COATED CUTTING TOOL

Abstract

The present invention relates to a coated cutting tool including a substrate and a coating. The coating has, from about 0.5 to about 10 m, a nano-multilayer of alternating nanolayers of a first nanolayer type of Ti.sub.1-xAl.sub.xN, wherein 0.45x<0.67, a second nanolayer type of Cr.sub.1-yAl.sub.yN, wherein 0.60y0.80, and a third nanolayer type of Ti.sub.1-zSi.sub.zN, wherein 0.14z0.25. An average nanolayer thickness of each of the nanolayer types Ti.sub.1-xAl.sub.xN, Cr.sub.1-yAl.sub.yN and Ti.sub.1-zSi.sub.zN in the nano-multilayer is 1 nm but <3 nm.

Claims

1. A coated cutting tool comprising a substrate and a coating, wherein the coating includes a from about 0.5 to about 10 m nano-multilayer of alternating nanolayers of a first nanolayer type being Ti.sub.1-xAl.sub.xN, wherein 0.45x<0.67, a second nanolayer type being Cr.sub.1-yAl.sub.yN, wherein 0.60y0.80, and a third nanolayer type being Ti.sub.1-zSi.sub.zN, wherein 0.14z0.25, an average nanolayer thickness of each of the nanolayer types Ti.sub.1-xAl.sub.xN, Cr.sub.1-yAl.sub.yN and Ti.sub.1-zSi.sub.zN in the nano-multilayer is being 1 nm, but <3 nm.

2. The coated cutting tool according to claim 1, wherein there is a ratio in the nano-multilayer between a sum of a thickness of all of each nanolayer types Ti.sub.1-xAl.sub.xN:Ti.sub.1-ySi.sub.yN:Ti.sub.1-zAl.sub.zN, being a:b:c, and wherein 0.5<a<3, 0.5<b<3, 0.5<c<3.

3. The coated cutting tool according to claim 1, wherein for the first nanolayer type being Ti.sub.1-xAl.sub.xN, suitably and wherein 0.50x0.62.

4. The coated cutting tool according to claim 1, wherein for the second nanolayer type being Cr.sub.1-yAl.sub.yN, and wherein 0.65y0.75.

5. The coated cutting tool according to claim 1, wherein for the third nanolayer type being Ti.sub.1-zSi.sub.zN, and wherein 0.15z0.23.

6. The coated cutting tool according to claim 1, wherein the average nanolayer thickness in the nano-multilayer, of each of the nanolayer types Ti.sub.1-xAl.sub.xN, Ti.sub.1-ySi.sub.yN, and Ti.sub.1-zAl.sub.zN in the nano-multilayer, is from 1 to 2.5 nm.

7. The coated cutting tool according to claim 1, wherein a ratio of average nanolayer thickness in the nano-multilayer between any one of the nanolayer types Ti.sub.1-xAl.sub.xN, Cr.sub.1-yAl.sub.yN and Ti.sub.1-zSi.sub.zN to any of the remaining two of the nanolayer types Ti.sub.1-xAl.sub.xN, Cr.sub.1-yAl.sub.yN and Ti.sub.1-zSi.sub.zN in the nano-multilayer is of from 0.1 to 10.

8. The coated cutting tool according to claim 1, wherein within a sequence of 10 consecutive nanolayers in the nano-multilayer all of the nanolayer types Ti.sub.1-xAl.sub.xN, Cr.sub.1-yAl.sub.yN and Ti.sub.1-zSi.sub.zN present are present.

9. The coated cutting tool according to claim 2, wherein there is a ratio in the nano-multilayer between the sum of nanolayer thicknesses of each nanolayer type, Ti.sub.1-xAl.sub.xN:Cr.sub.1-yAl.sub.yN:Ti.sub.1-zSi.sub.zN, in the nano-multilayer, a:b:c, wherein 0.75<a<1.25, 0.75<b<1.25, 1.5<c<2.5.

10. The coated cutting tool according to claim 2, wherein there is a ratio in the nano-multilayer between the sum of nanolayer thicknesses of each nanolayer type, Ti.sub.1-xAl.sub.xN:Cr.sub.1-yAl.sub.yN:Ti.sub.1-zSi.sub.zN, in the nano-multilayer, a:b:c, wherein 1.5<a<2.5, 0.75<b<1.25, 0.75<c<1.25.

11. The coated cutting tool according to claim 1, wherein the thickness of the nano-multilayer is from about 1 to about 8 m.

12. The coated cutting tool according to claim 1, wherein the coating includes an inner layer of TiN or N below the nano-multilayer closest to the substrate, the inner layer having a thickness of from about 0.1 to about 3 m.

13. The coated cutting tool according to claim 12, wherein the inner layer is Ti.sub.1-tAl.sub.tN, and wherein 0.35t0.70.

14. The coated cutting tool according to claim 1, wherein the substrate of the coated cutting tool is selected from the group of cemented carbide, cermet, ceramic, cubic boron nitride and high speed steel.

15. The coated cutting tool according to claim 1, wherein the coated cutting tool is a cutting tool insert, a drill, or a solid end-mill, for metal machining.

Description

BRIEF DESCRIPTIONS OF THE DRAWINGS

[0032] FIG. 1 shows a schematic view of one embodiment of a cutting tool being a milling insert.

[0033] FIG. 2 shows a schematic view of one embodiment of a cutting tool being a turning insert.

[0034] FIG. 3 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 multilayer coating.

[0035] FIG. 4 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.

DETAILED DESCRIPTION OF EMBODIMENTS IN DRAWINGS

[0036] FIG. 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. FIG. 2 shows a schematic view of one embodiment of a cutting tool 1 having a rake face 2 and flank face 3 and a cutting edge 4. The cutting tool 1 is in this embodiment a turning insert. FIG. 3 shows a schematic view of a cross section of an embodiment of the coated cutting tool of the present invention having a substrate 5 and a coating 6. The coating 6 consisting of a nano-multilayer 8 of alternating nanolayers 9, 10 and 11 being Ti.sub.1-xAl.sub.xN 9, Cr.sub.1-yAl.sub.yN 10 and Ti.sub.1-zSi.sub.zN 11. FIG. 4 shows a schematic view of a cross section of an embodiment of the coated cutting tool of the present invention having a substrate 5 and a coating 6. The coating 6 consisting of a first (Ti,Al)N innermost layer 7 followed by a nano-multilayer 8 of alternating nanolayers 9, 10 and 11 being Ti.sub.1-xAl.sub.xN 9, Cr.sub.1-yAl.sub.yN 10 and Ti.sub.1-zSi.sub.zN 11.

