JP5223743B2 - Cutting tool made of surface coated cubic boron nitride based ultra high pressure sintered material - Google Patents

Description

  The present invention provides excellent fracture resistance with a hard coating layer even when a material made of a hard material such as a hardened material of alloy tool steel or bearing steel is subjected to high-speed cutting, and the finished surface of the work material. Surface-coated cubic crystals 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 over a long period of time while maintaining accuracy The present invention relates to a cutting tool made of a boron nitride-based 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.

  Moreover, as a coated cBN-based sintered tool, a surface of a tool body made of various cubic boron nitride-based ultrahigh pressure sintered materials, a surface of a titanium nitride layer, a composite nitride layer of titanium and aluminum, or the like 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, an arc discharge is generated by applying a current of, for example, 90 A between a cathode electrode (evaporation source) made of metal Ti or a Ti—Al alloy and an anode electrode while being heated to 500 ° C. Inside, for example, nitrogen gas is introduced as a reaction gas to form a reaction atmosphere of, for example, 2 Pa, while titanium nitride is applied to the surface of the tool base under the condition that a bias voltage of, for example, −100 V is applied to the tool base. It is also known that it is produced by depositing a desired layer such as a physical layer or a composite nitride layer of titanium and aluminum.

JP 2001-234328 A JP-A-8-119774 JP 61-183187 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 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 cutting of hard materials such as hardened steel and bearing steel, abnormal damage to the boundary of the cutting edge of the cutting edge due to high load during cutting (hereinafter referred to as abnormal boundary damage) In the present situation, the service life is reached in a relatively short period of time.

In view of the above, the inventors of the present invention have excellent fracture resistance 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 stable cutting characteristics while maintaining excellent finished surface accuracy over a long period of use, the following knowledge was obtained. Obtained.
a) A composite nitride layer of Ti and Al (hereinafter referred to as a TiAlN layer) constituting the hard coating layer,
Composition formula: (Ti _1-X Al _X ) N
The TiAlN layer usually has a cubic crystal structure in which the {100} plane is preferentially oriented, and the value of the Al content ratio X (atomic ratio) in the total amount with Ti However, it has a predetermined high temperature hardness, oxidation resistance and high temperature strength within the range of 0.3 to 0.7, and has wear resistance required under normal cutting conditions, In high-speed cutting of hard materials such as hardened materials of alloy tool steel and bearing steel, the work material and chips are heated to extremely high temperatures due to the high heat generated in the cutting edge, so the boundary part of the cutting edge Causes abnormal boundary damage, and this causes defects.

(B) When the TiAlN layer of (a) is used as a lower layer of a hard coating layer, and a titanium nitride (hereinafter referred to as TiN) layer is deposited thereon as a first intermediate layer, the TiN layer is Since the crystal orientation history with TiAlN in the lower layer is strong, a cubic crystal structure oriented preferentially in the {100} plane is provided. Since the TiN layer with such orientation exhibits excellent toughness and high-temperature strength, by forming a TiN layer with a high {100} crystal orientation on the surface of the TiAlN layer, abnormal boundary damage and defects of the hard coating layer Although it is conceivable to prevent the occurrence of this, such a layer structure causes a problem that the finished surface accuracy of the work material is lowered.

(C) Therefore, various studies were made on the crystal orientation of the TiN layer and its characteristics. As a result, the slip system of the TiN crystal is the {111} plane, and instead of the TiN layer having high orientation on the {100} plane, {111 } When a TiN layer with high orientation to the plane is formed, the surface of the TiN layer and the slip system {111} plane are parallel to each other during cutting, thereby increasing the chipping resistance and plastic deformation of the TiN layer. The finished surface accuracy of the work material is improved.
And, in order to form a TiN layer having a high degree of crystal orientation on the {111} plane, it itself has excellent high-temperature hardness and high-temperature strength, and many nucleations used in the present invention enhance the {111} orientation. carbonitride layer of titanium is effective _{(Ti (C 1-Y N} Y) layer .Y is 0.5 to 0.9 (provided that an atomic ratio). hereinafter, indicated by TiCN layer) as a second intermediate layer If the crystal orientation history with the lower layer composed of the TiAlN layer is divided by the intervening formation, and the TiN layer is formed as the upper layer on the surface of the second intermediate layer, the degree of crystal orientation to the {111} plane is higher. It has been found that an upper layer composed of a TiN layer is formed.

