Coated cutting tool

Abstract

To provide a surface-coated cutting tool having excellent wear resistance or defect resistance even in intermittent cutting work.SOLUTION: A coating layer includes an I layer, and an II layer on the I layer, where the I layer has (Al1-xTix)N(0.35≤x≤0.60), the II layer has an interlaminate layer of an IIa layer and an IIb layer, the IIa layer has (Al1-y-zTiyBz)N(0.30≤y≤0.70,0.01≤z≤0.10), and the IIb layer has (Al1-p-qTipSiq)N(0.30≤p≤0.60, 0.01≤q≤0.10). An average thickness tI of the I layer and an average thickness tII of the II layer has tI+tII of 1.0 μm or more, 4.0 μm or less, and 2≤tII / tI≤10, where an average thickness of the II layer and an average thickness of the IIa layer and an average thickness of the IIb layer are 1 nm or more, 100 nm or less, and a half-value total width of a diffraction line strength derived from <100>priority orientation of the coating layer is 0.2° or more, and 1.0° or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a surface-coated cutting tool (hereinafter sometimes referred to as a coated tool).

Background Art

[0002] In order to improve the life of a cutting tool, there is a coated tool in which a coating layer is formed on the surface of a substrate such as a tungsten carbide (hereinafter referred to as WC) - based cemented carbide or a cBN sintered body, and the wear resistance of this coated tool is improved. And, in order to further improve the cutting performance of the coated tool, various proposals have been made regarding the composition and structure of the coating layer.

[0003] For example, Patent Document 1 describes a coated tool in which the coating layer contains (Al x Ti 1-x )(B y N 1-y )(0.05 ≦ x ≦ 0.75, 0.02 ≦ y ≦ 0.12) and has a thickness of 0.5 to 8 μm, and the coated tool is said to have improved hardness and wear resistance.

[0004] Also, for example, Patent Document 2 discloses (Al x M 1-x )N [M is one or more of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Si, 0.58 ≦ x ≦ 0.80] and (Al y M 1-y )N [M is one or more of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Si, 0.57 ≦ y ≦ 0.79], and has an alternating laminated structure of the absolute value of the difference between the amount of a specific metal element with respect to the total amount of metal elements contained in the layer and the amount of the specific metal element with respect to the total amount of metal elements contained in another layer adjacent to the layer exceeds 0 atomic% and is less than 5 atomic%, The average thickness of each of the layers is 1 nm or more and 50 nm or less, and the average thickness of the alternating laminated structure is 1.5 μm or more and 15.0 μm or less. A coated tool having a coating layer is described, and the coated tool is said to have chipping resistance and durability in cutting a material with low thermal conductivity.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] The present invention has been made in view of the above circumstances and the above proposal. In particular, an object of the present invention is to provide a surface-coated cutting tool having excellent wear resistance and chipping resistance in interrupted cutting.

Means for Solving the Problems

[0007] The surface-coated cutting tool according to an embodiment of the present invention 1) has a substrate and a coating layer on the surface of the substrate, 2) the coating layer includes an I layer and a II layer on the I layer, 3) the I layer is (Al 1-x Ti x )N (0.35 ≦ x ≦ 0.60), 4) the II layer has an alternating laminate of a IIa layer and a IIb layer, the IIa layer is (Al 1-y-z Ti y B z )N (0.30 ≦ y ≦ 0.70, 0.01 ≦ z ≦ 0.10), the IIb layer is (Al 1-p-q Ti p Si q )N (0.30 ≦ p ≦ 0.60, 0.01 ≦ q ≦ 0.10), 5) The average thickness t of the I layer I and the average thickness t of the II layer II are such that t I +t II is 1.0 μm or more and 4.0 μm or less, and 2 ≤ t II / t I ≤ 10, 6) The average thickness of the IIa layer and the average thickness of the IIb layer are both 1 nm or more and 100 nm or less, 7) The full width at half maximum of the diffraction line intensity derived from the <100> preferred orientation of the coating layer is 0.2° or more and 1.0° or less, and

[0008] Furthermore, the surface-coated cutting tool according to the embodiment may satisfy the following matters.

[0009] The diffraction line intensity I (111) derived from the <111> preferred orientation of the coating layer and the diffraction line intensity I (100) derived from the <100> preferred orientation are such that 2 ≤ I (100) / I (111) ≤ 20.

