JP5293330B2 - Cutting tool made of surface coated cubic boron nitride based ultra high pressure sintered material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface-coated cutting tool formed of a cubic boron nitride-based ultra high-pressure sintered material exhibiting excellent abrasion resistance, and defecting resistance in the high-speed heavy machining of a high hardness material. <P>SOLUTION: The surface-coated cutting tool formed of the cubic boron nitride-based ultra high-pressure sintered material is vapor-deposited with hard coating layers composed of a lower layer, an intermediate layer, and an upper layer on a surface of the tool base composed of a cBN-based ultra high-pressure sintered material containing 70 vol% or more of the cBN content. In the surface coated cutting tool, (1) the lower layer is a TiB2 layer with a layer thickness of 0.05-0.5 &mu;m, (2) the intermediate layer has a layer thickness of 0.3-1 &mu;m, has an average composition satisfying 0.15&le;X&le;0.60, 0.05&le;Y&le;0.35, and 0.50&le;X+Y&le;0.65 when the intermediate layer is expressed by a composition formula: Ti<SB>1-X-Y</SB>B<SB>X</SB>N<SB>Y</SB>(X and Y are atomic ratios), and is a two-phase mixed layer composed of TiB<SB>2</SB>and TiN phases having gradient compositions in which the value of X gradually decreases and the value of Y gradually increases toward an upper layer side from a lower layer side, and (3) the upper layer has a layer thickness of 0.5-5 &mu;m and is a Ti-Al complex nitride layer satisfying that Y is 0.3-0.65 (atomic ratio) when the upper layer is expressed by a composition formula: (Ti<SB>1-Y</SB>Al<SB>Y</SB>)N. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention provides excellent wear resistance with a hard coating layer and stable cutting over a long period of time even when a work material made of a hard material such as a hardened material of alloy tool steel or bearing steel is subjected to high-speed heavy cutting. A surface-coated cubic boron nitride group in which a hard coating layer is formed on the surface of a cutting tool base (hereinafter referred to as a tool base) made of a cubic boron nitride-based ultra-high pressure sintered material capable of exhibiting performance 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.

  Further, as a coated cBN-based sintered tool, a surface of a composite body of titanium and aluminum (indicated by TiAlN) or the like on the surface of a tool body made of various cubic boron nitride-based ultrahigh pressure sintered materials Coated cBN-based sintered tools formed by vapor-depositing a coating layer are known, and it is also known that these are used for cutting of various steels and cast irons, for example.

  Further, the above-mentioned coated cBN-based sintered tool is loaded with the above-mentioned tool base in an arc ion plating apparatus which is one type of physical vapor deposition apparatus schematically shown in FIG. For example, in a state heated to 500 ° C., for example, a current of 90 A is applied between the cathode electrode (evaporation source) made of a Ti—Al alloy and the anode electrode to generate an arc discharge. For example, a nitrogen gas is introduced as a reaction gas to obtain a reaction atmosphere of 2 Pa, for example. On the other hand, a TiAlN layer or the like is formed on the surface of the tool base under a condition that a bias voltage of, for example, −100 V is applied to the tool base. It is also known that it is manufactured by vapor deposition of the layers.

JP 2001-234328 A JP-A-8-119774

  In recent years, FA has been remarkable for cutting devices, but on the other hand, there is a strong demand for labor saving and energy saving and further cost reduction for cutting, and accordingly, cutting is performed at higher speed conditions in addition to normal cutting conditions. However, in the above-mentioned conventional coated tools, there is no particular problem when various types of steel and cast iron are machined under normal conditions. When used for high-speed heavy cutting of work materials made of hard materials such as hardened steel and bearing steel, high heat generation during cutting, due to insufficient adhesion strength of hard coating layer due to high load, or The present situation is that the service life is reached in a relatively short time due to the occurrence of defects or the like.

  In view of the above, the inventors of the present invention have an excellent adhesion strength with a hard coating layer in high-speed cutting of a work material made of a hard material such as a hardened material of alloy tool steel or bearing steel. As a result of research to develop a coated cBN-based sintered tool that exhibits excellent wear resistance and fracture resistance, and exhibits excellent cutting performance over a long period of use, the following knowledge was obtained. Obtained.

