METHOD OF PRODUCING A COATED CUTTING TOOL AND A COATED CUTTING TOOL

Abstract

A method for producing a coated cutting tool for metal machining having a substrate and coating is provided. The coating includes at least one layer of (Ti,Al)N having a cubic crystal phase. The method includes the deposition of a layer of Ti.sub.1-xAl.sub.xN, 0.70≤x≤0.98, the Ti.sub.1-xAl.sub.xN having cubic crystal phase. The layer of Ti.sub.1-xAl.sub.xN is deposited by cathodic arc evaporation at a vacuum chamber pressure of from 7 to 15 Pa of N.sub.2 gas, using a DC bias voltage of from −200 to −400 V and using an arc discharge current of from 75 to 250 A. A coated cutting tool for metal machining having a coating including a (Ti,Al)N multi-layer of alternating sub-layers of at least Ti.sub.1-yAl.sub.yN and Ti.sub.1-zAl.sub.zN, 0.35≤y≤0.65 and 0.80≤z≤0.98, with only cubic phase present is also provided.

Claims

1. A method for producing a coated cutting tool for metal machining having a substrate and coating, the coating including at least one layer of (Ti,Al)N having a cubic crystal phase, the method comprises deposition of a layer of Ti.sub.1-xAl.sub.xN, 0.70≤x≤0.98, the Ti.sub.1-xAl.sub.xN layer having a cubic crystal phase, the layer of Ti.sub.1-xAl.sub.xN being deposited by cathodic arc evaporation at a vacuum chamber pressure of from 7 to 15 Pa of N.sub.2 gas, using a DC bias voltage of from −200 to −400 V and using an arc discharge current of from 75 to 250 A.

2. The method according to claim 1, wherein the layer of Ti.sub.1-xAl.sub.xN is deposited at a vacuum chamber pressure of from 8 to 12 Pa of N.sub.2 gas.

3. The method according to claim 1, wherein the layer of Ti.sub.1-xAl.sub.xN is deposited using a DC bias voltage of from −250 to −350 V.

4. The method according to claim 1, wherein the layer of Ti.sub.1-xAl.sub.xN is a single-layer comprising a cubic crystal structure, 0.70≤x≤0.85.

5. The method according to claim 1, wherein the Ti.sub.1-xAl.sub.xN (Ti,Al)N layer is a sub-layer of a multi-layer, the Ti.sub.1-xAl.sub.xN sub-layer being present in a repeated manner with sub-layers of at least one further (Ti,Al)N.

6. The method according to claim 5, wherein the (Ti,Al)N multi-layer is a multi-layer of alternating sub-layers of at least Ti.sub.1-yAl.sub.yN and Ti.sub.1-zAl.sub.zN, 0.35≤y≤0.65 and 0.80≤z≤0.98, with only cubic phase present.

7. The method according to claim 6, wherein an average thickness of each (Ti,Al)N sub-layer is from 1 to 20 nm.

8. A coated cutting tool for metal machining having a coating comprising a (Ti,Al)N multi-layer of alternating sub-layers of at least Ti.sub.1-yAl.sub.yN and Ti.sub.1-zAl.sub.zN, 0.35≤y≤0.65 and 0.80≤z≤0.98, with only cubic phase present, average individual (Ti,Al)N sub-layer thicknesses being from 1 to 20 nm.

9. The coated cutting tool according to claim 8, wherein 0.40≤y≤0.6 and 0.85≤z≤0.96.

10. The coated cutting tool according to claim 8, wherein the average individual sub-layer thicknesses are from 1.5 to 5 nm.

11. The coated cutting tool according to claim 8, wherein the total thickness of the (Ti,Al)N multilayer is from 0.5 to 10 m.

12. The coated cutting tool according to claim 8, wherein the (Ti,Al)N multi-layer is a cathodic arc evaporation deposited multi-layer.

13. The coated cutting tool according to claim 8, 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.

14. The coated cutting tool according to claim 8, wherein the coated cutting tool is a cutting tool insert, a drill, or a solid end-mill, for metal machining.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] FIG. 1 shows a schematic illustration of a substrate (100) with a coating (101) according to the invention.

[0045] FIG. 2 shows X-ray diffractograms of samples from deposition of a (Ti,Al)N layers at different bias voltages and/or pressure.

[0046] FIG. 3 shows X-ray diffractograms of (Ti,Al)N single-layers with different Al contents deposited with a conventional method.

