Coated cutting tool

Abstract

To provide a surface-coated cutting tool having abrasion resistance and thermal crack resistance.SOLUTION: In a disclosed surface-coated cutting tool, a lower layer has a thickness in a range of 0.5 to 13.5 μm and includes a complex nitride B or carbonitride of (AlXBTi1-XB)(CYBN1-YB); the average values of XB and YB are in the ranges of 0.50≤XBAVG≤0.75 and 0.00≤YBAVG≤0.05, respectively; the lower layer has a crystal grain B of the NaCl type face-centered cubic structure of 80 area% or more; in the crystal grain B, the average value ΔXB of difference between adjacent maximal value and minimal value of XB is in a range of 0.01 to 0.05; and the interval thereof is in the range of 1-12 nm. An upper layer has the thickness in the range of 0.5 to 9.4 μm and includes the complex nitride C or carbonitride of (AlXCTi1-XC)(CYCN1-YC); the average values of XC and YC are in the ranges of 0.50≤XCAVG≤0.75 and 0.00≤YCAVG≤0.05, respectively; the upper layer has the crystal grain C of the NaCl type face-centered cubic structure of 80 area% or more; in the crystal grain C, the average value ΔXC of difference between adjacent maximal and minimal values of XC is in the range of 0.10 to 0.50; the interval thereof is in the range of 20 to 100nm; and the lower and upper layers satisfy 0.00≤XBAVG-XCAVG≤0.10.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] Conventionally, in order to increase the service life of a cutting tool, there is a coated tool in which a coating layer is coated on the surface of a substrate such as a tungsten carbide (hereinafter sometimes referred to as WC)-based cemented carbide, and the wear resistance and the like of this coated tool are 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 discloses a coating layer composed of one or more layers, at least one of which is a 1-x Ti x Al 1-y Al y N-based first unit layer and a 1-x Ti x Al 1-y Al y N-based second unit layer are alternately laminated, the first unit layer has an fcc crystal structure, and x in

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention has been made in view of the above circumstances and the above proposal, and an object thereof is to obtain a surface-coated cutting tool having excellent wear resistance and heat crack resistance.

Means for Solving the Problems

[0006] The surface-coated cutting tool according to an embodiment of the present invention has a substrate and a coating layer on the surface of the substrate, (a) The coating layer has a base layer in contact with the substrate, a lower layer in contact with the base layer, and an upper layer in contact with the lower layer, (b) The base layer has an average thickness of 0.05 to 2.00 μm and contains a nitride or carbonitride of Ti, (c) The lower layer has an average thickness of 0.5 to 13.5 μm, (Al XB Ti 1-XB )(C YB N 1-YB ) and contains a composite nitride B or a composite carbonitride B' represented by, and the average value XB of XB AVG , the average value YB of YB AVG are respectively 0.50 ≦ XB AVG ≦ 0.75, 0.00 ≦ YB AVG ≦ 0.05, (d) The composite nitride B or the composite carbonitride B' has crystal grains B having an NaCl-type face-centered cubic structure in an area of 80% or more in a cross section in the thickness direction of the coating layer, (e) The crystal grains B include crystal grains that repeat the increase and decrease of XB in the thickness direction, and the average value ΔXB of the difference between adjacent maximum and minimum values of XB is 0.01 to 0.05, and the interval of the repeated change in the thickness direction is 1 to 12 nm, (f) The upper layer has an average thickness of 0.5 to 9.4 μm, (Al XC Ti 1-XC )(C YC N 1-YC ) and contains a composite nitride C or a composite carbonitride C' represented by, and the average value XC of XC AVG , the average value YC of YC AVG are respectively 0.50 ≦ XCAVG ≤0.75, 0.00 ≤ YC AVG ≤0.05, and (g) The composite nitride C or the composite carbonitride C' has, in a cross-section in the thickness direction, crystal grains C having an NaCl-type face-centered cubic structure with an area of 80% or more, (h) The crystal grains C include crystal grains that repeat the increase and decrease of XC in the thickness direction, and the average value ΔXC of the difference between adjacent maximum and minimum values of XC is 0.10 to 0.50, and the interval of the repeated change in the thickness direction is 20 to 100 nm, (i) The lower layer and the upper layer satisfy 0.00 ≤ XB AVG - XC AVG ≤0.10.

[0007] Furthermore, the surface-coated cutting tool according to the embodiment may satisfy at least one of the following (1) to (3).

