JP2013046956A - Surface coated drill excellent in lubrication and wear resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface coated drill that maintains high wear resistance over the long period of time in the drilling condition for a deep hole of wet process high speed.SOLUTION: In the surface coated drill in which a hard coating layer consisting of a component system of (CrAl)N and having a layer thickness of 0.3-5.0 μm exists at the utmost surface on a drill base consisting of a cemented carbide sintered body or a high-speed steel as a grain size composition control layer directly or via an intermediate layer, (a) the value of the content ratio x of Al at the film cross section of the grain size composition control layer of the margin part of the drill exists in the range of at least 0.1 and at most 0.6, and a layer shape Cr high content region in which the value x becomes at most 0.2 and a layer shape Al high content region in which the value of x is at least 0.3 exist, and (b) the average aspect ratio A of the crystal grain in the Cr high content region is 1-5, and (c) the average aspect ratio B of the crystal grain in the Al high content region is 10-70, thereby the problem is solved.

Description

  In the present invention, a chip discharge groove is formed on the outer periphery of the tip of the drill body, and a cutting edge is provided at the tip of the inner peripheral surface of the chip discharge groove facing the drill rotation direction. The present invention relates to a surface-coated drill used for drilling, which maintains excellent lubrication characteristics and wear resistance over a long period of time.

  As such a drill, the tip side of a substantially cylindrical drill body rotated about the axis in the rotation direction of the drill is a cutting blade portion, and a pair of chip discharge grooves are formed on the outer periphery of the cutting blade portion. 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 drill rotation direction around the axis as it goes from the tip flank of the drill body toward the rear end, A so-called two-blade solid drill 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 circumferential surface of these chip discharge grooves facing the rotation direction of the drill. . Therefore, in such a solid drill, the tip side of the inner peripheral surface of the chip discharge groove facing the drill 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 drill, various methods are employed for improving the wear resistance of the drill body.

  For example, in Patent Document 1, an Al highest content point (Ti lowest content point) and an Al lowest content point (Ti highest content point) are alternately present at predetermined intervals in the thickness direction, and the Al highest content point is present. By forming a hard coating layer having a component concentration distribution structure in which the Al (Ti) content continuously changes from the content point to the Al minimum content point and from the Al minimum content point to the Al maximum content point, wear resistance is improved. An improved surface coated drill is disclosed.

  Further, in Patent Document 2, by coating the hard coating layer from the outer peripheral end of the cutting blade toward the rear end side in a range of a length M within 3 × D with respect to the outer diameter D of the cutting blade, There is disclosed a surface-coated drill that prevents chip clogging and does not break.

  Moreover, in patent document 3, the surface covering drill which prevents generation | occurrence | production of chip clogging and does not produce a breakage by carrying out polish processing after coat | covering a hard coating layer on the inner peripheral surface of a chip discharge groove | channel is not produced. It is disclosed.

  Further, in Patent Document 4, a coating layer comprising an outermost layer and an inner layer is provided on the surface of the substrate, the outermost layer is made of aluminum nitride or aluminum carbonitride, and chlorine is contained in the outermost layer in an amount of more than 0 and 0.5 atomic%. A surface-coated drill having excellent lubricity and a long service life is disclosed by containing the following.

  Moreover, in patent document 5, the outermost layer was comprised by CrOy (atomic ratio 0.3 <= y <= 1.5), and the film thickness was provided with the hard coating layer which is 0.01-2.0 micrometers. Discloses a surface-coated drill with improved adhesion resistance or welding resistance.

Further, in Patent Document 6, in a surface-coated cutting tool in which a hard coating layer made of a composite nitride of Cr and Al having a layer thickness of 0.8 to 5.0 μm is deposited on the surface of a tool base, The coating layer is configured as an alternately laminated structure of a thin layer A composed of a granular crystal structure of a composite nitride of Cr and Al and a thin layer B composed of a columnar crystal structure, and each of the thin layer A and the thin layer B is 0.1 The average crystal grain size of the granular crystals constituting the thin layer A is 30 nm or less, and the average crystal grain size of the columnar crystals constituting the thin layer B is 50 to 500 nm. The surface-coated cutting tool characterized by being, and the composite nitride of Cr and Al, when expressed by a composition formula: (Cr _1−X Al _X ) N, 0.55 ≦ X ≦ 0.75 ( However, a surface-coated tool satisfying X is an atomic ratio is disclosed.