[0047] FIG. 4 shows X-ray diffractograms of (Ti,Al)N single-layers with different Al contents deposited with the method of the invention.

[0048] FIG. 5 shows X-ray diffractograms of (Ti,Al)N multi-layers with different Al contents deposited with a conventional method.

[0049] FIG. 6 shows X-ray diffractograms of (Ti,Al)N multi-layers with different Al contents deposited with the method of the invention.

[0050] FIG. 7 shows X-ray diffractograms of Ti.sub.0.10Al.sub.0.90N/Ti.sub.0.50Al.sub.0.50N and Ti.sub.0.05Al.sub.0.95N/Ti.sub.0.50Al.sub.0.50N multi-layers.

EXAMPLES

Example 1

[0051] Different coatings of Ti.sub.0.20Al.sub.0.80N were deposited by cathodic arc evaporation on sintered cemented carbide cutting tool insert blanks SNMA120808-KR. The cemented carbide had a composition of 10 wt % Co and rest WC. The samples 1-4 were deposited in three-fold rotation using a rotating table with “trees” of pins on which blanks were mounted. The reaction chamber comprised four flanges for targets. Ti.sub.0.20Al.sub.0.80 targets were mounted on two opposing flanges with the two remaining flanges being empty. The chamber was pumped down to vacuum (less than 10.sup.−2 Pa) and heated to about 450° C. by heaters located inside the chamber. The blanks were etched for 60 minutes in an Ar plasma. The chamber pressure (reaction pressure) was set to 4 Pa, or set to 10 Pa, of N.sub.2 gas and a desired DC bias voltage which for the samples 1-4 were −50 V, −225 V, −300 V and −375 V, respectively, see Table 1. The cathodes were run in an arc discharge mode at a current of 150 A (each). A 3 μm layer was deposited.

TABLE-US-00001 TABLE 1 Bias voltage N2 pressure Sample (V) (Pa) 1 −50 4 2 −225 10 3 −300 10 4 −375 10

[0052] X-ray diffraction (XRD) analysis was conducted on the flank face of the coated inserts using a PANalytical CubiX3 diffractometer equipped with a PIXcel detector. The coated cutting tool inserts were mounted in sample holders that ensure that the flank face of the samples were parallel to the reference surface of the sample holder and also that the flank face was at appropriate height. Cu-K.sub.α radiation was used for the measurements, with a voltage of 45 kV and a current of 40 mA. Anti-scatter slit of ½ degree and divergence slit of ¼ degree were used. The diffracted intensity from the coated cutting tool was measured around 20 angles where relevant peaks occur.

[0053] FIG. 2 shows the diffractograms of the samples 1-4.

[0054] It is concluded that substantially no hexagonal signals are seen for the samples made using 10 Pa nitrogen pressure and substrate bias voltage of −300 V and −225 V. Sample 1 using conventional parameters showed no visible cubic signal in the diffractogram (for example a (2 0 0) reflection). Sample 4 showed a cubic (2 0 0) reflection but also a significant hexagonal (1 1-2 0) reflection.

Example 2

[0055] Different coatings of Ti.sub.0.10-0.40Al.sub.0.60-0.90N were made by using three different targets, Ti.sub.0.40Al.sub.0.60, Ti.sub.0.25Al.sub.0.75 and Ti.sub.0.10Al.sub.0.90, positioned as a set of three targets at different heights on all four flanges in the reaction chamber. Thereby the composition of the coatings differed in a gradual manner depending on the position of the blanks in the chamber.

[0056] A first set of samples were made by depositing a (Ti,Al)N layer on cutting tool insert cemented carbide blanks of the geometry SNMA120808-KR of the same composition as in Example 1 and by using the deposition procedure as described in Example 1 using a DC bias voltage of −50 V and a nitrogen pressure of 4 Pa. The blanks were first etched for 60 minutes in an Ar plasma. The thickness of the coating was about 3 μm.

[0057] A second set of samples were made by depositing a (Ti,Al)N layer on cutting tool insert cemented carbide blanks using the deposition procedure as described in Example 1 using a DC bias voltage of −300 V and a nitrogen pressure of 10 Pa. The blanks were first etched for 60 minutes in an Ar plasma. The thickness of the coating was about 3 μm.