[0008] (1) In the lower layer, ρB = [Cl] / ([Ti] + [Al] + [C] + [N] + [Cl]) ([Q] represents the number of atoms of element Q) is 0.001 to 0.050, In the upper layer, ρC = [Cl] / ([Ti] + [Al] + [C] + [N] + [Cl]) is 0.001 to 0.010. (2) In the coating layer, the intensity value I(200) of the 200 diffraction line and the intensity value I(111) of the 111 diffraction line of the crystal grains having an NaCl-type face-centered cubic crystal structure satisfy the relationship of 1.0 ≤ I(200) / I(111). (3) When a region surrounded by a line l that penetrates 25 nm into each grain from the grain boundaries of two adjacent crystal grains B is defined as region α, and a region surrounded by the line l and the grain boundaries is defined as region β, a location that satisfies 0.20 ≤ xβ ≤ xα - 0.10 (where xα is the average value of XB in region α, and xβ is the average value of XB in a region with a diameter of 50 nm at an arbitrary position in region β) exists in region β in an area of 5 to 20%.

Advantages of the Invention

[0009] The surface-coated cutting tool according to the above embodiment has excellent wear resistance and heat crack resistance.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0011] The present inventors have earnestly studied measures for a coated tool having a composite carbide and a composite nitride of Al and Ti (hereinafter sometimes referred to as (AlTi)CN) in the coating layer to have more excellent wear resistance and heat crack resistance. As a result, a (AlTi)CN layer having a composition excellent in wear resistance is provided on the surface side of the coated tool with a predetermined average thickness, and a (AlTi)CN layer having a composition with heat crack resistance is provided below (substrate side) with a predetermined average thickness, and both (AlTi)CN layers have a predetermined repeated change in Al content, and thus it has been found that the coated tool exhibits excellent wear resistance and heat crack resistance.

[0012] Hereinafter, the coated tool of the embodiment of the present invention will be described in detail. In this specification and the claims, when a numerical range is expressed as "L to M" (both L and M are numerical values), it is synonymous with "L or more and M or less", and the range includes the upper limit value (M) and the lower limit value (L), and when only the unit of the upper limit value is described, the unit of the lower limit value is also the same.

[0013] Fig. 1 schematically shows a longitudinal sectional view of a coated tool according to an embodiment of the present invention (a cross section perpendicular to a plane treating the surface of the substrate as a horizontal plane while ignoring minute irregularities on the surface of the substrate). As is apparent from Fig. 1, in the coated tool according to this embodiment, an underlayer (2) is in contact with the surface of a substrate (1), and a lower layer (3) is in contact with the underlayer (2) on the tool surface side of the underlayer (2), and an upper layer (4) is further in contact with the lower layer (3) on the tool surface side of the lower layer (3). Then, the underlayer (2), the lower layer (3), and the upper layer (4) constitute a coating layer (5). Further, as will be described later, an outermost layer (6) may be selectively provided. Hereinafter, each layer will be described in order.

[0014] 1. Underlayer The underlayer in contact with the substrate surface is made of a nitride or carbonitride of Ti and serves as a layer (adhesion layer) that provides adhesion between the base material and the lower layer.

[0015] (1) Average composition The composition of the underlayer is not particularly limited as long as it is a nitride or carbonitride of Ti (not limited to a stoichiometric composition). For example, the composition formula TiC Z N 1-Z (0 ≦ Z ≦ 0.5) may be used. Here, if Z is contained more than 0.5, the hardness of the underlayer may excessively increase, and the underlayer may be likely to peel off from the substrate interface.

[0016] Also, the ratio of Ti to (C Z N 1-Z ) is not particularly limited, but 1:0.8 to 1:1.2 is preferable. The reason is that the object of the present invention can be surely achieved within this range.

[0017] (2) Average thickness The average thickness of the underlayer is preferably 0.05 to 2.00 μm. The reason is that if it is thinner than 0.05 μm, its function as an adhesion layer is insufficient, while if it is 2.00 μm or more, the thickness of the adhesion layer in the coating layer becomes excessive, and sufficient wear resistance cannot be obtained. The average thickness of the underlayer is more preferably 0.10 to 1.50 μm.

[0018] 2. Lower layer The lower layer provided on the tool surface side in contact with the surface of the base layer is a (AlTi)CN layer, which acts as a layer for suppressing the progress of thermal cracks progressing in the substrate direction.

[0019] (1) Average composition The lower layer is (Al XB Ti 1-XB )(C YB N 1-YB ), and it is preferable that XB, which is the average content of XB, AVG and YB, which is the average content of YB, AVG satisfy 0.50 ≦ XB AVG ≦ 0.75 and 0.00 ≦ YB AVG ≦ 0.05.

[0020] The reason is that when XB AVG is less than 0.50, the high oxidation resistance property that the (AlTi)CN film originally has cannot be sufficiently obtained. On the other hand, when XB AVG exceeds 0.75, it becomes difficult to obtain good adhesion with the adjacent upper layer, and the upper layer is likely to peel off and the durability is inferior. The value of XB AVG is more preferably 0.65 ≦ XB AVG ≦ 0.75. Since the C component in (AlTi)CN has an effect of improving hardness, it may be contained. However, when YB AVG exceeds 0.05, the high-temperature strength of the lower layer decreases. Therefore, it is preferable that 0.00 ≦ YB AVG < 0.05.