DETAILED DESCRIPTION OF EMBODIMENTS

[0037] In one embodiment, there is a ratio in the nano-multilayer 8 between the sum of nanolayer thicknesses of each nanolayer type 9, 10, 11, Ti.sub.1-xAl.sub.xN:Cr.sub.1-yAl.sub.yN:Ti.sub.1-zSi.sub.zN, in the nano-multilayer 8, a:b:c, 0.75<a<1.25, 0.75<b<1.25, 1.5<c<2.5, preferably 0.9<a<1.1, 0.9<b<1.1, 1.75<c<2.25. In this embodiment the nano-multilayer 8 suitably comprises a repeating sequence of consecutive nanolayers of the first nanolayer type 9, Ti.sub.1-xAl.sub.xN, the second nanolayer type 10, Cr.sub.1-yAl.sub.yN, and the third nanolayer type 11, Ti.sub.1-zSi.sub.zN, in the order Ti.sub.1-xAl.sub.xN/Ti.sub.1-zSi.sub.zN/Cr.sub.1-yAl.sub.yN/Ti.sub.1-zSi.sub.zN. The nano-multilayer 8 is suitably composed of (Ti.sub.1-xAl.sub.xN/Ti.sub.1-zSi.sub.zN/Cr.sub.1-yAl.sub.yN/Ti.sub.1-zSi.sub.zN . . . ).sub.m, m=15-1500, suitably m=30-800.

[0038] In a further embodiment, there is a ratio in the nano-multilayer 8 between the sum of nanolayer thicknesses of each nanolayer type 9, 10, 11, Ti.sub.1-xAl.sub.xN:Cr.sub.1-yAl.sub.yN:Ti.sub.1-zSi.sub.zN, in the nano-multilayer 8, a:b:c, 1.5<a<2.5, 0.75<b<1.25, 0.75<c<1.25, preferably 1.75<a<2.25, 0.9<b<1.1, 0.9<c<1.1. In this embodiment the nano-multilayer 8 suitably comprises a repeating sequence of consecutive nanolayers of the first nanolayer type 9, Ti.sub.1-xAl.sub.xN, the second nanolayer type 10, Cr.sub.1-yAl.sub.yN, and the third nanolayer type 11, Ti.sub.1-zSi.sub.zN, in the order Ti.sub.1-xAl.sub.xN/Cr.sub.1-yAl.sub.yN/Ti.sub.1-xAl.sub.xN/Ti.sub.1-zSi.sub.zN. The nano-multilayer (8) is suitably composed of (Ti.sub.1-xAl.sub.xN/Cr.sub.1-yAl.sub.yN/Ti.sub.1-xAl.sub.xN/Ti.sub.1-zSi.sub.zN).sub.n, n=15-1500, suitably n=30-800.

[0039] In a further embodiment, there is a ratio in the nano-multilayer 8 between the sum of nanolayer thicknesses of each nanolayer type 9, 10, 11, Ti.sub.1-xAl.sub.xN:Cr.sub.1-yAl.sub.yN:Ti.sub.1-zSi.sub.zN, in the nano-multilayer 8, a:b:c, 0.75<a<1.25, 1.5<b<2.5, 0.75<c<1.25, preferably 1.75<a<2.25, 0.9<b<1.1, 0.9<c<1.1. In this embodiment the nano-multilayer 8 suitably comprises a repeating sequence of consecutive nanolayers of the first nanolayer type 9, Ti.sub.1-xAl.sub.xN, the second nanolayer type 10, Cr.sub.1-yAl.sub.yN, and the third nanolayer type 11, Ti.sub.1-zSi.sub.zN, in the order Ti.sub.1-xAl.sub.xN/Cr.sub.1-yAl.sub.yN/Ti.sub.1-zSi.sub.zN/Cr.sub.1-yAl.sub.yN. The nano-multilayer 8 is suitably composed of (Ti.sub.1-xAl.sub.xN/Cr.sub.1-yAl.sub.yN/Ti.sub.1-zSi.sub.zN/Cr.sub.1-yAl.sub.yN).sub.p, p=15-1500, suitably p=30-800.

[0040] In a further embodiment, there is a ratio in the nano-multilayer 8 between the sum of nanolayer thicknesses of each nanolayer type 9, 10, 11, Ti.sub.1-xAl.sub.xN:Cr.sub.1-yAl.sub.yN:Ti.sub.1-zSi.sub.zN, in the nano-multilayer 8, a:b:c, 0.75<a<1.25, 0.75<b<1.25, 0.75<c<1.25, preferably 0.9<a<1.1, 0.9<b<1.1, 0.9<c<1.1. In this embodiment the nano-multilayer 8 suitably comprises a repeating sequence of consecutive nanolayers of the first nanolayer type 9, Ti.sub.1-xAl.sub.xN, the second nanolayer type 10, Cr.sub.1-yAl.sub.yN, and the third nanolayer type 11, Ti.sub.1-zSi.sub.zN, in the order Ti.sub.1-xAl.sub.xN/Cr.sub.1-yAl.sub.yN/Ti.sub.1-zSi.sub.zN. The nano-multilayer 8 is suitably composed of (Ti.sub.1-xAl.sub.xN/Cr.sub.1-yAl.sub.yN/Ti.sub.1-zSi.sub.zN).sub.q, q=20-2000, suitably q=40-1000.

EXAMPLES

[0041] It should be noted that there will be a small deviation between the elemental relatation of Ti and Al, the elemental relation of Cr and Al and the elemental relatation of Ti and Si in the targets used in the PVD deposition process and their elemental relation in the respective deposited nitride layer. One reason for this can, for example, be due to different tendencies for re-sputtering for different elements.

[0042] The actual elemental composition in the different nano-multilayer types can, for example, be determined by using energy-dispersive X-ray spectroscopy (EDS) in Transmission Electron Microscopy (TEM) on a cross-section of the coating.

[0043] Alternatively, the actual elemental composition in the different nano-multilayer types can be found by using energy-dispersive X-ray spectroscopy (EDS) in TEM or in Scanning Electron Microscopy (SEM) of a monolayer deposited at the same conditions as a respective nanolayer.

[0044] Within the relevant ranges of the contents of elements in the nanolayers of the present invention the following estimations can be made:

[0045] For a (Ti, Al)N layer the actual percentage of Al out of Ti+Al will be about 1-2 at. % units below the Al content in the (Ti,Al) target.

[0046] For a (Cr, Al)N layer the actual percentage of Al out of Cr+Al will be about 2-3 at. % units below the Al content in the (Cr,Al) target.

[0047] For a (Ti, Si)N layer the actual percentage of Si out of Ti+Si will be about 2-3 at. % units below the Si content in the (Ti, Si) target.

[0048] Thus, there are only small deviations from the theoretical composition seen. In the following examples the Ti, Al, Cr and Si contents in the deposited nitride layers are written as present in the respective target compositions used in the PVD deposition process.

[0049] The nanolayer thicknesses can be measured by using transmission electron microscopy (TEM) analysis.

Example 1

[0050] Coated cutting tools were provided comprising a nano-multilayer of Ti.sub.0.40Al.sub.0.60N, Cr.sub.0.30Al.sub.0.70N and Ti.sub.0.80Si.sub.0.20N (based on target compositions) nanolayers deposited on sintered cemented carbide cutting tool insert blanks of the geometries CNMG120408MM and R390-11T308M-PM. The composition of the cemented carbide was 10 wt % Co, 0.4 wt % Cr and rest WC. The cemented carbide blanks were coated by cathodic arc evaporation in a vacuum chamber comprising four arc flanges, each flange comprising several cathode evaporators. Targets of Ti.sub.0.80Si.sub.0.20 were mounted in the evaporators in two of the flanges opposite each other. The remaining targets Cr.sub.0.30Al.sub.0.70 and Ti.sub.0.40Al.sub.0.60 were mounted in the evaporators in the two remaining flanges opposite each other. The targets were circular and planar with a diameter of 100 mm available on the open market. Suitable target technology packages for arc evaporation are available from suppliers on the market such as IHI Hauzer Techno Coating B.V., Kobelco (Kobe Steel Ltd.) and Oerlikon Balzers.