[0058] Samples from 14 different levels in the reaction chamber were analysed by XRD. The Al content (out of Ti+Al) in the coatings were also analysed by EDS. See Table 2 showing samples 5-18 from depositions at DC bias voltage of −50 V and a nitrogen pressure of 4 Pa and Table 3 showing samples 19-32 from depositions at DC bias voltage of −300 V and a nitrogen pressure of 10 Pa. Not all samples were analysed for the second set of samples (see Table 3) but the gradual increase in Al content for the different samples is apparent.

TABLE-US-00002 TABLE 2 Sample Ti.sub.1-xAl.sub.xN x 5 Ti.sub.1-xAl.sub.xN 0.61 6 Ti.sub.1-xAl.sub.xN 0.63 7 Ti.sub.1-xAl.sub.xN 0.64 8 Ti.sub.1-xAl.sub.xN 0.66 9 Ti.sub.1-xAl.sub.xN 0.67 10 Ti.sub.1-xAl.sub.xN 0.69 11 Ti.sub.1-xAl.sub.xN 0.70 12 Ti.sub.1-xAl.sub.xN 0.76 13 Ti.sub.1-xAl.sub.xN 0.78 14 Ti.sub.1-xAl.sub.xN 0.83 15 Ti.sub.1-xAl.sub.xN 0.82 16 Ti.sub.1-xAl.sub.xN 0.84 17 Ti.sub.1-xAl.sub.xN 0.86 18 Ti.sub.1-xAl.sub.xN 0.85

TABLE-US-00003 TABLE 3 Sample x 19 Ti.sub.1-xAl.sub.xN 0.60 20 Ti.sub.1-xAl.sub.xN —* 21 Ti.sub.1-xAl.sub.xN 0.63 22 Ti.sub.1-xAl.sub.xN —* 23 Ti.sub.1-xAl.sub.xN 0.67 24 Ti.sub.1-xAl.sub.xN —* 25 Ti.sub.1-xAl.sub.xN 0.72 26 Ti.sub.1-xAl.sub.xN 0.74 27 Ti.sub.1-xAl.sub.xN —* 28 Ti.sub.1-xAl.sub.xN 0.78 29 Ti.sub.1-xAl.sub.xN —* 30 Ti.sub.1-xAl.sub.xN 0.81 31 Ti.sub.1-xAl.sub.xN —* 32 Ti.sub.1-xAl.sub.xN 0.87 *not analysed

[0059] FIG. 3 shows X-ray diffractograms of (Ti,Al)N the single-layers of samples 5-18 with different Al contents deposited with a conventional method.

[0060] FIG. 4 shows X-ray diffractograms of (Ti,Al)N single-layers of samples 19-32 with different Al contents deposited with the method of the invention.

[0061] From FIG. 3 (coatings deposited using the conventional method) it is seen that the cubic (2 0 0) reflection is noticed up to a Al content (out of Ti+Al) of about 66 at. % and a clearly visible hexagonal reflection (0 0 0 2) is seen starting already at an Al content of about 63 at. % and visible hexagonal reflections (1 1-2 0) and (1 0-1 0) are seen starting at an Al content of about 76 at. %.

[0062] From FIG. 4 (coatings deposited using the method according to the invention) it is seen that the cubic (2 0 0) reflection is noticed up to a Al content (out of Ti+Al) of about 80 at. % and clearly visible hexagonal reflections (1 1-2 0) and (1 0-1 0) are seen only for Al contents starting at about 81 at. %.

[0063] It is concluded that the method according to the invention provides for cubic structure up to much higher Al contents than the conventional method.

Example 3

[0064] Different multi-layer coatings of Ti.sub.0.10-0.40Al.sub.0.60-0.90N/Ti.sub.0.50Al.sub.0.50N were made by using three different targets, Ti.sub.0.40Al.sub.0.60, Ti.sub.0.25Al.sub.0.75 and Ti.sub.0.10Al.sub.0.90, positioned as a set of three targets at different heights on two opposing flanges in the reaction chamber and Ti.sub.0.50Al.sub.0.50 targets positioned on the two remaining opposing flanges. Thereby the composition of one of the sub-layers in the multi-layered coating differed in a gradual manner depending on the position of the blanks in the chamber.

[0065] A first set of samples were made by depositing a multi-layer on cutting tool insert cemented carbide blanks of the geometry SNMA120808-KR of the same composition as in Example 1 and by using the deposition procedure as described in Example 1 using a DC bias voltage of −50 V and a nitrogen pressure of 4 Pa. The blanks were etched for 60 minutes in an Ar plasma. A start layer of about 0.3 μm Ti.sub.0.50Al.sub.0.50N was first deposited on the cemented carbide substrate using DC bias voltage of −50 V and a nitrogen pressure of 4 Pa. The thickness of the coating was about 3 μm. An aperiodic multi-layer was provided. The average sub-layer thickness for the two different types of sub-layers was each about 2 nm.