[0021] Also, the ratio of (Al XB Ti 1-XB ) to (C YB N 1-YB ) is not particularly limited, but 1:0.8 to 1:1.2 is preferable. The reason is that the object of the present invention can be surely achieved within this range. This is the same for the (Al XC Ti 1-XC ) and (C YC N1-YC ) is the same even in

[0022] (2) Grains with an NaCl-type face-centered cubic structure In the lower layer, the proportion of grains having an NaCl-type face-centered cubic structure is preferably 80 area% or more. The reason is that if it is less than 80 area%, the proportion of the wurtzite-type hexagonal crystal structure, which is the original stable phase of (AlTi)CN and is soft, increases in the lower layer, and sufficient durability of the coated tool cannot be obtained. The proportion of grains having an NaCl-type face-centered cubic structure is more preferably 90 area% or more. It may be 100 area%.

[0023] (3) Average thickness The average thickness of the lower layer is preferably 0.5 to 13.5 μm. The reason is that if it is less than 0.5 μm, sufficient suppression of the above-described thermal crack progression cannot be obtained. On the other hand, if it exceeds 13.5 μm, the crystal grains of the lower layer become coarser, and although wear resistance can be obtained, damage accompanied by the shedding of crystal grains due to machining impact is likely to occur, leading to abnormal damage of the coated tool. The average thickness of the lower layer is more preferably 2.0 to 7.0 μm.

[0024] (4) Repeated change in the increase and decrease of XB In the lower layer, the proportion of grains that repeat the increase and decrease of XB in the thickness direction of the coating layer is preferably 60 area% or more. The reason is that if it is less than 60 area%, sufficient suppression of the above-described thermal crack progression cannot be obtained. The proportion of grains that repeat the increase and decrease of XB may be 100 area%.

[0025] In the repeated change in the increase and decrease of XB, the average value ΔXB of the difference between adjacent maximum values and minimum values is preferably 0.01 to 0.05. The reason for setting ΔXB within this range is that if it is less than 0.01, suppression of crack progression is not sufficient and chipping resistance decreases. On the other hand, if it exceeds 0.05, the lattice strain generated at the boundary between the region with a high Al content and the region with a low Al content becomes large, serving as a fracture origin during cutting and causing abnormal damage such as chipping. ΔXB is more preferably 0.01 to 0.03.

[0026] Also, the average value of the intervals between adjacent maximum values and minimum values, that is, the average interval in the thickness direction of the coating layer is preferably 1 to 12 nm. The reason for setting the average interval within this range is that if the average interval is less than 1 nm, the number of boundaries between regions with high Al content and regions with low Al content increases, and local adhesion strength reduction and plastic deformation are likely to occur, resulting in a decrease in chipping resistance and hardness. On the other hand, if it exceeds 12 nm, the buffering effect of the lower layer for suppressing crack propagation during cutting is insufficient. More preferably, the average interval is 1 to 5 nm.

[0027] FIG. 2 is a diagram schematically showing a part of an example of the repeated change in the increase and decrease of XB (repeated change in Al content). In FIG. 2, each of the maximum value and the minimum value is the same value, and the intervals between adjacent maximum values and minimum values are also the same. However, for the repeated change in the increase and decrease of XB, XB only needs to change so as to alternately take the maximum value and the minimum value. The maximum value and the minimum value may or may not be the same value respectively, and the intervals between adjacent maximum values and minimum values may or may not be the same.

[0028] Here, the average interval between the position giving the maximum value and the position giving the adjacent minimum value in the lower layer having a repeated change in the increase and decrease of XB is obtained by measuring the Al content in the thickness direction of the lower layer for each crystal grain having an NaCl-type face-centered cubic structure and removing noise that cannot be considered as the repeated change in XB by known means such as a low-pass filter and then graphing.

[0029] That is, as shown in FIG. 2, for the curve showing the repeated change in the increase and decrease of XB, a straight line m is drawn across this curve (in FIG. 2, the straight line m shows the length crossing two maximum values and two minimum values respectively, but the length of the straight line m is not limited to this, and it is set to a length at which the average value of the maximum value and the minimum value, as well as the average interval, can be accurately obtained). This straight line m is drawn so that the area of the region surrounded by the curve is equal on the upper side and the lower side of the straight line m (m = XB AVGThat is, for each region where the straight line m crosses the curve showing the repeated change in the Al content, the maximum or minimum value of XB is determined, the interval between the two is measured, and the average value of this measured value at a plurality of locations is obtained, thereby obtaining the average interval of the repeated change in the increase and decrease of XB for each crystal grain having an NaCl-type face-centered cubic structure in the lower layer. Further, the average value of the difference between adjacent maximum and minimum values in the repeated increase and decrease of the Al content ratio XB is obtained and calculated as ΔXB.