(A) Cubic boron nitride (hereinafter referred to as cBN) in a tool base made of ultra-high pressure sintered material is extremely hard, forms a dispersed phase in the sintered material, and wear resistance is obtained by this dispersed phase. However, when the blending ratio of cBN is increased to 70% by volume or more, the hardness of the tool base can be increased, but the adhesion strength with the hard coating layer made of the TiAlN layer is high. In the high-speed heavy cutting process for high-hardness materials that are accompanied by high heat generation and a high load acts on the cutting edge because of the tendency to decrease, in the high-speed heavy cutting processing of the hard coating layer, The excellent high temperature hardness cannot be utilized to improve the cutting performance.

(B) Therefore, as a result of many experiments conducted on the hard coating layer structure that improves the adhesion strength between the tool base and the TiAlN layer, the hard coating layer is configured as a three-layer structure of a lower layer, an intermediate layer, and an upper layer. Furthermore, the lower layer is a TiB ₂ layer, the intermediate layer is a layer composed of a two-phase mixed structure of a TiB ₂ phase and a TiN phase (hereinafter referred to as a TiB ₂ -TiN mixed layer), and the upper layer is a TiAlN layer. When formed, the interlayer adhesion strength is high, and as a result, it has been found that the adhesion strength between the tool base and the TiAlN layer is greatly improved through the lower layer and the intermediate layer.

(C) In addition, the _TiB 2-TiN mixed layer of the intermediate layer, the lower layer side to increase the content ratio of TiB ₂ lowers the content of TiN, conversely, TiN lower the content of TiB ₂ in the upper layer side By adopting the gradient structure that increases the content ratio, the interlayer adhesion strength between the lower layer-intermediate layer and between the intermediate layer and the upper layer is further increased, so that the adhesion strength between the hard coating layers is further increased. I found out.

(D) Thus, at 70 volume% or more of the coated cBN-based sintered tool cBN content, the lower layer composed of TiB ₂ layer, an intermediate layer made of _TiB 2-TiN mixed layers of mound organizational structure, the upper consisting of TiAlN layer When the hard coating layer is composed of layers, in addition to the adhesion strength between the layers being increased, the strength of the tool base and the hard coating layer is also increased, so the hard coating layer as a whole, Excellent high-temperature hardness, toughness, and high-temperature strength. As a result, in high-speed heavy cutting of work materials made of hard materials such as hardened alloy tool steel and bearing steel with large heat generation and high load. It exhibits excellent wear resistance and fracture resistance over a long period of use without causing peeling, and exhibits stable cutting performance.

This invention has been made based on the above findings,
"Hard coating layer consisting of lower layer, intermediate layer and upper layer is deposited on the surface of tool base made of cubic boron nitride based ultra high pressure sintered material with cubic boron nitride content of more than 70% by volume In the surface-coated cubic boron nitride based ultra high pressure sintered material cutting tool,
(A) The lower layer is a TiB ₂ layer having a layer thickness of 0.05 to 0.5 μm,
(B) The intermediate layer has a layer thickness of 0.3 to 1 μm,
Composition formula: Ti _1-XY B _X N _Y
In this case, an average satisfying 0.15 ≦ X ≦ 0.60, 0.05 ≦ Y ≦ 0.35, 0.50 ≦ X + Y ≦ 0.65 (where X and Y are atomic ratios) Two-phase mixing of TiB ₂ phase and TiN phase having a gradient structure in which the value of X gradually decreases and the value of Y gradually increases as it moves from the lower layer side to the upper layer side. layer,
(C) The upper layer has a layer thickness of 0.5 to 5 μm,
Composition formula: (Ti _1-Z Al _Z ) When represented by an N layer, a composite nitride layer of Ti and Al in which Z is 0.3 to 0.65 (where Z is an atomic ratio),
A surface-coated cubic boron nitride-based ultra-high pressure sintered material cutting tool (coated cBN-based sintered tool). "
It has the characteristics.

  Next, each layer constituting the hard coating layer of the coated cBN-based sintered tool of the present invention will be described.