Advantages of the Invention

[0010] The surface-coated cutting tool has excellent wear resistance and chipping resistance even in interrupted cutting.

Brief Description of the Drawings

[0011]

Figure 1

Modes for Carrying Out the Invention

[0012] The present inventor has earnestly studied to obtain a coated tool having excellent wear resistance and chipping resistance, particularly in interrupted cutting. As a result, 1) It is necessary to increase the adhesion strength between the substrate and the coating layer 2) Since it is difficult for a single coating layer to satisfy all of high hardness, weld resistance, and oxidation resistance, it is preferable to alternately stack a layer with high hardness and excellent weld resistance and a layer with high hardness and excellent oxidation resistance. 3) When the difference in lattice constants of the alternately stacked layers is reduced, the wear resistance and toughness are improved, and as a result, it is possible to achieve both suppression of chipping and defects and wear resistance in interrupted cutting and continuous cutting. We have found this.

[0013] Hereinafter, the coated tool according to the embodiment of the present invention will be described in detail. Here, in this specification and the claims, interrupted cutting refers to a process in which the workpiece and the coated tool repeat cutting and idling.

[0014] Also, in this specification and the claims, when a numerical range is expressed as "L to M" (both L and M are numerical values), the range is synonymous with "L or more and M or less", includes the upper limit value (M) and the lower limit value (L), and when only the unit is described for the upper limit value (M), the units of the upper limit value (M) and the lower limit value (L) are the same.

[0015] 1. Coating layer FIG. 1 is a diagram schematically showing a longitudinal section of a coated tool according to an embodiment of the present invention (a cross section perpendicular to this surface ignoring minute irregularities on the surface of the substrate in the case of an insert. In the case of an axial tool such as an end mill or a drill, a cross section perpendicular to this central axis). In this embodiment, from the substrate (1) toward the surface of the coated tool, that is, the surface of the coating layer (2), there are an I layer (3) and an II layer (4) in order. And the II layer (4) has an alternating stack of a IIa layer (5) and a IIb layer (6). In FIG. 1, the IIa layer (5) and the IIb layer (6) are also alternately stacked in the white portion of the II layer. Hereinafter, each layer will be described in order.

[0016] (1) I layer The I layer has an average composition of (Al 1-x Ti x )N (0.35 ≦ x ≦ 0.60). The I layer is provided to enhance the adhesion between the substrate and the coating layer. When x is within this range, the improvement in this adhesion can be surely achieved. A more preferable range of x is 0.35 or more and 0.50 or less. And this I layer can ensure the adhesion between the substrate and the coating layer even in a cBN sintered body which is a substrate where it is difficult to ensure the adhesion with the coating layer.

[0017] Note that according to an example of the manufacturing method described later, the ratio of (AlTi) to N is formed into a film so as to be 1:1, but there may be cases where it does not unavoidably (unintentionally) become 1:1. This also applies to other composite nitrides and nitrides described below.

[0018] (2) II layer The II layer has an alternating laminate of a IIa layer and a IIb layer. The IIa layer has an average composition of (Al 1-y-z Ti y B z )N (0.40 ≤ y ≤ 0.70, 0.01 ≤ z ≤ 0.10). The IIb layer has an average composition of (Al 1-p-q Ti p Si q )N (0.40 ≤ p ≤ 0.60, 0.01 ≤ q ≤ 0.10).

[0019] Since the IIa layer contains B, it has high hardness and excellent weld resistance. On the other hand, since the IIb layer contains Si, it has high hardness and excellent oxidation resistance. Therefore, by alternately laminating this IIa layer and IIb layer, a coating layer excellent in both wear resistance and chipping resistance can be obtained.

[0020] And in order to surely obtain this excellent wear resistance and chipping resistance, it is preferable that the average content y of Ti, the average content z of B, the average content p of Ti, and the average content q of Si are within the above ranges. A more preferable range of y, z, p, and q is more preferably 0.35 ≤ y ≤ 0.55, 0.02 ≤ z ≤ 0.08, 0.35 ≤ p ≤ 0.55, and 0.02 ≤ q ≤ 0.08.