[0030] (5) Cl content In the lower layer, it is more preferable that ρB = [Cl] / ([Ti] + [Al] + [C] + [N] + [Cl]) ([Q] represents the number of atoms of element Q) is 0.001 to 0.050. The reason for setting ρB within this range is that if it is less than 0.001, the lubricity of the coating layer may not be sufficient, while if it exceeds 0.050, the toughness of the lower layer may be impaired and the chipping resistance may decrease.

[0031] (6) Relationship between near grain boundary of XB and others As shown in FIG. 3, in the lower layer, for adjacent crystal grains having an NaCl-type face-centered cubic structure, when the range surrounded by the line l(10) 25 nm away from the crystal grain boundaries of both into their respective crystal grains is region α(8), and the range surrounded by the line l(10) and the grain boundary is region β(9), It is even more preferable that the region β contains 5 to 20 area% of the locations satisfying 0.20 ≦ XBβ ≦ XBα - 0.10. Here, XBα is the average value of XB in region α, and XBβ is the average value of XB in a region with a diameter of 50 nm at an arbitrary position in region B.

[0032] The reason is as follows. Regarding the above relational expression, if XBβ > XBα - 0.10, the movement of dislocations may be suppressed, and the improvement in the hardness of the TiAlCN layer may not be sufficient. In addition, the lattice constant near the grain boundary may increase, and the effect of improving the chipping resistance due to the compressive stress applied to the (TiAl)CN layer may be small. On the other hand, if XBβ is less than 0.20, the high-temperature oxidation resistance of the (TiAl)CN layer is poor, and the chipping resistance may decrease. Therefore, it is more preferable that 0.20 ≤ XBβ ≤ XBα - 0.10 holds.

[0033] Regarding the area ratio of the portion satisfying the above relational expression regarding the compositions of region α and region β in region β, if the ratio existing in region β is less than 5 area%, the effect of improving the hardness of the (TiAl)CN layer and the improvement in chipping resistance may not be sufficient. If it exceeds 20 area%, the high-temperature oxidation resistance of the (TiAl)CN layer is poor, and the chipping resistance may decrease. Therefore, it is more preferable that this area ratio is 5 to 20 area%, and more preferably 10 to 20 area%.

[0034] Here, the method for measuring the compositions of region α and region β will be described. First, the grain boundaries of the crystal grains constituting the (TiAl)CN layer are obtained and the crystal grains are specified as follows. That is, using a crystal orientation analysis device attached to a Transmission Electron Microscope (TEM), in the polished longitudinal section, while irradiating an electron beam inclined at, for example, 0.5 to 1.0 degrees with respect to the normal direction of the surface polishing surface by Precession (precession movement), the electron beam is scanned at an arbitrary beam diameter and interval, continuously capturing electron diffraction patterns, and analyzing the crystal orientation of each measurement point. As the observation field of view, an example can be a width of 50 μm in the direction parallel to the substrate surface and a length corresponding to the thickness (average thickness) of the coating layer.

[0035] The acquisition conditions for the electron diffraction pattern used in this measurement are, for example, an acceleration voltage of 200 kV, a camera length of 20 cm, a beam size of 2.4 nm, and a measurement step of 5.0 nm. At this time, the measured crystal orientations are those discretely examined on the measurement plane, and the orientation distribution of the entire measurement plane is obtained by representing the region up to the middle between adjacent measurement points with the measurement results. Note that, as the regions represented by these measurement points (hereinafter sometimes referred to as pixels), those with a regular hexagonal shape can be exemplified. If there is an angular difference in crystal orientation of 5 degrees or more between adjacent ones of these pixels, or if only one of adjacent pixels shows a face-centered cubic structure of the NaCl type, the side of the region where these pixels are in contact is taken as a grain boundary. Then, the portion surrounded by the sides defined as this grain boundary is defined as one crystal grain. However, a single pixel that has an orientation difference of 5 degrees or more from all adjacent pixels, or that has no adjacent measurement points with a face-centered cubic structure of the NaCl type, is not regarded as a crystal grain, and those with two or more pixels connected are treated as crystal grains. In this way, grain boundary determination is performed to identify crystal grains.

[0036] Next, an observation field including at least 10 crystal grains having a face-centered cubic structure of the NaCl type identified by the above-described procedure is defined. Based on the grain boundaries determined in identifying the crystal grains, for adjacent crystal grains with a face-centered cubic structure of the NaCl type, lines l(10) 25 nm away from the respective crystal grains are drawn from both crystal grain boundaries into the crystal grains using software, and regions α and β are demarcated. Then, energy dispersive X-ray spectrometry (EDS) (for example, a beam diameter of 1 nm) using TEM is used for surface analysis. For region α, XBα in all regions α within the observation field is calculated. For region β, all regions β within the observation field are divided at 50 nm intervals, and surface analysis (a circular shape with a diameter of 50 nm) is performed for each divided range, and the area ratio occupied by the locations satisfying 0.20 ≦ XBβ ≦ XBα - 0.10 in region β is determined.

