JP2014046400A - Surface coating drill having superior thermal conductivity and lubrication property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface coating drill that maintains superior cutting performance for a long period of time, even if used for high speed drilling machining of high hardness materials.SOLUTION: A surface coating drill has a hard coating layer comprising a lower layer and a most surface layer formed at least on an outer circumference on an area of an effective cutting edge length and a chip discharge groove, the lower layer comprising a composite nitride of metal comprising either two kinds among Ti, Al, Cr, and the most surface layer comprising a component system of (TiAl)(NO)being a multiphase tissue layer. When observing a cross section tissue of the multiphase tissue layer, there are present a microfine crystal grain in which a content ratio y of oxygen is less than 0.2, a content ratio x of Al is less than 0.5, a content ratio z of non-metallic element is 0.40-0.60, and an average grain diameter is 30-100 nm, and a metallic phase area in which a content ratio y of oxygen is 0.8 or more, a content ratio x of Al is 0.6 or more, and a content ratio z of non-metallic element is 0.01-0.03 around the microfine crystal grain.

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 thermal conductivity and lubrication characteristics 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, in a surface-coated drill formed by forming a hard coating layer on the surface of a drill base, a composite carbide solid solution layer of Ti, Al, and Cr, a composite nitride solid solution layer of Ti, Al, and Cr, and Ti And a surface-coated drill excellent in wear resistance, including at least one of a composite carbonitride solid solution layer of Al and Cr.

Further, in Patent Document 2, the ratio of the land width / groove width of the drill is in the range of 1.2 to 2.0, and is in the range of a part to the entire drill effective length including the cutting edge portion of the drill. A hard coating made of CrN _{x of} 0.5 to 5.0 μm (satisfying 0.3 ≦ x ≦ 1.0 in atomic ratio) is formed, and C _r O _y (atomic ratio of 0 in the outermost layer) is formed. .3 ≦ y ≦ 1.5), and a lubricating hard film-coated drill having a hard surface coating with a film thickness of 0.01 to 2.0 μm is disclosed.

Moreover, in patent document 3, the hard coating layer of a surface coating drill is comprised by the upper layer and lower layer formed by chemical vapor deposition, and this upper layer is an aluminum oxide layer which has an average layer thickness of 1-15 micrometers, The lower layer is composed of an adhesive Ti compound layer having a total average layer thickness of 3 to 20 μm and a modified Ti-based carbonitride layer, and the modified Ti-based carbonitride layer has a thickness of 2.5 to Ti and Cr composite carbonitride matrix phase having an average layer thickness of 15 μm and satisfying (Ti _1-X Cr _X ) CN (where X = 0.01 to 0.10), and intermittent deposition An average particle size of 0 formed by changing the conditions, satisfying (Ti _1-Y Cr _Y ) CN (where Y = 0.2 to 0.8), and dispersively precipitated at the grain boundaries (island-like) A surface-coated drill comprising a composite carbonitride precipitation phase of 0.01-0.2 μm Ti and Cr It is disclosed.

JP-A-7-237010 JP-A-8-132310 JP 2008-1003006 A

  The automation of drilling machines in recent years is remarkable, and in addition, there is a strong demand for labor saving, energy saving, cost reduction, and efficiency for drilling. 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 is a high-hardness material that generates high temperatures during cutting. When it is used for high-speed drilling, heat conduction is not sufficient, so heat generated at the cutting edge during cutting cannot be released in the shank direction, and the cutting edge becomes hot, so abnormal wear tends to occur. The current situation is that the service life is reached in a relatively short time because the lubrication characteristics are not sufficient and work hardening is likely to occur and the cutting resistance increases.

  In view of the above, the present inventors have proposed a hard coating to provide a surface-coated drill that maintains excellent cutting performance over a long period of time even when used in high-speed drilling of a high-hardness material. The main research was to improve the thermal conductivity and lubrication properties of the layer. As a result, it was found that a hard coating layer formed by forming an outermost surface layer composed of a predetermined mixed phase structure on a predetermined lower layer maintains excellent thermal conductivity and lubrication characteristics over a long period of time. . Based on this knowledge, as a result of extensive research on the hard coating layer, the hard coating layer having a novel structure having both (a) and (b) has excellent heat conduction effect and lubricity. I found out.