[0021] (3) Average thickness of the coating layer The average thickness of the coating layer, that is, the average thickness t of layer I I and the average thickness t of layer II II The sum of (t I + t II ) is preferably 1.0 μm or more and 4.0 μm or less. The reason is that if it is less than 1.0 μm, the durability is not sufficient, while if it exceeds 4.0 μm, defects are likely to occur. The average thickness of the coating layer is more preferably 1.5 μm or more and 3.5 μm or less.

[0022] Also, t I and II are preferably such that 2 ≤ t II / t I ≤ 10. When t II / t I satisfies this range, the function of enhancing the adhesion between the substrate provided by layer I and the functions of excellent abrasion resistance and chipping resistance provided by layer II are surely achieved. t II / t I is more preferably 4 ≤ t II / t I ≤ 6.

[0023] (4) Average thickness of layer IIa and layer IIb In layer II, the average thickness (t a ) of layer IIa forming the alternating laminate and the average thickness (t b ) of layer IIb are both preferably 1 nm or more and 100 nm or less. The average thickness (t a ) of layer IIa and the average thickness (t b ) of layer IIb may be the same or different.

[0024] (5) Alternating laminate of layer IIa and layer IIb Layer IIa and layer IIb are alternately laminated, and this alternating lamination only requires that layer IIa and layer IIb are alternately laminated, and either the layer closest to layer I or the layer closest to the tool surface can be either layer IIa or layer IIb.

[0025] There is no restriction on the number of stacked layers of layer IIa and layer IIb that constitute the interactive laminate. However, it is more preferable that layer IIa and layer IIb each have 20 to 100 layers. When this number of stacked layers is satisfied, the wear resistance and chipping resistance of layer II can be improved more reliably.

[0026] (6) Full width at half maximum of the diffraction line derived from the <100> preferred orientation It is preferable that the full width at half maximum of the diffraction line intensity derived from the <100> preferred orientation of the coating layer is 0.2° or more and 1.0° or less. When the full width at half maximum is within this range, the difference in lattice constants between layer IIa and layer IIb becomes smaller, and the above object can be surely achieved.

[0027] (7) Diffraction line intensity derived from the <111> preferred orientation and diffraction line intensity derived from the <100> preferred orientation Diffraction line intensity I derived from the <111> preferred orientation of the coating layer (111) and diffraction line intensity I derived from the <100> preferred orientation (100) In this case, 2 ≤ I (100) / I (111) ≤ 20 is even more preferable. If I (100) / I (111) is within this range, the above object can be achieved more surely.

[0028] 2. Other layers (1) Outermost layer Even with only the coating layers (layer I and layer II), the above object can be achieved, but an outermost layer may be provided to make it more preferable as a coated tool. The outermost layer can be exemplified by a TiN layer (TiN is not limited to a stoichiometric composition). Since TiN has a golden color tone, for example, it can be utilized as an identification layer for discriminating whether the coated tool is unused or in use based on the color tone change on the surface of the coated tool. Here, the average thickness of the TiN layer as the identification layer may be, for example, 0.01 to 1.0 μm.

[0029] (2) Layers that may inevitably occur In this embodiment, the film is formed so that there are no layers other than the I layer, the II layer, and the outermost layer. However, when changing the layer to be formed, a change in the pressure inside the film forming apparatus inevitably occurs, and unintentional layers having a composition different from those of these layers may be formed.

[0030] 3. Substrate (1) Material As the material of the substrate, any material can be used as long as it is a conventionally known substrate material and does not inhibit the achievement of the above-described object. For example, cemented carbide (WC-based cemented carbide, including WC, Co, and those further added with carbonitrides such as Ti, Ta, Nb, etc.), cermet (those mainly composed of TiC, TiN, TiCN, etc.), ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, etc.), cBN sintered body, or diamond sintered body is preferably used.

[0031] (2) Shape The shape of the substrate is not particularly limited as long as it is a shape used as a cutting tool, and examples thereof include the shape of an insert and the shape of a drill.

[0032] 4. Measurement of the average thickness of each layer In this embodiment, the average thickness of each layer constituting the coating layer can be obtained by observing a cross section using an energy dispersive X-ray spectroscope (EDS) attached to a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

[0033] Regarding the average thickness of the alternating laminated portions IIa and IIb of the II layer, it can be determined by performing five TEM-EDS line analyses in the thickness direction of the coating layer. When performing TEM-EDS line analysis in the thickness direction of the coating layer, since the II layer is composed of alternating laminations of the IIa layer and the IIb layer, the contents of B and Si increase and decrease repeatedly. As a result of the TEM-EDS line analysis of the cross-section of the coating layer, the average distance between the maximum point of the B content and the adjacent minimum point of the content is (Al 1-y-z Ti y B z )N's average thickness, and the average distance between the maximum point of the Si content and the adjacent minimum point of the content is (Al 1-p-q Ti p Si q )N's average thickness.