[0051] The uncoated blanks were mounted on pins that undergo a three-fold rotation in the PVD chamber.

[0052] The chamber was pumped down to high vacuum (less than 10.sup.2 Pa) and heated to about 450-550 C. by heaters located inside the chamber. The blanks were then etched for 60 minutes in an Ar plasma.

[0053] At first, an innermost layer of Ti.sub.0.40Al.sub.0.60N (based on target composition) was deposited by only using the Ti.sub.0.40Al.sub.0.60 target.

[0054] The chamber pressure (reaction pressure) was set to 4 Pa of N.sub.2 gas, and a DC bias voltage of 50 V (relative to the chamber walls) was applied to the blank assembly. The cathodes were run in an arc discharge mode at a current of 150 A (each) for 70 minutes (2 flanges). The table rotational speed was 5 rpm. A layer of Ti.sub.0.40Al.sub.0.60N having a thickness of about 0.25 m was deposited on the blanks.

[0055] Then, the nano-multilayer was deposited by using all mounted targets.

[0056] The chamber pressure (reaction pressure) was set to 4 Pa of N.sub.2 gas, and a DC bias voltage of 70 V (relative to the chamber walls) was applied to the blank assembly. The cathodes were run in an arc discharge mode at a current of 150 A (each) for 35 minutes (4 flanges). The table rotational speed was 5 rpm. A nano-multilayer coating having a thickness of about 2.8 m was deposited on the blanks.

[0057] The rotational speed correlates to a certain period thickness and it was concluded that a table rotational speed of 5 rpm for the current deposition rate and equipment used correlates to an average individual nanolayer thickness of each of the nanolayers Ti.sub.0.40Al.sub.0.60N, Cr.sub.0.30Al.sub.0.70N and Ti.sub.0.80Si.sub.0.20N of about 2 nm. The number of nanolayers in the nano-multilayer is about 1400.

[0058] The nano-multilayer comprises a repeating sequence of consecutive nanolayers in the order Ti.sub.0.40Al.sub.0.60N/Ti.sub.0.80Si.sub.0.20N/Cr.sub.0.30Al.sub.0.70N/Ti.sub.0.80Si.sub.0.20N.

[0059] In the nano-multilayer, the ratio of the sum of nanolayer thicknesses of each of the nanolayers Ti.sub.0.40Al.sub.0.60N, Cr.sub.0.30Al.sub.0.70N and Ti.sub.0.80Si.sub.0.20N, respectively, i.e., Ti.sub.0.40Al.sub.0.60N:Cr.sub.0.30Al.sub.0.70N:Ti.sub.0.80Si.sub.0.20N, is about 1:1:2. The ratio is estimated from a deposition rate from each target assumed to be the same, the rotation during deposition and the deposition time.

[0060] The actual elemental relation in a (Ti,Al)N layer of the nano-multilayer deposited using Ti.sub.0.40Al.sub.0.60 targets was estimated to be Ti.sub.0.42Al.sub.0.58N.

[0061] The actual elemental relation in a (Cr,Al)N layer of the nano-multilayer deposited using Cr.sub.0.30Al.sub.0.70 targets was estimated to be Cr.sub.0.32Al.sub.0.68N.

[0062] From EDS in TEM of a (Ti, Si)N single layer deposited under the same conditions as the (Ti, Si)N layers within the nano-multilayer the actual elemental relation in a (Ti, Si)N layer of the nano-multilayer deposited using Ti.sub.0.80Si.sub.0.20 targets was estimated to be Ti.sub.0.83Si.sub.0.17N.

[0063] The coated cutting tools were called Sample 1 (invention).

Example 2

[0064] Coated cutting tools were provided comprising a nano-multilayer of Ti.sub.0.50Al.sub.0.50N, Cr.sub.0.30Al.sub.0.70N and Ti.sub.0.85Si.sub.0.15N (based on target compositions) nanolayers deposited on sintered cemented carbide cutting tool insert blanks of the geometries CNMG120408MM and R390-11T308M-PM. The composition of the cemented carbide was 10 wt % Co, 0.4 wt % Cr and rest WC. The cemented carbide blanks were coated by cathodic arc evaporation in a vacuum chamber comprising four arc flanges, each flange comprising several cathode evaporators. Targets of Ti.sub.0.50Al.sub.0.50 were mounted in the evaporators in two of the flanges opposite each other. The remaining targets Cr.sub.0.30Al.sub.0.70 and Ti.sub.0.85Si.sub.0.15 were mounted in the evaporators in the two remaining flanges opposite each other. The targets were circular and planar with a diameter of 100 mm available on the open market. Suitable target technology packages for arc evaporation are available from suppliers on the market such as IHI Hauzer Techno Coating B.V., Kobelco (Kobe Steel Ltd.) and Oerlikon Balzers.

[0065] The uncoated blanks were mounted on pins that undergo a three-fold rotation in the PVD chamber.

[0066] The chamber was pumped down to high vacuum (less than 10.sup.2 Pa) and heated to about 450-550 C. by heaters located inside the chamber. The blanks were then etched for 60 minutes in an Ar plasma.

[0067] At first, an innermost layer of Ti.sub.0.50Al.sub.0.50N (based on target composition) was deposited by only using the Ti.sub.0.50Al.sub.0.50 targets.

[0068] The chamber pressure (reaction pressure) was set to 4 Pa of N.sub.2 gas, and a DC bias voltage of 50 V (relative to the chamber walls) was applied to the blank assembly. The cathodes were run in an arc discharge mode at a current of 150 A (each) for 70 minutes (2 flanges). The table rotational speed was 5 rpm. A layer of Ti.sub.0.50Al.sub.0.50N having a thickness of about 1.4 m was deposited on the blanks.

[0069] Then, the nano-multilayer was deposited by alternating the use of the Cr.sub.0.30Al.sub.0.70 and Ti.sub.0.85Si.sub.0.15 targets, creating a first sequence of a Cr.sub.0.30Al.sub.0.70N/Ti.sub.0.85Si.sub.0.15N nano-multilayer of about 35 nm thickness. The table rotational speed was 5 rpm. Then only the Ti.sub.0.50Al.sub.0.50 targets were used creating a Ti.sub.0.50Al.sub.0.50N layer of about 35 nm thickness. This procedure was repeated until 20 sequences of a nano-multilayer sequence of nanolayers Cr.sub.0.30Al.sub.0.70N and Ti.sub.0.85Si.sub.0.15N combined with a monolayer of Ti.sub.0.50Al.sub.0.50N was completed. The total thickness of the deposited nano-multilayer was about 1.4 m.

