JP2011224767A - Surface-coated cutting tool having hard coating layer showing excellent chipping resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface-coated cutting tool having a hard coating layer showing excellent chipping resistance in dry intermittent heavy cutting or dry continuous high feed cutting in which high load is applied to a cutting edge.SOLUTION: The surface-coated cutting tool having the hard coating layer made of a CrN layer formed by physical vapor deposition on a surface of a cutting tool base body made of a cemented carbide sintered body has the hard coating layer structured of a region I where a grain size width of CrN crystal grains is small and a region II where the grain size width is larger than that of the region I, wherein a vertical section where a shift of crystal orientations between fine particles in the region I and coarse particles in the region II is 15 degrees or less occupies 60% or larger by an area ratio. Thus, excellent strength at high temperatures, chipping resistance and toughness are exhibited in dry interrupted heavy cutting and dry continuous high feed cutting.

Description

  The present invention provides a surface-coated cutting that has a hard coating layer with excellent fracture resistance even when used under severe cutting conditions such as high-speed intermittent heavy cutting such as steel and cast iron, and can extend the life of cutting tools. The present invention relates to a tool (hereinafter referred to as a coated tool).

  In general, for coated tools, inserts that are detachably attached to the tip of a cutting tool for turning of work materials such as various types of steel and cast iron, and the inserts are detachably attached to be used for chamfering and grooving. An insert type end mill that performs cutting processing in the same manner as a solid type end mill used for processing and shoulder processing is known.

For example, using a field emission scanning electron microscope on the surface of a tungsten carbide base cemented carbide substrate or a titanium carbonitride-based cermet substrate, each crystal grain having a cubic crystal lattice existing within the measurement range of the surface polished surface has electrons. The tilt angle formed by the normal of the <111> plane, which is the crystal plane of the crystal grain, is measured with respect to the normal of the surface-polished surface, and the range of 0 to 45 degrees of the measured tilt angle In the inclination angle distribution graph formed by summing up the measured inclination angles in each of the pitches of 0.25 degrees and totaling the frequencies existing in each section, the inclination angles are in the range of 3 to 15 degrees. An inclination angle frequency distribution graph is shown in which the highest peak is present and the sum of the frequencies existing in the range of 3 to 15 degrees occupies 45 to 65% of the entire frequency in the inclination angle frequency distribution graph, and 1 to Has an average layer thickness of 15 μm The lubricating coating layer composed of a chromium nitride layer is formed comprising the coating cemented carbide cutting tools are known that (for example, see Patent Document 1).
Also, a cutting tool in which a coating layer is coated on the surface of the substrate, and the cutting edge is the intersection ridge line between the rake face and the flank face, and the thickness of the coating layer on the rake face is thinner than the thickness of the coating layer on the flank face The coating layer is made of columnar crystals, and two layer regions in which the average crystal width of the upper layer region located on the surface side opposite to the substrate of the coating layer is larger than the average crystal width of the lower layer region located on the substrate side of the coating layer The ratio of the thickness of the upper layer region to the thickness of the entire coating layer on the rake surface is smaller than the ratio of the thickness of the upper layer region to the thickness of the entire coating layer on the flank surface, and the columnar crystals on the rake surface By configuring the average crystal width to be smaller than the average crystal width of the columnar crystals on the flank face, it is possible to suppress chipping of the coating layer on the rake face and improve the fracture resistance, thereby improving the wear resistance on the flank face. Surface-coated cutting tool is known (e.g., see Patent Document 2).

