Technical field

The present invention relates to a coated cutting tool comprising a coating comprising a nano-multilayer of alternating nanolayers of Tii- _X AI _X N, 0.45<x<0.67, Cn-yAlyN, 0.60<y<0.80, and Th-zSizN, 0.14<z<0.25.

Background

Metal machining operations include, for example, turning, milling, and drilling. 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. In order to increase wear resistance of a cutting tool various types of wear resistant coatings are known in the art.

A cutting tool generally has at least one rake face and at least one flank face. A cutting edge is present where a rake face and flank face meet.

Flank wear obviously takes place on a flank face of the cutting edge, mainly from an abrasive wear mechanism. The flank face is subjected to workpiece movement and too much flank wear will lead to poor surface texture of the workpiece, inaccuracy in the cutting process and increased friction in the cutting process.

If a better flank wear resistance is provided longer tool life is provided for certain metal machining operations.

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. Thermal load induces thermal tensions which may lead to so-called thermal cracks, herein referred to as "comb cracks", in the coatings, while the later may cause fatigue in the cutting edge leading to chipping, i.e. , small fragments of the cutting edge loosening from the rest of the substrate. Thus, common wear types of a coated cutting tool in milling are cracking and chipping. A high comb crack resistance is thus of great importance for tool lifetime in such cutting operations.

A high level of toughness of the coating, in particular at the cutting edge, may also reduce chipping. A high edge line toughness, thus, also increases tool lifetime.

There is a continuing demand for coated cutting tools in which the coating has excellent properties in terms of wear resistance, comb crack 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.

Nano-multilayered coatings are being 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.

Object of the invention

There is an object of the present invention to provide a coated cutting tool which, at least, shows high flank wear resistance and preferably also high comb crack resistance, most preferably also high edge line toughness.

Summary of the invention

The object of the invention is provided by a coated cutting tool comprising a substrate and a coating, wherein the coating comprises a from about 0.5 to about 10 pm nano-multilayer of alternating nanolayers of a first nanolayer type being Tii- _X AI _X N, 0.45<x<0.67, a second nanolayer type (10) being Cri- _y Al _y N, 0.60<y<0.80, and a third nanolayer type (11 ) being Tii-zSizN, 0.14<z<0.25, the average nanolayer thickness of each of the nanolayer types Tii- _X AI _X N (9), Cn- _y Al _y N (10) and Tii-zSizN (11 ) in the nano-multilayer (8) is > 1 nm but < 3 nm.

By "nano-multilayer of alternating nanolayers of a first nanolayer type, a second nanolayer type, and a third nanolayer type" is herein meant that the different types of nanolayers are generally alternating in a certain order in the nano-multilayer. However, due to the way chosen for depositing the nano- multilayer in a PVD reactor, for example using a so called three-fold rotation of the tools being coated, there may be an altering of the order of the three types of nanolayers at some places within the nano-multilayer.

In one embodiment there is a ratio in the nano-multilayer between the sum of nanolayer thicknesses of all of each nanolayer types, Tii- _X AI _X N: Cn- _y Al _y N:Tii-zSizN, being a:b:c, wherein 0.5<a<3, 0.5<b<3, 0.5<c<3, preferably 0.75<a<2.5, 0.75<b<2.5, 0.75<c<2.5, most preferably 0.9<a<2.25, 0.9<b<2.25, 0.9<c<2.25.

The ratio between the sum of nanolayer thicknesses of each nanolayer type, Tii- _x Al _x N:Cri- _y Al _y N:Tii-zSizN, in the nano-multilayer, i.e. , a:b:c, can be determined by Scanning Transmission Electron Microscopy (STEM) analysis, preferably in combination with Energy-dispersive X-ray spectroscopy (EDS), where over a distance along a normal to the substrate surface the elemental composition and thicknesses of individual nanolayers are determined. A distance of at least 25 times the average nanolayer thickness is used. The sum of nanolayer thicknesses for nanolayers of the first nanolayer type Tii- _X AI _X N is "a", the sum of nanolayer thicknesses for nanolayers of the second nanolayer type Cn-yAlyN is "b", and the sum of nanolayer thicknesses for nanolayers of the third nanolayer type Tii-zSizN is "c".

