A coated cutting tool

Abstract

The present invention relates to a coated cutting tool comprising a substrate and a coating, wherein the coating comprises a nano-multilayer of alternating layers of a first nanolayer being Ti1-xAlxN, 0.35≤x≤0.70, and a second nanolayer being Ti1-ySiyN, 0.05≤y≤0.25, the coating comprises a layer of Ti1-Z-vMezAlvN, O≤z≤O.10, 0.35≤v≤0.70, Me is one or more of Cr, Zr, or V, below the nano-multilayer and there is an innermost layer of the coating, closest to the substrate, of Ti1-wSiwN, 0.05≤w≤0.25, having a thickness of from about 1 to about 35 nm.

Description

[0001] A coated cutting tool

[0002] The present invention relates to a coated cutting tool with a coating comprising a nano-multilayer of (Ti,Si)N and (Ti,AI)N.

[0003] Introduction

[0004] Nano-multilayered coatings are commonly used in the area of cutting tools for metal machining. In these coatings at least two layers which are different in some respect alternate forming a coating of a stack of nanolayers.

[0005] Metal machining operations include, for example, turning, milling, and drilling.

[0006] In order to provide a long tool life a coated cutting tool, such as an insert, should have high resistance against different types of wear, e.g., flank wear resistance, crater wear resistance, chipping resistance and flaking resistance.

[0007] Different metal machining operations affect a coated cutting tool in different ways. Turning, for example, is a continuous metal machining operation while milling is more intermittent in nature. In milling the thermal and mechanical load will vary over time.

[0008] There is a continuing demand for coated cutting tools in which the coating has excellent properties in terms of flank wear resistance, crater wear resistance, edge line toughness, comb crack resistance, flaking resistance, etc. in order to provide a cutting tool with superior properties than currently available cutting tools on the market. If one or more of the above-mentioned properties are improved then longer tool life is provided.

[0009] There is an object of the present invention to provide a coated cutting tool which, at least, shows high flank wear resistance.

[0010] Definitions

[0011] By the term "average layer period thickness" is meant the average thickness of a combination A-B in the nano-multilayer coating of a first nanolayer A and second nanolayer B in a nano-multilayer A-B-A-B-A... If the deposition process is known the calculation of the average layer period thickness can be made by dividing the total thickness of the nano-multilayer by the number of A-B depositions (which corresponds to the number of revolutions when depositing a substrate in a rotating manner).

[0012] Alternatively the calculation can be made by using TEM analysis of a cross-section of the nano-multilayer counting the number of consecutive A-B nanolayer combinations over a length of at least 200 nm and calculating an average value.

[0013] By the term "average column width" in the nano-multilayer is meant an average value of the crystallite columns, or "grains", in the nano-multilayer. At least a length of 500 nm, perpendicular to the growth direction of the layer, is considered and column widths are measured over this length on at least 4 different places in the nano-multilayer at a distance of 500 nm from the lower interface of the nano-multilayer.

[0014] If the nano-multilayer has a total thickness of only 0.5 pm then the measuring places are located just below the outer surface of the nanomultilayer. Suitably methods of analysis include transmission electron microscopy (TEM).

[0015] The invention

[0016] It has now been provided a coated cutting tool having surprisingly high wear resistance, especially high flank wear resistance.

[0017] The present invention relates to a coated cutting tool comprising a substrate and a coating, wherein the coating comprises a nano-multilayer of alternating layers of a first nanolayer being Tii-xAlxN, 0.35^x^0.70, and a second nanolayer being Tii-ySiyN , 0.05^y^0.25, a sequence of one first nanolayer and one second nanolayer forms a layer period, the average layer period thickness in the nano-multilayer is < 20 nm, the nano-multilayer having a thickness of from about 0.3 to about 4 pm, the coating comprises a layer of Tii-z-vMezAlvN, O^z^O.10, 0.35^v^0.70, Me is one or more of Cr, Zr, or V, below the nanomultilayer having a thickness of from about 0.3 to about 2 pm, and there is an innermost layer of the coating, closest to the substrate, of Tii-wSiwN, 0.05^w^0.25, having a thickness of from about 1 to about 35 nm. It is herein to be understood that the layer of Tii-z-vMezAlvN is situated between the layer of Tii-wSiwN and the nano-multilayer in the coating.

[0018] For the first nanolayer Tii-xAlxN, suitably 0.45^x^0.67, preferably 0.55^x<0.65.