[0070] The chamber pressure (reaction pressure) was set to 4 Pa of N.sub.2 gas, and a DC bias voltage of 40 V (relative to the chamber walls) was applied to the blank assembly when using the Cr.sub.0.30Al.sub.0.70 and Ti.sub.0.85Si.sub.0.15 targets and a DC bias voltage of 80 V (relative to the chamber walls) when using the Ti.sub.0.50Al.sub.0.50 targets. The cathodes were run in an arc discharge mode at a current of 150 A (each) for 70 minutes (2 flanges at a time). The table rotational speed was 5 rpm. A nano-multilayer coating having a thickness of about 1.4 m was deposited on the blanks.

[0071] The rotational speed correlates to a certain period thickness and it was concluded that a table rotational speed of 5 rpm for the current deposition rate and equipment used correlates to an average individual nanolayer thickness of each of the nanolayers Cr.sub.0.30Al.sub.0.70N and Ti.sub.0.85Si.sub.0.15N of about 2 nm.

[0072] Finally, an outermost layer of Ti.sub.0.85Si.sub.0.15N (based on target composition), in order to obtain an even colour between the individual coated cutting tools made, was deposited by only using the Ti.sub.0.85Si.sub.0.15 target. All deposition parameters were the same as for depositing the previous layers, except for the bias being-60 V and the cathodes were run for 10 minutes (1 flange). A layer of Ti.sub.0.85Si.sub.0.15N was deposited to a thickness of about 0.2 m.

[0073] The actual elemental relation in a (Ti,Al)N layer deposited using Ti.sub.0.50Al.sub.0.50 targets was estimated to be Ti.sub.0.52Al.sub.0.48N.

[0074] The actual elemental relation in a (Cr,Al)N layer deposited using Cr.sub.0.30Al.sub.0.70 targets was estimated to be Cr.sub.0.32Al.sub.0.68N.

[0075] The actual elemental relation in a (Ti, Si)N layer deposited using Ti.sub.0.85Si.sub.0.15 targets was estimated to be Ti.sub.0.87Si.sub.0.13N.

[0076] The coated cutting tools were called Sample 2 (comparative).

Example 3

[0077] Coated cutting tools were provided comprising a nano-multilayer of Ti.sub.0.50Al.sub.0.50N, Cr.sub.0.30Al.sub.0.70N and Ti.sub.0.80Si.sub.0.20N (based on target compositions) nanolayers deposited on sintered cemented carbide cutting tool insert blanks of the geometries CNMG120408MM and R390-11T308M-PM. The composition of the cemented carbide was 10 wt % Co, 0.4 wt % Cr and rest WC. The cemented carbide blanks were coated by cathodic arc evaporation in a vacuum chamber comprising four arc flanges, each flange comprising several cathode evaporators. Targets of Ti.sub.0.50Al.sub.0.50 were mounted in the evaporators in two of the flanges opposite each other. The remaining targets Cr.sub.0.30Al.sub.0.70 and Ti.sub.0.80 Si.sub.0.20 were mounted in the evaporators in the two remaining flanges opposite each other. The targets were circular and planar with a diameter of 100 mm available on the open market. Suitable target technology packages for arc evaporation are available from suppliers on the market such as IHI Hauzer Techno Coating B.V., Kobelco (Kobe Steel Ltd.) and Oerlikon Balzers.

[0078] The uncoated blanks were mounted on pins that undergo a three-fold rotation in the PVD chamber.

[0079] The chamber was pumped down to high vacuum (less than 10.sup.2 Pa) and heated to about 450-550 C. by heaters located inside the chamber. The blanks were then etched for 60 minutes in an Ar plasma.

[0080] At first, an innermost layer of Ti.sub.0.50Al.sub.0.50N (based on target composition) was deposited by only using the Ti.sub.0.50Al.sub.0.50 targets.

[0081] The chamber pressure (reaction pressure) was set to 4 Pa of N.sub.2 gas, and a DC bias voltage of 50 V (relative to the chamber walls) was applied to the blank assembly. The cathodes were run in an arc discharge mode at a current of 150 A (each) for 70 minutes (2 flanges). The table rotational speed was 5 rpm. A layer of Ti.sub.0.50Al.sub.0.50N having a thickness of about 1.4 m was deposited on the blanks.

[0082] Then, the nano-multilayer was deposited by alternating the use of the Cr.sub.0.30Al.sub.0.70 and Ti.sub.0.80Si.sub.0.20 targets, creating a first sequence of a Cr.sub.0.30Al.sub.0.70N/Ti.sub.0.80Si.sub.0.20N nano-multilayer of about 35 nm thickness. The table rotational speed was 5 rpm. Then only the Ti.sub.0.50Al.sub.0.50 targets were used creating a Ti.sub.0.50Al.sub.0.50N layer of about 35 nm thickness. This procedure was repeated until 20 sequences of a nano-multilayer sequence of nanolayers Cr.sub.0.30Al.sub.0.70N and Ti.sub.0.80Si.sub.0.20N combined with a monolayer of Ti.sub.0.50Al.sub.0.50N was completed. The total thickness of the deposited nano-multilayer was about 1.4 m.

[0083] The chamber pressure (reaction pressure) was set to 4 Pa of N.sub.2 gas, and a DC bias voltage of 40 V (relative to the chamber walls) was applied to the blank assembly when using the Cr.sub.0.30Al.sub.0.70 and Ti.sub.0.80Si.sub.0.20 targets and a DC bias voltage of 80 V (relative to the chamber walls) when using the Ti.sub.0.50Al.sub.0.50 targets. The cathodes were run in an arc discharge mode at a current of 150 A (each) for 70 minutes (2 flanges at a time). The table rotational speed was 5 rpm. A nano-multilayer coating having a thickness of about 1.4 m was deposited on the blanks.

[0084] The rotational speed correlates to a certain period thickness and it was concluded that a table rotational speed of 5 rpm for the current deposition rate and equipment used correlates to an average individual nanolayer thickness of each of the nanolayers Cr.sub.0.30Al.sub.0.70N and Ti.sub.0.80Si.sub.0.20N of about 2 nm.

[0085] Finally, an outermost layer of Ti.sub.0.80Si.sub.0.20N (based on target composition), in order to obtain an even colour between the individual coated cutting tools made, was deposited by only using the Ti.sub.0.80Si.sub.0.20 target. All deposition parameters were the same as for depositing the previous layers, except for the bias being 60 V and the cathodes were run for 10 minutes (1 flange). A layer of Ti.sub.0.80Si.sub.0.20N was deposited to a thickness of about 0.2 m.

[0086] The actual elemental relation in a (Ti,Al)N layer deposited using Ti.sub.0.50Al.sub.0.50 targets was estimated to be Ti.sub.0.52Al.sub.0.48N.

[0087] The actual elemental relation in a (Cr,Al)N layer deposited using Cr.sub.0.30Al.sub.0.70 targets was estimated to be Cr.sub.0.32Al.sub.0.68N.

[0088] The actual elemental relation in a (Ti, Si)N layer deposited using Ti.sub.0.80 Si.sub.0.20 targets was estimated to be Ti.sub.0.83Si.sub.0.17N.

[0089] The coated cutting tools were called Sample 3 (comparative).

