JP5429693B2 - Surface coated cutting tool with excellent wear resistance due to hard coating layer - Google Patents

Description

  This invention has high-temperature hardness and high-temperature strength with an excellent hard coating layer even when, for example, high-hardness steel such as a hardened alloy tool steel is cut under high-speed cutting conditions with high heat generation. Thus, the present invention relates to a surface-coated cutting tool (hereinafter referred to as a coated tool) that prevents occurrence of chipping, chipping, peeling, and the like and exhibits excellent wear resistance over a long period of use.

  In general, surface-coated cutting tools include a throw-away tip that is detachably attached to the tip of a cutting tool for turning and planing of various steels and cast irons, and drilling of the work material. There are drills and miniature drills used for processing, etc., and solid type end mills used for chamfering, grooving, shoulder processing, etc. of the work material. A slow-away end mill tool that performs cutting work in the same manner as a type end mill is known.

  Conventionally, as one of surface-coated cutting tools, for example, as shown in Patent Document 1, a tungsten carbide (hereinafter referred to as WC) -based cemented carbide or titanium carbonitride (hereinafter referred to as TiCN) -based cermet is used. As a hard coating layer, a relatively Si-rich amorphous Cr, Al, Si, and N compound phase is relatively formed on the surface of the substrate (hereinafter collectively referred to as a tool substrate). In particular, there is known a coated tool in which a hard coating layer composed of crystalline Cr, Al, Si, N, and one compound phase, both of which is poor in Si, is formed. In addition, a coated tool in which a (Cr, Al, Si) N hard coating layer having an amorphous high Si concentration region phase and a crystalline low Si concentration region phase is formed on the surface of the tool base is also known. And this In conventional coated tools, the brittleness of the hard coating layer is greatly improved, and a coated tool with high toughness and excellent chipping resistance can be obtained without sacrificing the high hardness and oxidation resistance of the hard coating layer. It has been known.

  Furthermore, the above-mentioned conventional coated tool is, for example, a state in which a tool base is inserted into an arc ion plating (AIP) apparatus, which is a kind of physical vapor deposition apparatus shown in FIG. The tool base is formed by generating arc discharge between a plurality of cathode electrodes (evaporation sources) having a composition corresponding to the composition of the hard coating layer and the anode electrode, and simultaneously introducing nitrogen gas as a reaction gas into the apparatus. It is manufactured by vapor-depositing a hard coating layer composed of the (Cr, Al, Si) N layer having a desired compound phase and region phase on the surface.

JP 2002-337007 A JP 2003-89004 A

  In recent years, the performance of cutting devices has been dramatically improved. On the other hand, there is a strong demand for labor saving and energy saving and further cost reduction for cutting, and with this, cutting tends to be faster. In the case of a coated tool, chipping, chipping, peeling, etc. are likely to occur in the hard coating layer when it is used under high-speed cutting conditions of high-hardness steel with high heat generation and high load acting on the cutting edge. As a result, the service life is reached in a relatively short time.

  Therefore, the inventors have high-temperature hardness, high-temperature strength, high-temperature oxidation resistance with excellent hard coating layer from the above viewpoint, and particularly high-hardness steel such as a hardened material of alloy tool steel, Even when cutting is performed under high-speed cutting conditions with high heat generation and high load acting on the cutting edge, it has excellent resistance to long-term use without causing chipping, chipping or peeling. In order to develop a coated tool that exhibits wearability, the following knowledge was obtained as a result of research by paying attention to the crystal structure of the (Cr, Al, Si) N layer constituting the hard coating layer.

The Cr component, which is a component of the (Cr, Al, Si) N layer that constitutes the hard coating layer of the above conventional coated tool, improves the high-temperature strength and at the same time contains high-temperature oxidation resistance when Cr and Al coexist. In addition, the Si component has the effect of improving the heat resistance, and the hard coating layer contains these components, so that the predetermined chipping resistance, oxidation resistance, heat resistance and Demonstrate wear resistance.
By the way, in the conventional coated tool, the (Cr, Al, Si) N layer is composed of a crystalline phase and an amorphous phase, but a hard coating layer is formed by an arc ion plating (AIP) apparatus. In forming the film, as the deposition conditions, for example, by controlling the pressure of nitrogen gas introduced into the apparatus and the bias voltage applied to the tool base, the crystal grains of (Cr, Al, Si) N crystal grains formed The present inventors have found that the structure (particle size, morphology) can be adjusted.

