Coated Cutting Tools

Abstract

The present invention relates to a nanolayer coating comprising alternating first and second layer stacks, the average layer period thicknesses of the first and second layer stacks being different from each other. The nanolayer coating exhibits improved edge line toughness and improved resistance to flank wear and comb cracking.

Description

[Technical field]

[0001] The present invention relates to coated cutting tools comprising nano-multilayers of (Ti,Si,M)N and (Ti,Al,M)N. [Background technology]

[0002] Nano-multilayer coatings are commonly used in the field of cutting tools for metal machining, in which at least two layers that differ in some respect are alternated to form a nano-layer coating.

[0003] Metal machining operations include, for example, turning, milling, and drilling.

[0004] In order to provide a long tool life, coated cutting tools, such as inserts, should have high resistance to different types of wear, for example, resistance to flank wear, rake wear, chipping and spalling.

[0005] Different metal machining operations affect coated cutting tools in different ways. For example, turning is a continuous metal machining operation, while milling is more intermittent in nature. In milling, the thermal and mechanical loads change over time.

[0006] To provide cutting tools with superior properties over currently available cutting tools, there is a continuing need for coated cutting tools in which the coating has superior properties in terms of flank wear resistance, rake wear resistance, edge line toughness, comb crack resistance, spalling resistance, etc. If one or more of the above mentioned properties are improved, longer tool life will be provided.

[0007] EP 2 883 637 discloses a nanolayer coating having alternating layer stacks, in which a first layer stack having an average layer period thickness of 60 to 500 nm alternates with a second layer stack having an average layer period thickness of 2 to 60 nm.

[0008] It is an object of the present invention to provide a coated cutting tool that exhibits at least high resistance to flank wear and comb cracking, and also exhibits high edge line toughness.

[0009] definition The term "average layer period thickness" refers to the average thickness of a combination AB in a nanomultilayer coating of a first nanolayer A and a second nanolayer B in a nanomultilayer ABABA.... To determine the average layer period thickness, a calculation can be made from a TEM analysis of a cross-section of the nanomultilayer, counting the number of consecutive AB nanolayer combinations over a length of at least 200 nm and calculating the average value. In some cases, if the deposition method is known, the calculation can be made by dividing the total thickness of the nanomultilayer by the number of AB depositions. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of a nano-multilayer coating, where 1 and 2 show alternating first and second layer stacks, 3 is the starting layer, 4 is the nano-layer coating, and 5 is the substrate. [Diagram 2] FIG. 2 shows a scanning electron microscope (SEM) image of a coating according to the invention, where 1 and 2 show the alternating first and second layer stacks, 3 is the starting layer, 4 is the nanolayer coating, and 5 is the substrate. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention has provided a nano-multilayer coating of alternating (Ti,Si,M)N and (Ti,Al,M)N layers with improved flank wear resistance, excellent edge line toughness, and also high comb crack resistance.

[0012] The present invention relates to a coated cutting tool comprising a substrate and a nano multi-layer coating, the coating comprising: a first layer stack and a second layer stack that alternate at least twice; the first layer stack comprises alternating nanolayers A and B, with an average layer period thickness of A+B being between 15 and 50 nm; the second layer stack comprises alternating nanolayers A and B, with an average layer period thickness of A+B being between 2 and 10 nm; The composition of the nanolayer A is (Ti 1-a-b Al a M b )N, where 0.5≦a≦0.75, 0≦b≦0.10, and M is one or more elements selected from Cr, Zr, Nb, Mo, Ta and V; The composition of the nanolayer B is (Ti 1-c-d S c M d )N, where 0.10≦c≦0.25, 0≦d≦0.10, and M is one or more elements selected from Cr, Zr, Nb, Mo, Ta and V.

[0013] In the first layer stack comprising alternating nanolayers A and B, the average layer period thickness of A+B is 15-50 nm, preferably 18-35 nm.

[0014] In the second layer stack comprising alternating nanolayers A and B, the average layer period thickness of A+B is between 2 and 10 nm, preferably between 3 and 8 nm.

[0015] The thicknesses of the first and second layer stacks can be the same or different from each other. The thicknesses of the different first layer stacks in the nano multilayer coating can be the same or different for all first layer stacks. The same applies to the thicknesses of the different second layer stacks, which can also be the same or different. Suitably, the thickness is between 50 and 1000 nm, preferably between 100 and 500 nm. The total number of alternating stacks, i.e. the total of both the first and second layer stacks, is at least 4, preferably between 6 and 50, more preferably between 8 and 30.

[0016] In one embodiment of the present invention, the composition of nanolayer A (Ti 1-a-b Al a M b)N is preferably 0.55≦a≦0.7, 0≦b≦0.10.

[0017] In one embodiment of the present invention, the composition of the first nanolayer A (Ti 1-a-b Al a M b )N is preferably 0.55≦a≦0.7, 0≦b≦0.05.

