JP5287126B2 - A surface-coated cutting tool with a hard coating layer that provides excellent fracture resistance and wear resistance - Google Patents

Description

  The present invention exhibits excellent fracture resistance and wear resistance due to the controlled gradient composition, crystal orientation, and grain boundary character of the hard coating layer, and therefore intermittently large mechanical properties with respect to the cutting edge. The present invention relates to a surface-coated cutting tool (hereinafter referred to as a coated tool) that can extend the life of a cutting tool even when used under severe cutting conditions such as intermittent heavy cutting of steel and cast iron that are loaded. .

  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.

Further, as a coated tool, tungsten carbide (hereinafter referred to as WC) based cemented carbide, titanium carbonitride (hereinafter referred to as TiCN) based cermet, or various types of cubic boron nitride (hereinafter referred to as cBN) based ultra high pressure. A composite nitride of Cr and Al satisfying (Cr _X Al _1-X ) N (wherein X is 0.30 to 0.60 in atomic ratio) on the surface of the tool body made of a sintered material [ Hereinafter, a coated tool formed by physically vapor-depositing a hard coating layer composed of (Cr, Al) N] has been proposed and used for continuous cutting and intermittent cutting of various steels and cast iron.
Furthermore, in the coated tool in which the (Cr, Al) N layer is formed as the hard coating layer, the concentration distribution in the layer of Cr or Al, which is a component of the hard coating layer, is controlled, thereby improving the resistance to heavy cutting. It is known to improve the chipping property.
JP 2004-50381A JP 2006-524748 A Japanese Patent No. 3669700 Japanese Patent No. 3969230

  In recent years, 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 processing, and accordingly, heavy cutting processing such as high feed and high cutting is required. 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, but there is an intermittently large mechanical load on the cutting edge. When used in such intermittent heavy cutting, the cutting edge portion is likely to be damaged, and the progress of wear is promoted. This causes the service life to be reached in a relatively short time.

In view of the above, the present inventors pay attention to the (Cr, Al) N layer, which is a hard coating layer, in order to further extend the service life of the conventional coated tool. As a result of earnest research,
(A) The above-mentioned conventional coated tool is, for example, mounted on the tool base on an arc ion plating (AIP) apparatus which is one type of physical vapor deposition apparatus schematically shown in FIG.
In-apparatus heating temperature: 300-500 ° C
DC bias voltage applied to the carbide substrate: −60 to −100 V,
Cathode electrode: Cr-Al alloy,
Arc discharge current between the cathode electrode and the anode electrode: 60 to 100 A,
Nitrogen gas pressure in the apparatus: 1 to 6 Pa,
(Hereinafter referred to as normal conditions), the hard coating layer satisfies the above composition formula: (Cr _X Al _1-X ) N (where X is 0.30 to 0.60 in terms of atomic ratio) ( It is manufactured by forming a Cr, Al) N layer [hereinafter referred to as a conventional (Cr, Al) N layer].
However, the formation of the (Cr, Al) N layer is performed, for example, on 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. Wearing
Tool substrate temperature: 350 to 500 ° C.
Evaporation source: Metal Al, Metal Cr,
Plasma gun discharge power: 3-12 kW,
Nitrogen gas flow rate: 50-70 sccm,
In-apparatus gas pressure: 0.04-0.08 Pa,
DC bias voltage applied to tool base: -5 to -10 V
In addition, the Ar plasma gun discharge power for plasma assist is set to 2 to 4 kW, and the substrate is irradiated with plasma to increase the ionization rate of the deposited particles. When vapor deposition is performed while relatively changing the plasma gun discharge power applied to a certain metal Al and metal Cr, a (Cr, Al) N layer formed as a result [hereinafter, a modified (Cr, Al) N layer is formed. Is the content ratio of Cr in the total amount with Al from the lower side (tool base side) toward the upper side (surface side) along the thickness direction of the modified (Cr, Al) N layer. It has a gradient composition in which X (atomic ratio) gradually increases.

(B) Further, with respect to the modified (Cr, Al) N layer of (a) and the conventional (Cr, Al) N layer, individual crystal grains using an electron beam backscattering diffractometer (hereinafter referred to as EBSD). As shown in the schematic explanatory diagram of FIG. 1, the crystal orientation of the surface polished surface was irradiated with an electron beam on each crystal grain having a cubic crystal lattice existing within the measurement range of the surface polished surface. The tilt angle formed by the crystal orientation <111> of the crystal grains is measured with respect to the normal line, and the tilt angle between the measured tilt angle and the normal direction is within a range of 0 to 55 degrees. The angle is divided into pitches of 0.25 degrees, and the frequencies existing in each division are tabulated, and the angle θ between the crystal orientations <111> of adjacent crystal grains constituting each crystal grain boundary is measured. When the data is tabulated, the conventional (Cr, Al) N layer is the same as that illustrated in FIG. The distribution of the inclination angle formed by the crystal orientation <111> of the crystal grains with respect to the normal of the surface polished surface may have a peak in the inclination angle section within the range of 0 to 15 degrees with respect to the normal direction. However, the angle distribution of the crystal grain boundaries is as small as about 10% of the small-angle grain boundaries (0 <θ ≦ 15 °), whereas the crystal of the modified (Cr, Al) N layer of (a) above. As shown in FIG. 4, the distribution of the measured tilt angle of the orientation <111> is the area of the crystal grains where the crystal orientation <111> exists in the tilt angle section within the range of 0 to 15 degrees with respect to the normal direction. The crystal orientation is such that the ratio is 50% or more of the total area of the crystal grains, and the ratio of the small-angle grain boundaries (0 <θ ≦ 15 °) is 50% or more in the angular distribution diagram of the crystal grain boundaries.
Furthermore, the area ratio of crystal grains in which the crystal orientation <111> exists within a range of 0 to 15 degrees with respect to the normal direction of the surface polished surface, and the ratio of small-angle grain boundaries in the angular distribution of crystal grain boundaries Varies depending on the substrate temperature, bias voltage, nitrogen gas flow rate, and plasma assist conditions.