Example 4

[0090] Coated cutting tools were provided comprising a nano-multilayer of Ti.sub.0.40Al.sub.0.60N, Cr.sub.0.30Al.sub.0.70N and Ti.sub.0.80Si.sub.0.20N (based on target compositions) nanolayers deposited on sintered cemented carbide cutting tool blanks being solid endmills, geometry 2P342-1200-PA, diameter 12 mm, with 4 cutting edges. The composition of the cemented carbide was 10 wt % Co, 0.4 wt % Cr and rest WC. The cemented carbide blanks were coated by cathodic arc evaporation in a vacuum chamber comprising four arc flanges, each flange comprising several cathode evaporators. Targets of Ti.sub.0.40Al.sub.0.60 were mounted in the evaporators in two of the flanges opposite each other. The remaining targets Cr.sub.0.30Al.sub.0.70 and Ti.sub.0.80Si.sub.0.20 were mounted in the evaporators in the two remaining flanges opposite each other. The targets were circular and planar with a diameter of 100 mm available on the open market. Suitable target technology packages for arc evaporation are available from suppliers on the market such as IHI Hauzer Techno Coating B.V., Kobelco (Kobe Steel Ltd.) and Oerlikon Balzers.

[0091] The uncoated blanks were mounted on holders that undergo a three-fold rotation in the PVD chamber.

[0092] The chamber was pumped down to high vacuum (less than 10.sup.2 Pa) and heated to about 450-550 C. by heaters located inside the chamber. The blanks were then etched for 60 minutes in an Ar plasma.

[0093] At first, an innermost layer of Ti.sub.0.40Al.sub.0.60N (based on target composition) was deposited by only using the Ti.sub.0.40Al.sub.0.60 targets.

[0094] The chamber pressure (reaction pressure) was set to 4 Pa of N.sub.2 gas, and a DC bias voltage of 70 V (relative to the chamber walls) was applied to the blank assembly. The cathodes were run in an arc discharge mode at a current of 150 A (each) for 70 minutes (2 flanges). The table rotational speed was 5 rpm. A layer of Ti.sub.0.40Al.sub.0.60N having a thickness of about 1 m was deposited on the blanks.

[0095] Then, the nano-multilayer was deposited by using all mounted targets.

[0096] The chamber pressure (reaction pressure) was set to 4 Pa of N.sub.2 gas, and a DC bias voltage of 70 V (relative to the chamber walls) was applied to the blank assembly. The cathodes were run in an arc discharge mode at a current of 150 A (each) for 47 minutes (4 flanges). The table rotational speed was 5 rpm. A nano-multilayer coating having a thickness of about 2 m was deposited on the blanks.

[0097] The rotational speed correlates to a certain period thickness and it was concluded that a table rotational speed of 5 rpm for the current deposition rate and equipment used correlates to an average individual nanolayer thickness of each of the nanolayers Ti.sub.0.40Al.sub.0.60N, Cr.sub.0.30Al.sub.0.70N and Ti.sub.0.80Si.sub.0.20N of about 2 nm. The number of nanolayers in the nano-multilayer is about 1000.

[0098] The nano-multilayer comprises a repeating sequence of consecutive nanolayers in the order Ti.sub.0.40Al.sub.0.60N/Cr.sub.0.30Al.sub.0.70N/Ti.sub.0.40Al.sub.0.60N/Ti.sub.0.80Si.sub.0.20N.

[0099] In the nano-multilayer, the ratio of the sum of nanolayer thicknesses of each of the nanolayers Ti.sub.0.40Al.sub.0.50N, Cr.sub.0.30Al.sub.0.70N and Ti.sub.0.80Si.sub.0.20N, respectively, i.e., Ti.sub.0.40Al.sub.0.60N:Cr.sub.0.30Al.sub.0.70N:Ti.sub.0.80Si.sub.0.20N, is about 2:1:1. The ratio is estimated from a deposition rate from each target assumed to be the same, the rotation during deposition and the deposition time.

[0100] The actual elemental relation in a (Ti,Al)N layer of the nano-multilayer deposited using Ti.sub.0.40Al.sub.0.60 targets was estimated to be Ti.sub.0.42Al.sub.0.58N.

[0101] The actual elemental relation in a (Cr,Al)N layer of the nano-multilayer deposited using Cr.sub.0.30Al.sub.0.70 targets was estimated to be Cr.sub.0.32Al.sub.0.68N.

[0102] From EDS in TEM of a (Ti, Si)N single layer deposited under the same conditions as the (Ti, Si)N layers within the nano-multilayer the actual elemental relation in a (Ti,Si)N layer of the nano-multilayer deposited using Ti.sub.0.80Si.sub.0.20 targets was estimated to be Ti.sub.0.83Si.sub.0.17N.

[0103] The coated cutting tools were called Sample 4 (invention).

[0104] The samples 1-4 made are listed in Table 1.

TABLE-US-00001 TABLE 1 Nano-multilayer First Second Third Inner nanolayer nanolayer nanolayer Outer Sample layer* type* type* type* layer* 1 Ti.sub.0.40Al.sub.0.60N, Ti.sub.0.40Al.sub.0.60N Cr.sub.0.30Al.sub.0.70N Ti.sub.0.80Si.sub.0.20N invention 0.25 m 2.8 m 2 Ti.sub.0.50Al.sub.0.50N, Ti.sub.0.50Al.sub.0.50N** Cr.sub.0.30Al.sub.0.70N *** Ti.sub.0.85Si.sub.0.15N *** Ti.sub.0.85Si.sub.0.15N comparative 1.4 m 1.4 m 0.2 m 3 Ti.sub.0.50Al.sub.0.50N, Ti.sub.0.50Al.sub.0.50N** Cr.sub.0.30Al.sub.0.70N *** Ti.sub.0.80Si.sub.0.20N *** Ti.sub.0.80Si.sub.0.20N comparative 1.4 m 1.4 m 0.2 m 4 Ti.sub.0.40Al.sub.0.60N, Ti.sub.0.40Al.sub.0.60N Cr.sub.0.30Al.sub.0.70N Ti.sub.0.80Si.sub.0.20N invention 1 m 2 m *all elemental compositions based on target composition **about 35 nm TiAlN *** about 35 nm nano-multilayer of CrAlN/TiSiN

[0105] Table 2 further summarises the samples 1-4.

TABLE-US-00002 TABLE 2 Thickness ratio sum of nanolayer thicknesses of Inner Nanolayer sequence in each nanolayer type Sample layer* nano-multilayer* Ti.sub.1xAl.sub.xN:Cr.sub.1yAl.sub.yN:Ti.sub.1zSi.sub.zN 1 Ti.sub.0.40Al.sub.0.60N, (Ti.sub.0.40Al.sub.0.60N/Ti.sub.0.80Si.sub.0.20N/ 1:1:2 invention 0.25 m Cr.sub.0.30Al.sub.0.70N/Ti.sub.0.80Si.sub.0.20N).sub.350 2 Ti.sub.0.50Al.sub.0.50N, (35 nm Ti.sub.0.50Al.sub.0.50N + 35 nm 2:1:1 comparative 1.4 m (Cr.sub.0.30Al.sub.0.70N/Ti.sub.0.85Si.sub.0.15N).sub.9).sub.20 3 Ti.sub.0.50Al.sub.0.50N, (35 nm Ti.sub.0.50Al.sub.0.50N + 35 nm 2:1:1 comparative 1.4 m (Cr.sub.0.30Al.sub.0.70N/Ti.sub.0.80Si.sub.0.20N).sub.9).sub.20 4 Ti.sub.0.40Al.sub.0.60N, (Ti.sub.0.40Al.sub.0.60N/Cr.sub.0.30Al.sub.0.70N/ 2:1:1 invention 1 m Ti.sub.0.40Al.sub.0.60N/Ti.sub.0.80Si.sub.0.20N).sub.250 *all elemental compositions based on target composition

Example 5

[0106] Cutting tests were made in order to determine the performance of the cutting tool insert samples made.