JP 2006-21257 A JP 2008-296290 A

In recent years, the FA of cutting devices has been remarkable, and in addition, there are strong demands for labor saving, energy saving, cost reduction and efficiency for cutting, and with this, high-efficiency heavy cutting such as high feed and high cutting However, in the above-mentioned conventional coated tools, there are no particular problems when various types of steel and cast iron are machined under normal conditions, but they are shocking and intermittent to the cutting edge. When used for dry interrupted heavy cutting where high load is applied or dry continuous high feed cutting where continuous high load is applied, crack growth into the layer is unavoidable and peeling / missing of the surface coating layer occurs. The cutting edge is likely to be damaged, and due to this, the service life is reached in a relatively short time.
For example, in a technique in which a specific crystal orientation of CrN is oriented as in the coated tool disclosed in Patent Document 1, although it exhibits excellent lubrication characteristics, it can be applied to a cutting edge like high-speed intermittent cutting. Under cutting conditions where an impact load is applied, there is a disadvantage that the grain boundary bonding force is weak and the lack of particles occurs and the life is reached in a relatively short time.
In addition, a hard coating composed of columnar crystals as in the coated tool disclosed in Patent Document 2 has a low bonding force between particles, and has an upper limit for high-speed cutting due to lack of crystal grains.

  In view of the above, the inventors of the present invention focused on the crystal form of the hard coating layer composed of the CrN layer in order to increase the fracture resistance of the coated tool and to prolong the service life. As a result, the following findings were obtained.

For example, a hard coating layer made of a CrN layer of a conventional coated tool is formed by, for example, applying a tool substrate made of the above WC-based cemented carbide sintered body to a sputtering (SP) apparatus which is a kind of physical vapor deposition apparatus shown in FIG. Wearing, for example,
In-apparatus heating temperature: 300-500 ° C
DC bias voltage applied to the tool base: -20 to -50V,
Cathode electrode: metal Cr,
Sputtering power: 3-6 kW,
Gas flow in the apparatus: nitrogen (N ₂ ) gas + argon (Ar) gas,
In-apparatus gas pressure: 0.3 to 1.5 Pa,
In this condition, a CrN layer (hereinafter referred to as a conventional CrN layer) is formed.

However, the present inventors have formed a CrN layer by using, for example, an ion plating apparatus using a pressure gradient type Ar plasma gun, which is a kind of physical vapor deposition apparatus schematically shown in FIG. Mounting the tool base in the apparatus, for example,
Tool substrate temperature: 350 to 450 ° C.
Evaporation source: Metal Cr,
Plasma gun discharge power: 8-10 kW (relative to metal Cr),
Reaction gas flow rate: nitrogen _{(N 2)} gas 100 to 110 sccm,
Discharge gas: Argon (Ar) gas 50-60 sccm,
DC bias voltage applied to tool base: 0 to -20 V
In the initial stage of vapor deposition, the bias voltage was set to 0V, and the CrN layer on the tool base side (region I) was deposited. In the latter stage of vapor deposition, the bias voltage was switched from -10 to -20V. When the CrN layer on the surface side (region II) of the hard coating layer is deposited, the resulting CrN layer composed of region I and region II (hereinafter referred to as a modified CrN layer) is compared with the conventional CrN layer. Excellent wear resistance and fracture resistance in dry intermittent heavy cutting where impact and intermittent high load are applied to the cutting edge and dry continuous high feed cutting where continuous high load is applied I found out.