  Then, by controlling the above deposition conditions, the thin layer A composed of a fine grain size (Cr, Al, Si) N granular crystal structure and a relatively large grain size (Cr, Al, Si) N columnar crystal. When a hard coating layer is formed by an alternating laminated structure with a thin layer B composed of a structure, the thin layer A composed of a granular crystal structure is excellent in wear resistance, while the thin layer B composed of a columnar crystal structure is resistant to chipping, Since the thin layer A and the thin layer B have the same component composition and the same crystal structure, the adhesion strength between the thin layers is high and there is no possibility of delamination. The hard coating layer consisting of alternating layers of A and thin layers B generates high heat generation and generates chipping, chipping, peeling, etc. even during high-speed cutting of high-hardness steel with high load acting on the cutting edge. And better than conventional coated tools It was found to exert over the wear resistance in long-term.

This invention has been made based on the above findings,
“(1) Hard coating made of a composite nitride of Cr, Al, and Si having a layer thickness of 0.8 to 5.0 μm on the surface of a tool base made of tungsten carbide-based cemented carbide or titanium carbonitride-based cermet In a surface-coated cutting tool in which a layer is formed by vapor deposition,
The hard coating layer is configured as an alternately laminated structure of a thin layer A composed of a granular crystal structure of a composite nitride of Cr, Al, and Si and a thin layer B composed of a columnar crystal structure, and the thin layer A and the thin layer B are Each having a layer thickness of 0.05 to 2 μm, the average crystal grain size of the granular crystals constituting the thin layer A is 30 nm or less, and the average crystal grain size of the columnar crystals constituting the thin layer B is A surface-coated cutting tool having a thickness of 50 to 500 nm.
(2) The composite nitride of Cr, Al, and Si is
Composition formula: (Cr _1-XY Al _X Si _Y ) N
(1), wherein 0.40 ≦ X ≦ 0.70 and 0.005 ≦ Y ≦ 0.08 (wherein X and Y are atomic ratios) are satisfied. Surface coated cutting tool. "
It has the characteristics.

  Next, the hard coating layer of the coated tool of the present invention will be described in more detail.

(A) Composition of the hard coating layer The hard coating layer made of the (Cr, Al, Si) N layer has its crystal structure changed from cubic to hexagonal with an increase in the Al content, and the film hardness decreases. Therefore, in order to maintain at least a predetermined film hardness, the crystal structure needs to be cubic, and for that purpose, the composition of the hard coating layer is
Composition formula: (Cr _1-XY Al _X Si _Y ) N
It is desirable to determine the Al content ratio so that X is 0.70 or less (where X is an atomic ratio). However, when X is less than 0.40, the crystal structure remains in a cubic structure, but due to the relative increase in the Cr content, the high temperature hardness of the (Cr, Al, Si) N layer itself rapidly increases. Therefore, it is difficult to ensure the minimum wear resistance required in high-speed cutting, so the combination of Cr and Si in the (Cr, Al, Si) N layer that constitutes the hard coating layer. It is desirable that the Al content ratio X (atomic ratio) in the amount satisfies 0.40 ≦ X ≦ 0.70.
In the above composition formula, when the Si content ratio Y is less than 0.005, the effect of improving the heat resistance of the hard coating layer is small. On the other hand, when the Si content ratio Y exceeds 0.08, the relative Cr Since the content ratio decreases and the high temperature strength tends to decrease, the Si content ratio Y (atomic ratio) in the total amount of Cr and Al satisfies 0.005 ≦ Y ≦ 0.08. It is desirable to do.