(C) According to many test results, as described above, the modified (Cr, Al) N layer is physically applied to the tool base by an ion plating apparatus using a pressure gradient type Ar plasma gun which is a kind of physical vapor deposition apparatus. Conditions for vapor deposition, for example
Substrate temperature: 350-500 ° C
Bias voltage: -5 to -10 V
Nitrogen gas flow rate: 50-70 sccm
Plasma gun discharge power: 3-12 kW
Plasma assist conditions: Ar plasma gun discharge power 2-4 kW
By adjusting as described above, the area ratio of the crystal grains in which the crystal orientation <111> exists in the range of 0 to 15 degrees with respect to the normal line of the surface polished surface accounts for 50% or more of the total area of the crystal grains, In addition, in the angular distribution of the crystal grain boundaries, the crystal arrangement is such that the ratio of 0 <θ ≦ 15 ° occupies 50% or more of the total grain boundaries.

(D) Further, the composition (content ratio) of Cr and Al, which are constituent components of the hard coating layer, is controlled by, for example, controlling the plasma gun discharge power applied to the metal Al or metal Cr as the evaporation source. The overall average composition can be arbitrarily adjusted.
Furthermore, as the deposition time elapses, the plasma gun discharge power for either metal Al or metal Cr is changed / adjusted relatively, and according to the change / adjustment pattern, along the layer thickness direction. It is also possible to form a hard coating layer having a non-homogeneous composition having a desired gradient composition (component concentration gradient).
In any case, by adjusting the temperature of the substrate at the time of vapor deposition formation, bias voltage, nitrogen gas flow rate, plasma assist conditions, etc., a hard film having a desired crystal form and grain boundary characteristics can be vapor deposited, By adjusting the plasma gun discharge power, etc., a hard film having a desired overall average composition and a desired gradient composition (concentration gradient) can be formed by vapor deposition. It is possible to provide a coated tool provided with a hard coating layer that exhibits excellent fracture resistance and wear resistance in intermittent heavy cutting in which a high load acts intermittently.
The knowledge shown in (a) to (d) above has been obtained.

This invention has been made based on the above findings,
“A hard coating layer composed of a composite nitride layer of Cr and Al having an average layer thickness of 0.5 to 10 μm is deposited on the surface of a tool substrate made of cemented carbide, cermet or cubic boron nitride based ultra-high pressure sintered body. In the formed surface-coated cutting tool,
(A) A composite nitride layer of Cr and Al,
Composition formula: (Cr _X Al _1-X ) N
In the case of
As a whole of the composite nitride layer of Cr and Al, the Cr content ratio X (where X is an atomic ratio) has an overall average composition satisfying 0.40 to 0.70. The Cr content ratio X in the layer is from 0.3 to 1.0 as it goes from the lower side (tool base side) to the upper side (surface side) along the thickness direction of the Al composite nitride layer. Having a gradually increasing gradient composition;
(B) For the Cr and Al composite nitride layer, the crystal orientation of each crystal grain is analyzed using an electron beam backscattering diffractometer,
(A) The inclination angle formed by the crystal orientation <111> of the crystal grains with respect to the normal direction of the surface polished surface is measured, and the measurement inclination angle is within a range of 0 to 55 degrees with respect to the normal direction. When the measured tilt angles are divided into pitches of 0.25 degrees and the frequencies existing in each section are tabulated, the crystal grains having the crystal orientation <111> exist in the tilt angle sections within the range of 0 to 15 degrees. The crystal orientation in which the area ratio is 50% or more of the total area of the crystal grains,
(B) When the angle between the crystal orientations <111> of adjacent crystal grains constituting the crystal grain boundary is measured, the ratio of the small-angle grain boundaries where the angle formed is greater than 0 degree and equal to or less than 15 degrees is the total grain boundary Of 50% or more of
A surface-coated cutting tool, wherein a hard coating layer composed of a composite nitride layer of Cr and Al satisfying the above (a) and (b) is formed by vapor deposition. "
It has the characteristics.

(A) In the modified (Cr, Al) N layer constituting the hard coating layer of the coated tool of the present invention, the Cr component improves high temperature strength, while the Al component is high temperature hardness and heat resistance (high temperature characteristics). It contains for the purpose of improving.
First, the (Cr, Al) N layer is
Composition formula: (Cr _X Al _1-X ) N
When the X value indicating the content ratio of the Cr component representing the overall average composition of the entire layer is less than 0.40 in terms of the ratio (atomic ratio) to the total amount with the Al component, relatively Al When the X value indicating the ratio of Cr exceeds 0.70, the relative decrease in the high-temperature strength of the entire layer is unavoidable, and as a result, chipping is likely to occur. In addition, since the ratio of Al becomes too small, the desired excellent high-temperature characteristics cannot be ensured, and this causes acceleration of wear, so the X value was set to 0.40 to 0.70.

