smaller than the portion, peeling of the hard film of the coated cBN-based sintered tool is prevented and its wear resistance is improved.

JP 2008-302438 A JP 2004-17174 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, in the conventional cBN-based sintered tool, there is no particular problem when various steels and cast irons are cut under normal conditions. When used for high-speed intermittent cutting of hard materials such as alloy tool steel and bearing steel quenching materials, the work material and chips are heated to high temperatures due to the high heat generated at the cutting edge. The edge of the blade tends to be welded to the work material, and the cutting blade is subjected to high impact loads intermittently. The current situation is that the service life is reached in time.

In view of the above, the inventors of the present invention have excellent welding resistance with a hard coating layer in high-speed intermittent cutting of hard materials such as hardened materials of alloy tool steel and bearing steel. In order to develop a coated cBN-based sintered tool that exhibits excellent chipping resistance and wear resistance, the following findings were obtained as a result of research on both the material and structure of the hard coating layer.
First, from the surface of the material of the hard coating layer, as shown in Patent Document 1,
(B) Lower layer of hard coating layer
Composition formula: (Ti _1-X Al _X ) N
And a TiAlN layer having an average layer thickness of 0.5 to 4 μm where X is 0.3 to 0.6 (however, atomic ratio),
(B) The upper layer of the hard coating layer is configured as an alternately laminated structure of thin layers A and B each having an average layer thickness of 0.03 to 0.3 μm, and
Thin layer A
Composition formula: (Ti _1-X Al _X ) N
In the case of TiAlN layer where X is 0.3 to 0.6 (however, atomic ratio),
When the thin layer B is composed of a TiN layer,
In high-speed cutting of hard materials such as hardened materials of alloy tool steel and bearing steel, it is possible to prevent the occurrence of abnormal boundary damage and chipping to a certain extent.
However, in the high-speed intermittent cutting process in which a shocking high load acts intermittently on the cutting edge, the coated cBN-based sintered tool disclosed in Patent Document 1 prevents the occurrence of abnormal boundary damage and defects. Is not fully satisfactory.

  Therefore, the present inventors have further researched from the viewpoint of the structure of the coating layer, and in the upper layer structure composed of the alternately laminated structure shown in Patent Document 1, other than the ridge line portion between the honing surface and the flank surface. The outermost layer of the region is composed of a TiAlN layer having the same composition as that of the thin layer A, and the layer thickness is 0.1 to 0.8 μm. On the other hand, in the ridge line portion between the honing surface and the flank surface, the thin layer A ( By exposing the alternately laminated cross section of TiAlN layer) and thin layer B (TiN layer), it is possible to further improve the welding resistance, and to improve the chipping resistance and wear resistance. They found that a tool could be obtained.

This invention has been made based on the above findings,
“Surface-coated cubic nitriding in which a hard coating layer consisting of a lower layer and an upper layer is deposited on the surface of a tool substrate made of a cubic boron nitride-based ultrahigh pressure sintered material containing 50 to 85 volume% of cubic boron nitride. In a cutting tool made of boron-based ultra-high pressure sintered material,
(A) The tool base has a honing shape in which the honing width is 0.03 to 0.3 mm when viewed from the rake face direction, and the honing angle is in the range of 10 to 35 degrees with respect to the rake face.
(B) The lower layer of the hard coating layer is
Composition formula: (Ti _1-X Al _X ) N
X is 0.3 to 0.6 (provided that the atomic ratio) is composed of a composite nitride layer of Ti and Al having an average layer thickness of 0.5 to 4 μm,
(C) The upper layer of the hard coating layer is composed of an alternating laminated structure of thin layers A and B each having an average layer thickness of 0.03 to 0.3 μm,
The thin layer A is a composite nitride layer of Ti and Al,
The thin layer B is a Ti nitride layer,
(D) The outermost layer of the upper layer is composed of a composite nitride layer of Ti and Al having an average layer thickness of 0.1 to 0.8 μm except for the ridge line portion between the honing surface and the flank surface. The surface-coated cubic boron nitride group is characterized in that the outermost layer does not exist at the ridge line portion between the face and the flank face, and the alternately laminated sectional structure of the thin layer A and the thin layer B is exposed. Cutting tool made of ultra-high pressure sintered material (coated cBN-based sintered tool). "
It has the characteristics.

  Next, the coated cBN-based sintered tool of the present invention will be described in detail.

