JP5553013B2 - A surface-coated cutting tool that provides excellent peeling resistance and excellent chipping resistance in high-speed, high-feed cutting of hard difficult-to-cut materials. - Google Patents

Description

  In the present invention, the hard coating layer is composed of a surface layer having excellent welding resistance and excellent adhesion, and therefore, more difficult to cut hard difficult-to-cut materials such as various Ni-based alloys and Ti-based alloys. Surface coating that suppresses the peeling of the hard coating layer due to the occurrence of welding and exhibits excellent peeling resistance and chipping resistance over a long period of time even under high-speed, high-feed cutting conditions where chipping is likely to occur The present invention relates to a cutting tool (hereinafter referred to as a coated tool).

  In general, for coated tools, throwaway inserts that are detachably attached to the tip of the cutting tool for turning and planing of various steel and cast iron materials, drilling of the work material, etc. Drills and miniature drills, and solid type end mills used for chamfering, grooving and shouldering of the work material, etc. A slow-away end mill tool that performs cutting work in the same manner as an end mill is known.

In addition, as a coated tool, on the surface of a tool base composed of tungsten carbide (hereinafter referred to as WC) based cemented carbide or titanium carbonitride (hereinafter referred to as TiCN) based cermet,
(A) having an average layer thickness of 0.8 to 5 μm and a composition formula: (Ti _1-X Al _X ) N (wherein X is 0.40 to 0.75 in terms of atomic ratio) A lower layer consisting of a satisfactory (Ti, Al) N layer,
(B) an adhesive bonding layer comprising a CrN (chromium nitride) layer having an average layer thickness of 0.1 to 0.5 μm;
(C) an upper layer comprising a CrB ₂ (chromium boride) layer having an average layer thickness of 0.8 to 5 μm;
A coated tool (hereinafter referred to as a conventional coated tool) in which a hard coating layer composed of (a) to (c) is formed is known, and this conventional coated tool is composed of a Ti-based alloy or a high Si-containing Al. -It is known that even when hard difficult-to-cut materials such as Si-based alloys are cut under high-speed cutting conditions with high heat generation, excellent wear resistance is exhibited over a long period of time.

Further, in the conventional coated tool, the above-mentioned tool base is inserted into a physical vapor deposition apparatus provided with an arc ion plating apparatus and a direct current sputtering apparatus, and first, the reaction gas is introduced into the apparatus while the apparatus is heated by a heater. As described in (a) above, nitrogen gas is introduced and an arc discharge is generated between the anode electrode of the arc ion plating apparatus and the cathode electrode (evaporation source) on which a Ti—Al alloy having a predetermined composition is set. A lower layer made of a (Ti, Al) N layer is formed, and then sputtering of metal Cr arranged as a cathode electrode (evaporation source) is started while the atmosphere in the DC sputtering apparatus is kept in a nitrogen atmosphere. Thus, a CrN layer is formed as the adhesive bonding layer of (b), and then the atmosphere in the apparatus is set to an Ar atmosphere for a predetermined time. By performing the sputtering of CrB ₂ sintered body, it is also known to be produced by forming an upper layer composed of CrB ₂ layers of the superimposed on the CrN layer (c).

As means for forming a hard coating layer, not only arc ion plating and direct current sputtering but also film formation using high-power pulse sputtering has been proposed. For example, as shown in Patent Documents 2 and 3 (Al, M) ₂ O ₃ (where M is Mg, by applying high power pulse sputtering under the condition that the instantaneous applied power of the pulse is 200 W / cm ² or more and the one wavelength length of the pulse is 100 μsec or less. It is also known that Zn, Mn, Fe, etc.) or α-Al ₂ O ₃ can be deposited at a high deposition rate.

JP 2006-159340 A International Publication No. 2008/148673 International Publication No. 2009/010330

  The performance and automation of cutting machines in recent years have been remarkable. On the other hand, there are strong demands for labor saving and energy saving and further cost reduction for cutting. Accordingly, cutting speed has been increased and types of work materials have been increased. There is a tendency that a versatile coated tool that is not limited to the above is strongly desired. However, in the conventional coated tool, cutting of hard difficult-to-cut materials such as Ti-based alloys and high Si-containing Al-Si based alloys is performed with high heat. Although it exhibits excellent wear resistance when performed under high-speed cutting conditions with generation, it performs cutting of hard difficult-to-cut materials such as various Ni-based alloys and Ti-based alloys under high-speed, high-feed cutting conditions. In such a case, welding is likely to occur due to extremely high heat generated during cutting, and the hard coating layer is peeled off due to this, and the service life is reached in a relatively short time.