The present invention has been made based on the research results,
“(1) In a surface-coated cutting tool in which a hard coating layer made of a CrN film having an average layer thickness of 0.5 to 2 μm is physically vapor-deposited on the surface of a tool base made of a tungsten carbide-based cemented carbide sintered body,
Of (a) hard coating layer, a CrN grains with diameter width that is from the interface of the tool substrate and CrN film to the height position of 0.1 [mu] m W _iota, the depth position from the outermost surface of 0.1 [mu] m of CrN film When the grain width of a certain CrN crystal grain is W ₂ ,
_10nm <W Ι <50nm _{and,, 5 <W ΙΙ / W} Ι <100
There is a relationship that satisfies
(B) Further, the crystal orientation of the CrN crystal grains in the cross section of the hard coating layer is analyzed using an electron beam backscatter diffractometer, and the measured two-dimensional region is measured every 100 nm in a direction substantially perpendicular to the tool substrate surface. Each of the regions (cells) divided into 100 nm × 100 nm is divided into vertical sections at a pitch of 100 nm, and further, the inside of each vertical section is partitioned from the interface between the tool base and the CrN film in the growth direction of the CrN film at a pitch of 100 nm. Of each measuring point present in
The average inclination angle of the inclination angle formed by the <111> crystal orientation and the normal direction of the CrN film measurement cross section is calculated, and the difference between the maximum value and the minimum value of the measurement inclination angle is 15 degrees among cells existing in the same vertical section. And
The average inclination angle of the inclination angle formed by the <111> crystal orientation and the direction orthogonal to the normal line of the CrN film measurement cross section is calculated, and the difference between the maximum value and the minimum value of the measurement inclination angle among cells existing in the same vertical section Is 15 degrees or less,
The average inclination angle of the inclination angle formed by the <100> crystal orientation and the normal line of the CrN film measurement cross section is calculated, and the difference between the maximum value and the minimum value of the measurement inclination angle is 15 degrees or less among the cells existing in the same vertical section. A surface-coated cutting tool characterized in that the vertical section of 100 nm width occupies 60% or more of the total area measured.
(2) The surface-coated cutting tool according to (1), wherein the content ratio x of nitrogen with respect to Cr satisfies 0.7 ≦ x ≦ 2.0 when the composition of the CrN film is represented by CrN _x. . "
It has the characteristics.

  The present invention will be described in detail below.

As described above, the present invention uses, for example, an ion plating apparatus using a pressure gradient type Ar plasma gun schematically shown in FIG. A tool base is mounted, for example,
Tool substrate temperature: 350 to 450 ° C.
Evaporation source: Metal Cr,
Plasma gun discharge power: 8-10 kW (relative to metal Cr),
Reaction gas flow rate: nitrogen _{(N 2)} gas 100 to 110 sccm,
Discharge gas: Argon (Ar) gas 50-60 sccm,
DC bias voltage applied to tool base: 0 to -20 V
In the initial stage of vapor deposition, the bias voltage was set to 0V, and the CrN layer on the tool base side (region I) was deposited. In the latter stage of vapor deposition, the bias voltage was switched from -10 to -20V. A modified CrN layer composed of regions I and II is formed by vapor-depositing a CrN layer on the surface side (region II) of the hard coating layer.
It is well known that Cr, which is a constituent component of the conventional CrN layer, improves the high-temperature strength, and N has the effect of improving the strength of the layer. The high quality CrN layer exhibits excellent fracture resistance even under severe use conditions such as high-speed intermittent heavy cutting conditions.
The reason is strongly related to the specific crystal grain shape of the modified CrN layer as described below.

First, with respect to the modified CrN layer formed by vapor deposition, the change in the grain width of CrN crystal grains in a plane perpendicular to the film growth direction was observed. In the area I (hard coating layer on the tool base side), the particle size width is 10 as shown in the schematic view of the plane and in FIG. CrN crystal grains of ˜50 nm were observed, while CrN crystal grains having a grain size width larger than that of region I were observed in region II (the surface side of the hard coating layer).
Further, using the focused ion beam processing apparatus, the surface of the tool base and the hard coating layer are obtained for the thinned sample as shown, for example, in the Y plane of the schematic diagrams shown in FIGS. 3 (a) and 3 (b). grain radial width W from the interface at the location of 0.1μm in vertical height in terms _Ι and measures the particle radial width W _Iotaiota position 0.1μm vertical depth Convert hard coating layer surface, and their values measurement of the value of the _W ΙΙ / W _Ι, the _W ΙΙ / W Ι was confirmed to be 5 to 100.
Incidentally, the average layer thickness of the modified CrN layer, regions I and II of the CrN grains with diameter width, W _iota, the value of W _Iotaiota and _W ΙΙ / W Ι, especially, Ar plasma gun discharge to metal Cr Although it is influenced by the output, the WC particle size of the cemented carbide sintered body as the tool base, and the vapor deposition time among the vapor deposition conditions, the discharge power of the Ar plasma gun is 8 to 10 kW, and the average particle size of WC is 0. .2～3Myuemu, also, if the deposition time is 62～250Min, with an average layer thickness of 0.5 to 2 [mu] m, and, W _iota is 10~50nm _and,, W ΙΙ / W range _iota is from 5 to 100 The modified CrN layer can be formed.
The term “particle size width” as used herein means “a line passing through one particle when a line parallel to the tool base surface is drawn at a position where the height or depth is 0.1 μm. The average length of minutes.