(D) Therefore, in the coated cBN-based sintered tool, as the hard coating layer, the lower layer composed of the TiAlN layer, the first intermediate layer composed of the TiN layer, and the second layer composed of the TiCN layer that divides the crystal orientation history of the lower layer. By depositing an intermediate layer and an upper layer consisting of a highly oriented TiN layer on the {111} plane, the hard coating layer as a whole has excellent high temperature hardness, toughness, and high temperature strength, resulting in large heat generation. In high-speed cutting of work materials made of hard materials such as hardened alloy tool steel and bearing steel, it shows excellent chipping resistance and fracture resistance, without causing abnormal boundary damage and finishing. The surface performance is not degraded, and stable cutting performance is exhibited over a long period of use.

This invention has been made based on the above findings,
“(1) A surface-coated cube in which a hard coating layer composed of a lower layer, a first intermediate layer, a second intermediate layer, and an upper layer is deposited on the surface of a tool base made of a cubic boron nitride-based ultrahigh pressure sintered material. In the cutting tool made of crystal boron nitride based ultra high pressure sintered material,
(A) The lower layer has a layer thickness of 0.5 to 2.5 μm,
Composition formula: (Ti _1-X Al _X ) N
In this case, a composite nitride layer of titanium and aluminum whose X is 0.3 to 0.7 (atomic ratio),
(B) the first intermediate layer is a titanium nitride layer having a layer thickness of 0.1 to 1.5 μm;
(C) The second intermediate layer has a layer thickness of 0.1 to 1 μm,
Composition formula: Ti (C _1-Y N _Y )
, A carbonitride layer of titanium having Y of 0.5 to 0.9 (atomic ratio),
(D) The upper layer is a titanium nitride layer having a layer thickness of 0.3 to 2 μm and is within the measurement range of the surface polished surface of the upper layer using a field emission scanning electron microscope. Each crystal grain having a cubic crystal lattice is irradiated with an electron beam, and an inclination angle formed by a normal line of the {111} plane which is a crystal plane of the crystal grain is made with respect to a normal line of the surface polished surface. Measured and divided the measured inclination angle within the range of 0 to 45 degrees among the measured inclination angles for each pitch of 0.25 degrees, and the number of inclination angles obtained by totalizing the frequencies existing in each section In the distribution graph, the highest peak exists in the inclination angle section in the range of 0 to 15 degrees, and the total of the frequencies existing in the range of 0 to 15 degrees is 50% of the entire frequency in the inclination angle frequency distribution graph. Titanium angle distribution graph showing the above ratio Oxide layer,
A surface-coated cubic boron nitride-based ultra-high pressure sintered material cutting tool characterized by
(2) Average crystal grains of titanium and aluminum composite nitride grains in the lower layer cross section located on the lower layer side by a depth of 0.4 μm from the interface between the surface of the tool base and the lower layer Titanium nitride crystal grains in the upper layer cross section having a diameter of 100 to 300 nm and located on the upper layer side by a depth of 0.2 μm from the interface between the second intermediate layer and the upper layer The average crystal grain size is 10 to 70 nm.
The surface-coated cubic boron nitride-based ultrahigh pressure sintered material cutting tool according to claim 1. "
It has the characteristics.

  Next, the layer thickness, composition, crystal orientation and the like of the hard coating layer in the coated cBN-based sintered tool of the present invention will be described.