(A) The drill base has an average layer thickness of 1.5 to 3.0 [mu] m on at least the outer peripheral portion of the effective cutting edge length region and the chip discharge groove, and any one of Ti, Al, and Cr (Ti _1-x Al _x ) _1-z (N _1-y ) having a lower layer made of a composite nitride of metal of various types and an average layer thickness of 0.3 to 1.0 μm and being a mixed phase structure layer O _y ) forming a hard coating layer composed of an outermost surface layer composed of _z component system,
(B) When observing the cross-sectional structure of the mixed phase tissue layer,
(A) The oxygen content (atomic ratio) y in the total amount of nitrogen and oxygen is less than 0.2, and the Al content (atomic ratio) x in the total amount of Ti and Al is less than 0.5. And the content ratio (atomic ratio) z of nonmetallic elements in the total amount of Ti, Al, nitrogen, and oxygen is 0.40 to 0.60, and is an average included in the range of 30 to 100 nm. Fine crystal grains having a grain size;
(B) Around the fine crystal grains, the oxygen content (atomic ratio) y in the total amount of nitrogen and oxygen is 0.8 or more, and the Al content in the total amount of Ti and Al (atom Ratio) x is 0.6 or more, and there is a metal phase region in which the content ratio (atomic ratio) z of the nonmetallic element in the total amount of Ti, Al, nitrogen, and oxygen is 0.01 to 0.03. .

Further, in addition to the conditions (a) and (b),
(C) The area ratio occupied by the metal phase region in the mixed phase structure layer is 5 to 10% in the area ratio in the cross-sectional structure.
It has been found that the hard coating layer exhibits superior thermal conductivity and lubricity when the above conditions are also met.

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.
Plasma gun discharge power: 3kW
Discharge gas flow rate: Argon gas (Ar) gas 40 sccm,
DC bias voltage applied to the drill base: -400V,
After performing bombardment under specific conditions
Drill base temperature: 400-430 ° C.
Evaporation source 1: metal Ti or metal Cr,
Plasma gun discharge power for the evaporation source 1: 8 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 ratio: nitrogen (N ₂ ) gas 100 sccm,
Discharge gas flow rate ratio: Argon (Ar) gas 35 sccm,
DC bias voltage applied to the drill base: -5V,
Deposition time: 30 to 150 min.
The lower layer is formed under certain conditions, and
Drill base temperature: 400-430 ° C.
Evaporation source 1: metal Ti,
Plasma gun discharge power for the evaporation source 1: 7 to 8 kW,
Evaporation source 2: Metal Al,
Plasma gun discharge power to the evaporation source 2: 10 to 11 kW,
Reaction gas flow rate ratio: Nitrogen (N ₂ ) gas 50 sccm,
Reaction gas flow rate ratio: Oxygen (O ₂ ) gas 3-4 sccm,
Discharge gas flow rate ratio: Argon (Ar) gas 40 sccm,
Pulse bias voltage applied to drill base: + 3V / -10V, period 5-8 kHz, negative voltage duty cycle 15-30%
Deposition time: 10-30 min.
The inventors have found that the outermost surface layer can be formed with good reproducibility by forming the outermost surface layer under specific conditions.
The sccm is a general unit representing the flow rate of the reaction gas and discharge gas introduced into the vacuum apparatus. The sccm is a standard cc / min, that is, a normalized ccm (how many cc per minute). ). Normally, ccm standardized at a constant temperature such as 1 atm (atmospheric pressure 1,013 hPa), 0 ° C., 1 atm (atmospheric pressure 1,013 hPa), 25 ° C. or the like is used. Ccm is used.