Lower layer:
The TiB ₂ layer constituting the lower layer has excellent stability at high temperatures and high hardness, and has excellent adhesion to both the tool base and the TiB ₂ -TiN mixed layer constituting the intermediate layer. This contributes to an improvement in the adhesion strength between the tool base and the hard coating layer.
Furthermore, the Young's modulus of TiB _{2 in} the lower layer is close to that of the cBN phase, which is the main component of the tool base, and even when used for heavy cutting in which a large stress acts on the cutting edge, the difference in deformation behavior between the lower layer and the tool base. Is small, and peeling and destruction of the lower layer hardly occur. As a result, a stable cutting edge can be maintained for a long period of time.
The TiB ₂ layer can be formed by using a TiB ₂ sintered body as a target and performing high-frequency sputtering in an Ar gas atmosphere.
If the layer thickness of the TiB ₂ layer is less than 0.05 μm, the effect as an adhesion layer is not sufficient, while if the layer thickness exceeds 0.5 μm, the strength of the entire film is reduced and the load is high. Since the breakage is likely to occur during cutting, the thickness of the TiB ₂ layer is set to 0.05 to 0.5 μm.

Middle layer:
The TiB ₂ -TiN mixed layer constituting the intermediate layer,
Ti _1-XY B _X N _Y
X is 0.15 to 0.60, Y is 0.05 to 0.35, and X + Y is 0.50 to 0.65 (where X and Y are both atomic ratios). The composition further includes TiB ₂ in the intermediate layer so as to form a graded structure in which the value of X gradually decreases and the value of Y gradually increases from the lower layer side to the upper layer side. Adjust the ratio and TiN content ratio.
In the above composition formula, X, Y, and X + Y are 0.15 to 0.60, 0.05 to 0.35, and 0.50 to 0.65 (where X and Y are both atomic ratios), respectively. The reasons for satisfying are as follows.
When the content ratio X of B exceeds 0.60, or when the content ratio Y of N is less than 0.05, the adhesion strength between the upper layer and the TiAlN layer is not sufficient, and peeling between layers occurs. On the contrary, when the B content ratio X is less than 0.15, or when the N content ratio Y exceeds 0.35, predetermined adhesion with the TiB ₂ layer of the lower layer is obtained. Similarly, peeling between layers is likely to occur. Further, when the total content ratio X + Y of B and N exceeds 0.65, it means that the content ratio of N is relatively decreased, and the amount of TiB ₂ phase is substantially occupied, Adhesion strength with the upper TiAlN layer becomes insufficient.
When X + Y is less than 0.50, it becomes difficult to form a two-phase mixed layer of TiB ₂ phase and TiN phase, and in particular, the adhesion strength of the lower layer door cannot be obtained.
Therefore, the content ratio X of B indicating the average composition of the TiB ₂ -TiN mixed layer, the content ratio Y of N, and the total content ratio X + Y of B and N are 0.15 to 0.60 and 0.05 to 0, respectively. .35 and 0.50 to 0.65.
Furthermore, in order to increase the adhesion and adhesion strength between the lower layer and the upper layer, on the lower layer side, the content ratio of TiB ₂ is relatively increased and the content ratio of TiN is lowered, and conversely, on the upper layer side, It is necessary to form a TiB ₂ —TiN mixed layer having a textured gradient structure that relatively lowers the TiB ₂ content ratio and increases the TiN content ratio. The TiB ₂ -TiN mixed layer on the lower layer side with a high TiB ₂ content ratio and a low TiN content ratio, and the TiB ₂ -TiN mixed layer on the upper layer side with a low TiB ₂ content ratio and a high TiN content ratio are Since the interfaces of components and compositions similar to those of the lower layer and the upper layer are formed, respectively, adhesion and adhesion strength are further improved.

The TiB ₂ -TiN mixed layer can be formed by using high frequency sputtering in a mixed atmosphere of Ar gas and nitrogen gas, using two types of TiB ₂ sintered bodies and titanium metal as targets. However, in order to form a tilted structure in the TiB ₂ -TiN mixed layer, at the initial stage of film formation by sputtering, the nitrogen gas content ratio in the atmospheric gas and the power supplied to the titanium metal target are reduced, and the formation is completed. As the film progresses, it is necessary to sequentially increase the nitrogen gas content in the atmospheric gas and the power to the metal titanium target.
In addition, when the layer thickness of the TiB ₂ -TiN mixed layer to be formed is less than 0.3 μm, the effect as the adhesion layer is not sufficient, while when the layer thickness exceeds 1 μm, the strength of the entire film is reduced, Since breakage is likely to occur during cutting under high load, the thickness of the TiB ₂ -TiN mixed layer was determined to be 0.3 to 1 μm.