The average nanolayer thickness of each of the nanolayer types Tii- xAlxN, Cn-yAlyN, and Tii-zSizN in the nano-multilayer can also be determined by the above described STEM/EDS analysis.

For the first nanolayer type being Tii- _X AI _X N, suitably 0.50<x<0.62, preferably 0.55<x<0.62.

For the second nanolayer type being Cn-yAlyN, suitably 0.65<y<0.75.

For the third nanolayer type being Tii-zSizN, suitably 0.15<z<0.23, preferably 0.16<z<0.21 .

The average nanolayer thickness in the nano-multilayer of each of the nanolayer types Tii- _X AI _X N, Cn-yAlyN, and Tii-zSizN in the nano-multilayer is suitably from 1 to 2.8 nm, preferably from 1 to 2.5 nm, more preferably from 1.5 to 2.5 nm, most preferably from 1 .8 to 2.2 nm.

The ratio of average nanolayer thickness in the nano-multilayer between any one of the nanolayer types Tii- _X AI _X N, Cn-yAlyN, and Tii-zSizN to any of the remaining two of the nanolayer types Tii- _X AI _X N, Cri- _y Al _y N, and Tii-zSizN in the nano-multilayer is suitably of from 0.1 to 10, preferably from 0.5 to 5, most preferably from 0.8 to 2.

Suitably, within a sequence of 10 consecutive nanolayers, preferably 8, most preferably 6, consecutive nanolayers, in the nano-multilayer there are all of the nanolayer types Tii- _X AI _X N, Cn- _y Al _y N, and Tii-zSizN present.

The thickness of the nano-multilayer is suitably from about 1 to about 8 pm, preferably from about 1 .5 to about 5 pm.

In one embodiment, the coating comprises an inner layer of a nitride of one or more of Ti and Cr, or one or more of Ti and Cr in combination with Al, below the nano-multilayer, preferably closest to the substrate. More specifically, in one embodiment, the inner layer is TiN, CrN, (Ti, Cr)N, (Cr,AI)N or (Ti, AI)N. In one embodiment the inner layer is (Cr,AI)N or (Ti, AI)N. In another embodiment the inner layer is TiN or (Ti, AI)N. The (Ti, AI)N layer may either be a monolayer or a nano-multilayer of alternating nanolayers of different Ti/AI ratio. The (Cr,AI)N layer may either be a monolayer or a nano-multilayer of alternating nanolayers of different Cr/AI ratio.

Preferably, the inner layer is (Ti, AI)N. If (Ti, AI)N is used as the inner layer then the (Ti, AI)N is suitably Tii-tAltN, 0.45<t<0.67, preferably 0.50<t<0.62, most preferably 0.55<t<0.62. In a preferred embodiment the Ti-AI relation in the (Ti , AI)N of the inner layer is the same as the Ti-AI relation in the first nanolayer type of the nano-multilayer. This is because this simplifies the production when a same target can be used as already being used for the nano-multilayer.

The thickness of the inner layer is suitably from about 0.1 to about 3 pm, preferably from about 0.2 to about 2 pm, most preferably from about 0.5 to about 2 pm.

In one embodiment, for the purpose of having control of the colour of the coated cutting tool, the coating comprises an outermost single layer of any one of the first nanolayer type Tii- _X AI _X N, with 0.45<x<0.67 or 0.50<x<0.62 or 0.55<x<0.62, the second nanolayer type Cn- _y Al _y N with 0.60<y<0.80 or 0.65<y<0.75, or the third nanolayer type Tii-zSizN, with 0.14<z<0.25 or 0.15<z<0.23 or 0.16<z<0.21 . The values of x, y or z in the outermost layer is preferably the same as x, y or z in the Tii- _X AI _X N, Cri- _y Al _y N, or Tii-zSizN in the nano-multilayer. This is because this simplifies the production when a same target can be used as already being used for the nano-multilayer.

The thickness of this outermost layer is suitably from about 0.1 to about 0.5 pm, preferably from about 0.1 to about 0.3 pm.

The nanolayers of the first nanolayer type, the second nanolayer type and the third nanolayer type are suitably cathodic arc evaporation deposited layers. Also the optional inner layer of TiN or (Ti,AI)N, as well as the optional outermost single layer are suitably cathodic arc evaporation deposited layers.

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

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.