(B) Further, according to the present invention, the lower layer side (tool base side) of the (Cr, Al) N layer is directed to the upper side (surface side) along the layer thickness direction while maintaining the overall average composition. Accordingly, a modified (Cr, Al) N layer having a gradient composition (component concentration gradient) in which the Cr content ratio X in the layer gradually increases from 0.3 to 1.0 was formed by vapor deposition.
The formation of the above gradient composition (concentration gradient) in vapor deposition changes the plasma gun discharge power applied to at least one of metal Al and metal Cr as the vapor deposition time elapses (growth of the vapor deposition film). This is done by adjusting.
That is, at the start of vapor deposition, it is an evaporation source so that a vapor deposition film composed of (Cr _0.3 Al _0.7 ) N layer, that is, X = 0.3 is formed on the lower side (tool base side). The plasma gun discharge power to metal Cr and metal Al is adjusted to 7 kW and 12 kW, respectively, and, as the deposition progresses, the plasma gun discharge power to metal Cr is gradually increased to be an evaporation source. The plasma gun discharge power to the metal Al is relatively gradually reduced, and at the end of the deposition, the supply of the plasma gun discharge power to the metal Al is stopped and only the metal Cr is vaporized, so that the upper side (surface side) Substantially deposits a CrN layer, ie X = 1.0.
On the lower side (tool base side) of the modified (Cr, Al) N layer, the Al content is relatively high (X = 0.3), so sufficient high-temperature hardness and heat resistance (high-temperature characteristics) are maintained. As a result, wear resistance is ensured, while the upper side (surface side) is substantially formed of a CrN layer (X = 1.0). Chipping and chipping resistance are improved. And although the modified (Cr, Al) N layer has different film properties on the lower side (tool base side) and the upper side (surface side), the composition shows a continuous change. In addition, since there is no discontinuous region of composition, the modified (Cr, Al) N layer has excellent film strength as a whole, even in intermittent heavy cutting where intermittent high load acts on the cutting edge part, There will be no film loss or peeling.
However, if the average layer thickness of the hard coating layer made of the modified (Cr, Al) N layer is less than 0.5 μm, it is insufficient to ensure the desired wear resistance, while the average layer thickness is 10 μm. If it exceeds 1, the film tends to be peeled off or chipped, so the average layer thickness was determined to be 0.5 to 10 μm.

Further, regarding the crystal form of the hard coating layer composed of the modified (Cr, Al) N layer, the crystal orientation is within a range of 0 to 15 degrees with respect to the normal line of the surface polished surface of the (Cr, Al) N layer. The area ratio of the crystal grains in which <111> exists, the ratio of the small-angle grain boundaries in which the angle between the crystal orientations <111> of adjacent crystal grains constituting the crystal grain boundary is more than 0 degree and 15 degrees or less are vapor deposition. Depending on the conditions, for example, the substrate temperature, bias voltage, nitrogen gas flow rate and plasma assist conditions, many test results indicate that the deposition conditions by ion plating using a pressure gradient Ar plasma gun are the substrate temperature. : 350-500 ° C
Bias voltage: -5 to -10 V
Nitrogen gas flow rate: 50-70 sccm
Plasma assist conditions: Ar plasma gun discharge power 2-4 kW
Thus, the area ratio of the crystal grains having the crystal orientation <111> in the range of 0 to 15 degrees with respect to the normal line of the surface polished surface of the (Cr, Al) N layer is 50 of the total area of the crystal grains. And (Cr, Al) N layer showing a crystal arrangement in which the ratio of 0 ° <θ ≦ 15 ° occupies 50% or more of all grain boundaries in the angular distribution of crystal grain boundaries. it can.
However, the area ratio of the crystal grains having the crystal orientation <111> in the range of 0 to 15 degrees with respect to the normal line is less than 50%, or 0 ° <θ ≦ 15 ° in the angular distribution of the crystal grain boundaries. When the ratio of the amount is less than 50% of the total grain boundary, the (Cr, Al) N layer cannot be provided with the above crystal arrangement, and as a result, the coated tool is expected to have excellent fracture resistance. I can't do it.

  The coated tool of the present invention has a modified (Cr, Al) N layer that constitutes the hard coating layer thereof having a special gradient composition and crystal arrangement, so that a high load intermittently acts on the cutting blade. In intermittent heavy cutting such as cast iron, it exhibits excellent fracture resistance and wear resistance, contributing to the extension of the service life.

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

As raw material powders, 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 1 to 3 μm, were prepared. And then wet-mixed with a ball mill for 72 hours, dried, and press-molded into a green compact at a pressure of 100 MPa. The green compact was vacuumed at 6 Pa at a temperature of 1400 ° C. for 1 hour. Sintered under holding conditions, and after sintering, tool edge A-1 made of WC-based cemented carbide with ISO standard and CNMG120408 insert shape by applying a honing process of R: 0.03 to the cutting edge portion. A-10 was formed.

Further, as raw material powders, TiCN (mass ratio, TiC / TiN = 50/50) powder, Mo ₂ C powder, ZrC powder, NbC powder, TaC powder, WC, all having an average particle diameter of 0.5 to 2 μm. Prepare powder, Co powder, and Ni powder, mix these raw material powders into the composition shown in Table 2, wet mix for 24 hours with a ball mill, dry, and press-mold into green compact at 100 MPa pressure The green compact was sintered in a nitrogen atmosphere of 2 kPa at a temperature of 1500 ° C. for 1 hour. After sintering, the cutting edge portion was subjected to a honing process of R: 0.03 to meet ISO standards / Tool bases B-1 to B-6 made of TiCN-based cermet having an insert shape of CNMG120408 were formed.