Then, using a backscattering diffraction device for electron beam analysis, the crystal orientation of the CrN crystal grains in the cross section of the hard coating layer was analyzed, and the measured two-dimensional region was vertically divided into vertical sections at a pitch of every 100 nm. Each vertical section is divided from the interface between the tool base and the CrN film in the growth direction of the CrN film at a pitch of every 100 nm, and each measurement point existing in each region (cell) divided into 100 nm × 100 nm,
The average inclination angle of the inclination angle formed by the <111> crystal orientation and the normal direction of the CrN film measurement cross section is calculated, and the difference between the maximum value and the minimum value of the measurement inclination angle is 15 degrees among cells existing in the same vertical section. And
The average inclination angle of the inclination angle formed by the <111> crystal orientation and the direction orthogonal to the normal line of the CrN film measurement cross section is calculated, and the difference between the maximum value and the minimum value of the measurement inclination angle among cells existing in the same vertical section Is 15 degrees or less,
The average inclination angle of the inclination angle formed by the <100> crystal orientation and the normal line of the CrN film measurement cross section is calculated, and the difference between the maximum value and the minimum value of the measurement inclination angle is 15 degrees or less among the cells existing in the same vertical section. It has been found that a 100 nm wide longitudinal section occupies more than 60% of the total area measured.

In the region II (coarse grain region) of the modified CrN layer, the generation of cracks in the vertical direction generated from the rake face side is suppressed, and the crystal orientation of the fine grain group existing in the region I immediately below is strongly oriented. Since the crystal orientation is such that the deviation is 15 degrees or less, high consistency is introduced at the crystal interface between the region I and the region II, and not only the adhesion strength at the layer interface is increased but also the coarse particles in the region II are used as mediators. It has the effect of enhancing the bonding between the fine grains in the region I, exhibiting high toughness and improving fracture resistance.
In the region I, since a large number of crystal grain boundaries are introduced, the crack propagation in the modified CrN layer is dispersed and the fracture resistance is improved.

When the grain width of the CrN crystal grains in the region I exceeds 50 nm in the modified CrN layer, the above-described crack propagation and dispersion effect and the coarse grain loss suppressing effect in the region II are reduced, while the CrN crystal in the region I is reduced. When the grain size width of the grains is less than 10 nm, the strength of the CrN crystal grains themselves is not maintained, so the grain width of the CrN crystal grains in the region I is determined to be 10 to 50 nm.
Further, regions I and each of definitive to an intermediate height CrN grains with diameter width W of II _iota, the ratio of the values _W ΙΙ / W _Ι is less than 5 W _Iotaiota, coarse CrN crystal grain region II size is not sufficient, not to obtain the effect of enhancing the binding of the fine CrN crystal grain region I, _whereas, W ΙΙ / W Ι is too greater than the crystal grains are coarsened particle diameter width is increased to 100, the release since the easily occur, the value of _W ΙΙ / W Ι was defined as 5 to 100.
Furthermore, when the composition ratio of the CrN film is expressed by CrN _x , if the nitrogen content ratio x with respect to Cr is less than 0.7, the nitrogen content ratio is low and the desired wear resistance and heat resistance cannot be exhibited. It is not preferable, and if it exceeds 2.0, the Cr content is low, and a desired high-temperature strength cannot be obtained. Therefore, the value of x is set to 0.7 to 2.0.