[0037] 3. Upper layer The upper layer is a (AlTi)CN layer, which functions as a layer that improves the wear-resistant layer during cutting and suppresses the adhesion of welded materials caused by the workpiece.

[0038] (1) Average composition The upper layer is (Al XC Ti 1-XC )(C YC N 1-YC ) In which, XC is the average content of XC AVG , YC is the average content of YC AVG It is preferable that 0.50 ≦ XC AVG ≦ 0.75, 0.00 ≦ YC AVG ≦ 0.05.

[0039] The reason is that when XC AVG is less than 0.50, the high oxidation resistance of (AlTi)CN cannot be fully obtained. On the other hand, when XC AVG exceeds 0.75, the desired wear resistance and the desired welding suppression cannot be obtained. XC AVG is more preferably 0.65 ≦ XC AVG ≦ 0.75. Since the C component in (AlTi)CN has the effect of improving hardness, it may be contained. However, when YC AVG exceeds 0.05, the high-temperature strength decreases, so YC AVG is preferably less than 0.05.

[0040] (2) Grains with a face-centered cubic structure of the NaCl type In the upper layer, it is preferable that the proportion of grains having a face-centered cubic structure of the NaCl type is 80 area% or more. The reason is that when it is less than 80 area%, the proportion of the wurtzite-type hexagonal crystal structure, which is the original stable phase of (AlTi)CN and is soft, increases in the upper layer, and sufficient durability of the coated tool cannot be obtained. The proportion of grains having a face-centered cubic structure of the NaCl type is more preferably 90 area% or more. It may be 100 area%.

[0041] (3) Average thickness The average thickness of the upper layer is preferably 0.5 to 9.4 μm. The reason is that if it is less than 0.5 μm, sufficient wear resistance and welding suppression cannot be obtained. On the other hand, if it exceeds 9.4 μm, damage in the upper layer starting from thermal cracks progressing in the substrate direction during cutting will increase, which can cause abnormal tool wear. The average thickness of the upper layer is more preferably 2.0 to 5.0 μm.

[0042] (4) Repeated change in the increase and decrease of XC In the upper layer, the ratio of crystal grains repeating the increase and decrease of XC is preferably 60% or more by area in the thickness direction of the coating layer. The reason is that if it is less than 60% by area, sufficient wear resistance cannot be obtained. The ratio of crystal grains repeating the increase and decrease of XC may be 100% by area.

[0043] In the repeated change in the increase and decrease of XC, the average value ΔXC of the difference between adjacent maximum and minimum values is preferably 0.10 to 0.50. The reason for setting ΔXC within this range is that if it is less than 0.10, even if there is a repeated change in the increase and decrease of XB in the lower layer, the suppression of crack propagation in the upper layer is not sufficient and the chipping resistance decreases. On the other hand, if it exceeds 0.50, the lattice strain generated at the boundary between the region with a high Al content and the region with a low Al content in the upper layer increases, crystal defects increase, and the hardness of the upper layer decreases. ΔXC is more preferably 0.30 to 0.50.

[0044] Also, the average value of the intervals giving adjacent maximum and minimum values, that is, the average interval in the thickness direction of the coating layer is preferably 20 to 100 nm. The reason for setting the average interval within this range is that if the average interval is less than 20 nm, even if there is a repeated change in the increase and decrease of XB in the lower layer, the toughness of the coating layer is not sufficiently improved. On the other hand, if it exceeds 100 nm, the upper layer cannot sufficiently suppress crack propagation during cutting, and the chipping resistance and white layer formation resistance decrease. The average interval is more preferably 60 to 100 nm.

[0045] The average value ΔXC of the difference between adjacent maximum and minimum values in the repeated change of the increase and decrease of XC, and the definition and measurement method of the average interval of the repeated change of the increase and decrease of XC are the same as those of the repeated change of the increase and decrease of XB.

[0046] (5) Cl content In the upper layer, it is more preferable that ρC = [Cl] / ([Ti] + [Al] + [C] + [N] + [Cl]) ([Q] represents the number of atoms of element Q) is 0.001 to 0.010. The reason for setting ρC within this range is that if it is less than 0.001, the lubricity of the coating layer may not be sufficient. On the other hand, if it exceeds 0.010, the toughness of the upper layer may be impaired and the chipping resistance may decrease.

[0047] 4. XB AVG and XC AVG The relational expression (0.00 ≦ XB AVG - XC AVG ≦ 0.10) The upper layer and the lower layer preferably satisfy 0.00 ≦ XB AVG - XC AVG ≦ 0.10. When XB AVG - XC AVG > 0.1, the difference in the average content of Al becomes large, and the continuous crystal growth of the lower layer and the upper layer is inhibited. It is more preferable that 0.00 ≦ XB avg - XC avg ≦ 0.05.

