JP5565630B2 - Surface coated broach with excellent wear resistance and finished surface accuracy - Google Patents

Description

  The present invention maintains high wear resistance, high chip dischargeability, and high finished surface accuracy over a long period of time in high-speed broaching of high-hardness materials that tend to cause tooth loss in metal broaching. A surface-coated broach that provides tool life is provided.

  As such a broach, the front end side of a substantially cylindrical broach body rotated about the axis in the rotation direction of the broach is the cutting edge part, and a pair of chip discharge grooves are formed on the outer periphery of the cutting edge part. In order to be symmetrical with respect to the axis, the tip of the cutting edge, that is, a spiral that twists toward the rear side in the rotation direction of the broach around the axis as it goes from the tip flank of the broach body toward the rear end, A so-called two-blade solid broach is known in which a cutting edge is formed at an intersecting ridge line portion with the tip flank on the tip side of the inner peripheral surface of these chip discharge grooves facing the rotation direction of the broach. . Therefore, in such a solid broach, the tip side of the inner peripheral surface of the chip discharge groove facing the broach rotation direction is the rake face of the cutting blade, and the chips generated by the cutting blade are transferred from the rake face to the chip discharge groove. While being in sliding contact with the inner peripheral surface of the metal, it is sent to the rear end side by the twist of the chip discharge groove and discharged. Further, in such a broach, various methods are adopted for improving the wear resistance of the broach body.

  For example, in Patent Document 1, represented by the general formula (M, Al) (C, N) (M represents at least one metal element selected from Group 4, 5, 6 elements, Si, and rare earth elements). Two coating layers represented are laminated, and among the coating layers, the first coating layer coated on the substrate surface has a layer thickness of 0.1 to 1 μm and an average crystal diameter of 0.01 to 0.1 μm. The second coating layer composed of granular crystals and coated on the surface of the first coating layer is a columnar shape having a layer thickness of 0.5 to 5 μm and growing in a direction perpendicular to the substrate. An average crystal width of the columnar crystal in a direction parallel to the base body is 0.05 to 0.3 μm, and an average crystal width of the second coating layer is an average of the first coating layer A surface coated tool larger than the crystal diameter is disclosed.

  Further, in Patent Document 2, a hard coating layer having an average layer thickness of 1 to 3 μm and comprising a composite oxide film of Ti, Al, and Si as a lower layer on the surface of a broach body made of a tungsten carbide base superalloy. In addition, the upper layer contains W, Ti, and nitrogen, and the balance is composed of carbon and inevitable impurities, and the structure in which the fine particles of the crystalline titanium carbonitride compound are dispersed and distributed on the carbon-based amorphous body. And a coated broach made of a surface-coated cemented carbide obtained by vapor-depositing a lubricating amorphous carbon-based film having an average layer thickness of 1 to 3 μm.

  Further, in Patent Document 3, in a tool based on cemented carbide such as high speed steel, cemented carbide, cermet, etc., formed by coating a hard coating layer by ion plating method, 4a, 5a, 6a of the periodic table are used. A first layer composed of one or more of group and Al carbides and / or nitrides, and one or two of group 4a, 5a, 6a and Al carbides and / or nitrides of periodic table The above and the second layer containing oxygen are alternately laminated, and the first layer made of carbide and nitride and the second layer containing oxygen interposed therebetween have crystal continuity. A featured coated hard tool is disclosed.

  Further, in Patent Document 4, a coating film 3 such as diamond is formed on the cutting edges 1 and 2 of at least one finishing blade 2 adjacent to the final finishing blade 1 of the broach, and escapes to the cutting edge formed of the coating film. A broach is disclosed in which a straight land 6 machined to a predetermined dimension is provided between the face 5, the rake face 4 and the flank face.