[0107] Since sample 1 was run at a separate test run as samples 2-3 the results are presented as compared with a cutting insert having an about 3 m thick Ti.sub.0.40Al.sub.0.60N reference coating which was included in all test runs. For example, 155% in the results table means the performance (tool life) was 155% of the result for the reference having a Ti.sub.0.40Al.sub.0.60N coating (based on target composition). The reference coated cutting tools were made by depositing a layer of Ti.sub.0.40Al.sub.0.60N on sintered cemented carbide cutting tool blanks of the same type as for samples 1-3, i.e., cutting tool insert blanks of the geometries CNMG120408MM and R390-11T308M-PM. The cemented carbide also being the same, i.e., 10 wt % Co, 0.4 wt % Cr and rest WC. Targets of Ti.sub.0.40Al.sub.0.60 were mounted in the evaporators in four flanges. The chamber pressure (reaction pressure) was set to 4 Pa of N.sub.2 gas, and a DC bias voltage of 70 V (relative to the chamber walls) was applied to the blank assembly. The cathodes were run in an arc discharge mode at a current of 150 A (each) (4 flanges). The table rotational speed was 5 rpm. A layer of Ti.sub.0.40Al.sub.0.60N having a thickness of about 3 m was deposited on the blanks.

Explanations to Terms Used

[0108] The following expressions/terms are commonly used in metal cutting, but nevertheless explained in the table below: [0109] Vc (m/min): cutting speed in meters per minute [0110] fz (mm/tooth): feed rate in millimeter per tooth (in milling) [0111] fn (mm/rev) feed rate per revolution (in turning) [0112] z: (number) number of teeth in the cutter [0113] a.sub.e (mm): radial depth of cut in millimeter [0114] a.sub.p (mm): axial depth of cut in millimeter

Flank Wear Test:

Longitudinal Turning

[0115] Work piece material: Sverker 21 (tool steel), Hardness 210HB, D=180, L=700 mm, [0116] V.sub.c=125 m/min [0117] f.sub.n=0.072 mm/rev [0118] a.sub.p=2 mm
without cutting fluid

[0119] The cut-off criteria for tool life is a flank wear VB of 0.15 mm.

Comb Crack Resistance:

[0120] Operation: Shoulder milling [0121] Tool holder: C5-391.20-25 080 [0122] Work piece material: Toolox 33 (tool steel), L=600 mm, I=200 mm, h=100 mm, [0123] Insert type: R390-11T308M-PM [0124] Cutting speed V.sub.c=250 m/min [0125] Feed rate f.sub.z=0.2 mm/rev [0126] Depth of cut a.sub.p=3 mm [0127] Radial engagement a.sub.e=12.5 mm
with cutting fluid

[0128] The criteria for end of tool life is a max. chipped height VB>0.3 mm.

[0129] The results are presented in Table 3.

TABLE-US-00003 TABLE 3 Flank wear Comb crack resistance resistance (Tool life, % of (Tool life, % of Sample Ti.sub.0.40Al.sub.0.60N ref.) Ti.sub.0.40Al.sub.0.60N ref.) 1 155% 148% invention 2 91% 89% comparative 3 96% 86% comparative

[0130] It is concluded that sample 1, within the invention, have high flank wear resistance and show much less flank wear than comparative samples 2-3 outside the invention. Furthermore, sample 1 shows much higher comb crack resistance than the comparative samples.

Example 6

[0131] Cutting tests were made in order to determine the performance of the cutting tool of sample 4 being an endmill.

[0132] Furthermore, to be used as a reference, coated cutting tools were made by depositing a layer of Ti.sub.0.40Al.sub.0.60N (based on target composition) on sintered cemented carbide cutting tool blanks of the same type as above, i.e., solid endmills, geometry 2P342-1200-PA, diameter 12 mm, with 4 cutting edges. The cemented carbide also being the same, i.e., 10 wt % Co, 0.4 wt % Cr and rest WC. Targets of Ti.sub.0.40Al.sub.0.60 were mounted in the evaporators in four flanges. The chamber pressure (reaction pressure) was set to 4 Pa of N.sub.2 gas, and a DC bias voltage of 50 V (relative to the chamber walls) was applied to the blank assembly. The cathodes were run in an arc discharge mode at a current of 150 A (each) (4 flanges). The table rotational speed was 5 rpm. A layer of Ti.sub.0.40Al.sub.0.60N having a thickness of about 3 m was deposited on the blanks.

[0133] The coated cutting tools were called Sample 5 (reference).

Flank Wear Test:

Dry Shoulder Milling

[0134] Work piece material: C45 (P1 steel), Hardness 200 HB, Size: 60022050 mm [0135] Work piece material: 42CrMo4 (P2 steel), Hardness 302-305 HB, Size: 60020050 mm [0136] V.sub.c=235 m/min [0137] fz=0.055 (mm/tooth) [0138] a.sub.p=5 mm [0139] a.sub.e=1.2 mm [0140] z=4 teeth [0141] L=220 mm (C45, P1 steel), 200 mm (42CrMo4, P2 steel) without cutting fluid

[0142] The predetermined number of cutting passes is 400, or Vb30.1 mm.

[0143] Tool wear (Vb3-localised flank wear) was measured on tool corners and depth of cut (DOC) of the cutting edge. The lower values, the better.

[0144] Results from the test cutting in 42CrMo4, P2 steel, is seen in Table 4.

TABLE-US-00004 TABLE 4 Flank wear resistance Flank wear resistance on corners on depth of cut Sample (Vb3, mm) (Vb3, mm) 4 0.045 0.058 invention 5 0.072 0.073 reference

[0145] Results from the test cutting in C45, P1 steel, is seen in Table 5.

TABLE-US-00005 TABLE 5 Flank wear resistance Flank wear resistance on corners on depth of cut Sample (Vb3, mm) (Vb3, mm) 4 0.053 0.042 invention 5 0.078 0.076 reference

[0146] It is concluded from cutting in both work piece materials that sample 4, within the invention shows much less flank wear than the reference sample. The low levels of Vb3 are considered to be a very good result.

Example 7

[0147] In order to evaluate the effect of different nanolayer thicknesses in the nano-multilayer the following samples were made:

[0148] Coated cutting tools were provided comprising a nano-multilayer of Ti.sub.0.40Al.sub.0.60N, Cr.sub.0.30Al.sub.0.70N and Ti.sub.0.80Si.sub.0.20N (based on target compositions) nanolayers deposited on sintered cemented carbide cutting tool insert blanks of the geometries CNMG120408MM and R390-11T308M-PM. The composition of the cemented carbide was 10 wt % Co, 0.4 wt % Cr and rest WC. The cemented carbide blanks were coated by cathodic arc evaporation in a vacuum chamber comprising four arc flanges, each flange comprising several cathode evaporators. Targets of Ti.sub.0.40Al.sub.0.60 were mounted in the evaporators in two of the flanges opposite each other. The remaining targets Cr.sub.0.30Al.sub.0.70 and Ti.sub.0.80Si.sub.0.20 were mounted in the evaporators in the two remaining flanges opposite each other. The targets were circular and planar with a diameter of 100 mm available on the open market. Suitable target technology packages for arc evaporation are available from suppliers on the market such as IHI Hauzer Techno Coating B.V., Kobelco (Kobe Steel Ltd.) and Oerlikon Balzers.

