JP5488824B2 - Surface-coated cutting tool that exhibits excellent peeling resistance and excellent wear resistance due to high-speed cutting of hard difficult-to-cut materials - Google Patents

Description

In the present invention, the hard coating layer is constituted by a surface layer having excellent welding resistance and excellent hardness, and therefore cutting hard hard-to-cut materials such as various Ti-based alloys and high Si-containing Al-Si based alloys. Surface coating that exhibits excellent peeling resistance and wear resistance over a long period of time, even when processing is performed under high-speed cutting conditions with high heat generation, suppressing the peeling of the hard coating layer due to the occurrence of welding. The present invention relates to cutting tools (hereinafter referred to as coated tools).

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: (Al _1-X Ti _X ) N (wherein, X is 0.25 to 0.60 in atomic ratio) A lower layer consisting of a satisfactory (Al, Ti) N layer,
(B) an adhesive bonding layer comprising a ZrBN (zirconium boronitride) layer having an average layer thickness of 0.1 to 0.5 μm;
(C) an upper layer comprising a ZrB ₂ (zirconium 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 comprising the above (a) to (c) is formed is known, and this conventional coated tool is a hardened material of alloy tool steel or bearing steel. It is known to exhibit excellent wear resistance in high-speed cutting of high hardness steel such as.

Furthermore, the above-mentioned conventional coated tool is loaded with the above-mentioned tool base in a physical vapor deposition apparatus equipped with an arc ion plating apparatus and a direct current sputtering apparatus, and first reacts in the apparatus while being heated with a heater. Nitrogen gas is introduced as a gas, and 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). The lower layer composed of the (Al, Ti) N layer was formed, and then sputtering of the ZrB ₂ sintered body arranged as the cathode electrode (evaporation source) of the DC sputtering apparatus was started, and the atmosphere in the apparatus was changed to nitrogen. By sequentially replacing the atmosphere with an Ar atmosphere, a ZrBN layer is first formed as the adhesive bonding layer of (b), and then the Z It is also known that it is produced by depositing an upper layer composed of the ZrB ₂ layer of (c) above on the rBN layer.

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 2006-1004 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. However, in the above-mentioned conventional coated tool, this is used for high-speed cutting of high hardness steel such as alloy tool steel and hardened material of bearing steel. Although it exhibits excellent wear resistance in some cases, it is used to cut hard difficult-to-cut materials such as various Ti alloys and high Si-containing Al-Si alloys under high-speed cutting conditions. In the present situation, welding is likely to occur due to extremely high heat generated during cutting, and the hard coating layer peels off due to this, and the service life is reached in a relatively short time.

In view of the above, the present inventors have conducted intensive research in order to develop a coated tool that exhibits excellent welding resistance and peeling resistance in which a hard layer is excellent in high-speed cutting of the above-mentioned hard difficult-to-cut materials. As a result, the following knowledge was obtained.
First, in the conventional coated tool (Patent Document 1), the ZrB ₂ layer is formed by direct current sputtering, and when this is used for high-speed cutting of hardened steel such as a quenching material, there is a special problem. Although this does not occur, the surface structure is dense when this is used to cut hard difficult-to-cut materials such as various Ti-based alloys and high Si-containing Al-Si based alloys under high-speed cutting conditions. As a result, the contact area with the work material was large, welding was caused by extremely high heat generation, and the bond between the crystal grains of the ZrB _two layers was weak, and it was found that the hard coating layer was peeled off due to the welding. .
Accordingly, the present inventors have welding occurs hardly occurs, and, as a result of research by focusing on high ZrB ₂ layer tissue binding strength of the crystal grains mutually, when forming the ZrB ₂ layers, Patent Document 1 By adopting high-power pulse sputtering under specific conditions instead of direct current sputtering as shown in Fig. 4, it is possible to cut hard hard-to-cut materials such as various Ti alloys and high Si-containing Al-Si alloys under high-speed cutting conditions. Since the surface structure is porous, the contact area with the work material is small, so it is difficult for heat generation and welding to occur, and the bonding strength between the crystal grains of the ZrB ₂ layer is strong, so that the hard coating layer It has been found that a ZrB ₂ layer that does not easily peel off can be formed.