(B) Thin layer A
The thin layer A is made of (Cr, Al, Si) N having a granular crystal structure, has an excellent film hardness, and improves the wear resistance of the hard coating layer. However, if the average crystal grain size of the granular crystal structure exceeds 30 nm, the effect of improving the hardness of the film is reduced, so the average crystal grain size of the granular crystal structure is set to 30 nm or less.
The “average crystal grain size” as used in the present invention is measured and calculated by a transmission electron microscope (TEM) observation photograph on a plane orthogonal to the layer thickness direction (in other words, a plane parallel to the substrate surface). The average value of the crystal grain size is referred to, and the length of the crystal grain along the layer thickness direction is not called “average crystal grain size” in the present invention.
Also, if the layer thickness of the thin layer A is less than 0.05 μm, the effect of improving the wear resistance is small. On the other hand, if the layer thickness exceeds 2 μm, high-speed cutting of high-hardness steel in which a high load acts on the cutting edge. In order to easily cause chipping and defects, the layer thickness of the thin layer A is set to 0.05 to 2 μm.

(C) Thin layer B
The thin layer B composed of (Cr, Al, Si) N having a columnar crystal structure exhibits excellent high-temperature strength and toughness, but the average crystal of (Cr, Al, Si) N having a columnar crystal structure constituting the thin layer B. When the particle size exceeds 500 nm, the wear resistance is reduced due to the coarsening of crystal grains. On the other hand, when the average crystal particle size is less than 50 nm, the effect of improving chipping resistance and fracture resistance is not observed. The average crystal grain size of (Cr, Al, Si) N having a columnar crystal structure constituting the layer B was determined to be 50 to 500 nm.
Further, if the layer thickness of the thin layer B is less than 0.05 μm, the effect of improving chipping resistance and fracture resistance is small. On the other hand, if the layer thickness exceeds 2 μm, the wear resistance is significantly reduced. The layer thickness of B was set to 0.05 to 2 μm.

(D) Alternating lamination of thin layer A and thin layer B The hard coating layer of the present invention consisting of alternating lamination of thin layer A and thin layer B has the thin layer A having a granular crystal structure, while the thin layer B has a columnar crystal structure. However, although the crystal grain forms are different, since it is configured as a hard coating layer having the same component system and the same crystal structure (cubic crystal), it is possible to alternately stack thin layers A and B of different component systems. In comparison, the adhesion strength between the thin layer A and the thin layer B is large, and not only contributes to the high temperature strength improvement as the entire hard coating layer, but also there is no risk of delamination, etc., accompanied by high heat generation, In addition, it exhibits excellent peeling resistance even in high-speed cutting in which a high load acts on the cutting edge.
However, if the total thickness of the hard coating layer composed of the alternating layers of the thin layer A and the thin layer B is less than 0.8 μm, the excellent wear resistance of the hard coating layer cannot be exhibited over a long period of time, so that the tool life is short-lived. On the other hand, if the total layer thickness exceeds 5.0 μm, chipping and defects are likely to occur. Therefore, the total layer thickness is set to 0.8 to 5.0 μm.

  The coated tool of the present invention comprises a thin layer A composed of a (Cr, Al, Si) N layer having a granular crystal structure with excellent coating hardness and heat resistance, and excellent high-temperature strength, toughness and heat resistance. Since it is configured as an alternating layered structure of thin layers B consisting of (Cr, Al, Si) N layers with a columnar crystal structure that exhibits excellent properties, the hard coating layer as a whole has excellent high-temperature hardness, high-temperature strength, and heat resistance. As a result, chipping resistance and chipping resistance with excellent hard coating layer even in high-speed cutting of hardened steel such as hardened alloy tool steel with high heat generation and high load acting on the cutting edge. In addition to having peel resistance, it exhibits excellent wear resistance over a long period of use.

The arc ion plating apparatus used for forming the hard coating layer which comprises a surface coating cutting tool is shown, (a) is a schematic plan view, (b) is a schematic front view.

  Next, the coated tool of 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 into 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 chip shape of ISO standard CNMG120408 Alloy tool bases A-1 to A-10 were formed.

In addition, as raw material powders, all are 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. Tool bases B-1 to B-6 made of TiCN-based cermet having the following chip shape were formed.