International Publication No. 2007/111301 Pamphlet JP 2006-116643 A Japanese Patent Laid-Open No. 11-264066 JP-A-11-138330

  In recent years, the use of FA for broaching machines has been remarkable, and in addition, there are strong demands for labor saving, energy saving, cost reduction, and efficiency for broaching, and this has led to demands for more efficient broaching such as high speeds. However, in the conventional surface-coated tools and conventional surface-coated broaches exemplified in Patent Document 1, Patent Document 2, and Patent Document 3, there are special problems when various types of steel and cast iron are broached under normal conditions. However, when it is used for high-speed broaching where wear resistance is required and high finished surface accuracy is required, the slip characteristics of the surface film are not sufficient, and chipping peeling and chipping For this reason, it is the present situation that the service life is reached in a relatively short time, or the deterioration of the finished surface accuracy is unavoidable due to the progress of wear. Further, the conventional surface coating broach exemplified in Patent Document 4 can maintain high finished surface accuracy, but its manufacturing method is mechanical polishing of a remarkably hard surface coating layer made of vapor deposited cubic boron nitride or diamond. This is a process that forms a straight land portion by removing the material, and requires a great deal of labor to manufacture a desired tool.

In view of the above, the present inventors have demonstrated excellent wear resistance and chip evacuation even when used in high-speed, dry-type deep hole broaching, and prolonging the life of the surface-coated broach. In order to achieve this, the broach surface is composed of, for example, a hard coating layer made of a component system of (Cr _1-x Al _x ) N {x = 0.2 to 0.6}, and the crystal grain structure of the hard coating layer As a result of diligent research focusing on the following, the following findings were obtained.

(A) As a hard coating layer, for example, the formation of a layer made of a component system of (Cr _1-x Al _x ) N {x = 0.2 to 0.6} is shown, for example, in the schematic explanatory diagram of FIG. A broach substrate is attached to an ion plating apparatus using a pressure gradient type Ar plasma gun, which is a kind of physical vapor deposition apparatus.
Tool substrate temperature: 380 to 420 ° C.
Evaporation source 1: Metal Cr
Plasma gun discharge power for the evaporation source 1: 9 to 13 kW,
Evaporation source 2: Metal Al
Plasma gun discharge power for the evaporation source 2: 6 to 11 kW,
Reaction gas flow rate: nitrogen _{(N 2)} gas 75~100sccm
Discharge gas: Argon (Ar) gas 45-60 sccm,
DC bias voltage applied to broach substrate: +3 to +10 V,
When the reactive vapor deposition is performed under the specific conditions, and under the film formation conditions adjusted so that the film formation rate gradually increases along the distance from the tip of the broach substrate, the resulting hard coating layer is formed. It has been found that the surface coating broach provided with has excellent wear resistance and high finished surface accuracy in high-speed and dry deep hole machining as compared with the conventional surface coating broach.

(B) When the cross-sectional structure of the hard coating layer was observed with a transmission electron microscope, as shown in the cross-sectional perspective view of FIG. Columnar crystal grains grown in the upright direction are formed, and the average aspect ratio of the crystal grains is 1 to 100 from the broach tip to the rear, and the average aspect ratio of the tip cutting edge is 3 minutes. It was confirmed that there was a region that gradually decreased to 1 up to half the length of the entire cutting edge.

(C) When the hard coating layer of the surface coating broach is composed of the hard coating layer having the crystal grain structure (hereinafter referred to as a particle size control layer), the following effects are exhibited. In other words, the cutting edge flank at the tip of the tool is subject to high heat and high load, so it is made up of a columnar crystal film with a high aspect ratio to achieve high wear resistance, and the cutting edge at the rear edge is extended over a long period of time. In order to maintain a smooth finish surface, it is composed of granular crystals with a low aspect ratio, and the aspect ratio gradually decreases in response to a gradual decrease in heat and mechanical load from the tip edge to the rear edge. By realizing such a structure, excellent wear resistance is exhibited over a long period of time while maintaining the desired finished surface accuracy.