[0019] For the second nanolayer Tii-ySiyN, suitably 0.1 O^y^O.20.

[0020] The average layer period thickness of the nano-multilayer is suitably from 2 to 20, preferably from 4 to 10 nm.

[0021] The thickness of the nano-multilayer is suitably from about 0.7 to about 2 pm.

[0022] For the layer of Tii-z-vMezAlvN, suitably 0<z<0.05, preferably z=0.

[0023] For the layer of Ti-i^-vMe^lvN, suitably 0.45<v<0.67, preferably 0.55<v<0.65.

[0024] In case z=0, there is a preferred embodiment where the Ti-AI relation in the Tii-^vMe^lvN is the same as the Ti-AI relation in the first nanolayer of the nano-multilayer.

[0025] The thickness of the layer of Tii-z-vMezAlvN is suitably from about 0.7 to about 1.5 pm.

[0026] For the innermost layer of Tii-wSiwN, suitably 0.10^w<0.20.

[0027] The thickness of the layer of the innermost layer of Tii-wSiwN is suitably from about 2 to about 20 nm, preferably from about 3 to about 10 nm.

[0028] In one embodiment the coating comprises an outermost layer of Th- uSiuN, 0.05<u<0.25, preferably 0.10<u<0.20, having a thickness of from about 0.1 to about 1 pm, preferably from about 0.2 to about 0.7 pm. In a preferred embodiment the Ti-Si relation in the Tii-uSiuN is the same as the Ti-Si relation in the second nanolayer of the nano-multilayer.

[0029] In a preferred embodiment, the layer of Tii-^vMe^lvN and the innermost layer of Tii-wSiwN are adjacent to each other.

[0030] The nano-multilayer is suitably a HIPIMS deposited layer.

[0031] In a preferred embodiment, the coating comprises a nano-multilayer of alternating layers of a first nanolayer being Tii-xAlxN, 0.55^x<0.65, and a second nanolayer being Tii-ySiyN, 0.10<y<0.20, the average layer period thickness of the nano-multilayer is from 2 to 20 nm, the thickness of the nano-multilayer is from about 0.7 to about 2 pm, the coating comprises a layer of Th v.AlvN, 0.55<v<0.65, below the nano-multilayer having a thickness of from about 0.7 to about 1.5 pm, there is an innermost layer of the coating, closest to the substrate, of Tii-wSiwN, 0.10^w^0.20, having a thickness of from about 3 to about 10 nm.

[0032] The substrate of the coated cutting tool can 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 comprising from 5 to 18 wt% Co and from 0 to 10 wt% carbides, nitrides or carbonitrides of group 4 to 5 in the periodic table of elements.

[0033] Further components like Cr are possible in a cemented carbide substrate,

[0034] The coated cutting tool is suitably a cutting tool insert, a drill, or a solid end-mill, for metal machining. The cutting tool insert is, for example, a turning insert or a milling insert.

[0035] Brief descriptions of the drawings

[0036] Figure 1 shows a schematic view of one embodiment of a cutting tool being a milling insert.

[0037] Figure 2 shows a schematic view of a cross section of an embodiment of the coated cutting tool of the present invention showing a substrate and a coating comprising different layers.

[0038] Detailed description of embodiments in drawings

[0039] Figure 1 shows a schematic view of one embodiment of a cutting tool (1 ) having a rake face (2) and flank faces (3) and a cutting edge (4). The cutting tool (1) is in this embodiment a milling insert. Figure 2 shows a schematic view of a cross section of an embodiment of the coated cutting tool of the present invention having a substrate body (5) and a coating (6). The coating consists of a first (Ti,Si)N innermost layer (7) followed by a layer of (Ti,AI)N (8) and then followed by a nano-multilayer (9) of alternating nanolayers being (Ti,AI)N (10) and nanolayers being (Ti,Si)N (11). Examples

[0040] Example 1 (invention):

[0041] It was provided WC-Co based substrates being cutting tools being milling inserts of geometry SPHT120408, and as well flat inserts (for easier analysis of the coating). The substrates had a composition of 8 wt% Co and balance WC.

[0042] Then, a coating was deposited using HIPIMS mode in an Oerlikon Balzers Ingenia equipment using S3p technology. The uncoated insert blanks were mounted and rotated in the PVD chamber during deposition of the coating.