[0066] A second set of samples were made by depositing a multi-layer on cutting tool insert cemented carbide blanks using the deposition procedure as described in Example 1 using a DC bias voltage of −300 V and a nitrogen pressure of 10 Pa. The blanks were etched for 60 minutes in an Ar plasma. A start layer of about 0.3 μm Ti.sub.0.50Al.sub.0.50N was first deposited on the cemented carbide substrate using DC bias voltage of −50 V and a nitrogen pressure of 4 Pa. The thickness of the coating was about 3 μm. An aperiodic multi-layer was provided. The average sub-layer thickness for the two different types of sub-layers was each about 1.5 nm.

[0067] Samples from 17 different levels in the reaction chamber were analysed by XRD. The Al content (out of Ti+Al) in the coatings were also analysed by EDS. From each EDS result the sub-layer composition for the sub-layer Ti.sub.1-xAl.sub.xN other than Ti.sub.0.50Al.sub.0.50N was estimated from target composition and assuming equal sub-layer thicknesses of Ti.sub.1-xAl.sub.xN and Ti.sub.0.50Al.sub.0.50N.

[0068] See Table 4 showing samples 33-49 from depositions at DC bias voltage of −50 V and a nitrogen pressure of 4 Pa and Table 5 showing samples 50-66 from depositions at DC bias voltage of −300 V and a nitrogen pressure of 10 Pa. As seen in the tables not all samples were analysed but the gradual increase in Al content for the different samples is apparent.

TABLE-US-00004 TABLE 4 Al content from Sample EDS in whole Ti.sub.0.50Al.sub.0.50N/ (Ti, Al)N Ti.sub.1-xAl.sub.xN multilayer x 33 Ti.sub.1-xAl.sub.xN 0.543 0.59 34 Ti.sub.1-xAl.sub.xN 0.547 0.59 35 Ti.sub.1-xAl.sub.xN 0.555 0.61 36 Ti.sub.1-xAl.sub.xN 0.564 0.63 37 Ti.sub.1-xAl.sub.xN 0.575 0.65 38 Ti.sub.1-xAl.sub.xN 0.572 0.64 39 Ti.sub.1-xAl.sub.xN 0.588 0.68 40 Ti.sub.1-xAl.sub.xN —* —* 41 Ti.sub.1-xAl.sub.xN 0.598 0.70 42 Ti.sub.1-xAl.sub.xN —* —* 43 Ti.sub.1-xAl.sub.xN 0.635 0.77 44 Ti.sub.1-xAl.sub.xN 0.642 0.78 45 Ti.sub.1-xAl.sub.xN 0.658 0.82 46 Ti.sub.1-xAl.sub.xN 0.666 0.83 47 Ti.sub.1-xAl.sub.xN 0.673 0.85 48 Ti.sub.1-xAl.sub.xN 0.683 0.87 49 Ti.sub.1-xAl.sub.xN 0.686 0.87 *not analysed

TABLE-US-00005 TABLE 5 Al content from Sample EDS in whole Ti.sub.0.50Al.sub.0.50N/ (Ti, Al)N Ti.sub.1-xAl.sub.xN multilayer x 50 Ti.sub.1-xAl.sub.xN 0.506 0.51 51 Ti.sub.1-xAl.sub.xN —* —* 52 Ti.sub.1-xAl.sub.xN 0.516 0.53 53 Ti.sub.1-xAl.sub.xN —* —* 54 Ti.sub.1-xAl.sub.xN 0.552 0.60 55 Ti.sub.1-xAl.sub.xN —* —* 56 Ti.sub.1-xAl.sub.xN 0.588 0.68 57 Ti.sub.1-xAl.sub.xN —* —* 58 Ti.sub.1-xAl.sub.xN 0.615 0.73 59 Ti.sub.1-xAl.sub.xN —* —* 60 Ti.sub.1-xAl.sub.xN 0.614 0.73 61 Ti.sub.1-xAl.sub.xN —* —* 62 Ti.sub.1-xAl.sub.xN 0.648 0.80 63 Ti.sub.1-xAl.sub.xN —* —* 64 Ti.sub.1-xAl.sub.xN 0.672 0.84 65 Ti.sub.1-xAl.sub.xN —* —* 66 Ti.sub.1-xAl.sub.xN 0.683 0.87 *not analysed

[0069] FIG. 5 shows X-ray diffractograms of samples 33-49 of the whole (Ti,Al)N multi-layers with all sub-layers deposited with a conventional method.