The present invention has been made based on the above findings,
“(1) Of the drill base, at least on the outer peripheral portion on the region of the effective cutting edge length and on the chip discharge groove, it has an average layer thickness of 1.5 to 3.0 μm, and any one of Ti, Al, and Cr (Ti _1-x Al _x ) _1-z (N _{1 -x} ) has a lower layer made of a composite nitride of two kinds of metals and an average layer thickness of 0.3 to 1.0 μm and is a mixed phase structure layer. _y O _y ) forming a hard coating layer composed of an outermost surface layer consisting of _z component system,
When observing the cross-sectional structure of the mixed phase tissue layer,
(A) The oxygen content (atomic ratio) y in the total amount of nitrogen and oxygen is less than 0.2, and the Al content (atomic ratio) x in the total amount of Ti and Al is less than 0.5. And the content ratio (atomic ratio) z of nonmetallic elements in the total amount of Ti, Al, nitrogen, and oxygen is 0.40 to 0.60, and is an average included in the range of 30 to 100 nm. Fine crystal grains having a grain size;
(B) Around the fine crystal grains, the oxygen content (atomic ratio) y in the total amount of nitrogen and oxygen is 0.8 or more, and the Al content in the total amount of Ti and Al (atom Ratio) x is 0.6 or more, and there is a metal phase region in which the content ratio (atomic ratio) z of the nonmetallic element in the total amount of Ti, Al, nitrogen, and oxygen is 0.01 to 0.03. A surface-coated drill characterized by that.
(2) The surface ratio according to (1), wherein an area ratio occupied by a metal phase region in the mixed phase structure layer is 5 to 10% in an area ratio in a cross-sectional structure perpendicular to the drill base surface. Covered drill. "
It has the characteristics.

  The present invention will be described below.

Average layer thickness of lower layer and outermost layer:
Of the drill base made of cemented carbide sintered body or high-speed steel of the surface-coated drill of the present invention, an average layer thickness of 1.5 to 3 is provided at least on the outer peripheral portion and the chip discharge groove on the region of the effective cutting edge length. 0.0 μm, a lower layer made of a composite nitride of a metal composed of any two of Ti, Al, and Cr, an average layer thickness of 0.3 to 1.0 μm, and a mixed phase structure layer _{(Ti 1-x Al x)} to form a _{1-z (N 1-y} O y) z hard layer comprising the outermost surface layer composed of a component system. Here, the composite nitride of a metal composed of any two of Ti, Al, and Cr constituting the lower layer of the hard coating layer has excellent thermal conductivity and wear resistance, and has a drill base and an outermost surface layer. However, if the thickness of the lower layer is less than 1.5 μm, the desired wear resistance cannot be maintained, while if it exceeds 3.0 μm, chipping of the film occurs. Therefore, the average thickness of the lower layer is set to 1.5 to 3.0 μm. In addition, when the thickness of the outermost surface layer is less than 0.3 μm, a wide range of mixed-phase structure layers in the chip discharge groove are worn out early, and the outermost layer has thermal conductivity and lubricity. On the other hand, if the thickness exceeds 1.0 μm, for example, chipping is likely to occur under severe cutting conditions such as high-speed drilling of a high hardness material, so the average layer thickness of the outermost surface layer is 0.3 to 1.0 μm. It was determined.

Multiphase structure of the outermost layer:
The outermost surface layer has a composition (Ti _1-x Al _x ) _1-z (N _1-y O _y ) _z and an oxygen content ratio (atomic ratio) y in the total amount of nitrogen and oxygen is 0. The fine crystal grains having a grain size within a range of 30 to 100 nm and an Al content ratio (atomic ratio) x in the total amount of Ti and Al of less than 0.5 and the fine Around the crystal grains, the oxygen content (atomic ratio) y in the total amount of nitrogen and oxygen is 0.8 or more, and the Al content (atomic ratio) x in the total amount of Ti and Al is 0. .6 or more, and a mixed phase structure in which a metal phase region having a non-metallic element content ratio (atomic ratio) z of 0.01 to 0.03 in the total amount of Ti, Al, nitrogen, and oxygen is present. .