(A) cBN-based sintered material:
The cBN in the tool base made of an ultra-high pressure sintered material is extremely hard and forms a dispersed phase in the sintered material, and this dispersed phase can improve the wear resistance, but if the blending ratio is too small, it is desirable. However, if the blending ratio is too large, the sinterability of the cBN base material itself is lowered, and as a result, the cutting blade tends to be damaged. The mixing ratio is set to 50 to 85% by volume.
The cBN-based sintered material contains, for example, a Ti compound, Al and / or Al ₂ O ₃ , WC, etc. as components, but in the present invention, these contents are particularly limited. is not.
However, for example, for a Ti compound (one or more selected from TiN, TiCN and TiC), the effect of improving the sinterability and improving the strength by forming a continuous phase in the sintered body. However, if the blending ratio is too small, the desired strength cannot be ensured. On the other hand, if the blending ratio is too large, the cBN content is relatively small, and rake face wear tends to occur. Therefore, it is desirable to determine the blending amount from these viewpoints.
Further, Al and / or Al ₂ O ₃ preferentially aggregates on the surface of the cBN powder during the sintering, reacts to form a reaction product, and forms a continuous phase in the sintered cBN-based material. The reaction product is firmly attached to both the Ti compound phase forming the continuous phase and the cBN phase forming the hard dispersed phase. Since it has the property of bonding, the adhesion of the cBN phase to the Ti compound phase, which is the continuous bonding phase, is remarkably improved, and the chipping resistance of the cutting edge is improved. Since the amount decreases and rake face wear or the like tends to occur, it is necessary to determine the blending amount from these viewpoints.
Furthermore, for WC, a boride of W is generated in the vicinity of the cBN particles, and the generation of TiB ₂ is suppressed, which contributes to the improvement of chipping resistance. However, if the WC content is excessive, the WC component remains. On the other hand, since the chipping resistance is lowered, it is desirable that the blending ratio of WC is small.

(B) Honing shape:
As shown in FIG. 1, the honing shape of the tool body made of the cBN-based sintered material of the present invention is such that the honing width is 0.03 to 0.3 mm when viewed from the rake face direction, and the honing angle is the rake face. The angle is in the range of 10 to 35 degrees.
This is a shape for ensuring the strength of the cutting edge. When the honing angle is 10 degrees or less, the cutting edge strength cannot be maintained. When the honing angle is 35 degrees or more, the rake angle at the time of cutting becomes too negative and the sharpness becomes sharp. descend. In addition, when the honing width is less than 0.03 mm, the strength of the blade edge cannot be ensured, and when it exceeds 0.3 mm, the resistance of the blade edge increases and the sharpness decreases.

(C) The lower layer of the hard coating layer:
The Ti component in the TiAlN layer constituting the lower layer of the hard coating layer maintains the high temperature strength, and the Al component contributes to the improvement of the high temperature hardness and the oxidation resistance. Therefore, the lower layer of the hard coating layer is formed (Ti _{1− X} Al X) _N layer, a predetermined high-temperature strength, a layer having a high-temperature hardness and oxidation resistance, switching at a high speed interrupted cutting of high-hardness material such as hardened material of an alloy tool steel or bearing steel Basically plays the role of ensuring the wear resistance of the blade. However, if the Al content ratio X exceeds 60 atomic%, the high-temperature strength decreases due to a change in the crystal structure, and defects tend to occur. On the other hand, if the Al content ratio X is less than 30 atomic%, Since the oxidation resistance is lowered, and as a result, the wear resistance is lowered, the value of the Al content ratio X is set to 0.3 to 0.6.
Moreover, if the average layer thickness of the lower layer is less than 0.5 μm, the oxidation 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 4 μm, defects are likely to occur. Therefore, the average layer thickness was set to 0.5 to 4 μm.

  A thin layer of TiN can be interposed between the base and the lower layer in order to ensure sufficient adhesion between the cutting tool base made of the ultra-high pressure sintered material and the lower layer. The layer thickness is preferably 0.01 μm or more and 0.5 μm or less.