Lower layer:
Since the Ti component in the TiAlN layer constituting the lower layer of the hard coating layer maintains high temperature strength, and the Al component contributes to improvement in high temperature hardness and oxidation resistance, the TiAlN layer has a predetermined high temperature strength, high temperature hardness and It is a layer with heat resistance, and basically plays a role of ensuring the wear resistance of the cutting edge during high-speed cutting of work materials made of hard materials such as hardened materials of alloy tool steel and bearing steel. Bear.
However, the TiAlN layer constituting the lower layer is
Composition formula: (Ti _1-X Al _X ) N
In the case where the Al content ratio X exceeds 0.7, the crystal structure changes and the high-temperature strength decreases and defects tend to occur. On the other hand, when the Al content ratio X is less than 0.3, Since the high temperature hardness and heat resistance are lowered, and as a result, the wear resistance is lowered, the value of the Al content ratio X is set to 0.3 to 0.7 (however, the atomic ratio). It was.
On the other hand, if the thickness of the lower layer is less than 0.5 μm, the heat resistance, high temperature hardness and high temperature strength possessed by itself cannot be imparted to the hard coating layer over a long period of time, resulting in a short tool life. When the thickness exceeds 2.5 μm, defects tend to occur, so the layer thickness was determined to be 0.5 to 2.5 μm.
The “layer thickness” as used in the present invention is defined as “the average layer thickness at a position 0.1 mm (± 0.02 mm) from the edge of the blade edge to the flank surface in the portion assumed to be the cutting edge of the tool”. . For example, as shown in FIG. 3, 0.1 mm (± 0.02 mm) from the connecting portion of the nose R and the straight line portion (the portion assumed to be the cutting edge of the tool) and 0 to the flank from the edge of the cutting edge. The average layer thickness is 1 mm (± 0.02 mm). This is because the place where about 0.1 mm from the cutting edge to the flank is the most likely to wear, the reason that the layer thickness of this place has a great influence on the tool characteristics, and in the case of the present invention, In order to avoid variation due to the measurement location, measurement should be made at a certain position (0.1 mm (± 0.02 mm) in the case of this invention) from the joint between the nose R assumed to be the cutting edge and the straight portion. Because it has to be.
Furthermore, the crystal grain size of the TiAlN crystal grains in the lower layer is generally easier to grow as the layer thickness increases. As a result, the crystal grain size also increases, but the first grain size increases as the crystal grain size increases. Adhesion with the intermediate layer (TiN layer) decreases, and if the crystal grain size is small, the hardness increases but the grain boundary strength decreases and scraping wear occurs. The average crystal grain size is desirably 100 to 300 nm.
The average crystal grain size of the lower layer referred to here is the TiAlN crystal grains in the lower layer cross section located on the lower layer side by a depth of 0.4 μm from the interface between the surface of the tool base and the lower layer. Average grain size. The average crystal grain size is measured within a linear range of a predetermined length in the cross section of the lower layer located at the lower layer side by a depth of 0.4 μm from the interface between the surface of the tool base and the lower layer. It was determined by measuring the number of crystal grains present, and the average value of the values determined at any five locations was taken as the average crystal grain size value. For example, if there are 5 crystal grains in a linear range of 1 μm, the average crystal grain size is 200 nm.

First intermediate layer:
The first intermediate layer deposited on the surface of the lower layer is a TiN layer having a crystal structure with a high degree of orientation on the {100} plane depending on the crystal orientation of the lower layer.
Since this first intermediate layer (TiN layer) has predetermined toughness and high temperature strength, it has the effect of preventing the occurrence of abnormal boundary damage and defects in the hard coating layer during high-speed cutting of a hard material. However, when the layer thickness is less than 0.1 μm, the above-mentioned excellent characteristics cannot be sufficiently exhibited. On the other hand, when the layer thickness exceeds 1.5 μm, the high temperature hardness is insufficient and the wear resistance tends to decrease. Therefore, the thickness of the first intermediate layer was determined to be 0.1 to 1.5 μm.

Second intermediate layer:
The TiCN layer constituting the second intermediate layer divides the crystal orientation history with the lower layer made of the TiAlN layer, and since there are many nucleations under the film forming conditions in the present invention, the {111} orientation is increased, so that the upper layer The crystal orientation degree to the {111} plane of the TiN layer is increased.
The C component of the TiCN layer constituting the second intermediate layer has the effect of improving the hardness of the layer, and the N component has the effect of improving the strength of the layer.
Composition formula: Ti (C _1-Y N _Y )
When the content ratio Y of the N component is less than 0.5, the toughness and impact resistance of the TiCN layer are lowered and chipping is likely to occur, while the content ratio Y of the N component is 0.9. Since the improvement of the high-temperature hardness of the TiCN layer cannot be expected when the value exceeds 1, the value of the content ratio Y of the N component in the layer is set to 0.5 to 0.9 (however, the atomic ratio).
This second intermediate layer (TiCN layer) can not only exhibit excellent properties such as toughness and impact resistance when its layer thickness is less than 0.1 μm, but it also has the {100} plane orientation of the lower layer and the first intermediate layer. On the other hand, the layer thickness is insufficient for dividing. On the other hand, if the layer thickness exceeds 1 μm, the high-temperature hardness tends to decrease, so the layer thickness of the second intermediate layer is determined to be 0.1 to 1 μm. .