Composition of fine grains in a mixed phase structure:
If the oxygen content ratio (atomic ratio) y in the total amount of nitrogen and oxygen in the fine crystal grains exceeds 0.2, the desired thermal conductivity cannot be obtained, which is not preferable. Further, when the Al content ratio (atomic ratio) x in the total amount of Ti and Al is 0.5 or more, the lubricity of the outermost surface layer is lowered due to the characteristic that Al has a tendency to adhere or weld. Therefore, the oxygen content (atomic ratio) y in the total amount of nitrogen and oxygen in the fine crystal grains is less than 0.2, and the Al content (atomic ratio) x in the total content of Ti and Al is 0.5. Less than.

Fine grain size in mixed phase structure:
When the grain size of the fine crystal grains is less than 30 nm, the wear resistance as a nitride cannot be exhibited and the strength is lowered, and when it exceeds 100 nm, the crystal grains become excessively coarse and are easily lost and the lubrication characteristics are lowered. Therefore, the grain size of the fine crystal grains is determined to be 30 to 100 nm.

Composition of the metal phase region in the multiphase structure:
If the oxygen content (atomic ratio) y in the metal phase region is less than 0.8, the desired lubricating properties cannot be obtained. Further, if the Al content ratio (atomic ratio) x in the total amount of Ti and Al is less than 0.6, the Ti content ratio is relatively increased and the hardness of the metal phase region is increased, thereby causing chipping. It becomes easy. Moreover, even if the content ratio of oxygen and Al satisfies the above conditions, the content ratio (atomic ratio) z of nonmetallic elements in the total amount of Ti, Al, nitrogen and oxygen is less than 0.01. The formation of oxides during cutting cannot be promoted, and the layer wears out at an early stage. When the amount exceeds 0.03, the lubricating properties of the metal phase region cannot be exhibited. Accordingly, the oxygen content ratio (atomic ratio) y in the total amount of nitrogen and oxygen in the metal phase region is 0.8 or more, and the Al content ratio (atomic ratio) x in the total amount of Ti and Al is 0.00. The content ratio (atomic ratio) z of non-metallic elements in the total amount of 6 or more, Ti, Al, nitrogen and oxygen was determined to be 0.01 to 0.03.

Oxygen content in the total amount of nitrogen and oxygen contained in the multiphase tissue layer:
Furthermore, the oxygen content ratio (atomic ratio) y in the total amount of nitrogen and oxygen contained in the mixed phase structure layer measured without distinguishing between fine crystal grains and metal phase regions is in the range of 0.02 to 0.05. If it is, since it becomes easy to produce oxide formation in cutting, without sacrificing the heat conductive effect which a metal phase has, the characteristic as a tool can be improved further. That is, it is preferable not only to control the oxygen content in each of the fine crystal grains and the metal phase region as described above, but also to control the oxygen amount when viewed in the entire mixed phase structure layer to a predetermined amount. The content ratio (atomic ratio) y of oxygen in the total amount of nitrogen and oxygen contained in the mixed phase tissue layer is preferably in the range of 0.02 to 0.05.

Area ratio occupied by metal phase region in mixed phase structure layer:
The area ratio occupied by the region of the metal phase in the mixed phase structure layer is not necessarily limited, but if it is less than 5%, the thermal conductivity of the metal phase cannot be sufficiently exhibited, preferably Absent. On the other hand, if it exceeds 10%, the lubricating properties deteriorate due to the influence of the adhesion property of the metal phase, etc., which is not preferable. Therefore, the area ratio of the metal phase region in the mixed phase structure layer is preferably 5 to 10%.