  Further, the modified CrN layer of the present invention has an occupied area of 60% or more in the vertical section in which the crystal orientation deviation is 15 degrees or less in the growth direction from the surface of the tool base to the surface of the hard coating layer. As described above, high bonding force is exhibited at the interface between the coarse particles in region II and the fine particles in region I, and the fine crystal grains in region I exhibit high toughness through the coarse particles in region II. It is.

  In the coated tool of the present invention, the hard coating layer made of the modified CrN layer is composed of a region I in which the particle size width of CrN crystal grains is small and a region II in which the particle size width is larger than this, and the region I is fine. Because the area ratio of the vertical section where the deviation of the crystal orientation of the particles and the coarse particles in the region II is 15 degrees or less is high, the dry interrupted heavy cutting conditions in which impact / intermittent high load acts on the cutting blade, continuous Even under dry continuous high-feed cutting conditions where high loads are applied, it exhibits excellent fracture resistance and toughness in addition to excellent high-temperature strength, exhibits excellent tool characteristics, and contributes to the extension of tool life. is there.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic of the ion plating apparatus using the pressure gradient type | mold Ar plasma gun in order to vapor-deposit and form the hard coating layer (modified | denatured CrN layer) of the surface coating cutting tool of this invention is shown, (a) is a schematic front view, ( b) is a schematic plan view. The schematic of a sputtering (SP) apparatus for vapor-depositing and forming the hard coating layer (conventional CrN layer) of the conventional surface coating cutting tool is shown. The schematic diagram of the hard coating layer which consists of the modified CrN layer of the surface coating cutting tool of this invention is shown, (a) is a layer thickness direction longitudinal cross-sectional schematic diagram, (b) is along an II surface. FIG. It is a schematic explanatory drawing which shows the measurement range of the inclination angle with respect to the direction orthogonal to the normal line direction with respect to a cross-section grinding | polishing surface in the crystal orientation <111> of the CrN crystal grain in the area | region I of a hard coating layer.

Next, the coated tool of the present invention will be specifically described with reference to examples.
In addition, although demonstrated centering on a covering insert here, it is applicable not only to a covering insert but to various covering tools, such as a covering end mill and a covering drill.

WC powder, TiC powder, VC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder, and Co powder all having an average particle diameter of 0.8 to 3.0 μm are prepared as raw material powders. Were blended in the composition shown in Table 1, wet mixed by a ball mill for 72 hours, dried, and then pressed into a green compact at a pressure of 100 MPa. The green compact was heated at a pressure of 1400 in a vacuum of 6 Pa. Sintered under the condition of holding at 1 ° C. for 1 hour, and after sintering, a tool base made of a WC-based cemented carbide having an ISO standard / CNMG120408 insert shape by applying a honing process of R: 0.03 to the cutting edge portion. A1 to A11 were formed.

Next, the tool bases A1 to A11 are ultrasonically cleaned in acetone and dried, and then attached to the ion plating apparatus using the pressure gradient type Ar plasma gun shown in FIG. First, the inside of the apparatus was exhausted and the inside of the apparatus was heated to 400 ° C. with a heater while maintaining a vacuum of 1.0 × 10 ⁻³ Pa or less, and then Ar gas was introduced to 2.3 ×. After 10 ⁻² Pa, the discharge power of the pressure gradient type plasma gun is set to 2 kW, Ar ions are generated in the apparatus, and a bias voltage of −200 V is applied to the tool base, so that the tool base is placed in Ar for 10 minutes. After bombarding, the inside of the apparatus was once evacuated to about 1 × 10 ⁻³ Pa,
Under the conditions shown in Table 2, first, without applying a bias voltage to the tool base, the discharge power of the pressure gradient type Ar plasma gun was set to 8 to 10 kW, Ar gas was flowed from 50 sccm to 60 sccm, and nitrogen gas was allowed to flow from 100 sccm to 110 sccm. The pressure in the furnace was maintained at 3 × 10 ^{−2 to} 6 × 10 ⁻² Pa, a plasma beam was incident on the evaporation source to generate vapor of metallic Cr, and ionized with the plasma beam. The region I of the modified CrN layer is deposited for a predetermined time shown in FIG.
Subsequently, the modified CrN layer was applied to the tool base surface for a predetermined time shown in Table 4 in the same manner as described above with a bias voltage of −10 to −20 V applied to the tool base under the conditions shown in Table 2. The surface-coated inserts 1 to 15 of the present invention (hereinafter referred to as the present invention inserts) 1 to 15 as the present coated tool were produced by vapor deposition formation of the region II.
Table 2 shows various conditions for ion plating using a pressure gradient type Ar plasma gun, which are conditions for forming the modified CrN layer of the inserts 1 to 15 of the present invention.