Next, each of the tool bases A-1 to A-10 and B-1 to B-6 was ultrasonically cleaned in acetone and dried, and mounted on the vapor deposition apparatus shown in FIG. As a source, metal Al and metal Cr were mounted. First, the tool base was heated to 400 ° C. while maintaining a vacuum of 1 × 10 ⁻² Pa or less by evacuating the inside of the apparatus, and then Ar gas was introduced. After setting the pressure to 2.0 Pa, by applying a bias voltage of −500 V to the tool base, the tool base is subjected to Ar bombardment for 20 minutes, and then the inside of the apparatus is once evacuated to about 1 × 10 ⁻³ Pa. The discharge power of the pressure gradient type Ar plasma gun to metal Al and metal Cr was 7 kW and 12 kW, respectively, a bias voltage of -5 V was applied to the tool base, and the pressure in the furnace was reduced to 0. 0 Maintaining Pa, setting the discharge power of the Ar plasma gun to 3 kW, irradiating the substrate with Ar plasma, a plasma beam is incident on the evaporation source, and first, vapor of metal Cr and metal Al is generated and ionized by the plasma beam. Further, by gradually reducing the plasma beam irradiation amount to the metal Al as the evaporation source as the deposition progresses, the target overall average composition, target gradient composition, crystal characteristics and By subjecting the modified (Cr, Al) N layer having the target layer thickness to vapor deposition as a hard coating layer, the present surface coated inserts (hereinafter referred to as the present coated inserts) 1 to 16 as the coated tools of the present invention are formed. Each was manufactured.

  For comparison purposes, each of the tool bases A-1 to A-10 and B-1 to B-6 was ultrasonically cleaned in acetone and dried, and then the arc ion plating shown in FIG. Attached to the device, a Cr—Al alloy having a predetermined composition is attached as a cathode electrode (evaporation source). First, the device is evacuated and kept at a vacuum of 0.5 Pa or less with a heater. After heating the interior to 500 ° C., Ar gas is introduced to make an atmosphere of 0.7 Pa, and a DC bias voltage of −200 V is applied to the tool base, and the tool base surface is bombarded with argon ions. Then, nitrogen gas is introduced into the apparatus as a reaction gas to obtain a predetermined atmosphere within a range of 1 to 6 Pa, and a DC bias voltage applied to the tool base is −60 to −100V. An arc discharge is generated by applying a current of 80 A between the anode electrode and a Cr—Al alloy having a predetermined composition as the cathode electrode, and the surface of the tool base is shown in Table 4. Conventional coated inserts 1 to 16 as conventional coated tools were manufactured by depositing a conventional (Cr, Al) N layer having a target composition and a target layer thickness as a hard coating layer, respectively.

Next, for the above-described coated inserts 1 to 10 and the conventional coated inserts 1 to 10, in the state where this is screwed to the tip of the tool steel tool with a fixing jig,
Work material: JIS / SNCM439 round direction bar with 4 equal intervals in the length direction,
Cutting speed: 235 m / min. ,
Cutting depth: 2.5 mm,
Feed: 0.38 mm / rev. ,
Cutting time: 3 minutes,
A dry interrupted heavy cutting test of alloy steel under the following conditions (referred to as cutting conditions A1) (normal cutting and feeding are 1.5 mm and 0.15 mm / rev., Respectively),
The flank wear width of the cutting blade was measured.

Moreover, about the said invention covering inserts 11-16 and the conventional covering inserts 11-16, in the state which this was screwed to the front-end | tip part of the tool steel tool bit with a fixing jig,
Work material: JIS · SCM440 lengthwise equidistant 4 vertical grooved round bar,
Cutting speed: 220 m / min. ,
Cutting depth: 1.5 mm,
Feed: 0.24 mm / rev. ,
Cutting time: 3 minutes,
A dry interrupted heavy cutting test of alloy steel under the above conditions (referred to as cutting conditions A2) (normal cutting and feeding are 1.0 mm and 0.12 mm / rev., Respectively),
The flank wear width of the cutting blade was measured.
Table 5 shows the measurement results of the cutting tests A1 and A2.

Further, as raw material powders, cubic boron nitride (cBN) powder, titanium nitride (TiN) powder, Al powder, aluminum oxide (Al ₂ O ₃ ) powder each having an average particle diameter in the range of 0.5 to 4 μm. These raw material powders were blended in the blending composition shown in Table 6, wet-mixed with a ball mill for 80 hours, dried, and then had a size of diameter: 50 mm × thickness: 1.5 mm at a pressure of 120 MPa. The green compact is press-molded, and then the green compact is sintered in a vacuum atmosphere at a pressure of 1 Pa at a predetermined temperature within the range of 900 to 1300 ° C. for 60 minutes and pre-baked for cutting edge pieces. A WC-based cemented carbide support piece having a size of Co: 8% by mass, WC: remaining composition, and diameter: 50 mm × thickness: 2 mm was prepared as a sintered body. Normal super-high in a superposed state After charging into the pressure sintering machine, sintering at ultra high pressure at a predetermined temperature within the range of pressure: 5 GPa, temperature: 1200-1400 ° C., holding time: 0.8 hours, after sintering The upper and lower surfaces are polished with a diamond grindstone and divided into 3 mm regular triangles with a wire electric discharge machine, and Co: 5% by mass, TaC: 5% by mass, WC: remaining composition and CIS standard SNGA120412 The brazing part (corner part) of the WC-based cemented carbide insert body having a shape (thickness: 4.76 mm × one side length: 12.7 mm square) is mass%, Cu: 26%, Ti : 5%, Ni: 2.5%, 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 width of the cutting edge is 0.13 mm, angle : 25 ° honing is applied. The tool substrate C1~C10 having the insert shape of ISO standard SNGA120412 by performing finish polishing was produced, respectively.