Therefore, in order to develop a coated tool that exhibits excellent welding resistance and peeling resistance in which the hard layer is excellent in the high-speed high-feed cutting of the hard difficult-to-cut material from the above-described viewpoint, As a result of earnest research, the following findings were obtained.
First, in a conventional coated tool (Patent Document 1), a CrB ₂ layer is formed by direct current sputtering, and this is subjected to high-speed cutting such as hard difficult-to-cut materials such as Ti-based alloys and high Si-containing Al-Si based alloys. When used for machining, there is no particular problem, but when this is used to cut hard difficult-to-cut materials such as various Ni-based alloys and Ti-based alloys under high-speed, high-feed cutting conditions. Since the surface structure is dense, the contact area with the work material is large, welding is caused by extremely high heat generation, and the bond between the crystal grains of the CrB ₂ layer is weak, so the hard coating layer by the welding It was found that peeling occurred.
Accordingly, the present inventors have welding occurs hardly occurs, and, as a result of research by focusing on high CrB ₂ layer tissue binding strength of the crystal grains mutually, when forming the CrB ₂ layers, Patent Document 1 By adopting high-power pulse sputtering under specific conditions instead of the direct current sputtering shown in Fig. 4, surface texture can be obtained even in cutting operations under high-speed, high-feed cutting conditions for various difficult-to-cut materials such as Ni-based alloys and Ti-based alloys. Is porous, it is difficult to generate heat due to the small contact area with the work material, and it is difficult for welding to occur. In addition, the bond strength between the crystal grains of the CrB ₂ layer is strong, resulting in peeling of the hard coating layer. It has been found that a difficult CrB ₂ layer can be formed.

More specifically, FIG. 1 shows a schematic plan view of a high-power pulse sputtering apparatus. A sintered body of Cr boride (hereinafter referred to as CrB ₂ ) powder (hereinafter referred to as CrB ₂ ) is used in the high-power pulse sputtering apparatus. ₍ Sintered ₂ ) Target is placed, the atmosphere in the apparatus is Ar atmosphere, high power pulse sputtering is performed with a high average input power of 6 kW or more, and CrB ₂ layer is deposited on the surface of the tool base. CrB has excellent welding resistance, strong bonding strength between crystal grains, and high film hardness (for example, nanoindentation hardness measured at a load of 200 mg is 3800 kgf / mm ² or more), CrB It was found that _two layers were formed.
As a result, the resulting coated tool has excellent welding resistance and bond strength between grains, especially in high-speed, high-feed cutting of hard difficult-to-cut materials such as various Ni-based alloys and Ti-based alloys that generate significant heat. The surface layer composed of a CrB ₂ layer having hardness suppresses the peeling of the hard coating layer caused by welding, so that excellent peeling resistance and wear resistance can be exhibited over a long period of time. I found out.

The present invention has been made based on the above findings,
“A cutting tool in which a Cr boride layer having an average layer thickness of at least 0.5 to 5 μm is coated on the outermost surface of a tool base made of tungsten carbide-based cemented carbide or titanium carbonitride-based cermet,
The Cr boride layer is configured as a composite structure of a crystal grain structure having a plurality of average grain sizes, and the composite structure has an average grain size of 30 consisting of an aggregate of primary crystal grains having an average grain size of 5 to 15 nm. A surface-coated cutting tool comprising secondary crystal grains of ˜70 nm and tertiary crystal grains having an average grain size of 100 to 600 nm composed of aggregates of the secondary crystal grains. "
It has the characteristics.

  Next, the coated tool of the present invention will be described in detail.

Average thickness of hard coating layer Cr boride layer formed on the outermost surface of a tool base made of tungsten carbide-based cemented carbide or titanium carbonitride-based cermet is self-tangled if the average layer thickness is less than 0.5 μm. On the other hand, when the average layer thickness exceeds 5 μm, welding is difficult in high-speed, high-feed cutting of hard difficult-to-cut materials such as Ni-based alloys and Ti-based alloys. Peeling can be suppressed, but chipping is likely to occur at the cutting edge due to a large compressive residual stress resulting from a high driving effect on the film of high-power pulse sputtering. It was determined to be 5 to 5 μm.