[0018] In one embodiment of the present invention, the element M in nanolayer A is Cr.

[0019] In one embodiment of the present invention, the composition of the first nanolayer A (Ti 1-a-b Al a M b )N is preferably 0.55≦a≦0.7 and b=0.

[0020] In one embodiment of the present invention, the composition of the nanolayer B (Ti 1-c-d S c M d )N is preferably 0.15≦c≦0.22 and 0≦d≦0.10.

[0021] In one embodiment of the present invention, the composition of the nanolayer B (Ti 1-c-d S c M d )N is preferably 0.15≦c≦0.22 and 0≦d≦0.05.

[0022] In one embodiment of the present invention, the element M in the nanolayer B is Cr.

[0023] In one embodiment of the present invention, the composition of the nanolayer B (Ti 1-c-d S c M d )N is preferably 0.15≦c≦0.22 and d=0.

[0024] In one embodiment of the present invention, the nano-multilayer coating comprises a starting layer between the substrate and the alternating first and second layer stack. The starting layer has a thickness of 0.2 to 2 μm, preferably 0.5 to 1.5 μm. The composition is (Ti 1-a-b Ala M b )N, where 0.5≦a≦0.75, 0≦b≦0.10, and M is one or more elements selected from Cr, Zr, Nb, Mo, Ta, and V. Preferably, 0.55≦a≦0.7, 0≦b≦0.10, and more preferably, 0.55≦a≦0.7 and b=0.

[0025] In one embodiment of the present invention, the composition of the starting layer is the same as the composition of nanolayer A.

[0026] The total thickness of the coating is from 1 to 10 μm, preferably from 1 to 7 μm, and more preferably from 2 to 4 μm.

[0027] The nano-multilayer coating is suitably deposited using any of the PVD methods, preferably cathodic arc evaporation, magnetron sputtering or HIPIMS, more preferably cathodic arc evaporation.

[0028] The substrate of the coated cutting tool may be selected from the group of cemented carbide, cermet, ceramic, cubic boron nitride and high speed steel. In one embodiment, the substrate is a cemented carbide containing 5-18 wt.% Co and 0-10 wt.% carbides, nitrides or carbonitrides of one or more elements from groups 4-5 of the periodic table of the elements.

[0029] Further components such as Cr are possible in the cemented carbide substrate.

[0030] The coated cutting tool is preferably a cutting tool insert for metal machining, a drill or a solid end mill. The cutting tool insert is, for example, a turning insert or a milling insert. EXAMPLES

[0031] Example 1 (Invention Example) Different nanomultilayers of (Ti,Si)N and (Ti,Al)N were deposited on sintered cemented carbide cutting tool insert blanks of geometries CNMG120408MM and R390-11. The composition of the cemented carbide was 10 wt% Co, 0.4 wt% Cr, balance WC. The cemented carbide blanks were coated by cathodic arc evaporation in a vacuum chamber with four arc flanges. Targets of Ti-Si were attached to the two flanges facing each other. Targets of Ti-Al were attached to the two remaining flanges facing each other. The targets were circular, flat, 100 mm in diameter and available on the open market. Target technology packages suitable for arc evaporation are available from market suppliers such as IHI Hauzer Techno Coating BV, Kobelco (Kobe Steel Works Ltd.) and Oerlikon Balzers.

[0032] An uncoated blank was mounted on a pin that was subjected to 3 times rotation in a PVD chamber.

[0033] The chamber was placed under high vacuum (10 -2 The chamber was pumped down to a pressure of less than 100 Pa and heated to 450-550 °C by a heater placed inside the chamber. The blank was then etched in an Ar plasma for 60 min.

[0034] The same for all multi-nanolayers, 1 μm thick Ti 0.33 Al 0.67 The N starting layer was deposited at 10 Pa and 300V.

[0035] A nano-multilayer coating having a thickness of about 2 μm was then deposited on top of the starting layer.

[0036] Chamber pressure (reaction pressure) was 4 Pa ​​N 2 The gas was set and a DC bias voltage of -50 V (relative to the chamber walls) was applied to the blank assembly. The cathodes were operated in arc discharge mode for 75 minutes (four flanges) at a current of 150 A (each).

[0037] Ti 0.80 S 0.20 The deposition was performed using a Ti-Si target with a Ti 0.33 Al 0.67 A Ti-Al target having the formula: 0.33 Al 0.67 and Ti 0.50 Al 0.50 was used. The rotation speed correlates to a constant period thickness. To study the effect of alternating first and second layer stacks with different period thicknesses in the nanomultilayer, a series of depositions of blanks were performed using different table rotation speeds.

[0038] The rotation speeds, estimated average nanolayer period thicknesses and layer stack thicknesses are given in Table 1.