(D) Upper layer of hard coating layer:
Upper layer A:
The TiAlN layer constituting the thin layer A of the upper layer is composed of the thin layer A and the thin layer B, thereby forming a thin layer B without impairing the toughness and impact resistance of the thin layer B. Complements the properties (high temperature hardness, high temperature strength, oxidation resistance) that are lacking in
In addition, in constructing the alternate laminated structure, the wear resistance that can withstand high-speed intermittent cutting of high-hardness steel by configuring the outermost layer of the upper layer with a TiAlN layer for the portions other than the honing portion (mainly the flank). Secure.
(The layer structure of the honing part will be described later.)
And the TiAlN layer which comprises the thin layer A is
Composition formula: When represented by a (Ti _1-X Al _X ) N layer, as in the case of the lower layer (TiAlN layer represented by a composition formula (Ti _1-X Al _X ) N), excellent high-temperature hardness, In order to provide high-temperature strength and oxidation resistance, and to complement the properties lacking in the thin layer B, the value of X was set to 0.3 to 0.6.
In addition, since the material which comprises the lower layer of the hard coating layer and the thin layer A is a material of the same component system, for example, when forming a film by arc ion plating which is physical vapor deposition, a single type of target is used. When the lower layer (the TiAlN layer) and the thin layer A (the TiAlN layer) are formed, a TiAlN layer having the same composition is formed. However, the TiAlN layer of the lower layer and the TiAlN layer of the thin layer A do not necessarily have the same composition, and when performing physical vapor deposition, for example, when a plurality of targets having different compositions are used, the lower layer And in the thin layer A, TiAlN layers having different compositions are formed. In either case, the content ratio (atomic ratio) of X in the total amount with Ti is within the range of 0.3 to 0.6. If it exists, there will be no inconvenience in the characteristics of the hard coating layer.
In addition, as described later, the upper layer thin layer B is a layer having predetermined toughness and impact resistance, and suppresses the occurrence of abnormal boundary damage and defects during high-speed intermittent cutting of a high-hardness material. On the other hand, wear resistance tends to decrease due to lack of high-temperature hardness, so that the thin layers A having excellent high-temperature hardness, high-temperature strength, and oxidation resistance are alternately laminated with the thin layers B. By supplementing the shortage of high temperature hardness, and without deteriorating the properties of the thin layer B, as a whole upper layer consisting of an alternating laminated structure, excellent high temperature hardness, toughness, impact resistance is ensured, If the average layer thickness of the thin layer A is less than 0.03 μm, the decrease in high-temperature hardness of the TiN layer cannot be compensated. On the other hand, if the average layer thickness exceeds 0.3 μm, chipping tends to occur. Therefore, the average layer thickness of the thin layer A is 0.03 to 0.3 μm. It was defined as.

Top layer thin layer B:
Since the TiN layer constituting the thin layer B of the upper layer has predetermined toughness and impact resistance, it prevents the occurrence of abnormal boundary damage and chipping in the hard coating layer in high-speed intermittent cutting of a hard material. However, if the average layer thickness is less than 0.03 μm, the above-mentioned excellent characteristics cannot be sufficiently exhibited. On the other hand, if the average layer thickness exceeds 0.3 μm, the upper layer is hardened at high temperature. Therefore, the average layer thickness of the thin layer B is determined to be 0.03 to 0.3 μm.

(E) Average layer thickness of the upper layer on surfaces other than the honing surface (rake surface, flank surface):
The upper layer composed of the alternating layered structure of thin layers A and B on the surface other than the honing surface (rake surface, flank surface), when the total average layer thickness is less than 0.8 μm, high-speed intermittent cutting of a hard material Sufficient toughness and impact resistance required for processing cannot be exhibited. On the other hand, if the average layer thickness exceeds 3 μm, defects tend to occur. Desirably, the outermost layer of the upper layer composed of an alternately laminated structure is preferably composed of a TiAlN layer having excellent wear resistance. When the average layer thickness is less than 0.1 μm, the wear resistance is exhibited. On the other hand, if the average layer thickness exceeds 0.8 μm, defects are likely to occur. Therefore, the average layer thickness is preferably 0.1 to 0.8 μm.