The effect of the composite structure and the average grain size of the crystal grains The effect of the composite structure is that the bonding force between the secondary crystal grains as well as the primary crystal grains can be used by forming an aggregate of crystal grains. It is. The average grain size of the primary crystal grains constituting the composite structure is difficult to form a film having crystal grains of less than 5 nm. On the other hand, when the average grain size exceeds 15 nm, there is a grain boundary that inhibits dislocation motion. Since it decreases, it cannot maintain high hardness. Further, if the average grain size of the secondary crystal grains composed of the aggregate of primary crystal grains is less than 30 nm, the primary crystal grains constituting the secondary crystal grains for obtaining a strong bonding force between the crystal grains, which is an advantage of the composite structure The number of crystal grains is not sufficient, and if it exceeds 70 nm, the number of secondary crystal grains constituting the tertiary crystal grains is not sufficient. Furthermore, if the average grain size of the tertiary crystal grains composed of the aggregate of secondary crystal grains is less than 100 nm, the area in contact with the work material at the time of cutting becomes large, so that welding easily occurs, and the entire composite structure peels off. On the other hand, if it exceeds 600 nm, it becomes impossible to withstand the load during cutting.

Next, a method for manufacturing the coated tool of the present invention will be described.
FIG. 1 shows a high-power pulse sputtering apparatus as an example of an apparatus for producing the coated tool of the present invention.
That is, in the high-power pulse sputtering apparatus shown in FIG. 1, a tool base mounting rotary table is provided at the center of the high-power pulse sputtering apparatus, and CrB ₂ powder is sintered at two locations across the rotary table. A body (CrB ₂ sintered body) target is arranged, and a plurality of tool bases are mounted in a ring shape along the outer peripheral portion at a predetermined distance in the radial direction from the central axis on the rotary table. While rotating the rotary table with an Ar atmosphere as the inner atmosphere and rotating the tool base itself for the purpose of uniforming the thickness of the wear-resistant hard layer formed by vapor deposition, 6 kW or more with respect to the CrB ₂ sintered body target. perform high output pulse sputtering at a high average input power, it is prepared by the CrB ₂ layer with an average layer thickness of 0.5~5μm deposited film Kill.
It is also effective to coat a (Ti, Al) N layer, which is a wear-resistant layer, as an underlayer for the CrB _two layers.
For example, in the manufacturing method in this case, a Ti—Al alloy target having a predetermined composition is arranged at two locations facing each other across the rotary table, and the position is shifted by 90 degrees from the Ti—Al alloy target. Thus, a CrB ₂ powder sintered body (CrB ₂ sintered body) target is disposed at two locations facing each other across the rotary table. Then, while rotating the rotary table with the atmosphere inside the apparatus as a nitrogen atmosphere, and rotating the tool base itself for the purpose of uniforming the thickness of the wear-resistant hard layer formed by vapor deposition, 6 kW or more with respect to the Ti—Al alloy target High-power pulse sputtering with a high average input power is performed, and a (Ti, Al) N layer is deposited on the surface of the tool base as an abrasion-resistant hard layer with an average layer thickness of 0.5 to 0.8 μm. It can be manufactured by substantially changing the atmosphere in the apparatus to an Ar atmosphere and depositing the CrB ₂ layer.
In particular, the CrB ₂ layer formed by high-power pulse sputtering under the above specific conditions is superior to the (Ti, Al) N layer without using an adhesive bonding layer (CrN layer) as in the conventional coated tool. Further, the film hardness is increased.

Furthermore, in the high-power pulse sputtering, the sputtering conditions are preferably such that the generated plasma density at the time of applying the pulse is 10 ¹⁸ m ⁻³ or more, and the length of one wavelength of the pulse is 200 μsec or more. In addition, it is preferable to perform sputtering under sputtering conditions in which the pulse non-application time for each cycle is 10 μsec or more.

In high-power pulse sputtering using a rectangular pulse with an increased energy level, it is possible to reduce the thermal load on the target, and thus it is possible to suppress an unnecessary temperature increase of the target.
Further, the (Ti, Al) N layer and the CrB ₂ layer formed by the high-power pulse sputtering both have high adhesion strength and high hardness.