The present invention has been made based on the above findings,
“(1) (Cr _1−x Al _x ) N {x as a particle size control layer on the outermost surface directly or via an intermediate layer on a broach substrate made of cemented carbide sintered body or cermet or high speed steel = 0.2 to 0.6} In the surface coating broach having a hard coating layer having a layer thickness of 0.2 to 5 μm composed of a component system of
When observing the crystal grain size of the film cross-section of the cutting edge constituting the broach, the crystal grains constituting the grain size control layer are columnar crystals having a width of 15 to 120 nm and a height of 0.2 to 5 μm, and Among the cutting edges constituting the broach, the average aspect ratio of the crystal grains constituting the grain size control layer when observing the crystal grain size shape of the film cross section from the tip cutting edge to the rear end of the broach is In the range of 1 to 100, there is a region that gradually decreases to one third of the average aspect ratio of the crystal grains at the tip edge over the length of the broach in the length direction of the broach over more than half the length of the tool edge. A surface-coated broach that exhibits excellent wear resistance and high finished surface accuracy over a long period of time.
(2) The surface-coated broach according to (1), wherein the layer thickness of the particle size control layer gradually increases in the range of 0.2 to 5.0 μm from the position closest to the tip of the broach to the rear. .
(3) The intermediate layer is made of a nitride or carbide of Ti, a carbonitride, a composite nitride composed of Ti and Al, a composite nitride composed of Ti, Al, and Si, or a composite nitride composed of Cr and Al. Of these, the surface coating according to (1) or (2), wherein the surface coating has a laminated structure composed of any single layer or a plurality of layer structures selected from the hard film group, and has a layer thickness of 5 μm or less. brooch. "
It has the characteristics.

  The present invention will be described below.

In the grain size control layer constituting the outermost surface of the hard coating layer of the surface coating broach of the present invention, when the crystal grain shape of the coating cross section of the flank at the tip of the broach is observed, the grain constituting the grain size control layer is wide. Columnar crystals having a height of 15 to 120 nm and a height of 0.2 to 5 μm are used. Here, when the width is 15 nm or less, it is difficult to maintain the strength, and when the width is 120 nm or more, it becomes coarse and causes defects, so the width is determined to be 15 to 120 nm. Further, if the height is 0.2 μm or less, the wear resistance is insufficient, and if it is 5 μm or more, a defect due to residual stress tends to occur and sufficient tool performance cannot be exhibited. Therefore, the height is set to 0.2 to 5 μm. In addition, when the value of x, which is the Al content in the total amount of Cr and Al in the composition (Cr _1-x Al _x ) N exceeds 0.6, it changes from a NaCl-type crystal to a hexagonal structure. A desired unique structure cannot be provided, and it is difficult to maintain sufficient wear resistance. On the other hand, if the value of x is less than 0.2, the heat resistance characteristics of Al are not exhibited, which is not preferable. Therefore, the value of x was determined as x = 0.2 to 0.6. Moreover, if the area where the aspect ratio of the cutting edge gradually decreases is less than one half, the high chip discharge property of the low aspect ratio crystal grain structure is not maintained, and the desired tool performance cannot be achieved. For this reason, it was determined to be more than half. Further, the rate of gradually decreasing the aspect ratio of the cutting edge is obtained by dividing the aspect ratio measured by the cutting edge existing at the most distal end of the gradually decreasing region by the aspect ratio of the cutting edge existing at the most rear end. 3, preferably over 5.
And, as a result of conducting numerous tests for forming a particle size control layer, the present inventors used a pressure gradient type plasma gun to irradiate a hearth containing raw materials to evaporate, Reactive vapor deposition under film deposition conditions adjusted so that the film deposition rate on the broach substrate gradually increases along the distance from the tip of the broach substrate using a reactive vapor deposition method that physically deposits the film on the substrate. When the crystal grain shape of the coating cross section is observed from the front end to the rear end of the broach substrate among the cutting blades constituting the broach, as shown in FIG. While constituted by columnar crystals having a width of 15 to 120 nm and a height corresponding to the layer thickness, for example, among the cutting edges constituting the broach, the grain size control layer is located at the rear end of the broach. , Width 15 ~ 20 nm, composed of vertically-oriented columnar grains having a height equal to or less than the layer thickness, and having an aspect ratio in the range of 1 to 100 from the broach tip to the broach back end. It has been found that there is a region that gradually decreases to one third of the average aspect ratio over one half of the entire length of the tool cutting edge.