Next, the tool bases C-1 to C-10 are ultrasonically washed in acetone and dried, and then attached to the vapor deposition apparatus shown in FIG. 2, and metal Cr and metal Al are attached as evaporation sources. First, the inside of the apparatus is evacuated and the tool base is heated to 400 ° C. while maintaining a vacuum of 1 × 10 ⁻² Pa or less, Ar gas is introduced to 2.0 Pa, and then the tool base is − By applying a bias voltage of 200 V, the tool base was subjected to Ar bombardment for 20 minutes, and then the inside of the apparatus was once evacuated to about 1 × 10 ⁻³ Pa, and then pressure gradient type to metal Al and metal Cr The discharge power of the Ar plasma gun was set to 12 kW and 7 kW, a bias voltage of -3 V was applied to the tool base, the discharge power of the Ar plasma gun was set to 3 kW, and the base was irradiated with Ar plasma, while the evaporation source By injecting a plasma beam, generating vapor of metal Cr and metal Al, ionizing with the plasma beam, and further gradually reducing the amount of plasma beam irradiation to the metal Al as the evaporation source as the deposition proceeds, The coating of the present invention is performed by vapor-depositing a modified (Cr, Al) N layer having the target total average composition, target gradient composition, crystal characteristics and target layer thickness shown in Table 7 as a hard coating layer on the surface of the tool substrate. The surface-coated cBN-based insert of the present invention (hereinafter referred to as the present invention-coated insert) 21 to 30 as a tool was manufactured.

  For comparison purposes, each of the tool bases C-1 to C-10 is ultrasonically cleaned in acetone and dried, and then loaded into the ordinary arc ion plating apparatus shown in FIG. Then, as the cathode electrode (evaporation source), a Cr—Al alloy having a component composition corresponding to the target composition shown in Table 3 is mounted, and the inside of the apparatus is first evacuated and kept at a vacuum of 0.1 Pa or less. However, after heating the inside of the apparatus to 500 ° C. with a heater, Ar gas was introduced to create an atmosphere of 0.7 Pa, and a DC bias voltage of −200 V was applied to the tool base, so that the surface of the tool base was After bombarding with argon ions, nitrogen gas is introduced into the apparatus as a reaction gas to make a reaction atmosphere of 3 Pa, and a bias voltage applied to the tool base is set to −30V. Arc discharge is generated between the cathode electrode and the anode electrode of the Cr—Al alloy having the predetermined composition, and the target compositions and targets shown in Table 8 are formed on the surfaces of the tool bases C-1 to C-10. Conventional surface-coated cBN-based sintered inserts (hereinafter referred to as conventional coated inserts) 21 to 30 as conventional coated tools are manufactured by vapor-depositing a hard coating layer composed of a conventional (Cr, Al) N layer having a layer thickness. did.

Next, of the various coated inserts described above, the present coated inserts 21 to 30 and the conventional coated inserts 21 to 30 of the present invention with the fixing tool fixed to the tip of the tool steel tool. The invention coated inserts 21 to 25 and the conventional coated inserts 21 to 25 are subjected to a cutting test under the following cutting conditions B1, and the present invention coated inserts 26 to 30 and the conventional coated inserts 26 to 30 are also the following. A cutting test was performed under the cutting conditions C1 shown in FIG.
[Cutting conditions B1]
Work material: JIS / SCM415 quenching material (HRC60), 4 longitudinally spaced round bars with equal intervals in the length direction,
Cutting speed: 190 m / min. ,
Cutting depth: 0.28 mm,
Feed: 0.21 mm / rev. ,
Cutting time: 3 minutes,
Dry interrupted heavy cutting test of hardened alloy steel under the conditions (normal cutting and feeding are 0.15 mm and 0.10 mm / rev., Respectively),
[Cutting conditions C1]
Work material: JIS · SCr420 carburized quenching material (HRC60) in the longitudinal direction of four equally spaced round bars,
Cutting speed: 210 m / min. ,
Cutting depth: 0.20 mm,
Feed: 0.16 mm / rev. ,
Cutting time: 3 minutes,
Carved and hardened alloy steel under the conditions of dry interrupted heavy cutting test (normal cutting and feeding are 0.15 mm and 0.10 mm / rev., Respectively),
In each cutting test, the flank wear width (mm) of the cutting edge was measured. The measurement results are shown in Table 9.

  From the results shown in Tables 5 and 9, the coated inserts 1 to 16 and 21 to 30 of the present invention each have a hard coating layer made of a modified (Cr, Al) N layer and have excellent fracture resistance. Therefore, even when used in heavy cutting where a large mechanical load is applied to the cutting edge, there is no defect in the hard coating layer, and excellent wear resistance is demonstrated over a long period of time. On the other hand, it is clear that the conventional coated inserts 1-16, 21-30, in which the hard coating layer is a conventional (Cr, Al) N layer, have defects in the hard coating layer and reach the service life in a short time. .