Upper layer:
The TiN layer constituting the upper layer has a predetermined toughness and high-temperature strength, and has a crystal structure with a high orientation ratio to the {111} plane excellent in plastic deformability (from the lower layer or the first intermediate layer). The crystal orientation is divided by the second intermediate layer).
That is, for the TiN layer deposited on the second intermediate layer, an electron beam is applied to each crystal grain having a cubic crystal lattice existing within the measurement range of the surface polished surface using a field emission scanning electron microscope. Irradiate and measure the tilt angle formed by the normal of the {111} plane which is the crystal plane of the crystal grain with respect to the normal of the surface polished surface. The measured inclination angle within the range is divided for every pitch of 0.25 degrees, and the inclination angle number distribution graph obtained by summing up the frequencies existing in each division is obtained, and is within the range of 0 to 15 degrees. Inclination angle number distribution graph in which the highest peak exists in the inclination angle section and the total of the frequencies existing in the range of 0 to 15 degrees occupies 50% or more of the entire frequency in the inclination angle distribution graph (see FIG. 2), and from this, TiN layer is a top layer deposited on the surface of the layer is found to be one having an orientation ratio is high crystal structure of the {111} plane.

This upper layer (TiN layer) has excellent toughness and high-temperature strength, as well as excellent plastic deformability, and chipping, abnormal boundary damage, and chipping occur in the hard coating layer during high-speed cutting of hard materials. However, if the layer thickness is less than 0.3 μm, the above-mentioned excellent characteristics cannot be fully exhibited, and improvement in the finished surface accuracy of the work material cannot be expected. If the thickness exceeds 2.0 μm, defects are likely to occur, so the average layer thickness of the upper layer was determined to be 0.3 to 2.0 μm.
In addition, the grain size of the TiN crystal grains in the upper layer is generally larger as the layer thickness is larger, as in the lower layer, and the chipping resistance decreases as the crystal grain size increases. On the contrary, when the crystal grain size is reduced, the hardness is increased but the grain boundary strength is lowered and scraping wear occurs. Therefore, the average grain size of the TiN crystal grains in the upper layer may be 10 to 70 nm. desirable.
The average crystal grain size of the upper layer is the TiN crystal grains in the upper layer cross section located on the upper layer side by a depth of 0.2 μm from the interface between the second intermediate layer (TiCN layer) and the upper layer. The average crystal grain size is measured within the upper layer cross section located on the upper layer side by a depth of 0.2 μm from the interface between the second intermediate layer (TiCN layer) and the upper layer. In the above, the number of crystal grains present within a linear range of a predetermined length was determined, and the average value of the values determined at arbitrary five locations was defined as the average crystal grain size.

  The surface roughness of the tool substrate of the coated cBN-based sintered tool according to the present invention is preferably 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 base body and the lower layer of the hard coating layer can be expected due to the anchor effect. On the other hand, if Ra exceeds 1.0, the work material This is because it will adversely affect the accuracy of the finished surface.

  In the coated cBN-based sintered tool of the present invention, the hard coating layer is composed of the lower layer, the first intermediate layer, the second intermediate layer, and the upper layer, and the upper layer of the hard coating layer is TiN having a high degree of {111} plane orientation. Because it has excellent high-temperature hardness, toughness, and impact resistance, the high-speed cutting with high heat generation of work materials made of hard materials such as hardened materials of alloy tool steel and bearing steel. Even under severe cutting conditions, there is no occurrence of chipping, boundary abnormal damage, or chipping in the hard coating layer, and without causing deterioration of the finished surface accuracy of the work material, over a long period of use, Stable cutting performance can be exhibited.