JP 2003-326402 A JP 2003-275909 A JP 2003-275910 A JP 2005-297144 A JP-A-8-132310 JP 2010-94744 A

  The automation of drilling machines in recent years is remarkable, and in addition, there are strong demands for labor saving, energy saving, cost reduction and efficiency improvement for drilling, and accordingly, drills for deep holes with higher efficiency such as high feed and high cutting. Although there is a tendency to require machining, the conventional surface-coated drill does not cause any particular problems when drilling various steels and cast irons under normal conditions, but requires lubrication characteristics and wear resistance. In addition, when it is used for wet high-speed deep hole drilling, where chips are easily clogged in the drill chip discharge groove, chips are easily clogged in the chip discharge groove. This is the current situation.

In view of the above, the present inventors provide a surface-coated drill that maintains excellent lubrication characteristics and wear resistance over a long period of time even when used in wet high-speed deep hole drilling. Therefore, the particle size composition of the surface-coated drill in which a hard coating layer having a layer thickness of 0.3 to 5 μm made of the component system of (Cr _1-x Al _x ) N exists as the particle size composition control layer on the outermost surface layer of the drill. As a result of earnest research focusing on the structure of the control layer, the following findings were obtained.

(A) The Al content ratio x in the film cross section of the grain size composition control layer in the margin part of the drill exists in the range of x value of 0.1 to 0.6, and the value of x is 0.2 or less A layered high Cr content region and a layered Al high content region in which the value of x is 0.3 or more are each included in the grain size composition control layer, and (b) a high Cr content The average aspect ratio A of the crystal grains in the region is 1 to 5,
(C) When the average aspect ratio B of the crystal grains in the Al-rich region is 10 to 70, the surface-coated drill provided with such a hard coating layer has a higher wet speed than the conventional surface-coated drill. It has been found that in deep hole machining, it exhibits excellent lubrication properties, wear resistance and chipping resistance.
Moreover, the average layer thickness _{X Cr} of Cr-rich region is present in the range of 30 to 200 nm, and the average layer thickness _{X Al} of Al-rich region is present in the range of 30 to 200 nm, and, in the drill margin X _Cr is gradually increased toward the area from the drill tip to five times the distance of the drill outer diameter, and, X _Al in the drill margin is gradually reduced toward the region of the drill tip, to a distance of 5 times the drill outer diameter It has been found that the lubrication characteristics, wear resistance and chipping resistance are further improved when configured as described above.

The hard coating layer as described above has a drill base attached to an ion plating apparatus using a pressure gradient type Ar plasma gun, which is a kind of physical vapor deposition apparatus shown in the schematic explanatory diagram of FIG.
Drill base temperature: 400-430 ° C.
Evaporation source 1: metal Cr,
Plasma gun discharge power for the evaporation source 1: 9 to 11 kW,
Evaporation source 2: Metal Al,
Plasma gun discharge power for the evaporation source 2: 7 to 8 kW,
Reaction gas flow rate: Nitrogen (N ₂ ) gas 80-100 sccm,
Discharge gas: Argon (Ar) gas 30-35 sccm,
DC bias voltage applied to the drill base: -15 to -10 V,
The drill base that revolves under the specified conditions, with the tip of the drill base fixed in the direction toward the center of rotation and the rotary shaft tilted from the normal of the hearth loading surface by 0 degrees or 35 to 55 degrees The distance between the circumference through which the Cr passes and the Cr hearth is shorter than the distance between the circumference through which the revolving drill base passes and the Al Hearth, that is, in a region where the amount of Cr in the space is relatively high, the film forming speed is high. , while being adjusted to a slow deposition rate at relatively Al content is high region and in accordance with a target layer thickness of X _Cr and X _Al, the revolution speed, closest to the hearth of Cr It can be formed by using a triangular wave-shaped speed control pattern that is maximum at the position and minimum at the position closest to the Al hearth. It has been found that the surface-coated drill having the hard coating layer formed as a result exhibits superior lubrication characteristics and wear resistance in wet high-speed deep hole machining as compared with conventional surface-coated drills.