The coated tool of the present invention is a composite structure of a crystal grain structure having a porous surface structure with a small contact area with a work material and a strong bond strength between crystal grains as a hard coating layer, and has a high hardness. Because it consists of CrB ₂ layers, when performing high-speed high-feed cutting conditions with high heat generation of hard difficult-to-cut materials, it is possible to suppress peeling of the hard coating layer due to welding, and over a long period of use, It exhibits excellent wear resistance.

It is a schematic plan view of the high-power pulse sputtering apparatus used for forming the surface coating layer of the coated tool of the present invention. The scanning electron micrograph (magnification: 100,000 times) of the horizontal cross section of the Cr boride layer of this invention covering insert 9 is shown. The scanning electron micrograph (magnification: 100,000 times) of the horizontal section of the Cr boride layer of the conventional covering insert 9 is shown. The horizontal cross-sectional schematic diagram of the Cr boride layer which consists of a composite structure of this invention covering insert is shown.

  Next, the coated tool and the manufacturing method thereof according to the present invention will be specifically described with reference to examples.

WC powder, TiC powder, ZrC powder, VC powder, TaC powder, NbC powder, Cr ₃ C ₂ powder, TiN powder, TaN powder, and Co powder all having an average particle diameter of 1 to 3 μm are prepared as raw material powders. These raw material powders are blended in the composition shown in Table 1, wet mixed by a ball mill for 72 hours, dried, and then pressed into a green compact at a pressure of 100 MPa. Medium, sintered at 1400 ° C for 1 hour, after sintering, WC-based carbide with honing of R: 0.03 on the cutting edge and ISO standard / CNMG120408 insert shape Alloy tool bases A-1 to A-10 were formed.

In addition, as raw material powders, all of TiCN (weight ratio TiC / TiN = 50/50) powder, Mo ₂ C powder, ZrC powder, NbC powder, TaC powder, WC powder having an average particle diameter of 0.5 to 2 μm Co powder and Ni powder are prepared, and these raw material powders are blended in the blending composition shown in Table 2, wet mixed by a ball mill for 24 hours, dried, and then pressed into a compact at a pressure of 100 MPa. The green compact was sintered in a nitrogen atmosphere of 2 kPa at a temperature of 1500 ° C. for 1 hour, and after sintering, the cutting edge portion was subjected to a honing process of R: 0.03 to obtain ISO standard / CNMG120408. The tool bases B-1 to B-6 made of TiCN base cermet having the insert shape were formed.

(A) Next, each of the tool bases A-1 to A-8 is ultrasonically cleaned in acetone and dried, and the center axis on the rotary table in the high-power pulse sputtering apparatus shown in FIG. Is mounted along the outer periphery at a predetermined distance in the radial direction from the inside, while in the high-power pulse sputtering apparatus, CrB ₂ sintered body targets are arranged at four locations facing each other across the rotary table,
(B) First, the inside of the apparatus is evacuated and kept at a vacuum of 0.1 Pa or less, and the inside of the apparatus is heated to 400 ° C. with a heater, and then the tool base that rotates while rotating on the rotary table is −200V. The tool substrate is treated with Ar bombardment for 1 hour by applying a DC bias voltage,
(C) Ar gas is introduced as a reaction gas into the apparatus, the atmosphere in the apparatus is set to 0.5 Pa, sputtering is performed for a time corresponding to the layer thickness under the predetermined pulse sputtering conditions shown in Table 3, and Table 4 The surface coating inserts of the present invention (hereinafter referred to as the present invention coated inserts) 1 to 8 as the present invention coated tools are produced by forming the CrB ₂ layer having the target layer thickness shown in FIG. did.
(D) Moreover, this invention covering insert insert 9-16 which introduce | transduced the (Ti, Al) N layer as a foundation layer, each of the said tool base | substrate A-9-A-10 and B-1 to B-6, In the state of ultrasonic cleaning in acetone and drying, it is mounted along the outer periphery at a predetermined distance in the radial direction from the central axis on the rotary table in the high-power pulse sputtering apparatus shown in FIG. In the high-power pulse sputtering apparatus, a Ti—Al alloy target having a predetermined composition and a CrB ₂ sintered body target are arranged at four locations across the rotary table,
(E) First, the inside of the apparatus is evacuated and kept at a vacuum of 0.1 Pa or less, and the inside of the apparatus is heated to 400 ° C. with a heater, and then the tool base that rotates while rotating on the rotary table is −200V. By applying a DC bias voltage, the tool base was subjected to Ar bombardment treatment for 1 hour, nitrogen gas was introduced into the apparatus as a reaction gas to make a reaction atmosphere of 0.6 Pa, and the Ti-Al alloy target was exposed to the Ti-Al alloy target. The high power pulse sputtering is performed under the predetermined pulse sputtering conditions indicated by the condition symbol a in FIG. 3, and the (Ti, Al) N layer having the target composition and target layer thickness shown in Table 4 is hardened on the surface of the tool base. Deposited as a wear-resistant hard layer of the coating layer,
(F) High power pulse sputtering is performed on the CrB ₂ sintered body target under the predetermined pulse sputtering conditions shown in Table 3, the gas introduced into the apparatus is switched from nitrogen gas to Ar gas, and the atmosphere in the apparatus is set to 0. Sputtering was performed for 5 Pa under the conditions corresponding to the layer thickness, and a CrB ₂ layer having a target layer thickness shown in Table 4 was formed as a surface layer of the hard coating layer.