More specifically, FIG. 1 shows a schematic plan view of a high-power pulse sputtering apparatus. In the high-power pulse sputtering apparatus, Zr boride (hereinafter referred to as ZrB ₂ ) powder sintered body (hereinafter referred to as ZrB). ₍ 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 8 kW or more, and ZrB ₂ layer is deposited on the surface of the tool base. ZrB has excellent welding resistance, strong bonding strength between grains, and high film hardness (for example, nanoindentation hardness measured at a load of 200 mg is 3600 kgf / mm ² or more). It was found that _two layers were formed.
As a result, the resulting coated tool has excellent welding resistance and inter-grain intergration in high-speed cutting of hard difficult-to-cut materials such as various Ti-based alloys and high-Si-containing Al-Si-based alloys with particularly high heat generation. The surface layer consisting of ZrB ₂ layers with high bond strength and hardness, especially, prevents the peeling of the hard coating layer caused by welding, thereby providing excellent peeling resistance and wear resistance over a long period of time I found out that I would do it.

This invention has been made based on the above findings,
A cutting tool formed by coating a Zr boride layer having an average layer thickness of at least 0.5 to 5 μm on the outermost surface of a tool base made of tungsten carbide base cemented carbide or titanium carbonitride base cermet,
The Zr 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 50 consisting of an aggregate of primary crystal grains having an average grain size of 5 to 30 nm. A surface-coated cutting tool comprising secondary crystal grains of ˜100 nm and tertiary crystal grains having an average grain size of 200 to 1000 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 layer thickness of the hard coating layer The Zr boride layer formed on the outermost surface of the tool base made of tungsten carbide-based cemented carbide or titanium carbonitride-based cermet has its own tangling when the average layer thickness is less than 0.5 μm. However, when the average layer thickness exceeds 5 μm, high-speed cutting of hard difficult-to-cut materials such as Ti-based alloys and high Si-containing Al-Si-based alloys is not sufficient. In this case, peeling due to welding can be suppressed, but chipping is likely to occur at the cutting edge due to the large compressive residual stress resulting from the high driving effect on the coating of high-power pulse sputtering. It was set to 0.5 to 5 μm.

The effect of the composite structure and the average particle 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 utilized 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 30 nm, the number of grain boundaries that inhibit dislocation motion decreases. Therefore, high hardness cannot be maintained. Further, when the average grain size of the secondary crystal grains composed of the aggregate of the primary crystal grains is less than 50 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 100 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 200 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 1000 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 coated tool of the present invention, for example, a coated tool in which a (Ti, Al) N layer is formed on a tool base surface with a predetermined thickness and then a ZrB ₂ layer is deposited on the outermost surface. As an example of an apparatus for performing the above, a high-power pulse sputtering apparatus is shown.
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, for example, a predetermined composition is provided at two locations across the rotary table. And a ZrB ₂ powder sintered body (ZrB ₂ sintered) at _two positions facing each other across the rotary table at a position shifted by 90 degrees from the Ti-Al alloy target. Body) A target is placed, 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. In this state, the atmosphere in the apparatus is changed to a nitrogen atmosphere. While rotating the rotary table and rotating the tool base itself for the purpose of uniforming the thickness of the wear-resistant hard layer formed by vapor deposition, first, the Ti-A High power pulse sputtering with a high average input power of 6 kW or more is performed on the alloy target, 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 0.8 to 5 μm. Then, the atmosphere in the apparatus is substantially changed to an Ar atmosphere, and the ZrB ₂ sintered body target is subjected to high output pulse sputtering with a high average input power of 8 kW or more, and the (Ti, Al) N layer. It can be manufactured by depositing a ZrB ₂ layer as an outermost surface layer with an average layer thickness of 0.5 to 5 μm.
In particular, the ZrB 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 (ZrBN layer) like a conventional coated tool. Further, the film hardness is increased.