The present invention has been made based on the above findings,
“(1) (Cr _1-x Al _x ) N component system as a particle size composition control layer on the outermost surface directly or via an intermediate layer on a drill base made of cemented carbide sintered body or high speed steel In a surface-coated drill in which a hard coating layer having a layer thickness of 0.3 to 5.0 μm is present,
(A) The value of the Al content ratio x in the film cross section of the grain size composition control layer in the margin portion of the drill is in the range of 0.1 to 0.6, and the value of x is 0.2 or less. A layered Cr high-content region and a layered Al high-content region where the value of x is 0.3 or more are each included in the particle size composition control layer, and
(B) The average aspect ratio A of the crystal grains in the high Cr content region is 1 to 5, and
(C) A surface-coated drill that maintains high wear resistance over a long period of time, wherein the average aspect ratio B of crystal grains in the high Al content region is 10 to 70.
(2) Average layer thickness _{X Cr} of the Cr-rich region is present in the range of 30 to 200 nm, and the average layer thickness _{X Al} of the Al-rich region is present in the range of 30 to 200 nm, and X _{Cr at the} drill margin gradually increases over the region from the drill tip to a distance of 5 times the outer diameter of the drill, and X _{Al at the} drill margin increases from the drill tip to a distance of 5 times the outer diameter of the drill. The surface-coated drill as set forth in (1), wherein the surface-coated drill gradually decreases over a range of. "
It has the characteristics.

  The present invention will be described below.

A hard coating layer having a layer thickness of 0.3 to 5.0 μm composed of a component system of (Cr _1-x Al _x ) N is directly or via an intermediate layer on the drill base of the surface-coated drill of the present invention. Form. Here, if the thickness of the hard coating layer is less than 0.3 μm, desired wear resistance cannot be maintained, while if it exceeds 5 μm, chipping of the film occurs. Therefore, the layer thickness of the hard coating layer is determined to be 0.3 to 5.0 μm.
Further, in the composition of the hard coating layer (Cr _1-x Al _x ) N, if the value of the Al content ratio x is less than 0.1, the wear resistance of Al is not sufficient, and if it exceeds 0.6, hexagonal crystals The strength of the NaCl-type crystal cannot be maintained because it changes into a structure. Therefore, the value of the Al content ratio x was determined to be 0.1 to 0.6.

In addition, if the average aspect ratio A of the crystal grains in the Cr-rich region exceeds 5, the stable cutting performance of the granular structure cannot be realized. On the other hand, the value of the average aspect ratio A is an average value of values obtained by dividing the long sides of the individual crystal grains by the short sides, and thus does not become less than 1. Therefore, the value of the average aspect ratio A is set to 1-5.
Further, if the average aspect ratio B of the crystal grains in the high Al content region is less than 10, the wear resistance of the columnar structure cannot be realized. On the other hand, if the average aspect ratio B exceeds 70, the bending strength against the shearing force cannot be maintained. Therefore, the value of the aspect ratio B is set to 10 to 70.

The value of the average layer thickness X _Al average layer thickness X _Cr and Al-rich region of the Cr-rich region, it can not exhibit lubricating properties and wear resistance with each below the 30 nm. On the other hand, desired when X _Cr exceeds 200 nm, the proportion of Cr-rich region is relatively large and poor abrasion resistance as compared with Al-rich region, in order to destroy in a Cr-rich region is likely to occur It can not be maintained for tool performance, and if X _Al exceeds 200 nm, the integrated value of the compressive stress introduced in the Al-rich region becomes too large, causing chipping of the coating. _Therefore, the value of _{X Cr} and _{X Al} was determined to be 30 to 200 nm.
The “aspect ratio” as used in the present invention refers to the value of the long side, which is a line segment indicating the measured maximum diameter of each crystal grain, and the value of the short side indicating the maximum diameter in the direction perpendicular to the long side. The value divided by the value. The average aspect ratio is an average value of the measured aspect ratios of the five crystal grains.
In addition, the “region from the drill tip to the distance of 5 times the drill outer diameter” means that the center of the drill is measured in the direction of the shank backward from the tip of the drill cutting edge parallel to the center axis of the drill. An area up to 5 times the maximum diameter in a plane perpendicular to the axis.
In addition, when there are a plurality of Cr-rich regions or a plurality of Al-rich regions in the film thickness direction in the same measurement region, the average values are X _Cr and X _Al .