Brief descriptions of the drawings

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

Figure 2 shows a schematic view of one embodiment of a cutting tool being a turning insert.

Figure 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.

Figure 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

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 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. Figure 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 Tii- _X AI _X N 9, Cri- _y Al _y N 10 and Tii-zSizN 11 . Figure 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,AI)N innermost layer 7 followed by a nano-multilayer 8 of alternating nanolayers 9, 10 and 11 being Tii- _X AI _X N 9, Cn- _y Al _y N 10 and Tii-zSizN 11.

Detailed description of embodiments:

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 , Tii- _X AI _X N : Cn- _y Al _y N:Tii-zSizN, 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, Tii- _X AI _X N, the second nanolayer type 10, Cn- _y Al _y N, and the third nanolayer type 11 , Tii-zSizN, in the order Tii- _X AI _X N/ Tii-zSizN/ Cn- _y Al _y N/ Tii-zSizN. The nano-multilayer 8 is suitably composed of (Tii- xAl _x N/ Tii-zSizN/ Cn- _y Al _y N/ Tii-zSizN..)m, m=15-1500, suitably m=30-800.

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 , Th - >Al _x N:Cri- _y Al _y N:Tii-zSizN, 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, Tii- _X AI _X N, the second nanolayer type 10, Cn- _y Al _y N, and the third nanolayer type 11 , Tii-zSizN, in the order Tii- _X AI _X NZ Cri- _y Al _y N/ Tii- _X AI _X N/ Tii- _z SizN. The nano-multilayer (8) is suitably composed of (Tii- _X AI _X N/ Cn- _y Al _y N/ Tii- _X AI _X N/ Tii-zSizN)n, n=15-1500, suitably n=30-800.

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 , Th - >Al _x N:Cri- _y Al _y N:Tii-zSizN, 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, Tii- _X AI _X N, the second nanolayer type 10, Cn- _y Al _y N, and the third nanolayer type 11 , Tii-zSizN, in the order Tii- _X AI _X N/ Cn- _y Al _y N/ Tii-zSizN/ Cn- _y Al _y N. The nano-multilayer 8 is suitably composed of (Tii- _X AI _X N/ Cn- _y Al _y N/ Tii-zSizN/ Cn- _y Al _y N) _P , p=15-1500, suitably p=30-800.

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 , Th - >Al _x N:Cri- _y Al _y N:Tii-zSizN, 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, Tii- _X AI _X N, the second nanolayer type 10, Cn- _y Al _y N, and the third nanolayer type 11 , Tii-zSizN, in the order Tii- _X AI _X N/ Cn- _y Al _y N/ Tii-zSizN. The nano-multilayer 8 is suitably composed of (Tii-xAlxN/ Cn- _y Al _y N/ Th-zSizN) _q , q=20-2000, suitably q=40-1000.

Examples

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 resputtering for different elements.

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.

Alternatively, the actual elemental composition in the different nanomultilayer 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.

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

For a (Ti,AI)N layer the actual percentage of Al out of Ti+AI will be about

1-2 at.% units below the Al content in the (Ti, Al) target.

For a (Cr,AI)N layer the actual percentage of Al out of Cr+AI will be about

2-3 at.% units below the Al content in the (Cr,AI) target.

For a (Ti, S i)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.

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.

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

Example 1 :

Coated cutting tools were provided comprising a nano-multilayer of Tio.4oAlo.6oN, Cr0.30AI0.70N and Ti0.80Si0.20N (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 Ti0.80Si0.20 were mounted in the evaporators in two of the flanges opposite each other. The remaining targets Cr0.30AI0.70 and Ti0.40AI0.60 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.

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

The chamber was pumped down to high vacuum (less than 10’ 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.

At first, an innermost layer of Ti0.40AI0.60N (based on target composition) was deposited by only using the Ti0.40AI0.60 target.

The chamber pressure (reaction pressure) was set to 4 Pa of N2 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 Ti0.40AI0.60N having a thickness of about 0.25 pm was deposited on the blanks.

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

The chamber pressure (reaction pressure) was set to 4 Pa of N2 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 pm was deposited on the blanks.

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 Ti0.40AI0.60N, Cr0.30AI0.70N and Ti0.80Si0.20N of about 2 nm. The number of nanolayers in the nano-multilayer is about 1400.