(A) Next, each of the tool bases A-1 to A-10 and B-1 to B-6 is ultrasonically cleaned in acetone and dried, and then the arc ion plating shown in FIG. Along the outer peripheral portion at a predetermined distance in the radial direction from the central axis on the rotary table in the apparatus, a Cr—Al—Si alloy having a predetermined component composition as a cathode electrode (evaporation source), for example, Arranged opposite the rotary table,
(B) First, the inside of the apparatus is heated to 500 ° C. with a heater while the inside of the apparatus is evacuated and kept at a vacuum of 0.1 Pa or less, and then the tool base that rotates while rotating on the rotary table is −1000 V. A DC bias voltage is applied, and a current of 100 A is passed between the cathode electrode and the anode electrode made of one of the Cr—Al—Si alloys to generate an arc discharge.
(C) Next, the pressure of nitrogen gas as a reaction gas introduced into the apparatus is adjusted to a condition within the range of 5 to 7 Pa as shown in Table 3, and the same as the tool base rotating while rotating on the rotary table. As shown in Table 3, with a DC bias voltage in the range of −100 to −300 V being applied, a predetermined current in the range of 50 to 100 A is provided between the cathode electrode and the anode electrode of the Cr—Al—Si alloy. To generate an arc discharge, and deposit a thin layer A composed of a (Cr, Al, Si) N layer having a granular crystal structure of a predetermined layer thickness on the surface of the tool base,
(D) Next, the pressure of the nitrogen gas is adjusted to a condition in the range of 2 to 4 Pa as shown in Table 3, and the tool base that rotates while rotating on the rotary table is also set to -20 to 20 as shown in Table 3. With a DC bias voltage in the range of −90 V applied, a predetermined current in the range of 50 to 100 A is passed between the cathode electrode and the anode electrode of the Cr—Al—Si alloy to generate arc discharge. A thin layer B composed of a (Cr, Al, Si) N layer having a columnar crystal structure having a predetermined layer thickness is formed on the surface of the thin layer A;
(E) The formation of the thin layer A and the formation of the thin layer B are alternately repeated, so that the predetermined composition comprising the laminated structure of the thin layers A and B shown in Tables 4 and 5 on the surface of the tool base. The surface coated carbide throwaway tips (hereinafter referred to as the present invention coated carbide tips) 1 to 16 of the present invention were produced by vapor-depositing a hard coating layer having a predetermined crystal grain structure and a predetermined layer thickness, respectively.

  For comparison purposes, these tool bases A-1 to A-10 and B-1 to B-6 were ultrasonically cleaned in acetone and dried, respectively, and the arc ion plating shown in FIG. The device is charged and a Cr—Al—Si alloy having a predetermined composition is attached as a cathode electrode (evaporation source). First, the inside of the device is evacuated and kept at a vacuum of 0.1 Pa or less by using a heater. Is heated to 500 ° C., a DC bias voltage of −1000 V is applied to the tool base, and an arc discharge is generated by passing a current of 100 A between the Cr—Al—Si alloy of the cathode electrode and the anode electrode. Thus, the surface of the tool base is bombarded and then nitrogen gas is introduced as a reaction gas into the apparatus to adjust the pressure conditions shown in Table 3 and rotate while rotating on the rotary table. In the state where the DC bias voltage shown in Table 3 is applied to the tool base, arc discharge is generated between the cathode electrode and the anode electrode of the Cr-Al-Si alloy, and the tool bases A-1 to A- 10 and B-1 to B-6 are vapor-deposited with a hard coating layer composed of a (Cr, Al, Si) N layer having the composition, crystal grain structure and layer thickness shown in Tables 6 and 7. Thus, comparative surface coated carbide throw-away tips (hereinafter referred to as comparative coated carbide tips) 1 to 16 were produced.