[0149] The uncoated blanks were mounted on holders that undergo a three-fold rotation in the PVD chamber.

[0150] The chamber was pumped down to high vacuum (less than 10.sup.2 Pa) and heated to about 450-550 C. by heaters located inside the chamber. The blanks were then etched for 60 minutes in an Ar plasma.

[0151] At first, an innermost layer of Ti.sub.0.40Al.sub.0.60N (based on target composition) was deposited by only using the Ti.sub.0.40Al.sub.0.60 targets.

[0152] The chamber pressure (reaction pressure) was set to 4 Pa of N.sub.2 gas, and a DC bias voltage of 70 V (relative to the chamber walls) was applied to the blank assembly. The cathodes were run in an arc discharge mode at a current of 150 A (each) for 40 minutes (2 flanges). The table rotational speed was 5 rpm. A layer of Ti.sub.0.40Al.sub.0.60N having a thickness of about 0.8 m was deposited on the blanks.

[0153] Then, the nano-multilayer was deposited by using all mounted targets.

[0154] The chamber pressure (reaction pressure) was set to 4 Pa of N.sub.2 gas, and a DC bias voltage of 70 V (relative to the chamber walls) was applied to the blank assembly. The cathodes were run in an arc discharge mode at a current of 150 A (each) for 55 minutes (4 flanges). The table rotational speed was 5 rpm for a first sample, Sample 5 (invention).

[0155] In a further run a second set of coated cutting tools were made using using the same process conditions as for making Sample 5 (invention) above but using a table rotational speed of 2.4 rpm. The coated cutting tools made were called Sample 6 (comparative).

[0156] In a further run a third set of coated cutting tools were made using using the same process conditions as for making Sample 5 (invention) above but using a table rotational speed of 1.5 rpm. The coated cutting tools made were called Sample 7 (comparative).

[0157] In all cases, a nano-multilayer coating having a thickness of about 2.2 m was deposited on the blanks.

[0158] The rotational speed correlates to a certain period thickness and it was concluded that a table rotational speed of 5 rpm for the current deposition rate and equipment used correlates to an average individual nanolayer thickness of each of the nanolayers Ti.sub.0.40Al.sub.0.60N, Cr.sub.0.30Al.sub.0.70N and Ti.sub.0.80Si.sub.0.20N of about 2 nm. The number of nanolayers in the nano-multilayer is about 1000.

[0159] A table rotational speed of 2.4 rpm for the current deposition rate and equipment used correlates to an average individual nanolayer thickness of each of the nanolayers Ti.sub.0.40Al.sub.0.60N, Cr.sub.0.30Al.sub.0.70N and Ti.sub.0.80Si.sub.0.20N of about 4 nm. The number of nanolayers in the nano-multilayer is about 500.

[0160] A table rotational speed of 1.5 rpm for the current deposition rate and equipment used correlates to an average individual nanolayer thickness of each of the nanolayers Ti.sub.0.40Al.sub.0.60N, Cr.sub.0.30Al.sub.0.70N and Ti.sub.0.80Si.sub.0.20N of about 6 nm. The number of nanolayers in the nano-multilayer is about 330.

[0161] The nano-multilayers of Samples 5 to 7 all comprise a repeating sequence of consecutive nanolayers in the order Ti.sub.0.40Al.sub.0.60N/Cr.sub.0.30Al.sub.0.70N/Ti.sub.0.40Al.sub.0.60N/Ti.sub.0.80Si.sub.0.20N.

[0162] In the nano-multilayers, the ratio of the sum of nanolayer thicknesses of each of the nanolayers Ti.sub.0.40Al.sub.0.50N, Cr.sub.0.30Al.sub.0.70N and Ti.sub.0.80Si.sub.0.20N, respectively, i.e., Ti.sub.0.40Al.sub.0.60N:Cr.sub.0.30Al.sub.0.70N:Ti.sub.0.80Si.sub.0.20N, is about 2:1:1. The ratio is estimated from a deposition rate from each target assumed to be the same, the rotation during deposition and the deposition time.

[0163] The actual elemental relation in a (Ti,Al)N layer of the nano-multilayer deposited using Ti.sub.0.40Al.sub.0.60 targets was estimated to be Ti.sub.0.42Al.sub.0.58N.

[0164] The actual elemental relation in a (Cr,Al)N layer of the nano-multilayer deposited using Cr.sub.0.30Al.sub.0.70 targets was estimated to be Cr.sub.0.32Al.sub.0.68N.

[0165] From EDS in TEM of a (Ti, Si)N single layer deposited under the same conditions as the (Ti, Si)N layers within the nano-multilayer the actual elemental relation in a (Ti, Si)N layer of the nano-multilayer deposited using Ti.sub.0.80Si.sub.0.20 targets was estimated to be Ti.sub.0.83Si.sub.0.17N.

Example 8

[0166] A sample without an inner layer of (Ti,Al)N was made.

[0167] Coated cutting tools were provided comprising a nano-multilayer of Ti.sub.0.40Al.sub.0.60N, Cr.sub.0.30Al.sub.0.70N and Ti.sub.0.80Si.sub.0.20N (based on target compositions) nanolayers deposited on sintered cemented carbide cutting tool insert blanks of the geometries CNMG120408MM and R390-11T308M-PM. The composition of the cemented carbide was 10 wt % Co, 0.4 wt % Cr and rest WC. The cemented carbide blanks were coated by cathodic arc evaporation in a vacuum chamber comprising four arc flanges, each flange comprising several cathode evaporators. Targets of Ti.sub.0.40Al.sub.0.60 were mounted in the evaporators in two of the flanges opposite each other. The remaining targets Cr.sub.0.30Al.sub.0.70 and Ti.sub.0.80Si.sub.0.20 were mounted in the evaporators in the two remaining flanges opposite each other. The targets were circular and planar with a diameter of 100 mm available on the open market. Suitable target technology packages for arc evaporation are available from suppliers on the market such as IHI Hauzer Techno Coating B.V., Kobelco (Kobe Steel Ltd.) and Oerlikon Balzers.

[0168] The uncoated blanks were mounted on holders that undergo a three-fold rotation in the PVD chamber.

[0169] The chamber was pumped down to high vacuum (less than 10.sup.2 Pa) and heated to about 450-550 C. by heaters located inside the chamber. The blanks were then etched for 60 minutes in an Ar plasma.

[0170] A nano-multilayer was deposited by using all mounted targets.

[0171] The chamber pressure (reaction pressure) was set to 4 Pa of N.sub.2 gas, and a DC bias voltage of 70 V (relative to the chamber walls) was applied to the blank assembly. The cathodes were run in an arc discharge mode at a current of 150 A (each) for 75 minutes (4 flanges). The table rotational speed was 5 rpm.