[0048] 5. The value of I(200) / I(111) In the lower layer and the upper layer, the intensity value I(200) of the 200 diffraction line and the intensity value I(111) of the 111 diffraction line of the crystal grains with the face-centered cubic crystal structure of the NaCl type preferably satisfy the relationship of 1.0 ≦ I(200) / I(111).

[0049] In order to achieve the foregoing object, it is preferable that the upper layer continuously grows such that the crystal grains of the upper layer are fitted into the tips of the crystal grains of the lower layer at the interface between the lower layer and the upper layer. Since the upper layer grows in the <111> preferred direction, the I(200) / I(111) index was used to confirm that the upper layer is undergoing this continuous growth. When I(200) / I(111) is less than 1.0, this continuous growth may not be sufficient, and the suppression of the progress of thermal cracks in the lower layer may not be sufficient.

[0050] 5. Other Layers (1) Outermost Layer In this embodiment, the outermost layer may be provided in contact with the upper layer and may be composed of one or two or more Ti compound layers among a Ti nitride layer, a carbide layer, and a carbonitride layer (these are not limited to stoichiometric compositions), and has a total average layer thickness of 0.1 to 4.00 μm (the outermost layer may not be provided). When this outermost layer is provided, the clear color of these layers facilitates the identification of the corner after cutting use (identification of the used part) in the case of a coated tool being an insert. Here, if the total average layer thickness is less than 0.1 μm, the purpose of providing the outermost layer is not sufficiently achieved, while if it exceeds 4.0 μm, chipping is likely to occur.

[0051] (2) Unintended Layers When switching the film-forming gas, although there may be a very small amount, layers different from the underlying TiCN layer, Ti carbide, nitride, carbon oxide, and carbonitride oxide layers, (AlTi)CN layer, and α-Al2O3 layer may be produced unintentionally.

[0052] 6. Substrate (1) Composition In this embodiment, the substrate can be a cemented carbide (WC-based cemented carbide: including those containing Co in addition to WC and further adding carbonitrides such as Ti, Ta, Nb, etc.), cermet (those mainly composed of TiC, TiN, TiCN, etc.), ceramics (silicon nitride, sialon, aluminum oxide, etc.), or a cBN sintered body, but is not limited thereto.

[0053] (2) Shape The shape of the substrate is not particularly restricted 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.

[0054] 7. Measurement of Composition The Al content XB, XC and the C content YB, YC of the lower layer and the upper layer are obtained by averaging the analysis results of Auger electrons obtained by irradiating an electron beam onto a polished cross-section sample in the longitudinal section using Auger Electron Spectroscopy (AES) and performing line analysis of five or more lines in the thickness direction of the coating layer.

[0055] 8. Measurement of the Ratio of Grains with NaCl-Type Face-Centered Cubic Structure The area ratio of grains having an NaCl-type face-centered cubic crystal structure is determined by electron backscatter diffraction as described above. After defining the grain boundaries, the crystal structure of each grain having an NaCl-type face-centered cubic crystal structure is identified based on the diffraction pattern, and the area ratio occupied by grains having an NaCl-type face-centered cubic crystal structure is determined for each layer.

[0056] 9. Measurement of Average Thickness The average thickness of each layer constituting the coating layer can be obtained, for example, by using a focused ion beam system (FIB), a cross section polisher (CP), etc. to prepare a sample for observing the longitudinal section at an arbitrary position of the coating layer, and observing the longitudinal section at a plurality of locations (for example, five locations) using a scanning electron microscope (SEM) or TEM, a scanning transmission electron microscope (STEM), or energy dispersive X-ray spectrometry (EDX) attached to SEM or TEM, obtaining the thickness, and averaging these values.

[0057] 10. Measurement of I(111) and I(200) It is not possible to obtain the X-ray diffraction results of only the lower layer or only the upper layer. The X-ray diffraction results of the base layer, lower layer, upper layer (and further the outermost layer provided selectively) are shown integrally (summarized). That is, the X-ray diffraction results of the coating layer are shown.

[0058] The method for obtaining the value of I(200) / I(111) is as follows. For example, using Cu-Kα1 line as the X-ray source, with the measurement range (2θ): 20 to 120 degrees, scan step: 0.013 degrees, and measurement time per step: 0.48 sec / step, perform X-ray diffraction on the coating layer surface parallel to the substrate surface. Confirm the X-ray diffraction peaks that appear between the diffraction angles of the same crystal plane shown in JCPDS00-038-1420 cubic TiN and JCPDS00-046-1200 cubic AlN respectively (for example, 36.66 to 38.53°, 43.59 to 44.77°, 61.81 to 65.18°). Then, measure the measured values of the X-ray diffraction peak intensities at the 200 diffraction line and the 111 diffraction line, and obtain I(200) / I(111), which is the ratio of the intensity I(200) of the 200 diffraction line to the intensity I(111) of the 111 diffraction line.