The arc ion plating apparatus used for forming the hard coating layer which comprises a coated cBN group sintering tool is shown, (a) is a schematic plan view, (b) is a schematic front view. It is an inclination angle number distribution graph of {111} measured about the upper layer (TiN layer) of the hard coating layer of this invention tool. It is the schematic of the tool cutting blade vicinity which shows the location which measures the layer thickness of each layer which comprises a hard coating layer.

  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: 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 °. To finish polishing Further, tool bases A to J each having an insert shape of ISO standard SNGA12041 were manufactured.

(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. The first intermediate layer, the second intermediate layer and the upper layer forming metal Ti are used as the cathode electrode (evaporation source) on one side, and the cathode on the other side. As an electrode (evaporation source), Ti-Al alloy for forming a lower layer having a component composition corresponding to the target composition shown in Table 2, respectively, is arranged opposite to 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 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 −50 V on the tool base rotating while rotating on the rotary table. In a state where a predetermined DC bias voltage is applied, an arc discharge is generated by flowing a predetermined current in a range of 50 to 200 A between the cathode electrode and the anode electrode of the metal Ti, and the surface of the lower layer Forming a first intermediate layer made of a TiN layer having a predetermined layer thickness,
(E) Next,
Substrate temperature: 250-300 ° C.
Bias voltage: −50 to −300V
Arc discharge current: 60-100A
Gas flow rate in the apparatus: nitrogen (N ₂ ) gas 300 to 500 sccm,
Methane (CH ₄ ) gas 100-300 sccm,
In-apparatus gas pressure: 1.3-4 Pa,
To form a second intermediate layer consisting of a Ti (C _1-Y N _Y ) layer having a target composition and a target layer thickness shown in Table 2,
(F) Next, a TiN layer having a {111} plane orientation with a target layer thickness shown in Table 2 is formed by vapor deposition under the same conditions as in (d) except that the substrate temperature is changed to 250 to 300 ° C. By vapor-depositing the upper layer,
Coated cBN-based sintered tools 1 to 10 (referred to as inventive tools 1 to 10) of the present invention were produced, respectively.

For comparison purposes,
(A ′) Each of the tool bases A to J described above is ultrasonically cleaned in acetone and dried in a radial direction from the central axis on the rotary table in the arc ion plating apparatus shown in FIG. Attached along the outer periphery at a predetermined distance away from each other, TiN layer forming metal Ti and TiAlN layer forming Ti-Al alloy are arranged facing each other across the rotary table as a cathode electrode (evaporation source) on one side. ,
(B ′) First, the inside of the apparatus is evacuated and kept at a vacuum of 0.1 Pa or less, and 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. Applying a -200V DC bias voltage to the rotating tool base while rotating on the table, and bombarding the surface of the tool base with argon ions,
(C ′) Nitrogen gas is introduced as a reaction gas into the apparatus to make a reaction atmosphere of 3 Pa, and a DC bias voltage of −100 V is applied to the tool base rotating while rotating on the rotary table, and Ti—Al An arc discharge is generated by passing a current of 100 A between the cathode and anode electrodes of the alloy, so that the target composition and target layer thickness (Ti _1-X Al _X shown in Table 4) are formed on the surface of the tool base. ) 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 a reaction atmosphere of 2 Pa, and the tool base that rotates while rotating on the rotary table has a range of −10 to −50 V. 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 metal Ti to generate arc discharge, and the lower layer Conventionally coated cBN-based sintered tools 1 to 10 (referred to as conventional tools 1 to 10) were produced by forming TiN layers having a predetermined layer thickness shown in Table 3 on the surface.

About the lower layer of this invention tool 1-10 obtained as a result and the conventional tool 1-10, when the composition was measured by the energy dispersive X-ray analysis using a transmission electron microscope, each of target composition and substantial The composition of the second intermediate layer of the tools 1 to 10 of the present invention was measured in the same manner, and the composition was substantially the same as the target composition.
Furthermore, when the layer thickness of each layer of the present invention tools 1 to 10 and the conventional tools 1 to 10 was measured using a transmission electron microscope, the average value was substantially the same as the target layer thickness (average values at five locations). )showed that.
Further, constituting the lower layer of the present invention the tool _{1~10 (Ti 1-X Al X} ) N layer and TiN layer constituting the upper layer, further, conventional tools _{1~10 (Ti 1-X Al X} ) N The average crystal grain size of the crystal grains constituting each of the layers and the TiN layer was determined, and the values are shown in Tables 2 and 3. The average crystal grain size of the lower layer is within the lower layer cross section located at the lower layer side by a depth of 0.4 μm from the interface between the surface of the tool base and the lower layer. The particle size is within the linear range of 1 μm using a transmission electron microscope in the upper layer cross section located at the upper layer side by a depth of 0.2 μm from the interface between the second intermediate layer and the upper layer. The number of existing crystal grains was measured, this measurement was performed at five locations, the average value of each value was determined, and this was taken as the average crystal grain size.