For the purpose of comparison, the tool bases A1 to A11 are ultrasonically cleaned in acetone and dried, and mounted on the sputtering (SP) apparatus shown in FIG. 2, and metal Cr is used as a cathode electrode (evaporation source). First, the inside of the apparatus is evacuated and kept at a vacuum of 0.01 Pa or less while the inside of the apparatus is heated to 300 to 460 ° C. with a heater, Ar gas is introduced at 200 sccm, and the metal Cr and the tool base are mixed. A DC bias voltage of -800 V was applied between them, the tool substrate surface was Cr bombarded for 5 minutes, and then nitrogen gas and Ar gas were introduced into the apparatus as atmospheric gases under the conditions shown in Table 3 to obtain an O.D. In addition to an atmosphere of 5 Pa, a DC bias voltage of −30 V and −50 V is applied as a bias voltage between the metal Cr and the tool base, so that the tool base On the surface of, by depositing form a conventional CrN layer of the target layer thicknesses shown in Table 6 as a hard coating layer, the conventional surface-coated inserts as a conventional coated tool (hereinafter, referred to as conventional insert) 1 to 13 were prepared.
Table 3 shows sputtering conditions for forming the conventional CrN layers of the conventional inserts 1 to 13.

For the modified CrN layers of the inserts 1 to 15 of the present invention and the conventional CrN layers of the conventional inserts 1 to 13, the change in the grain size of the CrN crystal grains in the vertical longitudinal section of the hard coating layer was measured using a scanning electron microscope (manufactured by Carl Zeiss). When observed with ULTRA 55), for example, as illustrated in FIG. 3A, the vicinity of the tool base surface of the modified CrN layer is composed of a region I composed of fine grains having a width of 10 to 50 nm, and further, a hard coating layer. It was observed that the vicinity of the surface was composed of a region II composed of coarse particles having a width of 50 nm or more.
Further, using the focused ion beam processing apparatus, the sample is inclined at 5 degrees with respect to the substrate surface as exemplified by the Y-plane in the schematic diagram shown in FIGS. 3 (a) and 3 (b). Using a transmission electron microscope (JEM-2010F), a sample cut into a width of 7 μm × length of 10 μm × thickness of 100 nm was measured at a position of 0.1 μm in terms of vertical height from the tool base surface and the hard coating layer interface. and particle diameter width W _iota of, measuring the particle radial width W _Iotaiota position 0.1μm vertical depth Convert hard coating layer surface, tables 4 and 5 their values with numeric _W ΙΙ / W Ι It was shown to.
Incidentally, the particle size width referred to here means that “one line is drawn when a line parallel to the tool base surface is drawn at a position where the height or depth is converted to 0.1 μm in the observed surface. The average value of the lengths of the line segments passing through the particles.
From Table 4, modification CrN layer of the present invention the insert 15 may, from the grain diameter width W _iota and hard layer surface of the hard coating layer interface and the tool substrate surface at the location of 0.1μm in vertical height conversion The particle size width W _{の at} a position of 0.1 μm in terms of vertical depth is
_10nm <W Ι <50nm _{and,, 5 <W ΙΙ / W} Ι <100
It can be seen that this relationship is satisfied.
On the other hand, it can be seen from Table 5 that the conventional CrN layers of the conventional inserts 1 to 13 do not satisfy the relational expression.