[0059] 11. Manufacturing method The coating layer of the coated tool of this embodiment can be manufactured by chemical vapor deposition method, for example, under the following manufacturing conditions.

[0060] (1) Manufacturing of the base layer For example, the following manufacturing conditions 1) or 2) can be exemplified.

[0061] 1) Manufacturing condition 1 Film formation of the TiN layer Reaction gas composition (volume%) TiCl4: 3.0 to 6.0%, N2: 25.0 to 35.0%, H2: remainder Reaction ambient pressure: 4.0 to 12.0 kPa Reaction ambient temperature: 780 to 900 °C

[0062] 2) Manufacturing condition 2 Film formation of the TiCN layer Reaction gas composition (volume%) TiCl4: 3.0 - 6.0%, N2: 15.0 - 30.0% CH4 or CH3CN: 0.6 - 2.0%, H2: the balance Reaction ambient pressure: 5.0 - 12.0 kPa Reaction ambient temperature: 780 - 900 °C

[0063] (2) Manufacture of the lower layer Reaction gas composition (volume%) Gas group B1: NH3: 4.0 - 5.5%, H2: 65 - 76% Gas group B2: AlCl3: 0.45 - 0.90%, TiCl4: 0.20 - 0.55%, N2: 0.0 - 12.0%, C2H4: 0.0 - 0.5%, H2: the balance Reaction ambient pressure: 4.0 - 5.0 kPa Reaction ambient temperature: 700 - 900 °C Gas supply cycle: 1.0 - 5.0 s Gas supply time per cycle: 0.1 - 0.2 s Phase difference between the supply of gas group B1 and the supply of gas group B2: 0.1 - 0.2 s

[0064] (3) Manufacture of the upper layer Reaction gas composition (volume%) Gas group C1: NH3: 1.5 - 3.0%, H2: 65 - 76% Gas group C2: AlCl3: 0.45 - 0.75%, TiCl4: 0.20 - 0.55%, N2: 0.0 - 12.0%, C2H4: 0.0 - 0.5%, H2: the balance Reaction ambient pressure: 4.0 - 5.0 kPa Reaction ambient temperature: 700 - 900 °C Gas supply cycle: 6.0 - 10.0 s Gas supply time per cycle: 0.3 - 0.5 s Phase difference between the supply of gas group C1 and the supply of gas group C2: 0.1 - 0.3 s

Examples

[0065] Next, examples will be described. Here, as an example, an application to an insert cutting tool using a WC-based cemented carbide as a substrate will be described. However, the same applies when using the above-described substrate, and the same also applies when applied to a drill or an end mill.

[0066] As raw material powders, WC powder, TiC powder, TaC powder, NbC powder, Cr3C2 powder, and Co powder were prepared, and these raw material powders were blended as shown in Table 1. Wax was added and ball milled in acetone for 24 hours. After drying under reduced pressure, it was press-molded into a green compact of a predetermined shape at a pressure of 98 MPa, and this green compact was vacuum sintered at 1420 °C for 1 hour in a vacuum of 5 Pa to produce substrates A to C made of WC-based cemented carbide having the ISO standard SEEN1203AFSN shape. Incidentally, a small amount of inevitable impurities was contained in each raw material powder.

[0067] Next, an underlayer, a lower layer, and an upper layer were sequentially formed on the surfaces of these substrates A to C according to the manufacturing conditions shown in Tables 2 to 4, respectively, to obtain coated tools 1 to 8 (hereinafter, Examples 1 to 8) of the examples shown in Table 5. Incidentally, in Table 2, the film-forming gas for the underlayer is referred to as gas group A.

[0068] On the other hand, for comparison, an underlayer, a lower layer, and an upper layer were sequentially formed on the surfaces of substrates A to C according to the manufacturing conditions shown in Tables 2 to 4, respectively, to obtain coated tools 1 to 8 (hereinafter, Comparative Examples 1 to 8) of the comparative examples shown in Table 6.

[0069] Regarding Examples 1 to 8 and Comparative Examples 1 to 8, when obtaining the grain boundaries of the crystal grains constituting the TiAlCN layer by electron beam diffraction, the pixels were made into regular hexagonal shapes.

[0070]

Table 1

[0071]

Table 2

[0072]

Table 3

[0073]

Table 4

[0074]

Table 5

[0075]

Table 6

[0076] In Tables 5 and 6, in the column of "Does it satisfy 1.0 ≦ I(200) / I(111)?", "〇" indicates that 1.0 ≦ I(200) / I(111) is satisfied, and "×" indicates that 1.0 ≦ I(200) / I(111) is not satisfied (i.e., 1.0 > I(200) / I(111)).