[0039] The total thickness of the nano-multilayer coating on the rake and flank faces was measured on the ground cross section of the insert, approximately 200 μm from the cutting edge, using optical microscopy (LOM). The results are shown in Table 2. Table 1 TIFF2024538214000001.tif64170Table 2 TIFF2024538214000002.tif34170

[0040] Example 2 (Example supported by data) Cutting tests to examine different coatings for resistance to edge line toughness were performed with the following settings:

[0041] Operation: Shoulder milling Workpiece Material: Dievar Unhardened, P3.0.Z.AN Number of blades:z=1 Cutting speed:V c =215m / min Feed rate: f z =0.15mm Radial engagement: a e =12mm Cutting depth: a p=3.0 Cutting length = 12mm No cutting oil

[0042] The cut-off criteria are at least 0.5 mm chipping of the edge line or a measured depth of 0.2 mm in either the escape or rake phase. Tool life is presented as the number of cutting entries to achieve these criteria.

[0043] The results are shown in Table 3, with each result being the average of eight tests. Table 3 TIFF2024538214000003.tif30170

[0044] Example 3 (Example supported by data) Cutting tests to examine different coatings for resistance to flank wear were carried out with the following settings:

[0045] Operation: Vertical turning Workpiece material: Sverker 21 (tool steel), hardness approximately 210HB, D=180, L=700mm Cutting speed:V c =125m / min Feed rate: f n =0.072mm / rev Cutting depth: a p =2mm No cutting oil

[0046] The cut-off criterion for tool life is a flank wear VB of 0.15 mm.

[0047] The results are shown in Table 4, with each result being the average of two tests. Table 4 TIFF2024538214000004.tif29170

[0048] Example 4 (Example supported by data) Cutting tests to examine different coatings with respect to their resistance to comb cracking were carried out with the following settings:

[0049] Operation: Shoulder milling Tool holder: R390-11, 25mm Workpiece material: Toolox 33 (tool steel), L=600mm, I=200mm, h=100mm Insert type: R390-11 Cutting speed:V c =275m / min Feed rate: f z =0.2mm / rev Feed per tooth z=1 Cutting depth: a p =3mm Radial engagement: a e =12.5mm With cutting oil

[0050] The criterion for the end of tool life is maximum chipping height VB>0.3mm.

[0051] The results are shown in Table 5, with each result being the average of four tests. Table 5 TIFF2024538214000005.tif29170

Claims

1. 1. A coated cutting tool comprising a substrate and a nano-multilayer coating, the coating comprising: a first layer stack and a second layer stack, the stacks alternating at least two times; the first layer stack comprises alternating nanolayers A and B, with an average layer period thickness of A+B between 15 and 50 nm; the second layer stack comprises alternating nanolayers A and B, with an average thickness of layers A+B between 2 and 10 nm; The composition of the nanolayer A is (Ti １－ａ－ｂ Al ａ M ｂ ) N, wherein 0.5≦a≦0.75, 0≦b≦0.10, and M is one or more elements selected from Cr, Zr, Nb, Mo, Ta, and V; The composition of the nanolayer B is (Ti １－ｃ－ｄ Si ｃ M ｄ ) N, wherein 0.10≦c≦0.25, 0≦d≦0.10, and M is one or more elements selected from Cr, Zr, Nb, Mo, Ta, and V.

2. 2. The coated cutting tool of claim 1, wherein in the first layer stack, the average layer period thickness of A+B is 18 to 35 nm.

3. 2. The coated cutting tool of claim 1, wherein in the second layer stack, the average layer period thickness of A+B is 3 to 8 nm.

4. First nanolayer A (Ti １－ａ－ｂ Al ａ M ｂ 2. The coated cutting tool of claim 1, wherein N is 0.55≦a≦0.7, 0≦b≦0.10, and M is Cr.

5. First nanolayer B (Ti １－ｃ－ｄ Si ｃ M ｄ 2. The coated cutting tool of claim 1, wherein N is 0.15≦c≦0.22, 0≦d≦0.10, and M is Cr.

6. First nanolayer A (Ti １－ａ－ｂ Al ａ M ｂ 2. The coated cutting tool of claim 1, wherein for N, 0.55≦a≦0.7 and b=0.

7. First nanolayer B (Ti １－ｃ－ｄ Si ｃ M ｄ 2. The coated cutting tool of claim 1, wherein for N, 0.15≦c≦0.22 and d=0.

8. 2. The coated cutting tool of claim 1, wherein the number of alternating stacks, ie the total number of both first and second layer stacks, is at least 4, preferably 6-50.

9. 2. The coated cutting tool of claim 1, wherein the coating comprises a starting layer between the substrate and the alternating first and second layer stacks, the starting layer having a thickness of 0.2 to 2 μm.

10. 2. The coated cutting tool according to claim 1, wherein the total thickness of the coating is 1 to 10 μm.

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