Next, with respect to the modified CrN layers of the inserts 1 to 15 of the present invention and the conventional CrN layers of the conventional inserts 1 to 13, an electron beam backscatter diffraction apparatus (EBSD) is used in a state where the longitudinal section of the hard coating layer is a polished surface. Then, the crystal orientation of the longitudinal section of the hard coating layer was analyzed. That is, each measurement point is measured with respect to a normal direction of the cross-section polished surface and an arbitrary direction orthogonal to the normal line at an interval of 0.01 μm / step at an area corresponding to the thickness of the hard coating layer having a width of 10 μm and a height. Of the crystal orientation <111> and the normal direction of the cross-section polished surface and the crystal orientation <100> are measured. Based on the measurement result, the measured area is perpendicular to the substrate surface. Each of the regions divided into 100 nm × 100 nm by dividing each vertical section into a vertical section at a pitch of 100 nm, and further dividing the inside of each vertical section from the interface between the tool base and the CrN film at a pitch of 100 nm in the growth direction of the CrN film. The average value of the three measurement inclination angles of the measurement points existing in the (cell) is calculated, and the difference between the maximum value and the minimum value of the three measurement inclination angles of the plurality of cells existing in the same vertical section is calculated. The Each calculated Re showed these values in Tables 4 and 5.
Then, from Table 4, the modified CrN layer of the insert of the present invention has an average inclination angle formed between the normal direction of the cross-sectional polishing surface and the <111> direction in the cells existing in the longitudinal section, and the method of the cross-sectional polishing surface. Vertical section in which the difference between the average inclination angle formed between the direction perpendicular to the line and the <111> direction and the maximum value and minimum value of the average inclination angle formed between the normal direction of the cross-section polished surface and the <100> direction is 15 degrees or less Occupies 60% or more of the total area.
On the other hand, according to Table 5, the conventional CrN layer of the conventional insert has few vertical sections where the difference between the maximum value and the minimum value of each average inclination angle is 15 degrees or less in the same vertical section (50% or less). I understand that.

Next, about this invention inserts 1-15 and conventional inserts 1-13, in the state where this was screwed to the tip of the tool steel tool with a fixing jig,
Work material: JIS / S10C lengthwise equidistant round bars with 6 vertical grooves,
Cutting speed: 400 m / min. ,
Cutting depth: 3.0mm,
Feed: 0.4 mm / rev. ,
Cutting time: 2 minutes
Of carbon steel under the following conditions (referred to as cutting conditions 1) (normal cutting speed and feed are 250 m / min and 0.3 mm / rev., Respectively),
Work material: JIS / SS400 lengthwise equal 6 round bars with longitudinal grooves,
Cutting speed: 350 m / min. ,
Cutting depth: 3.0mm,
Feed: 0.4 mm / rev. ,
Cutting time: 2 minutes
Dry interrupted high feed cutting test of mild steel under the following conditions (referred to as cutting condition 2) (normal cutting speed and feed are 250 mm and 0.35 mm / rev., Respectively),
And
In any cutting test, the flank wear width of the cutting edge was measured.
The measurement results are shown in Table 6.