As raw material powders, medium coarse WC powder having an average particle diameter of 5.5 μm, fine WC powder of 0.8 μm, TaC powder of 1.3 μm, NbC powder of 1.2 μm, ZrC of 1.2 μm Powder, 2.3 μm Cr ₃ C ₂ powder, 1.5 μm VC powder, 1.0 μm (Ti, W) C [50/50 by mass ratio] powder, and 1.8 μm Co Prepare powders, mix each of these raw material powders with the composition shown in Table 10, add wax, ball mill mix in acetone for 24 hours, dry under reduced pressure, and then press various pressures of a predetermined shape at a pressure of 100 MPa. The powder compact is press-molded, and these green compacts are 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, and this temperature is maintained for 1 hour. After holding, sintering under the condition of furnace cooling, the diameter is 8 m, 13 mm, and 26 mm round bar sintered bodies for forming a carbide substrate were formed, and further, from the above three kinds of round bar sintered bodies, by grinding, in combinations shown in Table 6, Carbide substrate for end mill D- having a shape of a 4-blade square with a diameter x length of the cutting edge of 6 mm x 13 mm, 10 mm x 22 mm, and 20 mm x 45 mm, respectively, and a twist angle of 30 degrees. 1 to D-8 were produced.

  Then, these end mill carbide substrates D-1 to D-8 and the test pieces were ultrasonically cleaned in acetone and dried, and charged in the vapor deposition apparatus shown in FIG. 1 having the target overall average composition, target gradient composition, crystal characteristics and target layer thickness shown in Table 11 under the same conditions as the formation conditions of the modified (Cr, Al) N layer in the present invention coated inserts 1-16. The surface-coated cemented carbide end mills (hereinafter referred to as the present invention-coated end mills) 1 to 8 as the present invention coated tools are produced by vapor-depositing a quality (Cr, Al) N layer as a hard coating layer, respectively. did.

  For comparison purposes, the conventional (Cr, Al) N layer is formed by vapor deposition as a hard coating layer under the same conditions as the conventional (Cr, Al) N layer formation conditions in the conventional coating inserts 1 to 16 of Example 1 above. Thus, conventional surface-coated cemented carbide end mills (hereinafter referred to as conventional coated end mills) 1 to 8 as conventional coated tools as shown in Table 11 were produced.

Next, of the present invention coated end mills 1-8 and the conventional coated end mills 1-8,
About this invention coated end mills 1-3 and conventional coated end mills 1-3,
Work material: Plane dimensions: 100 mm × 250 mm, thickness: 50 mm JIS / SKD61 plate material,
Cutting speed: 130 m / min. ,
Groove depth (cut): 2.5 mm,
Table feed: 1450 mm / min. ,
Die steel dry high feed groove cutting test under the conditions (normal cutting and feed are 1.0 mm and 420 mm / min, respectively),
About this invention coated end mills 4-6 and conventional coated end mills 4-6,
Work material: Plane dimension: 100 mm × 250 mm, thickness: 50 mm JIS / SUS304 plate,
Cutting speed: 120 m / min. ,
Groove depth (cut): 4.5 mm,
Table feed: 1250 mm / min. ,
Stainless steel dry high feed groove cutting test (normal cutting and feed are 1.5 mm and 400 mm / min, respectively),
For the coated end mills 7 and 8 of the present invention and the conventional coated end mills 7 and 8,
Work material: Plane dimension: 100 mm × 250 mm, thickness: 50 mm JIS / SNCM439 plate material,
Cutting speed: 200 m / min. ,
Groove depth (cut): 8 mm,
Table feed: 1560 mm / min. ,
A high-feed groove cutting test of the alloy steel under the conditions (normal cutting and feed are 4 mm and 800 mm / min, respectively),
In each groove cutting test, the cutting groove length was measured until the flank wear width of the outer peripheral edge of the cutting edge reached 0.1 mm, which is a guide for the service life. The measurement results are shown in Table 11, respectively.

  The diameters manufactured in Example 3 above were 8 mm (carbide substrates D-1 to D-3 for end mills), 13 mm (carbide substrates D-4 to D-6 for end mills), and 26 mm (carbide substrates for end mills). D-7 and D-8) were used, and from these three types of round bar sintered bodies, the diameter x length of the groove forming portion was 4 mm x 13 mm (by grinding). Drilling carbide substrates E-1 to E-3), 8 mm × 22 mm (drilling carbide substrates E-4 to E-6), and 16 mm × 45 mm (drilling carbide substrates E-7 and E-8) And the carbide substrates E-1 to E-8 for drills each having a two-blade shape with a twist angle of 30 degrees were manufactured.

  Next, honing is performed on the cutting blades of these carbide substrates E-1 to E-8 for drilling, and ultrasonic cleaning is performed in acetone together with the above test pieces, and the state is also shown in FIG. The target overall average composition and target gradient shown in Table 12 were charged in the vapor deposition apparatus, under the same conditions as the conditions for forming the modified (Cr, Al) N layer in the inventive coated inserts 1-16 of Example 1 above. By drilling and forming a modified (Cr, Al) N layer having a composition, crystal characteristics and target layer thickness as a hard coating layer, a drill made of the surface-coated cemented carbide of the present invention as a coated tool of the present invention (hereinafter referred to as the present invention). 1 to 8 were manufactured.