The surface-coated drill of the present invention has an average layer thickness of 1.5 to at least an outer peripheral portion and a chip discharge groove on a region of an effective cutting edge length of a cemented carbide sintered body or a high-speed steel drill base. The lower layer is made of a composite nitride of a metal composed of any two of Ti, Al, and Cr, and has an average layer thickness of 0.3 to 1.0 μm. that _{(Ti 1-x Al x)} 1-z (N 1-y O y) to form a hard coating layer comprising an outermost layer made of a component system of _z, when observing the cross-sectional structure of the mixed-phase tissue layer (A) The oxygen content (atomic ratio) y in the total amount of nitrogen and oxygen is less than 0.2, and the Al content (atomic ratio) x in the total amount of Ti and Al is 0. A fine crystal grain having a grain size of less than 5 and in the range of 30 to 100 nm and the fine grain Around the crystal grains, the oxygen content (atomic ratio) y in the total amount of nitrogen and oxygen is 0.8 or more, and the Al content (atomic ratio) x in the total amount of Ti and Al is 0. Is a metal phase region in which the content ratio (atomic ratio) z of nonmetallic elements in the total amount of Ti, Al, nitrogen, and oxygen is 0.01 to 0.03, and Maintaining excellent thermal conductivity and lubrication characteristics over a long period of time because the oxygen content (atomic ratio) y in the combined amount of nitrogen and oxygen contained in the mixed phase structure layer is 0.02 to 0.05. It has an excellent effect of doing.
Furthermore, in addition to the above-described configuration, the area ratio occupied by the metal phase region in the mixed phase structure layer is 5 to 10% in terms of the area ratio in the cross-sectional structure perpendicular to the drill base surface. It has an excellent effect of maintaining excellent thermal conductivity and lubrication characteristics.

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 of the surface covering drill of the present invention is shown. The cross-sectional schematic diagram of the hard coating layer of the surface coating drill of this invention is shown.

  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.
Plasma gun discharge power: 3kW
Discharge gas flow rate: Argon gas (Ar) gas 40 sccm,
DC bias voltage applied to the drill base: -400V,
After performing bombardment treatment under the specific conditions shown in Table 2,
Drill base temperature: 400-430 ° C.
Evaporation source 1: Metal Ti or Metal Cr
Plasma gun discharge power for the evaporation source 1: 8 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 ratio: nitrogen (N ₂ ) gas 100 sccm,
Discharge gas flow rate ratio: Argon (Ar) gas 35 sccm,
DC bias voltage applied to the drill base: -5V,
Deposition time: 30 to 150 min.
The lower layer is formed under the specific conditions shown in Table 2, and
Drill base temperature: 400-430 ° C.
Evaporation source 1: metal Ti,
Plasma gun discharge power for the evaporation source 1: 7 to 8 kW,
Evaporation source 2: Metal Al,
Plasma gun discharge power to the evaporation source 2: 10 to 11 kW,
Reaction gas flow rate ratio: Nitrogen (N ₂ ) gas 50 sccm,
Reaction gas flow rate ratio: Oxygen (O ₂ ) gas 3-4 sccm,
Discharge gas flow rate ratio: Argon (Ar) gas 40 sccm,
Pulse bias voltage applied to drill base: + 3V / -10V, period 5-8 kHz, negative voltage duty cycle 15-30%
Deposition time: 10-30 min.
By forming the outermost surface layer under the specific conditions shown in Table 2, the outermost surface layer having the lower layer and the outermost surface layer having the composition shown in Table 4 and the target layer thickness shown in Table 4, The surface-coated drills 1 to 15 of the present invention having fine crystal grains having the composition and particle size range shown in Table 4 and the metal phase region having the composition shown in Table 4 around them were produced.

For comparison purposes, the cutting edges of the drill bases D-1 to D-4 were honed, ultrasonically cleaned in acetone, and used in the production of the surface-coated drill of the present invention. 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 diagram of FIG.
Drill base temperature: 400-430 ° C.
Plasma gun discharge power: 3kW
Discharge gas flow rate: Argon gas (Ar) gas 40 sccm,
DC bias voltage applied to the drill base: -400V,
After performing bombardment treatment under the specific conditions shown in Table 3,
Drill base temperature: 400-430 ° C.
Evaporation source 1: metal Ti or metal Cr,
Plasma gun discharge power for the evaporation source 1: 8 to 11 kW,
Evaporation source 2: Metal Al,
Plasma gun discharge power to the evaporation source 2: 10 to 11 kW,
Reaction gas flow rate ratio: nitrogen (N ₂ ) gas 100 sccm,
Discharge gas flow rate ratio: Argon (Ar) gas 35 sccm,
DC bias voltage applied to the drill base: -5V,
Deposition time: 30 to 150 min.
The lower layer is formed under the specific conditions shown in Table 3, and
Drill base temperature: 400-430 ° C.
Evaporation source 1: metal Ti,
Plasma gun discharge power for the evaporation source 1: 7 to 8 kW,
Evaporation source 2: Metal Al,
Plasma gun discharge power to the evaporation source 2: 10 to 11 kW,
Reaction gas flow rate ratio: Nitrogen (N ₂ ) gas 50 sccm,
Reaction gas flow rate ratio: Oxygen (O ₂ ) gas None,
Discharge gas flow rate ratio: Argon (Ar) gas 40 sccm,
DC bias voltage applied to drill base: -10V
Deposition time: 10-30 min. ,
By forming the outermost surface layer under the specific conditions shown in Table 3, the outermost surface layer having the lower layer and the outermost surface layer having the composition shown in Table 5 and the target layer thickness shown in Table 5, Comparative surface-coated drills 1 to 15 each having a fine crystal grain having the composition and particle size range shown in Table 5 and a metal phase region having the composition shown in Table 5 therearound were produced.