From the results shown in Tables 4 and 6, the inserts 1 to 15 of the present invention consist of a region I where the grain width of CrN crystal grains is small and a region II where the grain width is larger, and Since the area ratio of the vertical section where the deviation of the crystal orientation of the fine particles in the vertically continuous region I and the coarse particles in the region II is 15 degrees or less is high, impact and intermittent high loads act on the cutting edge. Clearly shows excellent tool characteristics as well as excellent fracture resistance and toughness in addition to excellent high-temperature strength, even in dry intermittent heavy cutting conditions and dry continuous high-feed cutting conditions that require continuous high loads. It is.
Furthermore, from Tables 4 and 6, among the modified CrN layers of the inserts of the present invention, those with particularly good performance are the average formed by the normal direction of the cross-section polished surface and the <111> direction in the cells existing in the vertical section. An inclination angle, an average inclination angle formed between the direction perpendicular to the normal line of the cross-section polished surface and the <111> direction, and a maximum value and a minimum value of an average inclination angle formed between the normal direction of the cross-section polished surface and the <100> direction. It can be seen that vertical sections with a difference of 5 degrees or less occupy 60% or more of the total area.
On the other hand, from Tables 5 and 6, in the conventional inserts 1 to 13, the conventional CrN layer is inferior in fracture resistance and toughness, and in dry interrupted heavy cutting conditions and in dry continuous high feed cutting conditions, due to defects, etc. It is clear that the service life is reached in a relatively short time.

  As described above, the coated tool of the present invention has not only a coated insert but also various coated tools such as a coated end mill and a coated drill because the hard coating layer (modified CrN layer) has excellent toughness and fracture resistance. As a result, it prevents tool breakage due to insufficient toughness, insufficient strength, etc., and exhibits excellent cutting performance over a long period of use. In addition to being able to respond satisfactorily, the tool life can be extended.

1: Tool substrate 2: Hard coating layer 3: Interface between tool substrate and hard coating layer 4: Outermost surface of hard coating layer 5: 0.1 μm in terms of height perpendicular to the substrate from the interface between the tool substrate and the hard coating layer Position 6: 0.1 μm position in terms of depth perpendicular to the substrate from the outermost surface of the hard coating layer

Claims (2)

In a surface-coated cutting tool in which a hard coating layer made of a CrN film having an average layer thickness of 0.5 to 2 μm is physically vapor-deposited on the surface of a tool base made of a tungsten carbide-based cemented carbide sintered body,
(A) The hard coating layer has a grain width of CrN crystal grains at a height of 0.1 μm from the interface between the tool base and the CrN film at W _I , and a depth position of 0.1 μm from the outermost surface of the CrN film. When the particle size width of a certain CrN crystal grain is W _II ,
10 nm <W _I <50 nm and 5 <W _II / W _I <100
There is a relationship that satisfies
(B) Further, the crystal orientation of the CrN crystal grains in the cross section of the hard coating layer is analyzed using an electron beam backscatter diffractometer, and the measured two-dimensional region is measured every 100 nm in a direction substantially perpendicular to the tool substrate surface. Each of the regions (cells) divided into 100 nm × 100 nm is divided into vertical sections at a pitch of 100 nm, and further, the inside of each vertical section is partitioned from the interface between the tool base and the CrN film in the growth direction of the CrN film at a pitch of 100 nm. Of each measuring point present in
The average inclination angle of the inclination angle formed by the <111> crystal orientation and the normal direction of the CrN film measurement cross section is calculated, and the difference between the maximum value and the minimum value of the measurement inclination angle is 15 degrees among cells existing in the same vertical section. And
The average inclination angle of the inclination angle formed by the <111> crystal orientation and the direction orthogonal to the normal line of the CrN film measurement cross section is calculated, and the difference between the maximum value and the minimum value of the measurement inclination angle among cells existing in the same vertical section Is 15 degrees or less,
The average inclination angle of the inclination angle formed by the <100> crystal orientation and the normal line of the CrN film measurement cross section is calculated, and the difference between the maximum value and the minimum value of the measurement inclination angle is 15 degrees or less among the cells existing in the same vertical section. A surface-coated cutting tool characterized in that the vertical section of 100 nm width occupies 60% or more of the total area measured. 2. The surface-coated cutting tool according to claim 1, wherein when the composition of the CrN film is expressed by CrN _x , the content ratio x of nitrogen with respect to Cr satisfies 0.7 ≦ x ≦ 2.0.

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