The nano-multilayer comprises a repeating sequence of consecutive nanolayers in the order Ti0.40AI0.60N/ Ti0.80Si0.20N/ Cr0.30AI0.70N/ Ti0.80Si0.20N.

In the nano-multilayer, the ratio of the sum of nanolayer thicknesses of each of the nanolayers Ti0.40AI0.60N, Cr0.30AI0.70N and Ti0.80Si0.20N, respectively, i.e., Tio.4oAlo.6oN: Cro.3oAlo.7oN:Tio.8oSio.2oN, 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.

The actual elemental relation in a (Ti,AI)N layer of the nano-multilayer deposited using Ti0.40AI0.60 targets was estimated to be Tio.42Alo.58N.

The actual elemental relation in a (Cr,AI)N layer of the nano-multilayer deposited using Cr0.30AI0.70 targets was estimated to be Cro.32Alo.68N.

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 Ti0.80Si0.20 targets was estimated to be Tio.83Sio.17N.

The coated cutting tools were called "Sample 1 (invention)".

Example 2:

Coated cutting tools were provided comprising a nano-multilayer of Ti0.50AI0.50N, Cr0.30AI0.70N and Tio.85Sio.15N (based on target compositions) nanolayers deposited on sintered cemented carbide cutting tool insert blanks of the geometries CNMG120408MM and R390-11 T308M-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 Ti0.50AI0.50 were mounted in the evaporators in two of the flanges opposite each other. The remaining targets Cr0.30AI0.70 and Tio.85Sio.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.

The uncoated blanks were mounted on pins that undergo a three-fold rotation in the PVD chamber. The chamber was pumped down to high vacuum (less than 10’ 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.

At first, an innermost layer of Ti0.50AI0.50N (based on target composition) was deposited by only using the Ti0.50AI0.50 targets.

The chamber pressure (reaction pressure) was set to 4 Pa of N2 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 Ti0.50AI0.50N having a thickness of about 1 .4 pm was deposited on the blanks.

Then, the nano-multilayer was deposited by alternating the use of the Cr0.30AI0.70 and Tio.85Sio.15 targets, creating a first sequence of a Cr0.30AI0.70N/ Tio.85Sio.15N nano-multilayer of about 35 nm thickness. The table rotational speed was 5 rpm. Then only the Ti0.50AI0.50 targets were used creating a Ti0.50AI0.50N layer of about 35 nm thickness. This procedure was repeated until 20 sequences of a nano-multilayer sequence of nanolayers Cr0.30AI0.70N and Tio.85Sio.15N combined with a "monolayer" of Ti0.50AI0.50N was completed. The total thickness of the deposited nano-multilayer was about 1.4 pm.

The chamber pressure (reaction pressure) was set to 4 Pa of N2 gas, and a DC bias voltage of -40 V (relative to the chamber walls) was applied to the blank assembly when using the Cr0.30AI0.70 and Tio.85Sio.15 targets and a DC bias voltage of -80 V (relative to the chamber walls) when using the Ti0.50AI0.50 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 pm was deposited on the blanks.

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 Cr0.30AI0.70N and Tio.85Sio.15N of about 2 nm.

Finally, an outermost layer of Tio.85Sio.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 Tio.ssSio.is 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 Tio.85Sio.15N was deposited to a thickness of about 0.2 pm.

The actual elemental relation in a (Ti,AI)N layer deposited using Ti0.50AI0.50 targets was estimated to be Tio.52Alo.48N.

The actual elemental relation in a (Cr,AI)N layer deposited using Cr0.30AI0.70 targets was estimated to be Cro.32Alo.68N.

The actual elemental relation in a (Ti,Si)N layer deposited using Tio.85Sio.15 targets was estimated to be Tio.87Sio.13N.

The coated cutting tools were called "Sample 2 (comparative)".

Example 3:

Coated cutting tools were provided comprising a nano-multilayer of Ti0.50AI0.50N, Cr0.30AI0.70N and Ti0.80Si0.20N (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 Ti0.50AI0.50 were mounted in the evaporators in two of the flanges opposite each other. The remaining targets Cr0.30AI0.70 and Ti0.80Si0.20 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.

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

The chamber was pumped down to high vacuum (less than 10’ 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. At first, an innermost layer of Ti0.50AI0.50N (based on target composition) was deposited by only using the Ti0.50AI0.50 targets.