[0034] 5. Measurement of the composition of each layer Regarding the average content ratio of each component in each layer, it can be determined by performing five TEM-EDS line analyses in the thickness direction of the coating layer.

[0035] 6. Measurement of diffraction line intensity The measurement of the diffraction line intensity can be obtained by analyzing the diffraction lines using an X-ray diffraction (XRD) apparatus. From the direction perpendicular to the substrate surface (the thickness direction of the coating layer), the total X-ray diffraction intensity (the overlapping X-ray diffraction intensity of the I layer, IIa layer, and IIb layer) derived from the (200) plane orientation of the I layer, IIa layer, and IIb layer was measured, and its full width at half maximum was calculated. Also, the X-ray diffraction intensity derived from the <100> preferred orientation obtained by X-ray diffraction was defined as I (200) , and the X-ray diffraction intensity derived from the <111> preferred orientation was calculated as I (111) . Note that the measurement of the diffraction line intensity can be performed, for example, under the measurement conditions: Cu tube target, measurement range (2θ): 30 to 70 degrees, scan step: 0.015 degrees, scan speed: 2 degrees / min.

[0036] 6. Manufacturing method The coating layer of the coating tool of this embodiment can be manufactured, for example, using an AIP apparatus (arc ion plating apparatus). Further, as the target, an AlTi target having a composition corresponding to the composition of the I layer for forming the I layer, an AlTiB target having a composition corresponding to the composition of the IIa layer for forming the II layer, and an AlTiSi target having a composition corresponding to the composition of the IIb layer are used respectively to form a film.

Example

[0037] Next, examples will be described. Here, as an example of the coating tool of the present invention, an example applied to an insert cutting tool using a cBN sintered body as a substrate will be described. However, a substrate made of the above-described material can be used, and the same applies when applied to a drill, an end mill, etc. as the shape as described above.

[0038] 1. Fabrication of a substrate made of cBN When fabricating the substrate, cBN powder and TiN powder, TiC powder, TiCN powder, Al powder, AlN powder, and Al2O3 powder as binders are prepared. Any one or more of the binder powders and cBN powder are mixed at the mixing ratios shown in Table 1 and sintered using an ultrahigh pressure and high temperature generating apparatus (sintering temperature: 1300 °C, sintering pressure: 4.0 GPa, sintering time: 30 minutes) to fabricate cBN substrates 1 to 3 having a shape equivalent to CNGA120408 in the ISO standard.

[0039]

Table 1

[0040] 2. Film formation of the coating layer (1) Substrates 1 to 3 are ultrasonically cleaned in acetone and, in a dried state, are mounted along the outer periphery at a position a predetermined distance away from the central axis on the rotating table in the AIP apparatus in the radial direction. Further, an alloy target having a predetermined composition is disposed as a cathode electrode (evaporation source).

[0041] (2) Next, the cBN substrate rotating on the rotating table was bombarded and cleaned with Ar ions.

[0042] (3) In the AIP apparatus, a nitrogen atmosphere with a partial pressure shown in Table 2 of 2 - 6 Pa was used as the reaction gas, and the furnace temperature was maintained at the temperature shown in Table 2. Then, a DC voltage of - 30 to - 100 V shown in Table 2 was applied to the substrate rotating on the rotating table, and a current of 70 to 180 A was passed between the AlTi alloy electrode for forming the I layer and the anode electrode to generate arc discharge to form an I layer with a predetermined thickness.

[0043] (4) Subsequently, a DC voltage of - 30 to - 100 V shown in Table 2 was applied, and a current of 70 to 200 A was passed between the AlTiB alloy electrode for forming the IIa layer of the II layer and the anode electrode to generate arc discharge to form a IIa layer with a predetermined thickness.

[0044] (5) Further, a DC voltage of - 30 to - 100 V shown in Table 2 was applied, and a current of 70 to 200 A was passed between the AlTiSi alloy electrode for forming the IIb layer of the II layer and the anode electrode to generate arc discharge to form a IIb layer with a predetermined thickness.