As used herein, “aspect ratio” refers to the value of the long side that is the line segment indicating the measured maximum diameter of each crystal grain, and the value of the short side that indicates the minimum diameter in the direction perpendicular to the long side. The “average aspect ratio” refers to the arithmetic average value of the aspect ratio of the crystal grains present in the region corresponding to the height film thickness × width 50 μm in the cross-sectional observation of the film.
In addition, the “width” of the crystal grain is a line segment having a length of 10 μm drawn to a height of one half of the film thickness substantially parallel to the broach substrate when the grain size control layer is observed from a cross section. It means the average value of the length of each section, excluding both ends of the line segment, divided by grain boundaries.
Further, the “height” of the crystal grains is a length of 10 long lines drawn at intervals of 0.1 μm perpendicular to a line segment substantially parallel to the broach substrate when the crystal grain layer is observed from a cross section. This refers to the average value of the lengths of the segments excluding both ends of each line segment, in which the line segments corresponding to the film thickness are segmented by the crystal grain boundaries.
Further, “the aspect ratio of the crystal grains gradually decreases in the range of 1 to 100 from the front end of the broach to the rear end” means that at any point in the region having a width of 1 mm around the specific position, When comparing the defined numerical value with the numerical value defined in the same way at any point in the 1 mm wide area centered on the position away from the specific position in the direction of the rear end of the broach by at least 5 mm, the tip side It indicates the correlation that the numerical value defined at the measurement point on the rear end side is smaller than that. That is, provided that the above condition is satisfied, for example, even if the aspect ratio of the crystal grains measured in the 1 mm width region is not gradually decreased, it does not depart from the scope of the present invention.

The surface-coated broach of the present invention is a cemented carbide sintered body, a cubic boron nitride sintered body, a cermet, or a broach substrate made of high-speed steel, directly or via an intermediate layer, with a particle size on the outermost surface. A surface-coated broach having a hard layer with a layer thickness of 0.2 to 5 μm made of (Cr _1-x Al _x ) N {x = 0.2 to 0.6} as a control layer, When observing the crystal grain shape of the coating cross section of the flank, the crystal grains constituting the grain size control layer are columnar crystals corresponding to a width of 15 to 120 nm and a height layer thickness, and among the chip discharge grooves of the broach In the region from the tip to the rear end of the broach along the length of the broach substrate, the average aspect ratio of the crystal grains constituting the grain size control layer when observing the crystal grain shape of the coating cross section is Tool cutting edge towards Total over one or more lengths region of 2 minutes, it has been gradually reduced to less than one third of the range of 1 to 100, excellent wear resistance and high surface finish can be achieved.

The schematic diagram of the ion plating apparatus using the pressure gradient type Ar plasma gun for carrying out vapor deposition formation of the hard coating layer (particle size control layer) of the surface coating broach of the present invention is shown. The cross-sectional perspective view of the hard coating layer (particle size control layer) of the surface coating broach of the present invention is shown. The relationship between the distance from the front-end | tip cutting edge of this invention surface coating broach and the crystal grain aspect ratio of a hard coating layer (grain size control layer) is shown. The relationship between the distance from the front-end | tip cutting edge of this invention surface coating broach and the crystal grain aspect ratio of a hard coating layer (grain size control layer) is shown. The relationship between the distance from the front-end cutting edge of this invention surface coating broach and the value which remove | divided the aspect ratio of the hard coating layer (particle-size control layer) by the aspect-ratio of the front-end cutting edge is shown. The relationship between the distance from the cutting edge of the comparative surface coating broach and the aspect ratio of the hard coating layer (grain size control layer) is related to the crystal grain aspect ratio of the cutting edge. The relationship between the distance from the front-end cutting edge of a comparative surface coating broach and the value which remove | divided the aspect ratio of the hard coating layer (particle size control layer) by the aspect-ratio of the front-end cutting edge is shown.