Next, the coated carbide chips 1 to 16 of the present invention and the comparative coated carbide chip 1 are compared with the above-mentioned various coated carbide chips, all of which are screwed to the tip of the tool steel tool with a fixing jig. About ~ 16
Work material: JIS · SKD61 hardened material (HRC52) round bar,
Cutting speed: 65 m / min. ,
Cutting depth: 0.20 mm,
Feed: 0.10 mm / rev. ,
Cutting time: 3 minutes,
Dry high-speed cutting test of alloy steel under the conditions (cutting condition A) (normal cutting speed is 30 m / min.),
Work material: JIS · SKD11 hardened material (HRC60) round bar,
Cutting speed: 60 m / min. ,
Cutting depth: 0.25 mm,
Feed: 0.10 mm / rev. ,
Cutting time: 2 minutes,
Dry high-speed cutting test of alloy steel under the following conditions (cutting condition B) (normal cutting speed is 25 m / min.),
Work material: JIS / SUJ2 hardened material (HRC60) round bar,
Cutting speed: 55 m / min. ,
Cutting depth: 0.3 mm,
Feed: 0.15 mm / rev. ,
Cutting time: 3 minutes,
The dry high speed cutting test (normal cutting speed is 30 m / min.) Of the bearing steel under the above conditions (cutting condition C) was performed, and the flank wear width of the cutting edge was measured in any cutting test. The measurement results are shown in Table 8.

As raw material powders, medium coarse WC powder having an average particle diameter of 5.5 μm, fine WC powder of 0.8 μm, TaC powder of 1.3 μm, NbC powder of 1.2 μm, ZrC of 1.2 μm Powder, 2.3 μm Cr ₃ C ₂ powder, 1.5 μm VC powder, 1.0 μm (Ti, W) C [by mass ratio, TiC / WC = 50/50] powder, and 1 .8 μm Co powder was prepared, each of these raw material powders was blended in the blending composition shown in Table 9, and then added with wax, ball milled in acetone for 24 hours, dried under reduced pressure, and then pressed into a predetermined shape at a pressure of 100 MPa. The green compacts were press-molded, and these green compacts were heated to a predetermined temperature in the range of 1370 to 1470 ° C. at a rate of temperature increase of 7 ° C./min in a 6 Pa vacuum atmosphere. After holding at temperature for 1 hour, sintering under furnace cooling conditions 3 types of sintered carbide forming round bar sintered bodies having diameters of 6.5 mm, 10.5 mm, and 20.5 mm were formed, and further, the above three types of round bar sintered bodies were ground by grinding. In the combinations shown in Table 9, the diameter × length of the cutting edge portion was 6 mm × 13 mm, 10 mm × 22 mm, and 20 mm × 45 mm, respectively, and each had a four-blade square shape with a twist angle of 30 degrees. WC base cemented carbide tool bases (end mills) C-1 to C-8 were produced.

  Then, the surfaces of these carbide substrates (end mills) C-1 to C-8 were ultrasonically cleaned in acetone and dried, and then charged into the arc ion plating apparatus shown in FIG. A thin layer A having a granular crystal structure was formed by alternately depositing thin layers A and B having the composition, crystal grain structure and layer thickness shown in Table 10 along the layer thickness direction under the same conditions as in Example 1. And surface-coated carbide end mills (hereinafter referred to as the present invention-coated carbide end mills) 1 to 8 each having a hard coating layer composed of an alternately laminated structure of a thin layer B having a columnar crystal structure.

  For the purpose of comparison, the surfaces of the tool bases (end mills) C-1 to C-8 are ultrasonically cleaned in acetone and dried, and then mounted on the arc ion plating apparatus shown in FIG. Then, under the same conditions as in Example 1, a hard coating layer composed of a (Cr, Al, Si) N layer having the composition, crystal grain structure, and layer thickness shown in Table 11 was also deposited. Coated carbide end mills (hereinafter referred to as comparative coated carbide end mills) 1 to 8 were produced.