Upper layer:
Since the Ti component in the TiAlN layer maintains high temperature strength and the Al component contributes to improvement in high temperature hardness and oxidation resistance, the TiAlN layer is a layer having predetermined high temperature strength, high temperature hardness and heat resistance. Basically, it plays a role of ensuring the wear resistance of the cutting edge part during high-speed cutting of a work material made of a hard material such as a hardened material of alloy tool steel or bearing steel.
However, the TiAlN layer constituting the upper layer is
_{Formula: (Ti 1-Z Al Z} ) N
In the case where the Al content ratio Z exceeds 0.65, the crystal structure changes and the high-temperature strength decreases and defects tend to occur. On the other hand, when the Al content ratio Z is less than 0.3, Since the high temperature hardness and heat resistance decrease, and as a result, the wear resistance decreases, the value of the Al content ratio Z is determined to be 0.3 to 0.65 (however, the atomic ratio). It was.
The upper layer made of a TiAlN layer may be formed by, for example, an arc ion plating method. However, if the thickness of the upper layer is less than 0.5 μm, the heat resistance, high-temperature hardness and high-temperature strength that it has are hard-coated. The layer cannot be applied to the layer for a long period of time, resulting in a short tool life. On the other hand, if the layer thickness exceeds 5 μm, defects are likely to occur. Therefore, the layer thickness of the upper layer is determined to be 0.5 to 5 μm. .

In the coated cBN-based sintered tool of the present invention, a hard coating layer composed of a lower layer, an intermediate layer, and an upper layer is formed on the surface of a tool base having a cBN compounding ratio of 70% by volume or more, and the lower layer is formed of TiB _2. By having a TiB ₂ -TiN mixed layer having a specific composition and a graded structure in the intermediate layer and a TiAl ₂ layer having a specific composition in the upper layer, the layer has a particularly excellent adhesion strength, and a high temperature Since it combines hardness, toughness, and impact resistance, high-speed heat generation is required for work materials made of hard materials such as hardened materials such as alloy tool steel and bearing steel, and a high load acts on the cutting edge. Even under severe cutting conditions such as heavy cutting, the hard coating layer does not peel off and can exhibit excellent wear resistance and fracture resistance over a long period of use.

The schematic explanatory drawing of the physical vapor deposition apparatus with which the high frequency sputtering (RF-SP) apparatus and arc ion plating (AIP) apparatus for forming the hard coating layer of the coating | coated cBN group sintered tool of this invention are shown together, (A) is a plan view and (b) is a side view. The schematic explanatory drawing of the arc ion plating (AIP) apparatus for forming the hard coating layer of a comparative coating cBN group sintered tool is shown.

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

  As the raw material powder, cBN powder, TiN powder, AlN powder, Ni powder, Al powder, Co powder, and W powder each having an average particle diameter in the range of 0.5 to 4 μm are prepared. The mixture is blended in the composition shown in FIG. 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. 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 to obtain a presintered body for a cutting edge piece. In addition, Co: 8% by mass, WC: remaining composition, and diameter: 50 mm × thickness: 2 mm, superposed on a WC-based cemented carbide support piece with a normal super-high pressure Charged into the sintering machine and under normal conditions Force: 4 GPa, temperature: Presence at a predetermined temperature in the range of 1200-1400 ° C. Holding time: 0.8 hours under high pressure sintering, after sintering, the upper and lower surfaces are polished with a diamond grindstone, and wire electric discharge machining It is divided into equilateral triangles with a side of 3 mm by an apparatus or a diamond cutter, and further Co: 5% by mass, TaC: 5% by 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: brazing using a brazing material of an Ag alloy having the remaining composition, and after processing the outer periphery to a predetermined dimension, the honing process is performed on the cutting edge portion with a width of 0.13 mm and an angle of 25 °. Finish polishing As a result, tool bases A to J having the insert shape of ISO standard SNGA120212 were produced.