The surface-coated drill of the present invention has a particle size composition control layer (Cr _1-x Al _x ) on the outermost surface directly or via an intermediate layer on a drill base made of cemented carbide sintered body or high-speed steel. In a surface-coated drill having a hard coating layer having a layer thickness of 0.3 to 5.0 μm composed of N component system, (a) Al content ratio in a film cross section of a grain size composition control layer in a margin portion of the drill A layered high Cr content region in which the value of x is in the range of 0.1 to 0.6, the value of x being 0.2 or less, and the layered Al having a value of x of 0.3 or more A high content region, and (b) the average aspect ratio A of the crystal grains in the Cr high content region is 1 to 5, and (c) the average aspect ratio of the crystal grains in the Al high content region When B is 10 to 70, high lubrication characteristics and resistance to long-term use The surface coating drill to maintain mappings and abrasion resistance and has a characteristic.
Moreover, the average layer thickness _{X Cr} of Cr-rich region is present in the range of 30 to 200 nm, and the average layer thickness _{X Al} of Al-rich region is present in the range of 30 to 200 nm, and the drill margin X _Cr at the drill section gradually increases over a region from the drill tip to a distance of 5 times the drill outer diameter, and X _{Al at the} drill margin section extends from a drill tip to a region of 5 times the drill outer diameter. By forming so as to gradually decrease, the wear resistance can be further improved.
That is, in general deep hole machining, at the tip portion where mechanical load is high and high heat resistance is required at the same time, a high Al content region having a high Al content ratio is larger than a Cr high content region. By configuring with a columnar structure, high wear resistance is maintained over a long period of time. On the other hand, in the chip discharge groove and the margin part behind the drill where slip characteristics and stable wear form are required rather than mechanical load, high Cr content with a high Cr content ratio to further utilize the lubrication characteristics of CrN By configuring the region with a granular structure having a low aspect ratio, it is possible to maintain high lubrication characteristics over a long period while maintaining a minimum wear resistance. At the same time, these regions are layered in the film thickness direction, so that the progress direction of cracks that develop in the film thickness direction generated in the high Al content region mainly composed of a columnar structure is the Cr high content region. Dispersed by the fine granular structure, the impact resistance of the film can be improved.
Furthermore, the X _Cr is gradually increased toward the area from the drill tip to five times the distance of the drill outer diameter, and, X _Al is gradually reduced toward the area from the drill tip to five times the distance of the drill outer diameter From the vicinity of the tip where wear resistance is required to the rear of the tool where lubrication characteristics are required, the effects of both can be expressed in a balanced manner, and the tool life can be extended.
Furthermore, according to the present invention, the composition ratio and the aspect ratio change continuously in the film thickness direction, or X _Al and X _Cr gradually change in the drill axis direction, which is not effective due to post-blast treatment or masking. It achieves extremely stable cutting and longer life than the conventional technology that is continuously processed. According to a general manufacturing method, even if the Al content ratio x is changed, the granular structure / columnar structure does not change dominantly depending on the Al content ratio x. The substrate rotation mechanism, the Cr evaporation source, and the Al evaporation source are arranged in a very unique manner to realize a specific film deposition rate distribution and a specific density distribution of Cr ions and Al ions on the substrate surface during film formation. The surface-coated drill of the invention can be manufactured in a controllable state.

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 (grain size composition control layer) of the surface coating drill of the present invention is shown. The cross-sectional schematic diagram of the hard coating layer (particle size composition control layer) of the surface coating drill of this invention is shown. The schematic of the arc ion plating apparatus for vapor-depositing and forming a conventional covering drill is represented.

  Next, the surface-coated drill 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 base sintered body for forming a drill base is formed, and from the round bar sintered body, the groove forming portion has a diameter x length of 10 mm x 80 mm and a twist angle of 30 degrees by grinding. Made of WC-based cemented carbide with 2 flute shape Le substrate D-1 to D-4 were prepared, respectively.