Next, for the surface-coated drills 1 to 15 and the comparative surface-coated drills 1 to 15 of the present invention,
Work material-planar dimensions: 100 mm × 250 mm, thickness: 80 mm JIS / SUS304 (HB230) plate material,
Spindle speed: 2100 rpm / min.
Feed: 0.20 mm / rev. ,
Hole depth: 50mm,
Stainless steel dry high-speed deep drilling cutting test under the following conditions (a normal rotation speed and feed of a drill having a diameter of 10 mm are 1700 rotations / min. And 0.20 mm / rev., Respectively),
Measure the flank wear width of the tool edge every 5 holes, until the flank wear width of the tip cutting edge surface reaches 0.3 mm, or due to chips, chipping, etc. The number of drilling processes until it was difficult to use was measured. The measurement results are shown in Tables 4 and 5, respectively.

  The lower layer and the outermost surface layer constituting the hard coating layer of the surface coating drills 1 to 15 of the present invention obtained as a result, and further the lower layer and the outermost surface layer constituting the hard coating layer of the comparative surface coating drill 1 to 15 When the average layer thickness was measured by cross-section 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 15 and the comparative surface-coated drills 1 to 15 of the present invention are height-wise equivalent to twice the layer thickness in the layer thickness direction by the focused ion beam processing apparatus. × width: 50 μm × thickness: 100 nm
Then, using a transmission electron microscope, under the condition of an observation acceleration voltage of 200 kV, the lower layer and the outermost layer of the hard coating layer of the surface coating drills 1 to 15 of the present invention and the comparative surface coating drills 1 to 15 are used. Observe the mixed phase structure layer (fine crystal grains and metal phase region) constituting the surface layer, and irradiate the mixed phase structure layer with an electron beam whose diameter is equivalent to the thickness of the mixed phase structure layer. As a result, the composition of each layer was determined, and it was confirmed that the composition in each layer had substantially the same composition as the target composition shown in Tables 4 and 5. Further, the electron beam is narrowed down to an area of 5 nm in diameter, irradiated to 10 of the fine crystal grains contained in the field of view, the composition is measured using an energy dispersive spectrometer, and the average composition is determined as the fine crystal. The values of x, y, and z were calculated from the composition of the grains and the ratio of each element. Similarly, 10 points of the metal phase region included in the visual field are irradiated with an electron beam, the composition is measured using an energy dispersive spectrometer, and the average composition is defined as the composition of the metal phase region. The values of x, y and z were calculated from the respective element ratios.
Furthermore, the particle diameter of the fine crystal grains contained in the mixed phase structure layer was measured, and the average particle diameter was obtained, that is, the diameter of a perfect circle having the same area as the area of the fine crystal grains contained in the mixed phase structure layer was determined. The grain size of fine crystal grains was used. Among the mixed phase structure layers, the same measurement was performed on crystal grains included in the visual field of height: equivalent to layer thickness × width: 10 μm, and the average value was defined as the average particle size. As a result, it was confirmed that the average particle size of the fine crystal grains contained in the mixed phase structure layer of any of the surface-coated drills 1 to 15 of the present invention was within the range of 30 to 100 nm as shown in Table 4. On the other hand, the measurement results of the comparative surface-coated drills 1 to 15 are shown in Table 5. In addition, the cross-section polished surface perpendicular to the drill base of the outermost layer is observed with a scanning electron microscope (SEM) in the range of 1 μm × 1 μm, and the area ratio (%) between the fine crystal grains and the metal phase region is determined from the observed image. It was measured. The results are also shown in Tables 4 and 5.