(F) Upper layer on the honing surface:
In the center of the honing surface of the honing portion, the average layer thickness of the TiAlN layer constituting the outermost layer of the upper layer is 0.1 to 0.8 μm, preferably 0.1 to 0.5 μm. At the ridge line with the surface, as shown in FIG. 2, the outermost layer is removed, and the alternately laminated sectional structure of the thin layers A and B is exposed.
Further, as a method of removing the outermost layer at the ridge line portion between the honing surface and the flank surface and forming the alternately laminated cross-sectional structure of the thin layer A and the thin layer B, for example, 43 to 47 ° with respect to the rake surface It can be formed by performing wet blasting on the upper layer at an inclination angle, removing the outermost layer at the ridge line portion of the honing surface and the flank surface, and exposing the alternately laminated sectional structure of the thin layer A and the thin layer B. .
The present invention is characterized by the upper layer structure in the cutting edge portion and the honing portion, and in particular, the wear resistance is ensured by using the TiAlN layer having high wear resistance as the outermost layer at the center and the flank face. In the ridge line portion between the honing surface and the flank surface, the strength of the hard coating layer of the cutting edge is increased by exposing the alternately laminated cross-sectional structure of the thin layer A and the thin layer B, and the hard edge from the cutting edge is hardened. Suppresses film peeling.
And, with such a layer structure, high-speed intermittent cutting of high-hardness materials such as hardened materials of alloy tool steel and bearing steel generates high heat at the cutting edge, and impact and intermittent high load are applied to the cutting edge. Even if it acts, it is possible to prevent the occurrence of welding at the ridge line portion between the honing surface and the flank surface and the peeling of the hard coating layer, and to ensure sufficient wear resistance.

  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 made of an alternately laminated structure of a thin layer A and a thin layer B. For the part, the thickness of the TiAlN layer that constitutes the outermost layer of the upper layer is appropriately secured at the center of the honing surface, while the outermost TiAlN layer is removed at the ridge line portion between the honing surface and the flank surface. In addition, by exposing the alternately laminated cross-sectional structure of the thin layer A and the thin layer B, the ridge line portion between the honing surface and the flank surface is particularly strong, and other portions (rake surface, flank surface) are sufficient. High-speed interrupted cutting, in which hard and hard materials such as hardened alloy tool steel and bearing steel are subjected to shock and intermittent high load on the cutting edge as heat is generated. Even under severe cutting conditions The welded hard layer, edge notching, no occurrence of defects, a long time, and can exhibit excellent wear resistance.

The schematic sectional drawing of the honing part vicinity of the covering cBN group sintered tool of this invention is shown. In the ridgeline part of the honing surface and flank of the coated cBN-based sintered tool of the present invention, a schematic explanatory view showing the alternately laminated cross-sectional structure of the thin layers A and B exposed is shown.

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

As raw material powders, cBN powder, TiN powder, TiCN powder, TiC powder, Al powder, Al ₂ O ₃ powder, and WC powder each having an average particle diameter in the range of 0.5 to 4 μm are prepared. Were mixed in the composition shown in Table 1, wet mixed with a ball mill for 80 hours, dried, and then pressed into a green compact having a diameter of 50 mm × thickness: 1.5 mm under a pressure of 120 MPa. Then, the green compact is sintered in a vacuum atmosphere at a pressure of 1 Pa at a predetermined temperature in the range of 900 to 1300 ° C. for 60 minutes to obtain a presintered body for a cutting edge piece. In a state in which the ligated body is superposed on a separately prepared WC-based cemented carbide support piece having a size of Co: 8% by mass, WC: remaining composition, and diameter: 50 mm × thickness: 2 mm. The ultra-high pressure sintering equipment of The pressure is 4 GPa, the temperature is 1200 to 1400 ° C., the holding time is 0.8 hours, and the upper and lower surfaces are polished with a diamond grindstone after sintering. Then, it is divided into a regular triangle shape with a side of 3 mm by a wire electric discharge machine, and further Co: 5 mass%, TaC: 5 mass%, WC: remaining composition and shape of CIS standard SNGA120212 (thickness: 4.76 mm × one side) Cu: 26%, Ti: 5%, Ni: 2.5% in the brazing part (corner part) of the WC-base cemented carbide insert body having a length of 12.7 mm square) , Ag: After brazing with a brazing material of Ag alloy having the remaining composition, processing the outer periphery to a predetermined dimension, 0.2 mm chamfer honing is applied to the cutting edge, and the edge line of the cutting edge is further diamond By brush The tool bases A to J having the insert shape of ISO standard SNGA12041 were manufactured by finishing polishing.