[0045] (6) The operations of (4) and (5) were repeated to laminate the IIa layer and the IIb layer.

[0046] (7) Further, in some examples, after the operation of (6), a DC voltage of - 20 to - 150 V was applied, and a current of 50 to 250 A was passed between the Ti electrode for forming the TiN layer and the anode electrode to generate arc current to form the outermost TiN layer, and the coated tool Examples 1 - 9 shown in Table 4 were obtained.

[0047] On the other hand, for comparison, for the substrates 1 - 5, using the same film - forming apparatus as above, a coating layer was vapor - deposited and formed under the conditions shown in Table 3, and the coated tools (hereinafter referred to as "comparative examples") 1 - 8 shown in Table 4 were produced. In some comparative examples, the outermost TiN layer was formed in the same manner as in the examples.

[0048] The average thickness and average composition of the coating layer were determined by the above-described method for the longitudinal cross-section of the coating layer perpendicular to the surface of the substrates of Examples 1 to 9 and Comparative Examples 1 to 8 prepared above, for a field of view set such that the width in the direction parallel to the surface of the substrate was 10 μm and the entire thickness region of the coating layer was included. The observation magnification was 5000 times, and the average layer thickness was calculated by obtaining the film thickness at 5 points. For the average content of each component in each layer, it was determined by performing 5 TEM-EDS line analyses in the thickness direction of the coating layer.

[0049]

Table 2

[0050]

Table 3

[0051]

Table 4

[0052] Next, the following cutting tests were performed on Examples 1 to 9 and Comparative Examples 1 to 9, and the wear width of the flank face was measured. The results of the cutting tests are shown in Table 5.

[0053] <Cutting Test> Workpiece material: hardened steel SCr420 (shape: a φ38×L120 round bar having 2 slits with a slit width of 23 mm) Cutting speed: 200 m / min Depth of cut: fr = 0.05 mm / rev, ap = 0.1 mm The cutting edge was observed every 30 seconds, and machining was carried out up to a maximum of 360 seconds. The end of tool life was defined as when chipping occurred at the tip of the cutting edge or when the maximum flank face wear width exceeded 200 μm.

[0054]

Table 5

[0055] In Table 5, "※" indicates the cutting life (seconds) because the service life was reached before the maximum cutting length was reached.

[0056] As is clear from the results shown in Table 5, it can be seen that Examples 1 to 9 also have excellent wear resistance and chipping resistance even in interrupted cutting. On the other hand, in all of Comparative Examples 1 to 8, wear and chipping of the coating layer occurred, resulting in a short life.

Explanation of Reference Signs

[0057] 1 Substrate 2 Coating layer 3 I layer 4 II layer 5 IIa layer 6 IIb layer

Claims

1. A surface-coated cutting tool having a substrate and a coating layer on the surface of the substrate, 1) The coating layer includes an I layer and an II layer on the I layer, 2) The I layer is (Al １－ｘ Ti ｘ )N(0.35 ≤ x ≤ 0.60), 3) The II layer has an alternating laminate of an IIa layer and an IIb layer, The IIa layer is (Al 1-ｙ-ｚ Ti ｙ B ｚ )N(0.30 ≤ y ≤ 0.70, 0.01 ≤ z ≤ 0.10), The IIb layer is (Al 1-ｐ-ｑ Ti ｐ Si ｑ )N(0.30 ≤ p ≤ 0.60, 0.01 ≤ q ≤ 0.10), 4) The average thickness t of the I layer Ｉ and the average thickness t of the II layer ＩＩ are such that t Ｉ + t ＩＩ is 1.0 μm or more and 4.0 μm or less, and 2 ≤ t ＩＩ / t Ｉ ≤ 10, and 5) The average thickness of the IIa layer and the average thickness of the IIb layer are both 1 nm or more and 100 nm or less, 6) The full width at half maximum of the diffraction line intensity derived from the <100> preferred orientation of the coating layer is 0.2° or more and 1.0° or less, A surface-coated cutting tool characterized by the above.

2. The diffraction line intensity I derived from the <111> preferred orientation of the coating layer （１１１） and the diffraction line intensity I derived from the <100> preferred orientation （１００） wherein 2 ≤ I （１００） / I （１１１） ≤ 20, and the surface-coated cutting tool according to claim 1

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