From the results shown in Table 4, the surface-coated drills 1 to 15 of the present invention have a particle size of 30 to 100 nm on the predetermined lower layer (Ti _1-x Al _x ) _1-z (N _1-y O _{y ) z (x <0.5, y} <0.2) consisting of component fine crystal grains and of _{(Ti 1-x Al x)} 1-z (N 1-y O y) z (0.6 ≦ x , 0.8 ≦ y), the formation of the outermost surface layer composed of a mixed phase structure composed of a metal phase region, and thereby improving the thermal conductivity and lubrication characteristics, thereby increasing the hardness of the material. It is clear that excellent cutting performance is maintained over a long period of time in high-speed drilling.
On the other hand, from the results shown in Table 5, the component composition of the outermost surface layer of the hard coating layer, the grain size of the fine crystal grains, etc. are different from those of the surface coating drill of the present invention, or the lower layer or the outermost surface layer. In comparative surface-coated drills that have a hard coating layer whose average layer thickness is not controlled within a predetermined range, the heat conduction characteristics and lubrication characteristics are not sufficient, so that they are relatively short due to the occurrence of chipping, chipping, peeling, etc. It is clear that the service life is reached in time.

As described above, the surface-coated drill according to the present invention has an average layer thickness of 0.3 to 1. as the outermost surface layer on a drill base made of cemented carbide sintered body or high-speed steel with a predetermined lower layer interposed therebetween. Fine crystal grains having a particle size of 30 to 100 nm at 0 μm and comprising a component system of (Ti _1-x Al _x ) _1-z (N _1-y O _y ) _z (x <0.5, y <0.2) And (Ti _1-x Al _x ) _1-z (N _1-y O _y ) _z (0.6 ≦ x, 0.8 ≦ y) are formed. As a result, excellent heat conduction characteristics and lubrication characteristics are exhibited, and excellent cutting performance is maintained for a long time even in high-speed drilling of high hardness materials, and its industrial applicability is extremely high. large.

Claims (2)

The drill base has an average layer thickness of 1.5 to 3.0 μm on at least the outer peripheral portion on the region of the effective cutting edge length and the chip discharge groove, and consists of any two of Ti, Al, and Cr. a lower layer formed of a composite nitride of a metal, has an average layer thickness 0.3 to 1.0 [mu] m, are mixed-phase tissue layer _{(Ti 1-x Al x)} 1-z (N 1-y O y) forming a hard coating layer composed of an outermost surface layer composed of the component system of _z ,
When observing the cross-sectional structure of the mixed phase tissue layer,
(A) The oxygen content (atomic ratio) y in the total amount of nitrogen and oxygen is less than 0.2, and the Al content (atomic ratio) x in the total amount of Ti and Al is less than 0.5. And the content ratio (atomic ratio) z of nonmetallic elements in the total amount of Ti, Al, nitrogen, and oxygen is 0.40 to 0.60, and is an average included in the range of 30 to 100 nm. Fine crystal grains having a grain size;
(B) Around the fine crystal grains, the oxygen content (atomic ratio) y in the total amount of nitrogen and oxygen is 0.8 or more, and the Al content in the total amount of Ti and Al (atom Ratio) x is 0.6 or more, and there is a metal phase region in which the content ratio (atomic ratio) z of the nonmetallic element in the total amount of Ti, Al, nitrogen, and oxygen is 0.01 to 0.03. A surface-coated drill characterized by that. 2. The surface-coated drill according to claim 1, wherein an area ratio of the metal phase region in the mixed phase structure layer is 5 to 10% in an area ratio in a cross-sectional structure perpendicular to the drill base surface.