The chamber pressure (reaction pressure) was set to 4 Pa of N2 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 Ti0.50AI0.50N having a thickness of about 1 .4 pm was deposited on the blanks.

Then, the nano-multilayer was deposited by alternating the use of the Cr0.30AI0.70 and Ti0.80Si0.20 targets, creating a first sequence of a Cr0.30AI0.70N/ Ti0.80Si0.20N nano-multilayer of about 35 nm thickness. The table rotational speed was 5 rpm. Then only the Ti0.50AI0.50 targets were used creating a Ti0.50AI0.50N layer of about 35 nm thickness. This procedure was repeated until 20 sequences of a nano-multilayer sequence of nanolayers Cr0.30AI0.70N and Ti0.80Si0.20N combined with a "monolayer" of Ti0.50AI0.50N was completed. The total thickness of the deposited nano-multilayer was about 1.4 pm.

The chamber pressure (reaction pressure) was set to 4 Pa of N2 gas, and a DC bias voltage of -40 V (relative to the chamber walls) was applied to the blank assembly when using the Cr0.30AI0.70 and Ti0.80Si0.20 targets and a DC bias voltage of -80 V (relative to the chamber walls) when using the Ti0.50AI0.50 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 pm was deposited on the blanks.

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 Cr0.30AI0.70N and Ti0.80Si0.20N of about 2 nm.

Finally, an outermost layer of Ti0.80Si0.20N (based on target composition), in order to obtain an even colour between the individual coated cutting tools made, was deposited by only using the Ti0.80Si0.20 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 Ti0.80Si0.20N was deposited to a thickness of about 0.2 pm.

The actual elemental relation in a (Ti,AI)N layer deposited using Tio.5oAlo.5o targets was estimated to be Tio.52Alo.48N.

The actual elemental relation in a (Cr,AI)N layer deposited using Cr0.30AI0.70 targets was estimated to be Cro.32Alo.68N.

The actual elemental relation in a (Ti,Si)N layer deposited using Ti0.80Si0.20 targets was estimated to be Tio.83Sio.17N.

The coated cutting tools were called "Sample 3 (comparative)".

Example 4:

Coated cutting tools were provided comprising a nano-multilayer of Ti0.40AI0.60N, Cr0.30AI0.70N and Ti0.80Si0.20N (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 Ti0.40AI0.60 were mounted in the evaporators in two of the flanges opposite each other. The remaining targets Cr0.30AI0.70 and Ti0.80Si0.20 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.

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

The chamber was pumped down to high vacuum (less than 10’ 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. At first, an innermost layer of Ti0.40AI0.60N (based on target composition) was deposited by only using the Ti0.40AI0.60 targets.

The chamber pressure (reaction pressure) was set to 4 Pa of N2 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 Ti0.40AI0.60N having a thickness of about 1 pm was deposited on the blanks.

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

The chamber pressure (reaction pressure) was set to 4 Pa of N2 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 pm was deposited on the blanks.

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 Ti0.40AI0.60N, Cr0.30AI0.70N and Ti0.80Si0.20N of about 2 nm. The number of nanolayers in the nano-multilayer is about 1000.

The nano-multilayer comprises a repeating sequence of consecutive nanolayers in the order Ti0.40AI0.60N/ Cr0.30AI0.70N/ Ti0.40AI0.60N/ Ti0.80Si0.20N.

In the nano-multilayer, the ratio of the sum of nanolayer thicknesses of each of the nanolayers Ti0.40AI0.50N, Cr0.30AI0.70N and Ti0.80Si0.20N, respectively, i.e., Ti0.40AI0.60N: Cro.3oAlo.7oN:Tio.8oSio.2oN, 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.

The actual elemental relation in a (Ti,AI)N layer of the nano-multilayer deposited using Ti0.40AI0.60 targets was estimated to be Tio.42Alo.58N.

The actual elemental relation in a (Cr,AI)N layer of the nano-multilayer deposited using Cr0.30AI0.70 targets was estimated to be Cro.32Alo.68N.

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 Ti0.80Si0.20 targets was estimated to be Tio.83Sio.17N.

The coated cutting tools were called "Sample 4 (invention)".

The samples 1-4 made are listed in Table 1.

Table 1 .