[0070] FIG. 6 shows X-ray diffractograms of samples 50-66 of the whole (Ti,Al)N multi-layers with all sub-layers deposited with the method of the invention.

[0071] From FIG. 5 (multi-layer coatings deposited using the conventional method) it is seen that clearly visible hexagonal reflection (0 0 0 2) is seen starting at an Al content (out of Ti+Al) in one of the sub-layers being about 77 at. %.

[0072] From FIG. 6 (multi-layer coatings deposited using the method according to the invention) no hexagonal reflection is seen at all even at an Al content (out of Ti+Al) in one of the sub-layers being about 87 at. %.

[0073] It is concluded that the method according to the invention provides for a single phase cubic structure up to much higher Al contents than the conventional method. Also, a single phase cubic structure is provided in a multi-layer according to the invention having an Al content (out of Ti+Al) in one sub-layer of at least 87 at. %.

Example 4

[0074] Further samples of a multi-layer coating of Ti.sub.0.10Al.sub.0.90N/Ti.sub.0.50Al.sub.0.50N and Ti.sub.0.05Al.sub.0.95N/Ti.sub.0.50Al.sub.0.50N were made by using Ti.sub.0.10Al.sub.0.90 targets (resp. Ti.sub.0.05Al.sub.0.95 targets) positioned on two opposing flanges in the reaction chamber and Ti.sub.0.50Al.sub.0.50 targets positioned on the two remaining opposing flanges.

[0075] A set of samples (“Sample 67 and 68”) were made by depositing a multi-layer of alternating sub-layers of Ti.sub.0.10Al.sub.0.90N/Ti.sub.0.50Al.sub.0.50N and Ti.sub.0.05Al.sub.0.95N/Ti.sub.0.50Al.sub.0.50N, respectively, on cutting tool insert cemented carbide blanks of the turning insert geometry CNMG120804-MM (Sample 67a and 68a) and the milling insert geometry R390-11T308M-PM (Sample 67b and 68b). The cemented carbide being of the same composition as in Example 1 and by using the deposition procedure as described in Example 1 using a DC bias voltage of −50 V and a nitrogen pressure of 4 Pa. The blanks were etched for 60 minutes in an Ar plasma. A start layer of about 0.3 μm Ti.sub.0.50Al.sub.0.50N was first deposited on the cemented carbide substrate using DC bias voltage of −50 V and a nitrogen pressure of 4 Pa. The thickness of the coating was about 3 μm. An aperiodic multi-layer was provided. The average sub-layer thickness for the two different types of sub-layers in the respective sample was each about 2 nm.

[0076] A set of samples (“Sample 69 and 70”) were then made by depositing a multi-layer of alternating sub-layers of Ti.sub.0.10Al.sub.0.90N/Ti.sub.0.50Al.sub.0.50N and Ti.sub.0.05Al.sub.0.95N/Ti.sub.0.50Al.sub.0.50N, respectively, on cutting tool insert cemented carbide blanks of the turning insert geometry CNMG120804-MM (Sample 69a and 70a) and the milling insert geometry R390-11T308M-PM (Sample 69b and 70b). The cemented carbide being of the same composition as in Example 1 and by using the deposition procedure as described in Example 1 using a DC bias voltage of −300 V and a nitrogen pressure of 10 Pa. The blanks were etched for 60 minutes in an Ar plasma. A start layer of about 0.3 μm Ti.sub.0.50Al.sub.0.50N was first deposited on the cemented carbide substrate using DC bias voltage of −50 V and a nitrogen pressure of 4 Pa. The thickness of the coating was about 3 μm. An aperiodic multi-layer was provided. The average sub-layer thickness for the two different types of sub-layers in the respective sample was each about 1.5 nm. There was no analysis made on the actual composition of multi-layers but the composition of the multi-layers were estimated to be very similar to the target composition, i.e., Ti.sub.0.10Al.sub.0.90N/Ti.sub.0.50Al.sub.0.50N and Ti.sub.0.05Al.sub.0.95N/Ti.sub.0.50Al.sub.0.50N. A few percentage difference may be present.