Next, the cutting blades of these drill bases D-1 to D-4 are honed, 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,
Drill base temperature: 400-430 ° C.
Evaporation source 1: metal Cr,
Plasma gun discharge power for the evaporation source 1: 9 to 11 kW,
Evaporation source 2: Metal Al,
Plasma gun discharge power for the evaporation source 2: 7 to 8 kW,
Reaction gas flow rate: Nitrogen (N ₂ ) gas 80-100 sccm,
Discharge gas: Argon (Ar) gas 30-35 sccm,
DC bias voltage applied to the drill base: -15 to -10 V,
Under the specific conditions shown in Table 2, the tip of the drill base is fixed in the direction toward the center of rotation, and for the present invention coated drills 1-15, the revolution axis of rotation is 0 degrees from the normal of the hearth loading surface. The invention-coated drills 16 to 30 are rotated at an angle of 35 to 55 degrees, and the rotation speed is maximum at a position closest to the Cr hearth, and is minimum at a position closest to the Al hearth. The present invention surface-coated drills 1 to 30 each having a composition shown in Table 2 and a particle size composition control layer having a target layer thickness and an average aspect ratio shown in Tables 4 and 5 are formed. Manufactured.

For comparison purposes, the surfaces of the drill bases D-1 to D-4 are subjected to honing, ultrasonically cleaned in acetone, and dried, and the target is a Cr—Al alloy shown in FIG. While holding and rotating in a state where the drill base is fixed in the vertical direction in the arc ion plating apparatus attached as, while revolving around the axis in the vertical direction as the rotation center axis,
Drill base temperature: 410-420 ° C.
Target 1: Cr-Al alloy,
Arc discharge current for target 1: 80-140A,
Target 2: Cr—Al alloy,
Arc discharge current for target 2: 60-120A
Reaction gas pressure: Nitrogen (N ₂ ) gas 6-10 Pa,
DC bias voltage applied to the drill base: −25 to −5V,
Under the conditions, a conventional coating layer is formed by vapor deposition, and the composition shown in Table 3 and the target layer thickness and average aspect ratio shown in Table 6 are formed on the surfaces of the drill bases D-1 to D-4. Comparative surface-coated drills 1 to 8 each having a conventional layer were manufactured.

Next, for the surface-coated drills 1 to 30 and the comparative surface-coated drills 1 to 8 of the present invention,
Work material-planar dimensions: 100 mm × 250 mm, thickness: 80 mm JIS / SC55 (HB260) plate material,
Cutting speed: 130 m / min. ,
Feed: 0.30 mm / rev. ,
Hole depth: 50mm,
Wet high-speed deep drilling machining test of alloy steel under the conditions of (normal cutting speed and feed rate of drilling hole depth 5D are 110 m / min. And 0.20 mm / rev., Respectively),
Then, the number of drilling operations was measured until the flank wear width of the cutting edge surface reached 0.3 mm, or until the tool chipped. The measurement results are shown in Tables 4, 5, and 6, respectively.

  The particle diameter composition control layer constituting the hard coating layer of the surface coating drills 1 to 30 of the present invention obtained as a result, and further the average layer thickness of the conventional layer constituting the hard coating layer of the comparative surface coating drills 1 to 8, When the cross-section was measured using a scanning electron microscope, all showed the same average value (average value of five locations) as the target layer thickness.

Further, the surface-coated drills 1 to 30 and the comparative surface-coated drills 1 to 8 according to the present invention are height-wise equivalent to twice the layer thickness in the layer thickness direction by a focused ion beam processing apparatus. × width: 5 μm × thickness: 100 nm
After being processed into a thin piece, a particle size composition control layer constituting a hard coating layer of the surface coating drills 1 to 30 of the present invention and a comparative surface coating drill under the condition of an observation acceleration voltage of 200 kV using a transmission electron microscope After observing the grain size structure of the conventional layer constituting the hard coating layer of 1 to 8, from the intersection of the center line in the width direction of the flake and the drill base, toward the surface of the film substantially perpendicular to the drill base, The composition was measured at intervals of 10 nm, and it was confirmed that the composition at each point had substantially the same composition range as the target composition range shown in Tables 2 and 3. Further, the Al content ratio x was the average layer of Cr-rich region of 0.1 to 0.2 thickness _{X Cr} and, included in the Cr-rich region _{(Cr 1-x Al x)} N individual crystal grains of the long sides consisting of component systems Measure the short side and average aspect ratio A Calculated, similarly, Al content ratio x is 0.3 or more 0.6 Al high average layer thickness _{X Al-containing} region and that the following are included in the Al-rich region of _{(Cr 1-x Al x)} N The long side and the short side of each crystal grain composed of the component system were measured, the average aspect ratio B was calculated, and the respective results are shown in Tables 4, 5, and 6. In addition, the long side said here represents the length of the line segment which shows the maximum length in a crystal grain, and a short side is the length of the line segment with the maximum length among the line segments perpendicular to the long side. The aspect ratio is a value obtained by dividing the long side by the short side.