For comparison purposes, these tool bases A-1 to A-10 and B-1 to B-6 are ultrasonically cleaned in acetone and dried, respectively, and an arc ion plating apparatus and a direct current sputtering apparatus, respectively. In the apparatus, a Ti-Al alloy target having various component compositions, a metal Cr target, and a CrB ₂ sintered body target are mounted.
First, the inside of the apparatus is evacuated and kept at a vacuum of 0.1 Pa or less, the inside of the apparatus is heated to 400 ° C. with a heater, and then a DC bias voltage of −200 V is applied to the tool base that rotates while rotating on the rotary table. By applying, the tool substrate was Ar bombarded for 1 hour, nitrogen gas was introduced into the apparatus as a reaction gas to make a reaction atmosphere of 0.6 Pa, and the apparatus was heated to 500 ° C. with a heater, Arc discharge is generated between the Ti—Al alloy target and the anode electrode, and the (Ti, Al) N layer having the target composition and target layer thickness shown in Table 6 is hard-coated on the surface of the tool base as a lower layer. Deposited as a wear-resistant hard layer. Next, the arc discharge between the cathode electrode (evaporation source) and the anode electrode of the Ti—Al alloy is stopped, and the direct current sputtering of the metal Cr arranged as the cathode electrode (evaporation source) of the direct current sputtering apparatus is started. A CrN layer having a target composition and a target layer thickness is formed as an adhesive bonding layer of the hard coating layer. Then, the arc discharge between the cathode electrode (evaporation source) of metal Cr and the anode electrode is stopped, and the atmosphere in the DC sputtering apparatus is set as an Ar atmosphere, and is arranged as the cathode electrode (evaporation source) of the DC sputtering apparatus. By starting direct current sputtering of the CrB ₂ sintered body and depositing a CrB ₂ layer having an average layer thickness shown in Table 6 under the predetermined direct current sputtering conditions shown in Table 5 as an upper layer on the CrN layer. Conventional surface-coated inserts (hereinafter referred to as conventional coated inserts) 1 to 16 as conventional coated tools were produced, respectively.

  For reference, in the same apparatus as the apparatus for manufacturing the present invention coated inserts 1-16 shown in FIG. 1, by forming a film with a composition, film thickness, and sputtering conditions different from those of the present invention coated inserts 1-16, Reference surface-coated inserts (hereinafter referred to as reference coated inserts) 1 to 4 as reference coated tools shown in Table 6 were produced.

About the CrB _two layers of the present invention coated inserts 1-16, the conventional coated inserts 1-16, and the reference coated inserts 1-4, the crystal grain structure of the CrB _two layers is 100,000 times by a scanning electron microscope (Carl Zeiss, ultra55). Observation with a visual field, the result is assumed to be a plane, and the area of the crystal grain is calculated as the area of the grain cross section. Furthermore, the average diameter of primary crystal grains, secondary crystal grains, and tertiary crystal grains was measured at 10 points when the cross-sectional area of the crystal grains was calculated as the area of a circle, and the average value was obtained.
Tables 4 and 6 show the measured values.
FIG. 2 shows a scanning electron micrograph (magnification: 100,000 times) of the horizontal section of the CrB ₂ layer of the coated insert 9 of the present invention, and FIG. 3 shows the scanning of the horizontal section of the CrB ₂ layer of the conventional coated insert 9. A scanning electron micrograph (magnification: 100,000 times) is shown in FIG. 4, and a horizontal cross-sectional schematic view of a Cr boride layer made of a composite structure of the coated insert of the present invention is shown.