Next, each of the tool bases A to J is ultrasonically cleaned in acetone and dried, and the arc ion plating (AIP) apparatus and the RF sputtering (RF-SP) apparatus shown in FIG. The Ti-Al alloy having a predetermined composition as a cathode electrode (evaporation source) of the AIP device and a target of the RF-SP device (evaporation) are mounted on the rotary table in the vapor deposition apparatus along the outer periphery. A metal Ti and TiB ₂ sintered body as a source),
(A) First, the inside of the apparatus is evacuated and kept at a vacuum of 0.5 Pa or less, and the inside of the apparatus is heated to 450 to 600 ° C. with a heater, and then is rotated to −200 V on the rotating tool base while rotating on the rotary table. Then, the tool base surface is cleaned with Ar gas bombardment by further applying a pulse bias voltage of
(B) Next, argon gas is introduced as a reaction gas into the apparatus to form a reaction atmosphere of 0.3 Pa, and a high frequency power of 300 W is applied to the target of the TiB ₂ sintered body using a high frequency power source and sputtered. In addition, a lower layer (TiB ₂ layer) having a target layer thickness is formed on the surface of the tool base that rotates while rotating on the rotary table by applying a pulse voltage of −200 V,
(C) Next, an argon-nitrogen mixed gas is introduced as a reaction gas into the apparatus, and while adjusting the nitrogen content to increase with the progress of sputtering, the reaction atmosphere is set to 0.3 Pa, and the rotation A DC bias voltage of −100 V is applied to the rotating tool base while rotating on the table, and sputtering is performed on the target of the TiB ₂ sintered body using a high-frequency power source, and a high-frequency power source is used on the metal Ti target. Sputtering is performed, and each applied power is adjusted to be a target structure, and an intermediate layer (TiB ₂ -TiN mixed layer) having a target layer thickness and a target gradient structure is formed on the surface of the tool base,
(D) Next, nitrogen gas is introduced as a reaction gas into the apparatus to form a reaction atmosphere of 2 to 4 Pa, and a pulse bias voltage of −10 to −50 V is applied to the tool base that rotates while rotating on the rotary table. Then, an arc discharge is generated by flowing a current of 100 A between the cathode electrode and the anode electrode made of the Ti—Al alloy, so that the tool substrate surface has the target composition and target layer thickness shown in Table 2. By depositing an upper layer consisting of a TiAlN layer,
The coated cBN-based sintered tools 1 to 10 of the present invention (referred to as the present invention tools 1 to 10) each having a throwaway tip shape defined in ISO standard SNGA12041 were manufactured.

For comparison purposes,
(A) Each of the above tool bases A to J is ultrasonically cleaned in acetone and dried, and is radiused from the central axis on the rotary table in the ordinary arc ion plating apparatus schematically shown in FIG. Attached along the outer periphery at a position separated by a predetermined distance in the direction, and a cathode electrode made of a Ti-Al alloy for forming a hard coating layer (TiAlN layer) is arranged in the apparatus,
(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 2.0 Pa. A pulse 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 into the apparatus as a reaction gas to make a reaction atmosphere of 2 to 4 Pa, and a pulse bias voltage of −10 to −50 V is applied to the tool base that rotates while rotating on the rotary table. Then, a current of 100 A is passed between the cathode electrode and the anode electrode of the Ti—Al alloy to generate an arc discharge, so that a TiAlN layer having a target composition and a target layer thickness shown in Table 3 is formed on the surface of the tool base. By vapor deposition as a hard coating layer,
Comparative coated cBN-based sintered tools 1-10 (referred to as comparative tools 1-10) were produced.

About each layer of the hard coating layer of the present invention coated cBN-based sintered tool 1-10 and comparative coated cBN-based sintered tool 1-10 obtained as a result, the composition was measured by Auger electron spectroscopic analysis. The composition was substantially the same as the composition.
In addition, regarding the B and N content ratio of the intermediate layer in Table 2, the lower layer side is the average value of the measurement in the region of 0.1 μm (film thickness direction) × 1 μm (direction parallel to the interface), the upper layer side Means the average value of the measurement in the region of 0.1 μm (film thickness direction) × 1 μm (direction parallel to the interface), and the average composition (X value) and average composition (Y value) Denotes a value measured by a region of the entire intermediate layer (intermediate layer thickness) × width 1 μm.
Further, when the layer thicknesses of the respective layers of the present coated cBN-based sintered tool 1 to 10 and the comparative coated cBN-based sintered tool 1 to 10 were measured with a transmission electron microscope, both were substantially equal to the target layer thickness. The same average value (average value of 5 locations) was shown.