From the results shown in Tables 2, 4 and 5, in the surface-coated drill of the present invention, the particle size composition control layer composed of the component system of (Cr _1-x Al _x ) N is formed on the outermost surface, and the average layer thereof The thickness is 0.3 to 5 μm, the Al content ratio x in the film cross section of the grain size composition control layer in the margin portion of the drill is in the range of 0.1 to 0.6, and the value of x is 0 .2 or less layered Cr high content region and x value of 0.3 or more layered Al high content region exists, and the average aspect ratio A of the crystal grains in the Cr high content region is 1 to 5 and the average aspect ratio B of the crystal grains in the Al-rich region is 10 to 70, it is possible to obtain a surface-coated drill that maintains excellent lubrication characteristics and wear resistance over a long period of time. it is obvious.
The average layer thickness _{X Cr} of Cr-rich region is present in the range of 30 to 200 nm, and the average layer thickness _{X Al} of Al-rich region is present in the range of 30 to 200 nm, and the drill margin X _Cr at the drill section gradually increases over a region from the drill tip to a distance of 5 times the drill outer diameter, and X _{Al at the} drill margin section extends from a drill tip to a region of 5 times the drill outer diameter. It is clear that the gradual decrease results in a surface-coated drill that maintains even better lubricating properties and wear resistance over the long term.
On the other hand, from the results shown in Tables 3 and 6, there is no high content region of Cr and Al in the hard coating layer, or the average aspect ratio and average layer thickness of the high content region of Cr and Al are predetermined. In comparison surface-coated drills with conventional layers that are not controlled within the range, the lubrication characteristics and wear resistance are not sufficient, so that the service life is reached in a relatively short time due to chipping, chipping, peeling, etc. It is clear.

As described above, the surface-coated drill of the present invention has a particle size composition control layer (Cr _{1) on the} outermost surface directly or via an intermediate layer on a drill base made of cemented carbide sintered body or high-speed steel. _{-x Al} x) hard coating layer having an average layer thickness 0.3~5.0μm consisting component system of _N are present, the content ratio x of Al in the film cross-section of the particle size composition control layer of the margin of the drill A layered high Cr content region where the value is in the range of 0.1 to 0.6, and the value of x is 0.2 or less, and the layered Al content of x is 0.3 or more The regions are included in the grain size composition control layer at least one or more, the average aspect ratio A of the crystal grains in the Cr-rich region is 1 to 5, and the average grain size in the Al-rich region With aspect ratio B of 10 to 70, it has excellent lubrication characteristics Ri, and this excellent lubricating properties, even in wet fast deep hole drill processing conditions, is to maintain high wear resistance for a long period of time.

Claims (2)

An average layer made of a component system of (Cr _1-x Al _x ) N as a particle size composition control layer on the outermost surface directly or via an intermediate layer on a drill base made of cemented carbide sintered body or high-speed steel In a surface-coated drill having a hard coating layer having a thickness of 0.3 to 5.0 μm,
(A) The value of the Al content ratio x of the grain size composition control layer in the margin part of the drill is
The layered high Cr content region in the range of 0.1 to 0.6, the value of x being 0.2 or less, and the layered Al high content region of x value being 0.3 or more, At least one layer in each of the particle size composition control layers, and
(B) The average aspect ratio A of the crystal grains in the high Cr content region is 1 to 5, and
(C) A surface-coated drill that maintains high wear resistance over a long period of time, wherein the average aspect ratio B of crystal grains in the high Al content region is 10 to 70. The average layer thickness _{X Cr} of the Cr-rich region is present in the range of 30 to 200 nm, and the average layer thickness _{X Al} of the Al-rich region is present in the range of 30 to 200 nm, and the drill margin X _Cr at the drill section gradually increases over a region from the drill tip to a distance of 5 times the drill outer diameter, and X _{Al at the} drill margin section extends from a drill tip to a region of 5 times the drill outer diameter. The surface-coated drill according to claim 1, which gradually decreases.