* all elemental compositions based on target composition ** about 35 nm TiAIN

*** about 35 nm nano-multilayer of CrAIN/ TiSiN

Table 2 further summarises the samples 1-4. Table 2. all elemental compositions based on target composition

Example 5:

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

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 pm thick Tio.4oAlo.6oN 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 Ti0.40AI0.60N coating (based on target composition). The reference coated cutting tools were made by depositing a layer of Ti0.40AI0.60N 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 Tio.4oAlo.6o were mounted in the evaporators in four flanges. The chamber pressure (reaction pressure) was set to 4 Pa of N2 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 Ti0.40AI0.60N having a thickness of about 3 pm was deposited on the blanks.

Explanations to terms used:

The following expressions/terms are commonly used in metal cutting, but nevertheless explained in the table below:

Vc (m/min): cutting speed in meters per minute fz (mm/tooth): feed rate in millimeter per tooth (in milling) fn (mm/rev) feed rate per revolution (in turning) z: (number) number of teeth in the cutter a _e (mm): radial depth of cut in millimeter a _P (mm): axial depth of cut in millimeter

Flank wear test:

Longitudinal turning

Work piece material: Sverker 21 (tool steel), Hardness ~210HB, D=180, L=700 mm,

V _c =125 m/min fn=0.072 mm/rev a _P =2 mm without cutting fluid

The cut-off criteria for tool life is a flank wear VB of 0.15 mm. Comb crack resistance:

Operation: Shoulder milling

Tool holder: C5-391 .20-25 080

Work piece material: Toolox 33 (tool steel), L=600 mm, l=200 mm, h=100 mm,

Insert type: R390-11T308M-PM

Cutting speed V _c =250 m/min

Feed rate f _z =0.2 mm/rev

Depth of cut a _P =3 mm

Radial engagement a _e = 12.5 mm with cutting fluid

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

The results are presented in Table 3.

Table 3.

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:

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

Furthermore, to be used as a reference, coated cutting tools were made by depositing a layer of Ti0.40AI0.60N (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 Ti0.40AI0.60 were mounted in the evaporators in four flanges. The chamber pressure (reaction pressure) was set to 4 Pa of N2 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 Ti0.40AI0.60N having a thickness of about 3 pm was deposited on the blanks.

The coated cutting tools were called "Sample 5 (reference)".

Flank wear test:

Dry shoulder milling Work piece material: C45 (P1 steel), Hardness 200 HB, Size: 600x220x50 mm Work piece material: 42CrMo4 (P2 steel), Hardness 302-305 HB, Size: 600x200x50 mm V _c =235 m/min fz=0.055 (mm/tooth) a _P =5 mm a _e =1 .2 mm z= 4 teeth

L=220 mm (C45, P1 steel), 200 mm (42CrMo4, P2 steel) without cutting fluid

The predetermined number of cutting passes is 400, or Vb3>0.1 mm.

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

Table 4.

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

Table 5. 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:

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

Coated cutting tools were provided comprising a nano-multilayer of Tio.4oAlo.6oN, Cr0.30AI0.70N and Ti0.80Si0.20N (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 Ti0.40AI0.60 were mounted in the evaporators in two of the flanges opposite each other. The remaining targets Cr0.30AI0.70 and Ti0.80Si0.20 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.

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

The chamber was pumped down to high vacuum (less than 10’ 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.

At first, an innermost layer of Ti0.40AI0.60N (based on target composition) was deposited by only using the Ti0.40AI0.60 targets.

The chamber pressure (reaction pressure) was set to 4 Pa of N2 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 Ti0.40AI0.60N having a thickness of about 0.8 pm was deposited on the blanks.

Then, the nano-multilayer was deposited by using all mounted targets. The chamber pressure (reaction pressure) was set to 4 Pa of N2 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)".

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)".

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)".

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

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 Ti0.40AI0.60N, Cr0.30AI0.70N and Ti0.80Si0.20N of about 2 nm. The number of nanolayers in the nano-multilayer is about 1000.

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 Ti0.40AI0.60N, Cr0.30AI0.70N and Ti0.80Si0.20N of about 4 nm. The number of nanolayers in the nano-multilayer is about 500.

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 Ti0.40AI0.60N, Cr0.30AI0.70N and Ti0.80Si0.20N of about 6 nm. The number of nanolayers in the nano-multilayer is about 330.