  For comparison purposes, the conventional (Cr, Al) N layer is formed by vapor deposition as a hard coating layer under the same conditions as the conventional (Cr, Al) N layer formation conditions in the conventional coating inserts 1 to 16 of Example 1 above. Thus, conventional surface-coated cemented carbide drills (hereinafter referred to as conventional coated drills) 1 to 8 as conventional coated tools as shown in Table 12 were produced.

Next, of the present invention coated drills 1 to 8 and the conventional coated drills 1 to 8, the present invention coated drills 1 to 3 and the conventional coated drills 1 to 3 are:
Work material: Plane dimension: 100 mm × 250 mm, thickness: 50 mm JIS / SS400 plate material,
Cutting speed: 124 m / min. ,
Feed: 0.24 mm / rev. ,
Hole depth: 6 mm
Wet high feed drilling test of mild steel under the conditions of (normal feed is 0.12 mm / rev.),
About this invention coated drill 4-6 and conventional coated drills 4-6,
Work material: Plane size: 100 mm × 250 mm, thickness: 50 mm JIS / SUS316 plate material,
Cutting speed: 68 m / min. ,
Feed: 0.17 mm / rev. ,
Hole depth: 10 mm
Wet high feed drilling test of stainless steel under normal conditions (normal feed is 0.10 mm / rev.)
About this invention covering drills 7 and 8 and conventional covering drills 7 and 8,
Work material: Plane dimension: 100 mm × 250 mm, thickness: 50 mm JIS / SCMnH2 plate material,
Cutting speed: 68 m / min. ,
Feed: 0.16 mm / rev. ,
Hole depth: 20 mm
Wet high feed drilling test of high manganese steel under the conditions of (normal feed is 0.10 mm / rev.),
In each wet drilling cutting test (using water-soluble cutting oil), the number of drilling processes until the flank wear width of the tip cutting edge surface reached 0.3 mm was measured. The measurement results are shown in Table 12.

The present invention coated inserts 1-16, 21-30, the present coated end mills 1-8, and the modified (Cr, Al) N layers of the present coated drills 1-8 as the present coated tools obtained as a result, In addition, the composition of the conventional (Cr, Al) N layers of the conventional coated inserts 1 to 16, 21 to 30, the conventional coated end mills 1 to 8 and the conventional coated drills 1 to 8 as a conventional coated tool using an Auger spectroscopic analyzer. It was measured.
First, the total average composition of the modified (Cr, Al) N layer was determined by measuring the composition in the region including the total layer thickness, and obtaining this value as the total average composition.
As for the graded composition of the modified (Cr, Al) N layer, when the layer thickness is t (μm), the thickness is t / 5 (μm) from the lower side (tool base side) of the layer. and is the Cr content in the region value _X L (average of five points measurement), the thickness of the region (the layer of the layer of the lower side 2t / 5 from (tool substrate side) (μm) ~3t / 5 ( μm) Cr content ratio value X _M (average value of 5-point measurement) in the thickness direction intermediate region) and Cr content ratio value X in the thickness region t / 5 (μm) from the upper side (surface side) of the layer _U (average value of 5-point measurement) was measured, and the values of X _L , X _M , and X _U were used as gradient composition index values. That is, in this invention, each index value _{X L, X M, X U} reforming (Cr, Al) N layer is to satisfy _{0.3 ≦ X L <X M <} X U ≦ 1.0 is necessary.
Further, the average composition of the conventional (Cr, Al) N layer was measured in the region including the entire layer thickness as in the case of the modified (Cr, Al) N layer, and this value was obtained as the overall average composition. .
The overall average composition and gradient composition of the modified (Cr, Al) N layer obtained above are substantially the same as the target overall average composition and target gradient composition, and the conventional (Cr, Al) N layer The average composition was substantially the same as the target average composition.

  Further, when the thickness of the modified (Cr, Al) N layer and the conventional (Cr, Al) N layer of the present invention coated tool and the conventional coated tool was measured using a scanning electron microscope, both were measured. The average layer thickness (average value of 5-point measurement) substantially the same as the target value was shown.

Further, with respect to the modified (Cr, Al) N layer of the above-described coated tool of the present invention and the conventional (Cr, Al) N layer of the conventional coated tool, the surfaces of both of the above (Cr, Al) N layers were used as polished surfaces. In the state, the crystal orientation of each crystal grain was analyzed using an electron beam backscatter diffractometer (EBSD) (i.e., the method of the surface polished surface in a 30 × 50 μm region at an interval of 0.1 μm / step). The inclination angle formed by the normal of the (111) plane, which is the crystal plane of the crystal grain, is measured with respect to the line. Based on the measurement result, the inclination angle is within the range of 0 to 55 degrees. A certain tilt angle is divided into pitches of 0.25 degrees and the frequency existing in each zone is totaled to create a tilt angle number distribution graph. In the same region, all crystal grains for Industry, crystal grains of the crystal adjacent its constituent Position measured <111> angle between, was created a graph showing the respective proportions of the said angle, the conventional (Cr, Al) N layer, the crystal orientation of the crystal grains relative to the normal of the surface polishing plane Even if the distribution of the inclination angle formed by <111> has a peak in the inclination angle section in the range of 0 to 15 degrees with respect to the normal direction, the angle distribution of the crystal grain boundary is a small-angle grain boundary ( While the ratio of 0 ° <θ ≦ 15 °) is as small as about 10% (FIG. 5), the measured inclination angle of the crystal orientation <111> of the modified (Cr, Al) N layer of (a) is As illustrated in FIG. 4, the distribution is such that the area ratio of the crystal grains in which the crystal orientation <111> exists in the tilt angle section within the range of 0 to 15 degrees with respect to the normal direction is 50% of the total area of the crystal grains. The crystal orientation is as described above. Further, in the angular distribution of crystal grain boundaries, the ratio of 0 ° <θ ≦ 15 ° is all Indicates 50% or more the crystal orientation of the field (Fig. 4), modification (Cr, Al) N layer had a crystalline sequence as described above.