Moreover, about the upper layer (TiN layer) of this invention tool 1-10, using a field emission type | mold scanning electron microscope, an electron beam is individually sent to the crystal grain which has the cubic crystal lattice which exists in the measurement range of the surface polishing surface. Irradiate and measure the tilt angle formed by the normal of the {111} plane which is the crystal plane of the crystal grain with respect to the normal of the surface polished surface. The measured inclination angle within the range was divided for each pitch of 0.25 degrees, and the inclination angle number distribution graph obtained by counting the frequencies existing in each division was obtained. The results are shown in Table 2 as the {111} plane orientation ratio.
As is apparent from Table 2, the total number of frequencies existing in the tilt angle section within the range of 0 to 15 degrees for the upper layer (TiN layer) of the tools 1 to 10 of the present invention is the frequency in the tilt angle number distribution graph. It can be seen that it accounts for 50% or more of the total.
For reference, an inclination angle number distribution graph was created for the {111} plane and {100} plane of the first intermediate layer (TiN layer) of the present invention tools 1 to 10 and the TiN layer of the conventional tools 1 to 10. However, with respect to the {111} plane, the highest peak does not exist in the inclination angle section within the range of 0 to 15 degrees, and the sum of the frequencies existing within the range of 0 to 15 degrees is also the distribution of the inclination angle number. It was only 20% or less of the total frequency in the graph. On the other hand, with respect to the {100} plane, the highest peak exists in the tilt angle section within the range of 0 to 15 degrees, and the total frequencies within the range of 0 to 15 degrees are shown in Tables 3 and 4 below. As shown in FIG. 6, a value of 40% or more of the entire frequency in the inclination angle number distribution graph was shown. From this, it is clear that the first intermediate layer (TiN layer) of the inventive tools 1 to 10 and the TiN layer of the conventional tools 1 to 10 each have {100} plane orientation.

Next, with the above various coated cBN-based sintered tools, the present invention tools 1 to 10 and the conventional tools 1 to 10 in a state where they are all screwed to the tip of the tool steel tool with a fixing jig, A high-speed continuous cutting test was performed under the following cutting conditions A to C.
[Cutting conditions A]
Work material: JIS / SCM420 (Hardness: HRC60) round bar,
Cutting speed: 250 m / min. ,
Cutting depth: 0.12 mm,
Feed: 0.08 mm / rev. ,
Cutting time: 10 minutes,
Dry continuous high-speed cutting test of carburized and hardened alloy steel under normal conditions (normal cutting speed is 180 m / min.),
[Cutting conditions B]
Work material: JIS · SCr420 (hardness: HRC61) round bar,
Cutting speed: 225 m / min. ,
Cutting depth: 0.08 mm,
Feed: 0.10 mm / rev. ,
Cutting time: 10 minutes,
Dry continuous high speed cutting test of carburized and quenched chrome steel under the conditions of (normal cutting speed is 180 m / min.),
[Cutting conditions C]
Work material: JIS / SUJ2 (Hardness: HRC61) round bar,
Cutting speed: 275 m / min. ,
Cutting depth: 0.06 mm,
Feed: 0.08 mm / rev. ,
Cutting time: 10 minutes,
Dry continuous high-speed cutting test of quenched bearing steel under the conditions of (normal cutting speed is 170 m / min.),
And Rz (micrometer) was measured according to JIS * B0601-1994 about the finishing surface precision of the work material in each said cutting test. The measurement results are shown in Table 4.
For the conventional tools 1 to 10, after the cutting time is finished, the finished surface accuracy (Rz (μm)) of the work material is the reference value (1.0 μm for the cutting conditions A and B, 0.7 μm for the cutting condition C). ), The cutting time when the predetermined reference value was exceeded was determined as the life (minutes), and Table 4 shows the life (minutes) of the conventional tools 1-10.