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 and the comparative coating are used. The cBN-based sintered tools 1 to 10 were subjected to a high speed heavy cutting test of high hardness steel under the cutting conditions A and B shown below.
[Cutting conditions A]
Work material: JIS / SCr420 (Hardness: HRC60) round bar,
Cutting speed: 280 m / min. ,
Cutting depth: 0.3 mm,
Feed: 0.3 mm / rev. ,
Cutting time: 10 minutes,
Dry continuous high-speed high-feed cutting test of hardened chrome steel under the conditions of (normal cutting speed and feed are 120 m / min. And 0.15 mm / rev., Respectively),
[Cutting conditions B]
Work material: JIS / SUJ2 (Hardness: HRC61) round bar,
Cutting speed: 230 m / min. ,
Cutting depth: 0.3 mm,
Feed: 0.3 mm / rev. ,
Cutting time: 10 minutes,
Dry continuous high-speed high-feed cutting test of hardened bearing steel under the conditions (normal cutting speed and feed are 130 m / min. And 0.12 mm / rev., Respectively).
Table 4 shows the cutting test results.

From the results shown in Tables 2 to 4, the coated cBN-based sintered tool of the present invention forms a hard coating layer composed of a lower layer, an intermediate layer, and an upper layer on the surface of a tool base having a cBN blending ratio of 70% by volume or more. In addition, a tool having a high cBN content ratio is obtained by using a TiB ₂ -TiN mixed layer with a specific composition having a TiB ₂ layer as a lower layer, a gradient structure as an intermediate layer, and a TiAlN layer having a specific composition as an upper layer. Even for the base, the hard coating layer has particularly excellent adhesion strength, and also has high-temperature hardness, toughness, and impact resistance, so it is made of a hard material such as a hardened material of alloy tool steel or bearing steel. Even when the work material is used under severe cutting conditions such as high-speed heavy cutting that is accompanied by high heat generation and a high load acts on the cutting edge, the hard coating layer may be damaged, peeled, etc. No occurrence, long-term use Te, excellent wear resistance can be exhibited chipping resistance.
On the other hand, the comparative coated cBN-based sintered tool in which the lower layer and intermediate layer are not formed and the TiAlN layer is directly coated on the surface of the tool base is not sufficient in adhesion strength between the tool base and the TiAlN layer. Therefore, flank wear is likely to occur and the wear resistance is inferior, and it is apparent 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 heavy cutting of work materials made of materials, the hard coating layer has excellent adhesion strength and excellent wear resistance and fracture resistance, so it exhibits stable cutting performance over a long period of time Therefore, it is possible to satisfactorily meet the demand for higher performance of the cutting apparatus, labor saving and energy saving of the cutting process, and further cost reduction.

Claims (1)

A hard coating layer composed of a lower layer, an intermediate layer, and an upper layer was deposited on the surface of a tool substrate made of a cubic boron nitride-based ultrahigh pressure sintered material having a cubic boron nitride content of 70% by volume or more. In the cutting tool made of surface coated cubic boron nitride based ultra high pressure sintered material,
(A) The lower layer is a TiB ₂ layer having a layer thickness of 0.05 to 0.5 μm,
(B) The intermediate layer has a layer thickness of 0.3 to 1 μm,
Composition formula: Ti _1-XY B _X N _Y
In this case, an average satisfying 0.15 ≦ X ≦ 0.60, 0.05 ≦ Y ≦ 0.35, 0.50 ≦ X + Y ≦ 0.65 (where X and Y are atomic ratios) Two-phase mixing of TiB ₂ phase and TiN phase having a gradient structure in which the value of X gradually decreases and the value of Y gradually increases as it moves from the lower layer side to the upper layer side. layer,
(C) The upper layer has a layer thickness of 0.5 to 5 μm,
Composition formula: (Ti _1-Z Al _Z ) When represented by an N layer, a composite nitride layer of Ti and Al in which Z is 0.3 to 0.65 (where Z is an atomic ratio),
A surface-coated cubic boron nitride-based ultra-high pressure sintered material cutting tool characterized by

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