[0172] A nano-multilayer coating having a thickness of about 3 m was deposited on the blanks.

[0173] The rotational speed correlates to a certain period thickness and it was concluded that a table rotational speed of 5 rpm for the current deposition rate and equipment used correlates to an average individual nanolayer thickness of each of the nanolayers Ti.sub.0.40Al.sub.0.60N, Cr.sub.0.30Al.sub.0.70N and Ti.sub.0.80Si.sub.0.20N of about 2 nm. The number of nanolayers in the nano-multilayer is about 1000.

[0174] The nano-multilayer comprises a repeating sequence of consecutive nanolayers in the order Ti.sub.0.40Al.sub.0.60N/Cr.sub.0.30Al.sub.0.70N/Ti.sub.0.40Al.sub.0.60N/Ti.sub.0.80Si.sub.0.20N.

[0175] In the nano-multilayer, the ratio of the sum of nanolayer thicknesses of each of the nanolayers Ti.sub.0.40Al.sub.0.50N, Cr.sub.0.30Al.sub.0.70N and Ti.sub.0.80Si.sub.0.20N, respectively, i.e., Ti.sub.0.40Al.sub.0.60N:Cr.sub.0.30Al.sub.0.70N:Ti.sub.0.80Si.sub.0.20N, is about 2:1:1. The ratio is estimated from a deposition rate from each target assumed to be the same, the rotation during deposition and the deposition time.

[0176] The actual elemental relation in a (Ti,Al)N layer of the nano-multilayer deposited using Ti.sub.0.40Al.sub.0.60 targets was estimated to be Ti.sub.0.42Al.sub.0.58N.

[0177] The actual elemental relation in a (Cr,Al)N layer of the nano-multilayer deposited using Cr.sub.0.30Al.sub.0.70 targets was estimated to be Cr.sub.0.32Al.sub.0.68N.

[0178] From EDS in TEM of a (Ti, Si)N single layer deposited under the same conditions as the (Ti, Si)N layers within the nano-multilayer the actual elemental relation in a (Ti, Si)N layer of the nano-multilayer deposited using Ti.sub.0.80Si.sub.0.20 targets was estimated to be Ti.sub.0.83Si.sub.0.17N.

[0179] The coated cutting tools were called Sample 8 (invention).

[0180] Table 6 summarises the samples 5-8.

TABLE-US-00006 TABLE 6 Average nanolayer thickness of each nanolayer type Inner Nanolayer sequence in Ti.sub.1xAl.sub.xN, Cr.sub.1yAl.sub.yN Sample layer* nano-multilayer* and Ti.sub.1zSi.sub.zN 5 Ti.sub.0.40Al.sub.0.60N, (Ti.sub.0.40Al.sub.0.60N/Cr.sub.0.30Al.sub.0.70N/ 2 nm invention 0.8 m Ti.sub.0.40Al.sub.0.60N/Ti.sub.0.80Si.sub.0.20N).sub.250 6 Ti.sub.0.40Al.sub.0.60N, (Ti.sub.0.40Al.sub.0.60N/Cr.sub.0.30Al.sub.0.70N/ 4 nm comparative 0.8 m Ti.sub.0.40Al.sub.0.60N/Ti.sub.0.80Si.sub.0.20N).sub.125 7 Ti.sub.0.40Al.sub.0.60N, (Ti.sub.0.40Al.sub.0.60N/Cr.sub.0.30Al.sub.0.70N/ 6 nm comparative 0.8 m Ti.sub.0.40Al.sub.0.60N/Ti.sub.0.80Si.sub.0.20N).sub.83 8 (Ti.sub.0.40Al.sub.0.60N/Cr.sub.0.30Al.sub.0.70N/ 2 nm invention Ti.sub.0.40Al.sub.0.60N/Ti.sub.0.80Si.sub.0.20N).sub.250 *all elemental compositions based on target composition

Example 9

[0181] Cutting tests were made in order to determine the performance of the cutting tool insert samples 5 to 8.

[0182] A cutting insert having an about 3 m thick Ti.sub.0.40Al.sub.0.60N reference coating which was included in all test runs. The reference coated cutting tools were made by depositing a layer of Ti.sub.0.40Al.sub.0.60N on sintered cemented carbide cutting tool blanks of the same type as for samples 5-8 to be tested, i.e., cutting tool insert blanks of the geometries CNMG120408MM and R390-11T308M-PM. The cemented carbide also being the same, i.e., 10 wt % Co, 0.4 wt % Cr and rest WC. Targets of Ti.sub.0.40Al.sub.0.60 were mounted in the evaporators in four flanges. The chamber pressure (reaction pressure) was set to 4 Pa of N.sub.2 gas, and a DC bias voltage of 70 V (relative to the chamber walls) was applied to the blank assembly. The cathodes were run in an arc discharge mode at a current of 150 A (each) (4 flanges). The table rotational speed was 5 rpm. A layer of Ti.sub.0.40Al.sub.0.60N having a thickness of about 3 m was deposited on the blanks.

Flank Wear Test:

Longitudinal Turning

[0183] Work piece material: Sverker 21 (tool steel), Hardness 210HB, D=180, L=700 mm, [0184] V.sub.c=125 m/min [0185] f.sub.n=0.072 mm/rev [0186] a.sub.p=2 mm
without cutting fluid

[0187] The cut-off criteria for tool life is a flank wear VB of 0.15 mm.

Comb Crack Resistance:

[0188] Operation: Shoulder milling [0189] Tool holder: C5-391.20-25 080 [0190] Work piece material: Toolox 33 (tool steel), L=600 mm, I=200 mm, h=100 mm, [0191] Insert type: R390-11T308M-PM [0192] Cutting speed V.sub.c=250 m/min [0193] Feed rate f.sub.z=0.2 mm/rev [0194] Depth of cut a.sub.p=3 mm [0195] Radial engagement a.sub.e=12.5 mm
with cutting fluid

[0196] The criteria for end of tool life is a max. chipped height VB>0.3 mm.

[0197] The results are presented in Table 7.

TABLE-US-00007 TABLE 7 Flank wear Comb crack resistance Comb crack resistance Flank wear (Tool life, resistance (Tool life, resistance % of (Tool life, % of (Tool life, Ti.sub.0.40Al.sub.0.60N number of Ti.sub.0.40Al.sub.0.60N Sample minutes) ref.) passes) ref.) 5 22 129% 37 95% invention 6 19 119% 40 103% comparative 7 17 106% 46 118% comparative 8 25 156% 44 113% invention Ti.sub.0.40Al.sub.0.60N 16 100% 39 100% reference

[0198] It is concluded that sample 5, within the invention, has high flank wear resistance and shows less flank wear than comparative samples 6-7 outside the invention which have larger nanolayer thicknesses (averages 4 nm and 6 nm, respectively). Sample 8, without any inner (Ti,Al)N layer did also perform very well in the flank wear test and also shows a good result in comb crack resistance test. All samples did well in the comb crack resistance test, also Sample 5 within the invention with 37 passes in the test, but the samples within the invention show a combination of outstanding flank wear resistance in combination with a high comb crack resistance.