FIG. 4 shows the measured inclination angle distribution of the crystal orientation <111> with respect to the normal direction of the surface polished surface of the modified (Cr, Al) N layer of the coated tool 1 of the present invention and the angular distribution of the grain boundaries.
FIG. 5 shows the measured tilt angle distribution of the crystal orientation <111> with respect to the normal direction of the surface polished surface of the conventional (Cr, Al) N layer of the conventional coated tool 1 and the angular distribution of the crystal grain boundaries.
As is clear from the comparison between FIG. 4 and FIG. 5, the modified (Cr, Al) N layer shows a crystal structure with a high (111) orientation and a high small-angle grain boundary ratio, It is apparent that the conventional (Cr, Al) N layer has a crystal structure that has no particular characteristics in the grain boundary character.

  From the results shown in Tables 3, 4, 7, 8, 11, and 12, the coated tool of the present invention has a modified (Cr, Al) N layer that constitutes a hard coating layer and has a predetermined gradient composition. (111) Highly oriented and small-angle grain boundary ratio shows a high ratio of crystal structure. As a result, it has excellent fracture resistance. Therefore, in the above various intermittent heavy cutting tests, excellent fracture resistance. In contrast to showing wear resistance, in the conventional coated tool, the hard coating layer has a uniform composition, the proportion of small-angle grain boundaries is low, and as a result, improvement in fracture resistance is not seen, It is clear that intermittent heavy cutting with intermittently large mechanical load generates defects in a relatively short time and reaches the service life.

  As described above, the coated tool of the present invention exhibits excellent tool characteristics in continuous cutting and intermittent cutting of various steels and cast irons, and also has a large machine for cutting edges such as high cutting and high feeding. Even under intermittent heavy cutting conditions where the mechanical load is intermittent, the hard coating layer made of the modified (Cr, Al) N layer has excellent fracture resistance, so it has excellent cutting performance over a long period of time. It can be fully satisfied to meet the demands of FA for cutting devices, labor saving and energy saving of cutting, and cost reduction.

It is a schematic explanatory drawing which shows the measurement range of the inclination angle with respect to the normal line of the surface polishing surface, with the normal line of the (111) plane being the crystal plane of the crystal grains in the various (Cr, Al) N layers constituting the hard coating layer. It is a schematic explanatory drawing of the ion plating apparatus using the plasma used for vapor deposition formation of the modification | reformation (Cr, Al) N layer which has the peculiar crystal arrangement which comprises the hard coating layer of this invention coating tool. It is a schematic explanatory drawing of the arc ion plating (AIP) apparatus used for vapor deposition formation of the conventional (Cr, Al) N layer which comprises the hard coating layer of the conventional coating tool. The modified (Cr, Al) N layer constituting the hard coating layer of the coated insert 1 of the present invention is measured by EBSD, and the measurement inclination angle formed by the crystal orientation <111> of the crystal grains with respect to the normal direction of the surface polished surface; It is an angle distribution graph of a grain boundary. The conventional (Cr, Al) N layer constituting the hard coating layer of the conventional coated insert 1 is measured by EBSD, and the measured inclination angle formed by the crystal orientation <111> of the crystal grain with respect to the normal direction of the surface polished surface, and the crystal grain It is an angle distribution graph of a field.

Claims (1)

A hard coating layer composed of a composite nitride layer of Cr and Al with an average layer thickness of 0.5 to 10 μm is deposited on the surface of a tool substrate made of cemented carbide, cermet or cubic boron nitride based ultra-high pressure sintered body. Surface coated cutting tool
(A) A composite nitride layer of Cr and Al,
Composition formula: (Cr _X Al _1-X ) N
In the case of
As a whole of the composite nitride layer of Cr and Al, the Cr content ratio X (where X is an atomic ratio) has an overall average composition satisfying 0.40 to 0.70. The Cr content ratio X in the layer is from 0.3 to 1.0 as it goes from the lower side (tool base side) to the upper side (surface side) along the thickness direction of the Al composite nitride layer. Having a gradually increasing gradient composition;
(B) For the Cr and Al composite nitride layer, the crystal orientation of each crystal grain is analyzed using an electron beam backscattering diffractometer,
(A) The inclination angle formed by the crystal orientation <111> of the crystal grains with respect to the normal direction of the surface polished surface is measured, and the measurement inclination angle is within a range of 0 to 55 degrees with respect to the normal direction. When the measured tilt angles are divided into pitches of 0.25 degrees and the frequencies existing in each section are tabulated, the crystal grains having the crystal orientation <111> exist in the tilt angle sections within the range of 0 to 15 degrees. The crystal orientation in which the area ratio is 50% or more of the total area of the crystal grains,
(B) When the angle between the crystal orientations <111> of adjacent crystal grains constituting the crystal grain boundary is measured, the ratio of the small-angle grain boundaries where the angle formed is greater than 0 degree and equal to or less than 15 degrees is the total grain boundary Of 50% or more of
A surface-coated cutting tool, wherein a hard coating layer composed of a composite nitride layer of Cr and Al satisfying the above (a) and (b) is formed by vapor deposition.