(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. And a thin layer A forming Ti having a component composition corresponding to the target composition shown in Table 2 as a cathode electrode (evaporation source) on one side at a predetermined distance away from the outer periphery. -Al alloy and the other side cathode electrode (evaporation source), the upper layer thin layer B forming metal Ti is placed opposite to the rotary table (not shown in FIG. When the layer and the thin layer A have different compositions, two types of cathode electrodes (evaporation source) of the Ti-Al alloy for forming the lower layer and the Ti-Al alloy for forming the thin layer A are arranged)
(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 rotating tool base while rotating on the rotary table, and a lower layer is formed. An arc discharge is generated by flowing a current of 100 A between the Ti-Al alloy and the anode electrode, so that the target composition and target layer thickness (Ti _1-X Al) shown in Table 2 are formed on the surface of the tool base. _X ) depositing the N layer 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. With a predetermined DC bias voltage applied, a predetermined current within a range of 100 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, After forming a thin layer B composed of a TiN layer having a predetermined layer thickness on the surface of the tool base,
(E) Next, in a nitrogen gas reaction atmosphere of 2 Pa, arc discharge is generated by applying a predetermined current within the range of 100 to 200 A between the cathode electrode and the anode electrode of the Ti-Al alloy for forming the thin layer A. After forming the thin layer A composed of the (Ti _1-X Al _X ) N layer having the target composition and the target layer thickness,
(F) The above steps (d) and (e) are repeated alternately until the predetermined upper layer total layer thickness is reached. Finally, the outermost layer composed of the (Ti _1-X Al _X ) N layer is formed with the predetermined layer thickness. An upper layer (although the upper layer of the target composition shown in Table 2 along with the target composition and the alternate layer of the thin layer A and the thin layer B having a single target layer thickness) is formed on the surface of the tool base. The outermost layer was composed of a TiAlN layer) and was formed by vapor deposition with the total thickness of the upper layer shown in Table 2.

  Next, the tool base on which the hard coating layer composed of the lower layer and the upper layer was formed by vapor deposition was applied to the hard coating layer at a tilt angle of 43 to 47 ° with respect to the rake face (media: alumina particles (particle size 20 μm ), Blasting pressure: 0.1 MPa, blasting time: 10 sec, insert rotation speed: 60 rpm), and removing the outermost layer at the ridge line portion between the honing surface and the flank surface. By exposing and forming the alternately laminated cross-sectional structure of the layer B, the present invention coated cBN-based sintered tools 1 to 10 shown in Table 2 were produced.

For the purpose of comparison, conventional coated cBN-based sintered tools 1 to 10 in which hard coating layers similar to those of the present coated cBN-based sintered tools 1 to 10 are formed on the respective tool bases A to J are manufactured. did.
That is, in the conventional coated cBN-based sintered tools 1 to 10, wet blasting is not performed, and the layer thickness of the hard coating layer is the same for any of the flank, rake, and honing surfaces, The thin layer A and the thin layer B are positively and alternately laminated at any place, and there is no place where the alternately laminated cross-sectional structure is exposed.

For reference, a hard coating layer having a structure described in Patent Document 2 was formed using the tool bases A and B.
That is, for the tool base A, a reference coated cBN-based sintered tool 1 is produced in which a single layer of TiN layer is coated with a layer thickness of 3 μm and wet blasting is performed on the ridgeline portions of the honing surface and the flank surface. did.
Further, for the tool base B, a single layer of TiAlN (Ti 50 atomic% -Al 50 atomic%) layer was coated with a layer thickness of 3 μm, and wet blasting was performed on the ridge line portions of the honing surface and the flank surface. A reference coated cBN-based sintered tool 2 was produced.