Furthermore, in the above 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 the high-power pulse sputtering using the rectangular pulse with the 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.
In addition, the (Ti, Al) N layer and the ZrB ₂ layer formed by the high-power pulse sputtering 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 the work material and a strong bond strength between crystal grains as a hard coating layer, and has a high hardness. Since it has a surface layer consisting of _two ZrB layers, it is possible to suppress peeling of the hard coating layer caused by welding when performing high-speed cutting condition processing accompanied by high heat generation of hard hard-to-cut materials. 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 Zr boride layer of this invention covering insert 9 is shown. The scanning electron micrograph (magnification: 100,000 times) of the horizontal section of the Zr boride layer of the conventional covering insert 9 is shown. The horizontal cross-section schematic diagram of the Zr 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-10 and B-1 to B-6 was ultrasonically cleaned in acetone and dried, and then the high power pulse sputtering shown in FIG. Attached along the outer periphery at a predetermined distance in the radial direction from the central axis on the rotary table in the apparatus, while in the high-power pulse sputtering apparatus, Ti is placed at four locations across the rotary table. -An Al alloy target and a ZrB ₂ sintered body target are arranged,
(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) Nitrogen gas is introduced as a reaction gas into the apparatus to make a reaction atmosphere of 0.6 Pa, and high power pulse sputtering is performed on the Ti—Al alloy target under predetermined pulse sputtering conditions shown in Table 3 Condition symbol a. Thus, a (Ti, Al) N layer having the target composition and target layer thickness shown in Table 4 was formed on the surface of the tool base as an abrasion-resistant hard layer of the hard coating layer. (D) Subsequently, ZrB ₂ High power pulse sputtering is performed on the 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 0.5 Pa. in performed sputtering in time corresponding to the layer thickness, also by the ZrB ₂ layers of the target layer thicknesses shown in Table 4 film as the surface layer of the hard coating layer, the present invention coated tool To the present invention surface-coated inserts (hereinafter, the present invention of coated inserts) 1-16 were prepared, respectively.

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 and a ZrB ₂ sintered body target are mounted,
First, while the inside of the apparatus is evacuated and maintained at a vacuum of 0.1 Pa or less, the inside of the apparatus is heated to 500 ° C. with a heater, and then an arc discharge is generated between the Ti—Al alloy target and the anode electrode, A (Ti, Al) N layer having a target composition and a target layer thickness is formed as a wear-resistant hard layer on the surface of the tool substrate as a lower layer, and then the cathode electrode (evaporation source) of the Al—Ti alloy is formed. ) And the anode electrode are stopped, DC sputtering of the ZrB ₂ sintered body arranged as the cathode electrode (evaporation source) of the DC sputtering apparatus is started, and the atmosphere in the vapor deposition apparatus is changed to a nitrogen atmosphere. Instead, a mixed gas atmosphere of Ar and nitrogen is used, and adhesion bonding is performed under the condition that the Ar introduction ratio is gradually increased over time while the nitrogen introduction ratio is gradually reduced. The ZrBN layer as the layer is deposited with an average layer thickness shown in Table 6, the atmosphere in the deposition apparatus subsequently finally as an Ar atmosphere, ZrB ₂ sintered arranged as a cathode electrode of the DC sputtering device (evaporation source) A conventional coated tool is obtained by continuing DC sputtering of the bonded body, and depositing a ZrB ₂ layer having an average layer thickness shown in Table 6 under the predetermined DC sputtering conditions shown in Table 5 as an upper layer on the ZrBN layer. Conventional surface-coated inserts (hereinafter referred to as conventional coated inserts) 1 to 16 were produced.

For reference, the same apparatus as the apparatus for manufacturing the coated inserts 1 to 16 of the present invention shown in FIG. 1 (that is, a Ti—Al alloy target and a ZrB ₂ sintered body target are mounted in the apparatus. ), A reference surface coating insert (hereinafter referred to as a reference coating insert) 1 as a reference coating tool shown in Table 6 by forming a film with a composition, film thickness, and sputtering conditions different from those of the present invention coated inserts 1-16. 4 were produced respectively.

The ZrB _two layers of the present invention coated inserts 1-16, the conventional coated inserts 1-16, and the reference coated inserts 1-4 are 100,000 times as large as the crystal grain structure by a scanning electron microscope (Carl Zeiss, ultra55). The average diameter of the primary crystal grains, secondary crystal grains, and tertiary crystal grains is measured at 10 points when the area of the cross section of the crystal grains is replaced with the area of a circle, did.
Tables 4 and 6 show the measured values.
FIG. 2 is a scanning electron micrograph (magnification: 100,000 times) of the ZrB _two- layer horizontal section of the coated insert 9 of the present invention, and FIG. 3 is a horizontal section scan of the ZrB _two- 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 Zr boride layer composed of a composite structure of the coated insert of the present invention is shown.

For the ZrB ₂ layers of the present invention coated inserts 1-16, the conventional coated inserts 1-16 and the reference coated inserts 1-4, the surface hardness was measured by an ultra micro indentation hardness tester (manufactured by Elionix, ENT-1100a ).
Tables 4 and 6 show the measured values.

Further, 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 dispersed using an electron microscope. When measured by X-ray analysis, each showed substantially the same composition as the target composition.
Furthermore, when the average layer thickness of the ZrB ₂ layer and the wear-resistant hard layer of the hard coating layer was subjected to cross-sectional measurement using a scanning electron microscope, the average value was substantially the same as the target layer thickness (average of 5 locations). Value).