For the CrB _two layers of the present invention coated inserts 1-16, conventional coated inserts 1-16, and reference coated inserts 1-4, the surface hardness was measured by an ultra-fine indentation hardness tester (manufactured by Elionix, ENT-1100a). It was measured by.
Tables 4 and 6 show the measured values.

In addition, the composition of the wear-resistant hard layers constituting the hard coating layers of the present invention coated inserts 1 to 16, the conventional coated inserts 1 to 16 and the reference coated inserts 1 to 4 is expressed by energy dispersion X using a transmission electron microscope. When measured by the line analysis method, each showed substantially the same composition as the target composition.
Further, when the average thicknesses of the CrB ₂ layer and the wear-resistant hard layer of the hard coating layer were measured by cross-section using a scanning electron microscope, the average value was substantially the same as the target layer thickness (average value of 5 locations). )showed that.

Next, in the state where all the above-mentioned various coated inserts are screwed to the tip of the tool steel tool with a fixing jig, the present coated inserts 1-16, the conventional coated inserts 1-16, and the reference coated insert 1 About ~ 4
Work material: Ti-6% Al-4% V alloy round bar by mass%,
Cutting speed: 100 m / min. ,
Incision: 1.5mm,
Feed: 0.4 mm / rev. ,
Cutting time: 5 minutes
Dry high-speed high-feed cutting test of Ti-based alloy under the following conditions (referred to as cutting condition A) (normal cutting speed is 50 m / min, cutting feed is 0.2 mm / rev.),
The flank wear width of the cutting blade was measured.
The measurement results are shown in Table 7.

As raw material powder, WC powder having an average particle size of 5.5 μm, 0.8 μm fine WC powder, 1.3 μm TaC powder, 1.2 μm NbC powder, 1.2 μm ZrC powder, 2.3 μm Cr ₃ C ₂ powder, 1.5 μm VC powder, 1.0 μm (Ti, W) C [by mass ratio, TiC / WC = 50/50] powder, and 1.8 μm Co powder was prepared, and these raw material powders were blended in the blending composition shown in Table 8 respectively. Further, wax was added, ball milled in acetone for 24 hours, dried under reduced pressure, and then dried into various shapes at a pressure of 100 MPa. The green compact was press-molded, and these green compacts were heated to a predetermined temperature in the range of 1370 to 1470 ° C. at a temperature increase rate of 7 ° C./min in a 6 Pa vacuum atmosphere. After holding time, sintering under furnace cooling conditions, A tool bar forming round bar sintered body having a diameter of 6 mm is formed, and further, the diameter x length of the cutting edge portion is 6 mm x 12 mm and the helix angle 30 by grinding from the round bar sintered body. Tool bases (end mills) C-1 to C-8 having a two-blade square shape were manufactured.

Subsequently, the surfaces of these tool bases (end mills) C-1 to C-8 were ultrasonically cleaned in acetone and dried, and then charged into the vapor deposition apparatus shown in FIG. Under the same conditions, a hard coating layer composed of a surface layer composed of _two CrB layers having the target layer thickness shown in Table 9 in C-1 to C-4 is formed by vapor deposition. Inventive surface-coated end mills (hereinafter referred to as the present invention-coated end mills) 1 to 4 are composed of (Ti, Al) N layers having the target composition and target layer thickness shown in Table 9 in C-5 to C-8. The coated end mills 5 to 8 of the present invention were manufactured by vapor-depositing a layer and a hard coating layer composed of a surface layer composed of _two CrB layers having the target layer thickness shown in Table 9 respectively.

Further, for comparison purposes, the surfaces of the tool bases (end mills) C-1 to C-8 were ultrasonically cleaned in acetone and dried under the same conditions as in Example 1 and also in Table 10. A conventional surface-coated end mill (hereinafter referred to as a conventional coated end mill) 1 as a conventional coated tool is obtained by depositing a wear-resistant hard layer comprising a (Ti, Al) N layer having a target composition and a target layer thickness as a hard coating layer. ~ 8 were produced respectively.
Further, for reference, the surfaces of the tool bases (end mills) C-1, C-3, C-5, and C-7 are ultrasonically cleaned in acetone and dried. The reference surface coating end mill (hereinafter referred to as a reference coating end mill) 1 to 1 as a reference coating tool shown in Table 10 by forming a film with a composition, film thickness, and sputtering conditions different from those of the present invention coated end mills 1 to 8 4 were produced respectively.