[0077] FIG. 7 shows X-ray diffractograms of the whole Ti.sub.0.10Al.sub.0.90N/Ti.sub.0.50Al.sub.0.50N and Ti.sub.0.05Al.sub.0.95N/Ti.sub.0.50Al.sub.0.50N multi-layers of Sample 67a and 68a made with a conventional method and Sample 69a and 70a made with the method according to the invention.

[0078] From FIG. 7 it is concluded that a sample having a multi-layer coating deposited using the conventional method has a clearly visible hexagonal (0 0 0 2) reflection in the diffractogram. The sample having a multi-layer coating deposited using the method according to the invention shows no hexagonal reflections. It is concluded that the method according to the invention provides for a single phase cubic structure up to much higher Al contents than the conventional method.

[0079] Also, a single phase cubic structure is provided in a multi-layer according to the invention having an Al content (out of Ti+Al) in one sub-layer of at least about 95 at. %.

Explanations to Terms Used in Examples 5-7

[0080] The following expressions/terms are commonly used in metal cutting, but nevertheless explained in the table below:

V.sub.c (m/min): cutting speed in meters per minute
f.sub.n (mm/rev) feed rate per revolution (in turning)
a.sub.p (mm): axial depth of cut in millimeter

Example 5

Flank Wear Test:

[0081] Longitudinal turning
Work piece material: Uddeholm Sverker 21 (tool steel), Hardness ˜210HB, D=180,

L=700 mm,

[0082] V.sub.c=125 m/min
f.sub.n=0.072 mm/rev
a.sub.p=2 mm
without cutting fluid

[0083] The cut-off criteria for tool life is a flank wear VB of 0.15 mm.

[0084] The coating of Sample 67a, Ti.sub.0.10Al.sub.0.90N/Ti.sub.0.50Al.sub.0.50N made by the conventional method, containing hexagonal phase was compared with the coating of Sample 69a, Ti.sub.0.10Al.sub.0.50N/Ti.sub.0.50Al.sub.0.50N made by the method according to the invention and being of single phase cubic structure.

Example 6

Crater Wear Test:

[0085] Longitudinal turning
Work piece material: Ovako 825B, ball bearing steel. Hot rolled and annealed,

Hardness ˜200HB, D=160, L=700 mm,

[0086] V.sub.c=160 m/min
f.sub.n=0.3 mm/rev
a.sub.p=2 mm
with cutting fluid

[0087] The criteria for end of tool life is a crater area of 0.8 mm.sup.2.

[0088] The coating of Sample 67a, Ti.sub.0.10Al.sub.0.50N/Ti.sub.0.50Al.sub.0.50N made by the conventional method, containing hexagonal phase was compared with the coating of Sample 69a, Ti.sub.0.10Al.sub.0.50N/Ti.sub.0.50Al.sub.0.50N made by the method according to the invention and being of single phase cubic structure.

Example 7

Thermal Crack Resistance (“Comb Crack” Resistance) Test:

Milling

[0089] Work piece material: Toolox33, PK158 600×200×100 mm, P2.5.Z.HT
z=1
V.sub.c=250 m/min
f.sub.z=0.20 mm
a.sub.e=12.5 mm
a.sub.p=3.0
with cutting fluid

[0090] The cut off criteria is reached when the cracks have resulted in chipping of the edge >0.30 mm. Tool life is presented as the number of cut entrances in order to achieve these criteria.

[0091] The coating of Sample 67b, Ti.sub.0.10Al.sub.0.50N/Ti.sub.0.50Al.sub.0.50N made by the conventional method, containing hexagonal phase was compared with the coating of Sample 69b, Ti.sub.0.10Al.sub.0.50N/Ti.sub.0.50Al.sub.0.50N made by the method according to the invention and being of single phase cubic structure.

[0092] The results from the testings in Examples 5-7 are seen in Table 6.

TABLE-US-00006 TABLE 6 Crater Comb Flank wear wear cracks Sample Coating (estimated from Tool life Tool life Tool life No. target composition) Comment (min) (min) (min) 67 Ti.sub.0.10Al.sub.0.90N/ comparative 5.5 3.6 30 Ti.sub.0.50Al.sub.0.50N 69 Ti.sub.0.10Al.sub.0.90N/ invention 8.0 4.6 40 Ti.sub.0.50Al.sub.0.50N

[0093] It is concluded that the sample according to the invention has better resistance to flank wear, crater wear and comb cracks than the comparative sample.