  Next, the surface-coated broach of the present invention will be specifically described with reference to examples.

As raw material powders, WC powder having an average particle size of 0.8 μm, 2.3 μm Cr ₃ C ₂ powder, 1.5 μm VC powder, and 1.8 μm Co powder were prepared. 1 is added to the compounding composition shown in FIG. 1, and a wax is further added, followed by ball mill mixing in acetone for 24 hours, drying under reduced pressure, and then press-molding into various compacts of a predetermined shape at a pressure of 100 MPa. The body is heated to a predetermined temperature in the range of 1370 to 1470 ° C. at a heating rate of 7 ° C./min in a vacuum atmosphere of 6 Pa, held at this temperature for 1 hour, and then sintered under furnace cooling conditions. Then, a round bar sintered body for forming a tool base is formed, and further, a round bar sintered body for forming a carbide broach body having a diameter of 50 mm and a length of 1000 mm is obtained by grinding from the round bar sintered body. Further, from the round bar sintered body, In processing, the maximum cutting edge diameter: 40 mm, the cutting edge length: 600 mm, the overall length: 800 mm, the shape shown in FIG. 2 and the shape shown in FIG. Broach substrates D-1 to D-4 made of WC-base cemented carbide having 25 blades were produced.

Next, the cutting blades of these broach substrates D-1 to D-4 are subjected to honing, ultrasonically cleaned in acetone, and dried, with one type of physical vapor deposition apparatus shown in the schematic diagram of FIG. Attached to an ion plating device using a certain pressure gradient type Ar plasma gun,
Tool substrate temperature: 380 to 420 ° C.
Evaporation source 1: Metal Cr
Plasma gun discharge power for the evaporation source 1: 9 to 13 kW,
Evaporation source 2: Metal Al
Plasma gun discharge power for the evaporation source 2: 6 to 11 kW,
Reaction gas flow rate: Nitrogen (N ₂ ) gas 75-100 sccm,
Discharge gas: Argon (Ar) gas 45-60 sccm,
DC bias voltage applied to broach substrate: +3 to +10 V,
For the purpose of adjusting the film forming rate on the broach substrate so as to gradually increase along the distance from the tip of the broach substrate, the broach substrate is, for example, as shown in FIG. In addition, the tip of the broach base body is turned from the horizontal to the upper side and is rotated while maintaining the angle shown in Table 3 with respect to the vertical axis of the hearth mounting plane, and at the same time, the vertical axis is rotated. Reactive vapor deposition was performed while revolving as the central axis, and surface coating broaches 1 to 12 of the present invention each having a particle size control layer having the composition and structure shown in Table 3 were produced.

  For the purpose of comparison, the pressure gradient type Ar plasma gun shown in FIG. 1 is also applied to the surfaces of the broach substrates D-1 to D-4, which are subjected to honing, ultrasonically cleaned in acetone, and dried. For the purpose of forming a uniform hard coating layer over the entire area of the broach substrate in the ion plating apparatus utilizing the above, simultaneously rotating the broach substrate while maintaining parallel to the hearth mounting plane (not shown), Reactive vapor deposition was performed while revolving around the vertical axis as a rotation center axis to form a conventional layer having a uniform composition and structure shown in Table 4 on the surface of the broach substrate D-1 to D-4. Comparative surface coating broaches 1-12 were produced respectively.

Next, for the surface coating broach 1-12 of the present invention and the comparative surface coating broach 1-12,
Work Material: Outer Diameter 80mm Center Hole Diameter 40mm, Thickness 40mm, JIS S55C Perforated Material Pulling Speed: 9m / min. ,
Life Judgment Condition: Dry high-speed drilling test of carbon steel under the condition that chipping of the cutting edge or flank wear width exceeds 0.15 mm (normal drawing speed is 5 m / min.)
The number of machining until the tool life was reached was measured. The measurement results are shown in Tables 3 and 4, respectively.