  About the surface coating layer of each coated cBN-based sintered tool produced above, the composition was measured by energy dispersive X-ray analysis using a transmission electron microscope. Moreover, when the average layer thickness was cross-sectional 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, the above-mentioned various coated cBN-based sintered tools are screwed to the tip of the tool steel tool with a fixing jig, and the present coated cBN-based sintered tools 1 to 10, the conventional coated The cBN-based sintered tools 1 to 10 and the reference coated cBN-based sintered tools 1 and 2 were subjected to a high-speed intermittent cutting test under the following cutting conditions A to C.
[Cutting conditions A]
Work material: JIS SCM420 (Hardness: HRC60) lengthwise equidistantly 4 round bars with vertical grooves,
Cutting speed: 250 m / min. ,
Cutting depth: 0.2 mm,
Feed: 0.11 mm / rev. ,
Cutting time: 8 minutes,
Dry high-speed intermittent cutting test of carburized and quenched alloy steel under the conditions of (normal cutting speed is 120 m / min.),
[Cutting conditions B]
Work material: JIS · SCr420 (Hardness: HRC61) lengthwise equidistant four round grooved round bars,
Cutting speed: 270 m / min. ,
Cutting depth: 0.16 mm,
Feed: 0.10 mm / rev. ,
Cutting time: 8 minutes,
Dry high-speed intermittent cutting test of carburized and quenched chrome steel under the conditions of (normal cutting speed is 120 m / min.),
[Cutting conditions C]
Work material: JIS / SUJ2 (Hardness: HRC61) lengthwise equidistant four round grooved round bars,
Cutting speed: 260 m / min. ,
Cutting depth: 0.20 mm,
Feed: 0.11 mm / rev. ,
Cutting time: 8 minutes,
Dry high-speed intermittent cutting test of hardened bearing steel under the conditions of (normal cutting speed is 120 m / min.),
And the flank wear width (mm) of the cutting edge in each said cutting test was measured. The measurement results are shown in Table 4.

From the results shown in Tables 2 to 4, in the coated cBN-based sintered tool of the present invention, the hard coating layer is composed of an alternately laminated structure of the lower layer, the thin layer A, and the thin layer B, and in particular, the honing surface In the ridge line between the flank and the flank, the outermost layer does not exist, and the alternately laminated cross-sectional structure of the thin layer A and the thin layer B is exposed, so that the hard coating layer has excellent overall high-temperature strength and high temperature. In addition to hardness, oxidation resistance, toughness and impact resistance, the ridgeline between the honing surface and the flank surface has particularly excellent welding resistance and strength. Even when used for high-speed intermittent cutting of hardened materials such as hardened materials, there is no peeling or abnormal boundary damage on the hard coating layer from the cutting edge, and excellent wear resistance over a long period of time To demonstrate.
On the other hand, a conventional coated cBN-based sintered tool in which the alternately laminated cross-sectional structure is not exposed at the ridge line portion between the honing surface and the flank surface, or a hard coating layer is formed at the ridge line portion between the honing surface and the flank surface. In the reference coated cBN-based sintered tool that is a layer and the alternating laminated film is not exposed, due to welding of the hard coating layer, toughness, insufficient impact resistance, etc., peeling or abnormal boundary damage occurs on the cutting edge, 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 has high hardness such as hardened material of alloy tool steel and bearing steel, as well as cutting under normal cutting conditions such as various steels and cast iron. Even in high-speed intermittent cutting of materials, the hard coating layer has excellent welding resistance and strength especially at the ridgeline between the honing surface and the flank surface, so it exhibits excellent cutting performance over a long period of time. Therefore, it is possible to satisfactorily meet the demands for higher performance of the cutting device, labor saving and energy saving of the cutting, and cost reduction.

Claims (1)

Surface-coated cubic boron nitride formed by vapor-depositing a hard coating layer composed of a lower layer and an upper layer on the surface of a tool substrate made of a cubic boron nitride-based ultrahigh pressure sintered material containing 50 to 85 volume% of cubic boron nitride In a cutting tool made of a basic ultra-high pressure sintered material,
(A) The tool base has a honing shape in which the honing width is 0.03 to 0.3 mm when viewed from the rake face direction, and the honing angle is in the range of 10 to 35 degrees with respect to the rake face.
(B) The lower layer of the hard coating layer is
Composition formula: (Ti _1-X Al _X ) N
X is 0.3 to 0.6 (provided that the atomic ratio) is composed of a composite nitride layer of Ti and Al having an average layer thickness of 0.5 to 4 μm,
(C) The upper layer of the hard coating layer is composed of an alternating laminated structure of thin layers A and B each having an average layer thickness of 0.03 to 0.3 μm,
The thin layer A is a composite nitride layer of Ti and Al,
The thin layer B is a Ti nitride layer,
(D) The outermost layer of the upper layer is composed of a composite nitride layer of Ti and Al having an average layer thickness of 0.1 to 0.8 μm except for the ridge line portion between the honing surface and the flank surface. The surface-coated cubic boron nitride group is characterized in that the outermost layer does not exist at the ridge line portion between the face and the flank face, and the alternately laminated sectional structure of the thin layer A and the thin layer B is exposed. Cutting tool made of ultra high pressure sintered material.

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