The nano-multilayers of Samples 5 to 7 all comprise a repeating sequence of consecutive nanolayers in the order Ti0.40AI0.60N/ Cr0.30AI0.70N/ Ti0.40AI0.60N/ Ti0.80Si0.20N.

In the nano-multilayers, the ratio of the sum of nanolayer thicknesses of each of the nanolayers Ti0.40AI0.50N, Cr0.30AI0.70N and Ti0.80Si0.20N, respectively, i.e., Ti0.40AI0.60N: Cro.3oAlo.7oN:Tio.8oSio.2oN, 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.

The actual elemental relation in a (Ti,AI)N layer of the nano-multilayer deposited using Ti0.40AI0.60 targets was estimated to be Tio.42Alo.58N.

The actual elemental relation in a (Cr,AI)N layer of the nano-multilayer deposited using Cr0.30AI0.70 targets was estimated to be Cro.32Alo.68N. 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 Ti0.80Si0.20 targets was estimated to be Tio.83Sio.17N.

Example 8:

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

Coated cutting tools were provided comprising a nano-multilayer of Ti0.40AI0.60N, Cr0.30AI0.70N and Ti0.80Si0.20N (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 Ti0.40AI0.60 were mounted in the evaporators in two of the flanges opposite each other. The remaining targets Cr0.30AI0.70 and Ti0.80Si0.20 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.

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

The chamber was pumped down to high vacuum (less than 10’ 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.

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

The chamber pressure (reaction pressure) was set to 4 Pa of N2 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. A nano-multilayer coating having a thickness of about 3 pm was deposited on the blanks.

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 Ti0.40AI0.60N, Cr0.30AI0.70N and Ti0.80Si0.20N of about 2 nm. The number of nanolayers in the nano-multilayer is about 1000.

The nano-multilayer comprises a repeating sequence of consecutive nanolayers in the order Ti0.40AI0.60N/ Cr0.30AI0.70N/ Ti0.40AI0.60N/ Ti0.80Si0.20N.

In the nano-multilayer, the ratio of the sum of nanolayer thicknesses of each of the nanolayers Ti0.40AI0.50N, Cr0.30AI0.70N and Ti0.80Si0.20N, respectively, i.e., Ti0.40AI0.60N: Cro.3oAlo.7oN:Tio.8oSio.2oN, 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.

The actual elemental relation in a (Ti,AI)N layer of the nano-multilayer deposited using Ti0.40AI0.60 targets was estimated to be Tio.42Alo.58N.

The actual elemental relation in a (Cr,AI)N layer of the nano-multilayer deposited using Cr0.30AI0.70 targets was estimated to be Cro.32Alo.68N.

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 Ti0.80Si0.20 targets was estimated to be Tio.83Sio.17N.

The coated cutting tools were called "Sample 8 (invention)".

Table 6 summarises the samples 5-8.

Table 6. all elemental compositions based on target composition Example 9:

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

A cutting insert having an about 3 pm thick Ti0.40AI0.60N reference coating which was included in all test runs. The reference coated cutting tools were made by depositing a layer of Ti0.40AI0.60N 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 R390-11 T308M-PM. The cemented carbide also being the same, i.e., 10 wt% Co, 0.4 wt% Cr and rest WC. Targets of Ti0.40AI0.60 were mounted in the evaporators in four flanges. The chamber pressure (reaction pressure) was set to 4 Pa of N2 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 Tio.4oAlo.6oN having a thickness of about 3 pm was deposited on the blanks.

Flank wear test:

Longitudinal turning

Work piece material: Sverker 21 (tool steel), Hardness ~210HB, D=180, L=700 mm,

V _c =125 m/min fn=0.072 mm/rev a _P =2 mm without cutting fluid

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

Comb crack resistance:

Operation: Shoulder milling

Tool holder: C5-391 .20-25 080

Work piece material: Toolox 33 (tool steel), L=600 mm, l=200 mm, h=100 mm, Insert type: R390-11T308M-PM

Cutting speed V _c =250 m/min

Feed rate f _z =0.2 mm/rev

Depth of cut a _P =3 mm

Radial engagement a _e = 12.5 mm with cutting fluid

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

The results are presented in Table 7. Table 7.

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,AI)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.