  As a result, the composition of the particle size control layer constituting the hard coating layer of the surface coating brooches 1 to 12 of the present invention and the conventional layer constituting the hard coating layer of the comparative surface coating broach 1 to 12 was changed to transmission electron. When measured by an energy dispersive X-ray analysis method using a microscope, each showed substantially the same composition as the target composition.

  Moreover, when the cross-sectional measurement was carried out using the scanning electron microscope for the average layer thickness of the said hard coating layer, all showed the average value (average value of five places) substantially the same as target layer thickness.

From the results shown in Tables 3 and 4, according to the surface coating broach of the present invention, when the crystal grain shape of the coating cross section of the flank face of the broach tip is observed, the crystal grains constituting the grain size control layer have a width of 15 to 120 nm, When observing the crystal grain shape of the cross section of the coating film of the cutting edge constituting the broach and having a columnar crystal equivalent to the height layer thickness, the average aspect ratio of the crystal grains constituting the grain size control layer is Excellent wear resistance and high because it gradually decreases to 1/3 or less in the range of 1-100 over the length region of 1/2 or more of the entire tool cutting edge toward the end. Finished surface accuracy can be realized.
On the other hand, in the comparative surface coating broach having a conventional layer in which the average aspect ratio of the crystal grains constituting the hard coating layer does not change from the broach tip to the rear, the wear resistance is not sufficient. It is clear that the service life is reached in a relatively short time due to the occurrence of defects and peeling.
Further, for the surface-coated broaches 1 and 2 of the present invention, the relationship between the distance from the tip (the length in the range where the cutting edge exists is 1), the grain size of the grain size control layer of the cutting edge, and the film thickness. Are shown in Table 5.

  As described above, in the surface coating broach of the present invention, the average aspect ratio of the crystal grains constituting the hard coating layer (grain size control layer) is 2 minutes of the entire tool cutting edge portion from the broach tip to the rear. Since it gradually decreases to 1/3 or less in the range of 1 to 100 over one or more length regions, it has high finished surface accuracy, and this high finished surface accuracy is high speed, Even under dry deep hole broaching conditions, high wear resistance is maintained over a long period of time.

Claims (3)

On a broach substrate made of cemented carbide sintered body or cermet or high speed steel, directly or through an intermediate layer,
Surface coated broach having a hard coating layer having a layer thickness of 0.2 to 5 μm made of a component system of (Cr _1-x Al _x ) N {x = 0.2 to 0.6} as a particle size control layer on the outermost surface In
Among the cutting edges constituting the broach, when the crystal grain size of the hard coating layer cross section of the cutting edge at the tip is observed, the crystal grains constituting the grain size control layer have a width of 15 to 120 nm and a height of 0.2. The particle size control when observing the crystal grain size of the film cross section from the tip cutting edge of the broach toward the rear end among the cutting edges comprising a columnar crystal of ˜1.8 μm and constituting the broach. The area where the average aspect ratio of the crystal grains constituting the layer gradually decreases to 1/3 of the average aspect ratio of the crystal grains in the tip cutting edge in the range of 1 to 100 is the length of the tool cutting edge in the length direction of the broach. A surface-coated broach that exhibits excellent wear resistance and high finished surface accuracy over a long period of time, characterized in that it exists over a length of one-half of the total length.   2. The surface-coated broach according to claim 1, wherein the layer thickness of the particle size control layer gradually increases in a range of 0.2 to 5.0 μm from the position closest to the tip of the broach to the rear.   The intermediate layer is any one of Ti nitride or carbide, carbonitride, composite nitride composed of Ti and Al, composite nitride composed of Ti, Al and Si, and composite nitride composed of Cr and Al. 3. The surface-coated broach according to claim 1, wherein the surface-coated broach has a laminated structure composed of a single layer or a plurality of layer structures selected from the hard film group, and has a layer thickness of 5 μm or less.

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