[0077] Subsequently, for the coated tools 1 to 8 and the comparative coated tools 1 to 8 of the present invention, with each of the various tool bases A to C (ISO standard SEEN1203AFSN shape) clamped by a fixing jig to the tip of an alloy steel cutter with a cutter diameter of 80 mm, the following wet high-speed face milling and center cut cutting tests of Ti alloy were carried out, and the flank wear width of the cutting edge was measured. Table 7 shows the results of the cutting tests. For the comparative coated tools 1 to 8, since chipping occurred and the life was reached before the end of the cutting time, the time until the life was reached is shown.

[0078] Cutting test: Wet high-speed face milling, center cut cutting test Cutter diameter: 80 mm Workpiece material: Block material of JIS·Ti-6Al-4V alloy (60 types) Cutting speed: 100 m / min Depth of cut: 2.5 mm Feed: 0.25 mm / tooth Cutting time: 10 minutes

[0079]

Table 7

[0080] In Table 7, the cutting time (minutes) until the life of the comparative example reaches is the cutting time (minutes) until the life is reached due to chipping occurrence.

[0081] As is clear from Table 7, all of the examples had a long maximum processing time, which is the processing time until the cutting edge reached wear, and had excellent durability.

Explanation of symbols

[0082] 1 Substrate 2 Underlayer 3 Lower layer 4 Upper layer 5 Coating layer 6 Outermost layer 7 Grain boundary 8 Region α 9 Region β 10 Line l

Claims

1. A surface-coated cutting tool having a substrate and a coating layer on the surface of the substrate, wherein (a) the coating layer has a base layer in contact with the substrate, a lower layer in contact with the base layer, and an upper layer in contact with the lower layer; wherein (b) the base layer has an average thickness of 0.05 to 2.0 μm and contains a nitride or carbonitride of Ti; wherein (c) the lower layer has an average thickness of 0.5 to 13.5 μm; (Al ＸＢ Ti １－ＸＢ ) (C ＹＢ N １－ＹＢ ) and contains a composite nitride B or a composite carbonitride B', and XB ＡＶＧ , which is the average value of XB, and YB ＡＶＧ are respectively 0.50 ≦ XB ＡＶＧ ≦ 0.75 and 0.00 ≦ YB ＡＶＧ ≦ 0.05, wherein (d) the composite nitride B or composite carbonitride B' has crystal grains B having a face-centered cubic structure of the NaCl type with an area of 80% or more in the cross-section in the thickness direction of the coating layer; wherein (e) the crystal grains B include crystal grains that repeat the increase and decrease of XB in the thickness direction, and the average value ΔXB of the difference between adjacent maximum and minimum values of XB is 0.01 to 0.05, and the interval of the repeated change in the thickness direction is 1 to 12 nm; wherein (f) the upper layer has an average thickness of 0.5 to 9.4 μm; (Al ＸＣ Ti １－ＸＣ )(C ＹＣ N １－ＹＣ ) contains a composite nitride C or a composite carbonitride C', and XC ＡＶＧ , which is the average value of XC, and YC ＡＶＧ are respectively 0.50 ≤ XC ＡＶＧ ≤ 0.75 and 0.00 ≤ YC ＡＶＧ ≤ 0.05, wherein (g) the composite nitride C or composite carbonitride C' has crystal grains C having a face-centered cubic structure of the NaCl type with an area of 80% or more in the cross-section in the thickness direction; wherein (h) the crystal grains C include crystal grains that repeat the increase and decrease of XC in the thickness direction, and the average value ΔXC of the difference between adjacent maximum and minimum values of XC is 0.10 to 0.50, and the interval of the repeated change in the thickness direction is 20 to 100 nm; (i) For the lower layer and the upper layer, 0.00 ≦ XB ＡＶＧ - XC ＡＶＧ ≦ 0.10 is satisfied The surface-coated cutting tool characterized by the above.

2. In the lower layer, ρB = [Cl] / ([Ti] + [Al] + [C] + [N] + [Cl]) (where [Q] represents the number of atoms of element Q) is 0.001 to 0.050, and in the upper layer, ρC = [Cl] / ([Ti] + [Al] + [C] + [N] + [Cl]) is 0.001 to 0.010, The surface-coated cutting tool according to claim 1, characterized by the above.

3. In the coating layer, the intensity value I(200) of the 200th diffraction line and the intensity value I(111) of the 111th diffraction line of the crystal grains having a face-centered cubic crystal structure of the NaCl type satisfy the relationship of 1.0 ≦ I(200) / I(111), The surface-coated cutting tool according to claim 1 or 2, characterized by the above.

4. When a region α is defined as the range surrounded by a line l that penetrates 25 nm into each of the crystal grains B from the grain boundaries of two adjacent crystal grains B, and a region β is defined as the range surrounded by the line l and the grain boundaries, A region where 0.20 ≦ xβ ≦ xα - 0.10 (where xα is the average value of XB in region α, and xβ is the average value of XB in a region with a diameter of 50 nm at an arbitrary position in region β) exists within region β in an area percentage of 5 to 20%. The surface-coated cutting tool according to any one of claims 1 to 3, characterized in that...

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