[0043] A standard Ar etching procedure for cleaning the substrate surface was made so that about 20-50 nm of the uppermost part of the substrate was removed.

[0044] At first an innermost layer of (Ti,Si)N was deposited onto the WC-Co based substrates using three targets with the composition Tio.85Sio.15.

[0045] The deposition process was run in HIPIMS mode using the following process parameters

[0046] Innermost layer of (Ti,Si)N:

[0047] Target material: Tio.s5Sio.15 (three targets)

[0048] Target size: circular, diameter 160 mm

[0049] Thickness: 12 mm

[0050] Average power per target: 8 kW

[0051] Peak pulse power: 60 kW

[0052] Pulse on time: 4.46 ms

[0053] Temperature: 500°C

[0054] Total pressure: 0.52 Pa (N2+Ar)

[0055] Argon pressure: 0.43 Pa

[0056] Bias potential: -40 V

[0057] Number of repeating pulses per cycle: 1 A layer thickness of about 5 nm was deposited.

[0058] Then, a (Ti,AI)N layer was further deposited using three targets with the composition Tio.4oAlo.6o.

[0059] The deposition process was run in HIPIMS mode using the following process parameters:

[0060] Layer of (Ti,AI)N:

[0061] Target material: Ti0.40AI0.60 (three targets)

[0062] Target size: circular, diameter 160 mm

[0063] Thickness: 12 mm

[0064] Average power per target: 9 kW

[0065] Peak pulse power: 60 kW

[0066] Pulse on time: 7.56 ms

[0067] Temperature: 500°C

[0068] Total pressure: 0.60 Pa (N2+Ar)

[0069] Argon pressure: 0.43 Pa

[0070] Bias potential: -40 V

[0071] Number of repeating pulses per cycle: 1

[0072] A layer thickness of about 1 pm was deposited.

[0073] Then, a nano-multilayer of (Ti,AI)N / (Ti,Si)N was further deposited using three targets each of the composition Ti0.40AI0.60 and Tio.85Sio.15. The deposition process was run in HIPIMS mode using the following process parameters:

[0074] Nano-multilayer of (Ti,AI)N / (Ti,Si)N:

[0075] Target material: Ti0.40AI0.60 and Tio.85Sio.15

[0076] Target size: circular, diameter 160 mm

[0077] Thickness: 12 mm

[0078] Average power per target: Ti / AI 4.5 kW / / TiSi 4.0 kW Peak pulse power: Ti / AI 45 kW / / TiSi 45 kW

[0079] Pulse on time: Ti / AI 5.00 ms / / TiSi 4.46 ms

[0080] Temperature: 500°C

[0081] Total pressure: 0.58 Pa (N2+Ar)

[0082] Argon pressure: 0.43 Pa

[0083] Bias potential: -50 V

[0084] Number of repeating pulses per cycle: 1

[0085] A layer thickness of about 1 pm was deposited. The average layer period thickness was about 5 nm.

[0086] The coated cutting tool made is called Sample 1 (invention).

[0087] Example 2 (reference):

[0088] A reference sample of a coated cutting tool was made. The reference coated cutting tool is currently used commercially in ISO-P milling.

[0089] A layer of Ti4oAleoN was deposited onto a WC-Co based cutting insert substrate using HIPIMS mode in a 6-flange INGENIA S3p (Oerlikon Balzers) equipment.

[0090] The substrate had a composition of 12 wt% Co, 1 .6 wt% (Ta,Nb)C and balance WC with a WC grain size, dWC, of about 0.8 pm. The geometry of the cutting insert was SPHT120408.

[0091] Six Ti4oAleo targets were used being circular with a diameter of 160 mm. An about 2 pm thick HIPIMS Ti4oAleoN monolayer was deposited using the following deposition parameters.

[0092] Total pressure: 0.59 Pa

[0093] Ar pressure: 0.43 Pa (the rest is filled up with N2 until total pressure)

[0094] Bias DC voltage: -40V

[0095] Temperature: 430°C

[0096] Power supply: 60 kW

[0097] Average power per target: 9.04 kW Pulse on-time: 7.56 ps

[0098] Frequency: 20 Hz

[0099] # repetitions: 1

[0100] Then, an about 1 .8 m wear resistant (Ti,AI)N layer having an average composition Ti36Al64N was deposited by HIPIMS. Six targets were used being circular with a diameter of 160 mm, three TiaaAh? targets and three Ti4oAleoN targets. The following deposition parameters were used:

[0101] Total pressure: 0.64 Pa (7 min) 0.61 Pa (52 min)

[0102] Ar pressure: 0.43 Pa (the rest is filled up with N2 until total pressure)

[0103] Bias DC voltage: -40V

[0104] Temperature: 430°C

[0105] Power supply: 60 kW

[0106] On time: TI33AI67: 2.00 ms, TI40AI60: 2.53 ms

[0107] Average power per target: TI33AI67: 7.2 kW, TI40AI60: 9.0 kW

[0108] The coated cutting tool made is called Sample 2 (reference).