  From the results shown in Tables 2 to 4, the coated cBN-based sintered tool of the present invention (tool of the present invention) has a hard coating layer having a lower layer having a layer thickness of 0.5 to 2.5 μm, A first intermediate layer having a layer thickness of 1 to 1.5 μm, a second intermediate layer having a layer thickness of 0.1 to 1 μm, and an upper layer having a layer thickness of 0.3 to 2 μm; In particular, since the upper layer has {111} plane orientation and has excellent toughness, impact resistance, and plastic deformation, the work material is made of a hard material such as a hardened material of alloy tool steel or bearing steel. Even under severe cutting conditions such as high-speed cutting with high heat generation, there is no occurrence of chipping, abnormal boundary damage, or chipping in the hard coating layer, and without lowering the finished surface accuracy of the work material. , While exhibiting stable cutting performance over a long period of use, hard coating layer Conventional coated cBN-based sintered tools (conventional tools) consisting of a TiAlN layer and TiN with {100} plane orientation tend to cause abnormal boundary damage or chipping at the cutting edge, especially due to insufficient toughness of the hard coating layer. It is clear that the finished surface accuracy of the work material decreases with use (the surface roughness of the work material increases), and 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 cutting of a work material made of a material, the hard coating layer exhibits excellent boundary abnormal damage resistance and fracture resistance, and without incurring a decrease in the finished surface accuracy of the work material, Since it exhibits stable cutting performance over a long period of time, it can sufficiently satisfy the high performance of the cutting device, the labor saving and energy saving of the cutting work, and the cost reduction.

Claims (2)

Surface-coated cubic boron nitride in which a hard coating layer composed of a lower layer, a first intermediate layer, a second intermediate layer, and an upper layer is deposited on the surface of a tool base made of a cubic boron nitride-based ultrahigh pressure sintered material In the cutting tool made of super high pressure sintered material,
(A) The lower layer has a layer thickness of 0.5 to 2.5 μm,
Composition formula: (Ti _1-X Al _X ) N
In this case, a composite nitride layer of titanium and aluminum whose X is 0.3 to 0.7 (atomic ratio),
(B) the first intermediate layer is a titanium nitride layer having a layer thickness of 0.1 to 1.5 μm;
(C) The second intermediate layer has a layer thickness of 0.1 to 1 μm,
Composition formula: Ti (C _1-Y N _Y )
, A carbonitride layer of titanium having Y of 0.5 to 0.9 (atomic ratio),
(D) The upper layer is a titanium nitride layer having a layer thickness of 0.3 to 2 μm and is within the measurement range of the surface polished surface of the upper layer using a field emission scanning electron microscope. Each crystal grain having a cubic crystal lattice is irradiated with an electron beam, and an inclination angle formed by a normal line of the {111} plane which is a crystal plane of the crystal grain is made with respect to a normal line of the surface polished surface. Measured and divided the measured inclination angle within the range of 0 to 45 degrees among the measured inclination angles for each pitch of 0.25 degrees, and the number of inclination angles obtained by totalizing the frequencies existing in each section In the distribution graph, the highest peak exists in the inclination angle section in the range of 0 to 15 degrees, and the total of the frequencies existing in the range of 0 to 15 degrees is 50% of the entire frequency in the inclination angle frequency distribution graph. Titanium angle distribution graph showing the above ratio Oxide layer,
A surface-coated cubic boron nitride-based ultra-high pressure sintered material cutting tool characterized by The average crystal grain size of the composite nitride of titanium and aluminum in the lower layer cross section located at the lower layer side by a depth of 0.4 μm from the interface between the surface of the tool base and the lower layer is 100. Average crystal of titanium nitride crystal grains in the upper layer cross section located at the upper layer side by a depth of 0.2 μm from the interface between the second intermediate layer and the upper layer. The particle size is 10-70 nm,
The surface-coated cubic boron nitride-based ultrahigh pressure sintered material cutting tool according to claim 1.

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