Next, of the present invention coated carbide end mills 1-8 and comparative coated carbide end mills 1-8,
About this invention coated carbide end mills 1-3 and comparative coated carbide end mills 1-3,
Work material-Plane: 100 mm × 250 mm, thickness: 50 mm JIS / SKD61 (hardened material (HRC52)) plate material,
Cutting speed: 55 m / min. ,
Groove depth (cut): 0.5 mm,
Table feed: 200 mm / min,
A dry high-speed grooving test of the alloy steel under the conditions (normal cutting speed is 30 m / min.)
For the coated carbide end mills 4-6 of the present invention and the comparative coated carbide end mills 4-6,
Work material-plane: 100 mm x 250 mm, thickness: 50 mm JIS SKD11 (hardened material (HRC60)) plate material,
Cutting speed: 50 m / min. ,
Groove depth (cut): 1.2 mm,
Table feed: 250 mm / min,
A dry high-speed grooving test of the alloy steel under the conditions (normal cutting speed is 30 m / min.)
For the coated carbide end mills 7 and 8 of the present invention and the comparative coated carbide end mills 7 and 8,
Work material-plane: 100 mm × 250 mm, thickness: 50 mm JIS / SUJ2 (hardened material (HRC60)) plate material,
Cutting speed: 30 m / min. ,
Groove depth (cut): 2 mm,
Table feed: 150 mm / min,
A dry high-speed grooving test of the bearing steel under the conditions (normal cutting speed is 25 m / min.),
In any of the above groove cutting tests, the cutting groove length was measured until the flank wear width of the outer peripheral edge of the cutting edge reached 0.1 mm, which is a guide for the service life.
The measurement results are shown in Table 10 and Table 11, respectively.

The diameters produced in Example 2 above were 6.5 mm (for forming carbide substrates C-1 to C-3), 10.5 mm (for forming carbide substrates C-4 to C-6), and 20.5 m. Using three types of round bar sintered bodies (for forming carbide substrates C-7 and C-8), from these three types of round bar sintered bodies, the diameter x length of the groove forming portion was obtained by grinding. 4 mm × 13 mm (Carbide substrates D-1 to D-3), 8 mm × 22 mm (Carbide substrates D-4 to D-6), and 16 mm × 45 mm (Carbide substrates D-7 and D-8), respectively. And WC-based cemented carbide tool bases (drills) D-1 to D-8 each having a two-blade shape with a twist angle of 30 degrees were manufactured.

  Next, the cutting edges of these tool bases (drills) D-1 to D-8 are subjected to honing, ultrasonically cleaned in acetone, and dried to the arc ion plating apparatus shown in FIG. Under the same conditions as in Example 1 above, thin layers A and B having the composition, crystal grain structure and layer thickness shown in Table 12 were alternately deposited, and the thin layer A having a granular crystal structure and Surface-coated carbide drills of the present invention (hereinafter referred to as the present invention-coated carbide drills) 1 to 8 having a hard coating layer composed of an alternately laminated structure with a thin layer B having a columnar crystal structure were manufactured.

  For comparison purposes, honing is applied to the surfaces of the tool bases (drills) D-1 to D-3, D-4 to D-6, D-7, and D-8, and ultrasonic waves are obtained in acetone. In the washed and dried state, the same was inserted into the arc ion plating apparatus shown in FIG. 1 and the composition, crystal grain structure and layer thickness shown in Table 13 were also obtained under the same conditions as in Example 1 above ( Comparative surface-coated carbide drills (hereinafter referred to as comparative coated carbide drills) 1 to 8 were manufactured by vapor-depositing a hard coating layer composed of a Cr, Al, Si) N layer.

Next, of the present invention coated carbide drills 1-8 and comparative coated carbide drills 1-8,
About this invention coated carbide drills 1-3 and comparative coated carbide drills 1-3,
Work material-Plane: 100 mm × 250 mm, thickness: 50 mm JIS / SKD61 (hardened material (HRC52)) plate material,
Cutting speed: 50 m / min. ,
Feed: 0.12 mm / rev,
Hole depth: 6 mm,
Wet high-speed drilling cutting test of alloy steel under the conditions (normal cutting speed is 20 m / min.),
About this invention coated carbide drills 4-6 and comparative coated carbide drills 4-6,
Work material-plane: 100 mm x 250 mm, thickness: 50 mm JIS SKD11 (hardened material (HRC60)) plate material,
Cutting speed: 55 m / min. ,
Feed: 0.15 mm / rev,
Hole depth: 10 mm,
Wet high-speed drilling test of alloy steel under the conditions (normal cutting speed is 25 m / min.)
About the coated carbide drills 7 and 8 of the present invention and the comparative coated carbide drills 7 and 8,
Work material-plane: 100 mm × 250 mm, thickness: 50 mm JIS / SUJ2 (hardened material (HRC60)) plate material,
Cutting speed: 50 m / min. ,
Feed: 0.2 mm / rev,
Hole depth: 32 mm,
A wet high-speed drilling test of the bearing steel under the conditions (normal cutting speed is 30 m / min.),
In any of the above wet high-speed drilling tests (using water-soluble cutting oil), the number of drilling processes until the flank wear width of the tip cutting edge surface reached 0.3 mm was measured. The measurement results are shown in Tables 12 and 13, respectively.