[0109] Example 3:

[0110] Cutting tests were made in order to determine the performance of the samples made.

[0111] Sample 1 (invention) and Sample 2 (reference), being milling inserts of type SPHT120408 were tested in a milling test, and the flank wear was measured. The cutting conditions are summarized in Table 1 . As workpiece material steel ISO-P, 42CrMo4, was used. Cutting conditions:

[0112] Table 1. The wear value (as averaged over the cutting edge) for a cutting length of 5800 mm is shown in Table 2.

[0113] Table 2. Sample 1 (invention) performs better (less flank wear) than Sample 2

[0114] (reference).

Claims

Claims1 . A coated cutting tool (1 ) comprising a substrate (5) and a coating (6), wherein the coating (6) comprises a nano-multilayer (9) of alternating layers of a first nanolayer (10) being Tii-xAlxN, 0.355x<0.70, and a second nanolayer (11 ) being Tii-ySiyN, 0.05<y<0.25, a sequence of one first nanolayer (10) and one second nanolayer (11 ) forms a layer period, the average layer period thickness in the nano-multilayer (9) is 5 20 nm, the nano-multilayer (9) having a thickness of from about 0.3 to about 4 pm, the coating (6) comprises a layer (8) of Tii-Z- vMezAlvN, 05z50.10, 0.355v50.70, Me is one or more of Cr, Zr, or V, below the nano-multilayer (9) having a thickness of from about 0.3 to about 2 pm, and there is an innermost layer (7) of the coating (6), closest to the substrate (5), of Tii-wSiwN, 0.055w50.25, having a thickness of from about 1 to about 35 nm.

2. A coated cutting tool (1 ) according to claim 1 , wherein for the first nanolayer (10) Tii-xAlxN, 0.455x50.67.

3. A coated cutting tool (1 ) according to any one of claims 1-2, wherein for the second nanolayer (11) Tii-ySiyN, 0.105y<0.20.

4. A coated cutting tool (1 ) according to any one of claims 1-3, wherein the average layer period thickness in the nano-multilayer (9) is from 2 to 20 nm.

5. A coated cutting tool (1 ) according to any one of claims 1-4 wherein the thickness of the nano-multilayer (9) is from about 0.7 to about 2 pm.

6. A coated cutting tool (1 ) according to any one of claims 1-5, wherein for the layer (8) of Tii-z-vMezAlvN, 05z50.05, 0.455v50.67.

7. A coated cutting tool (1 ) according to any one of claims 1-6, wherein the layer (8) of Tii-z vMezAlvN has a thickness of from about 0.7 to about 1.5 pm.

8. A coated cutting tool (1 ) according to any one of claims 1-7, wherein for the innermost layer (7) of Tii-wSiwN, 0.10^w<0.20.

9. A coated cutting tool (1 ) according to any one of claims 1-8, wherein the innermost layer (7) of Tii-wSiwN has a thickness of from about 3 to about 10 nm.

10. A coated cutting tool (1 ) according to any one of claims 1 -9, wherein there is an outermost layer of Tii-uSiuN, 0.05^u^0.25, preferably 0.10^u^0.20, having a thickness of from about 0.1 to about 1 pm, preferably from about 0.2 to about 0.7 pm.

11. A coated cutting tool (1 ) according to any one of claims 1-10, wherein the layer (8) of Tii-z-vMezAlvN and the innermost layer (7) of Tii-wSiwN are adjacent to each other.

12. A coated cutting tool (1 ) according to any one of claims 1-11, wherein the substrate (5) of the coated cutting tool (1) is selected from the group of cemented carbide, cermet, ceramic, cubic boron nitride and high speed steel.

13. A coated cutting tool (1 ) according to any one of claims 1-12, wherein the coated cutting tool (1) is a cutting tool insert, a drill, or a solid end-mill, for metal machining.

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