Next, the above-mentioned various coated inserts are screwed to the tip of the tool steel tool with a fixing jig, and the coated inserts 1 to 16, the conventional coated inserts 1 to 16, and the reference coated inserts. About 1-4
Work material: Ti-6% Al-4% V alloy round bar by mass%,
Cutting speed: 100 m / min. ,
Incision: 1.5mm,
Feed: 0.2 mm / rev. ,
Cutting time: 5 minutes
A dry continuous high-speed cutting test of a Ti-based alloy under the following conditions (referred to as cutting condition A) (normal cutting speed is 60 m / min.),
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.

Next, 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 wear-resistant hard layer composed of a (Ti, Al) N layer having a target composition and a target layer thickness shown in Table 9 and a surface layer composed of a ZrB ₂ layer having a target layer thickness also shown in Table 9 The surface coating end mills (hereinafter referred to as the present invention coated end mills) 1 to 8 as the present invention coated tools were produced by vapor-depositing the constituted hard coating layers, 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 above. A conventional surface-coated end mill (hereinafter referred to as a conventional coated end mill) as a conventional coated tool by depositing a hard-wearing hard layer comprising a (Ti, Al) N layer having a target composition and a target layer thickness shown in FIG. 1 to 8 were produced.
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, and the same as in Example 1 above. The reference surface-coated end mill (hereinafter referred to as the reference coated end mill) 1 as a reference coated tool shown in Table 10 is formed by forming a film with a composition, film thickness, and sputtering conditions different from those of the coated end mills 1 to 8 of the present invention. ~ 4 were produced respectively.

The ZrB _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 are 100,000 times larger in crystal grain structure with a scanning electron microscope (made by Curl Zeiss, ultra 55). The average diameter of the primary crystal grains, secondary crystal grains, and tertiary crystal grains is measured at 10 points when the area of the cross section of the crystal grains is replaced with the area of a circle, did.
Tables 9 and 10 show the measured values.

For the ZrB _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 (manufactured by Elionix, ENT-1100a ).
Tables 9 and 10 show the measured values.

Further, the composition of the hard coating layer constituting the hard coating layer 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 dispersed using an electron microscope. When measured by X-ray analysis, each showed substantially the same composition as the target composition.
Furthermore, when the average layer thickness of the ZrB ₂ layer and the wear-resistant hard layer of the hard coating layer was subjected to cross-sectional measurement using a scanning electron microscope, the average value was substantially the same as the target layer thickness (average of 5 locations). Value).

Next, for the above-described coated end mills 1 to 8, the conventional coated end mills 1 to 8, and the reference coated end mills 1 to 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: 960 mm / min,
A dry high-speed grooving test of a Ti-based alloy under the conditions (cutting condition B) (normal cutting speed is 80 m / 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 ZrB ₂ layer is a hard difficult-to-cut material such as various Ti-based alloys and high Si-containing Al-Si based alloys. Excellent peeling resistance and wear resistance by high-speed cutting with high heat generation.
On the other hand, as shown in Tables 6 and 10, in the conventional coated tool, the composite structure is not formed, so that the welding resistance is inferior, and the hard tool is hard under high-speed cutting conditions with high heat generation. Since peeling of the coating layer cannot be suppressed and the hardness is not sufficient, the wear resistance is poor. In the case of a reference coated tool having a ZrB ₂ layer that is out of the range specified in the present invention, the wear of the cutting edge portion is fast in high-speed cutting with high heat generation of hard difficult-to-cut materials, and the service life is relatively short. It is clear that

As described above, according to the coated tool and the manufacturing method thereof of the present invention, the hard hard-to-cut material having a particularly high heat generation as well as cutting under normal cutting conditions such as various steels and cast irons. Excellent peeling resistance and wear resistance even in high-speed cutting, and excellent cutting performance over a long period of time. High performance and automation of cutting equipment, labor saving and energy saving of cutting. It is possible to cope with the reduction of cost and cost.

Claims (1)

A cutting tool in which a Zr 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 a tungsten carbide-based cemented carbide or a titanium carbonitride-based cermet,
The Zr 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 50 consisting of an aggregate of primary crystal grains having an average grain size of 5 to 30 nm. A surface-coated cutting tool comprising secondary crystal grains of ˜100 nm and tertiary crystal grains having an average grain size of 200 to 1000 nm composed of aggregates of the secondary crystal grains.

Images