About the CrB ₂ layers of the present invention coated end mills 1 to 8, the conventional coated end mills 1 to 8, and the reference coated end mills 1 to 4, the crystal grain structure of the CrB _two layers is 100,000 times by a scanning electron microscope (made by Curl Zeiss, ultra 55). Observation with a visual field, the result is assumed to be a plane, and the area of the crystal grain is calculated as the area of the grain cross section. Furthermore, the average diameter of primary crystal grains, secondary crystal grains, and tertiary crystal grains was measured at 10 points when the cross-sectional area of the crystal grains was calculated as the area of a circle, and the average value was obtained.
Tables 9 and 10 show the measured values.

For the CrB _two layers of the present invention coated end mills 1 to 8, the conventional coated end mills 1 to 8, and the reference coated end mills 1 to 4, the surface hardness was measured by an ultra fine indentation hardness tester (ENT-1100a, manufactured by Elionix). It was measured by.
Tables 9 and 10 show the measured values.

Further, the composition of the hard coating layer constituting the hard coating layers of the present invention coated end mills 1 to 8, the conventional coated end mills 1 to 8 and the reference coated end mills 1 to 4 is expressed by energy dispersion X using a transmission electron microscope. When measured by the line analysis method, each showed substantially the same composition as the target composition.
Further, when the average thicknesses of the CrB ₂ layer and the wear-resistant hard layer of the hard coating layer were measured by cross-section using a scanning electron microscope, the average value was substantially the same as the target layer thickness (average value of 5 locations). )showed that.

Next, for the present invention coated end mills 1-8, conventional coated end mills 1-8 and reference coated end mills 1-4,
Work material-plane: 100 mm × 250 mm, thickness: 50 mm Ti-based alloy (mass%, Ti-6% Al-4% V alloy) plate material,
Cutting speed: 150 m / min. ,
Groove depth (cut): 4 mm
Table feed: 1400mm / min,
A dry high-speed high-feed groove cutting test of a Ti-based alloy under the following conditions (referred to as cutting condition B) (normal cutting speed is 75 m / min, table feed is 960 mm / min,.),
The cutting groove length was measured until the flank wear width of the outer peripheral edge of the cutting edge in the groove cutting test reached 0.1 mm, which is a guide for the service life.
The measurement results are shown in Table 11, respectively.

From the results shown in Tables 3 to 11, the present coated tool having excellent welding resistance and hardness with a CrB ₂ layer is accompanied by high heat generation of hard difficult-to-cut materials such as various Ni-based alloys and Ti-based alloys. High-speed, high-feed cutting provides excellent peel resistance and wear resistance.
On the other hand, in the conventional coated tool, as shown in Tables 6 and 10, since the composite structure is not formed, the welding resistance is inferior, and the high-speed and high-feed cutting conditions accompanied by the high heat generation of hard difficult-to-cut materials. Therefore, the peeling of the hard coating layer cannot be suppressed, and the hardness is not sufficient, so that the wear resistance is poor. In addition, in the reference coated tool having a CrB ₂ layer deviating from the range specified in the present invention, the wear progress of the cutting edge portion is high in high-speed high-feed cutting with high heat generation of hard difficult-to-cut materials, and in a relatively short time. It is clear that the service life is reached.

  As described above, according to the coated tool and the manufacturing method thereof of the present invention, not only cutting under normal cutting conditions such as various steels and cast irons, but also high speeds of the hard difficult-to-cut materials with particularly high heat generation. It exhibits excellent peeling resistance and wear resistance even in high-feed cutting, and exhibits excellent cutting performance over a long period of time. It can cope with energy saving and cost reduction sufficiently satisfactorily.

Claims (1)

A cutting tool in which a Cr boride layer having an average layer thickness of at least 0.5 to 5 μm is coated on the outermost surface of a tool base made of tungsten carbide-based cemented carbide or titanium carbonitride-based cermet,
The Cr boride layer is configured as a composite structure of a crystal grain structure having a plurality of average grain sizes, and the composite structure has an average grain size of 30 consisting of an aggregate of primary crystal grains having an average grain size of 5 to 15 nm. A surface-coated cutting tool comprising secondary crystal grains of ˜70 nm and tertiary crystal grains having an average grain size of 100 to 600 nm composed of aggregates of the secondary crystal grains.

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