The present invention coated carbide tips 1 to 16, the present invention coated carbide end mills 1 to 8, the present invention coated carbide drills 1 to 8, and the comparative surface coated cutting tool as the surface coated cutting tool of the present invention obtained as a result. The composition of hard coating layers of comparative coated carbide tips 1-16, comparative coated carbide end mills 1-8, comparative coated carbide drills 1-8 as energy dispersive X-ray analysis using a transmission electron microscope As a result of measurement, each showed substantially the same composition as the target composition.
Moreover, when the average layer thickness of each said hard coating layer was cross-sectional measured with the transmission electron microscope, all showed the average value (average value of five places) substantially the same as target layer thickness.

  Furthermore, the (Cr, Al, Si) N layer constituting the thin layer A and the thin layer B of the surface-coated cutting tool of the present invention and the (Cr, Al, Si) N layer constituting the hard coating layer of the comparative surface-coated cutting tool. The crystal grain structure of each layer was determined by a transmission electron microscope, and the results are shown in Tables 4-7 and 10-13.

  From the results shown in Tables 8 and 10-13, the surface-coated cutting tool of the present invention has a thin layer A that exhibits excellent wear resistance and a thin layer B that exhibits excellent chipping resistance and fracture resistance. In addition, it has high heat resistance and high interlayer adhesion strength. As a result, it is accompanied by high heat generation, and high-speed cutting of high-hardness steel with high load acting on the cutting edge. In contrast to excellent chipping and chipping resistance and excellent wear resistance over a long period of time, the hard coating layer has a single crystal grain structure consisting of only granular crystals or columnar crystals (Cr, It is apparent that a coated tool made of an Al, Si) N layer has a poor service life in a relatively short time because of any inferior chipping resistance, chipping resistance or wear resistance.

  As described above, the surface-coated cutting tool of the present invention is not only for cutting under normal cutting conditions such as various types of steel and cast iron, but is particularly high in which a high load acts on the cutting blade with high heat generation. Even in high-speed cutting of hardened steel, it exhibits excellent wear resistance over a long period of time, so we are fully satisfied with the high performance of the cutting machine, labor saving and energy saving of cutting, and cost reduction It can cope with.

Claims (2)

A hard coating layer composed of a composite nitride of Cr, Al, and Si having a layer thickness of 0.8 to 5.0 μm is formed on the surface of a tool base made of tungsten carbide-based cemented carbide or titanium carbonitride-based cermet. In the surface-coated cutting tool made,
The hard coating layer is configured as an alternately laminated structure of a thin layer A composed of a granular crystal structure of a composite nitride of Cr, Al, and Si and a thin layer B composed of a columnar crystal structure, and the thin layer A and the thin layer B are Each having a layer thickness of 0.05 to 2 μm, the average crystal grain size of the granular crystals constituting the thin layer A is 30 nm or less, and the average crystal grain size of the columnar crystals constituting the thin layer B is A surface-coated cutting tool having a thickness of 50 to 500 nm. The composite nitride of Cr, Al and Si is
Composition formula: (Cr _1-XY Al _X Si _Y ) N
2, wherein 0.40 ≦ X ≦ 0.70 and 0.005 ≦ Y ≦ 0.08 (wherein X and Y are atomic ratios) are satisfied. Surface coated cutting tool.

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