COATED CUTTING TOOL

Abstract

Coated cutting tool comprising: a substrate and a coating comprising a refractory layer deposited by physical vapor deposition and adhered to the substrate, wherein the refractory layer comprises a plurality of sublayer groups, wherein one sublayer group comprises a titanium aluminum nitride sublayer and an adjacent composite sublayer comprising alternating nanolayers of titanium silicon nitride and titanium aluminum nitride, and wherein the titanium aluminum nitride sublayer has the formula Ti 1-x Al x N, where 0.72 ≤ x ≤ 0.9.

Description

FIELD OF THE INVENTION

[0001] The present invention relates to multilayer nitride hard coatings and, more particularly, to multilayer nitride hard coatings deposited by physical vapor deposition comprising alternating nanolayers comprising titanium aluminum nitride and titanium silicon nitride. BACKGROUND

[0002] Often, one or more layers of refractory material are deposited onto cutting tool surfaces using physical vapor deposition (PVD) techniques to enhance properties including abrasion resistance, performance, and cutting tool life. Titanium nitride (TiN) coatings, for example, are commonly applied to cemented carbide cutting tool substrates using PVD. However, TiN begins to oxidize at around 500 °C, forming rutile TiO2, which promotes rapid deterioration of the coating. Incorporating aluminum into the cubic lattice can slow the oxidative degradation of a TiN coating by forming a protective aluminum-rich oxide layer on the coating surface.

[0003] Although aluminum provides improved resistance to high temperatures, it can also induce structural changes in a TiN coating that negatively impact the coating's performance. Increasing the amount of aluminum incorporated into a TiN coating can induce the growth of a hexagonal close-packed (HDP) aluminum nitride (AlN) phase, changing the coating's crystal structure from single-phase cubic to a mixture of cubic and hexagonal phases. In some cases, an aluminum content above 70 atomic percent can further change the crystal structure of the AlTiN layer to single-phase HDP. Significant amounts of a hexagonal phase can lead to a significant reduction in the hardness of AlTiN, resulting in premature coating failure or other undesirable performance characteristics.Difficulties in controlling the formation of the hexagonal phase can prevent the full realization of the benefits offered by aluminum additions to TiN coatings.

[0004] DE 11 2011 101 826 T5 discloses a wear-resistant multilayer nitride hard coating for substrates. The coating comprises a first layer of titanium aluminum nitride and a second layer with several sublayer groups. The composition of the titanium aluminum nitride in both the first layer and the sublayer groups is based on the formula (Ti x Al 1-x )N, where 0.4 ≤ x ≤ 0.6.

[0005] JP 2012 - 35 377 A discloses a surface-coated cutting tool with a hard coating layer that is vapor-deposited onto the surface of the tool body. The coating consists of a double-layer region with a thin layer A and a thin layer B, as well as a single-layer region. Layer A is made of (Al 1-x Ti x )N, where x is between 0.3 and 0.8.

[0006] JP 2011 - 167 793 A also shows a surface-coated cutting tool whose coating is multi-layered. A thin layer A is made of (Ti 1-x Si x )N, where x is between 0.01 and 0.3, and a thin layer B consists of (Ti 1-y Al y )N, where y is between 0.4 and 0.7.

[0007] US 2014 / 0 147 683 A1 discloses a coating for a substrate with a nanolaminated coating structure consisting of layers A and B. Layer A is made of (Alx Ti 1-x-y W y )N with 0.5 ≦ x ≦ 0.65 and 0 ≦ y ≦ 0.1.

[0008] A cutting tool with a multilayer structure is known from CN 1 05 112 858 A. The multilayer system consists of an AlTiN transition layer, an AlTiN / TiSiN carrier layer, and a TiSiN functional layer. The AlTiN layer consists of 15-40% Al, 10-35% Ti, and 30-60% N. SUMMARY

[0009] In one aspect, coatings are described herein that utilize composite architectures that provide high aluminum content and high hardness for various cutting applications. For example, a coated cutting tool comprises a substrate and a coating comprising a refractory layer deposited by physical vapor deposition and adhered to the substrate, wherein the refractory layer comprises a plurality of sublayer groups, wherein one sublayer group comprises a titanium aluminum nitride sublayer and an adjacent composite sublayer comprising alternating nanolayers of titanium silicon nitride and titanium aluminum nitride, and wherein the titanium aluminum nitride sublayer has the formula Ti 1-x Al xN, where 0.72 ≤ x ≤ 0.9. In some embodiments, the coating adhered to the substrate further comprises one or more intermediate layers between the refractory layer and the substrate. An intermediate layer may, for example, comprise titanium aluminum nitride. In some embodiments, the titanium aluminum nitride of the intermediate layer has the formula Ti 1-z Al z N, where z ≥ 0.68. In other embodiments, z may be less than 0.68.

[0010] These and other embodiments are described in more detail in the detailed description that follows. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 illustrates a cutting tool substrate according to an embodiment described herein. Fig. Figure 2 provides non-limiting reference examples of PVD coating flaking for determining a critical load (L c) according to embodiments described herein. Fig. 3 is a schematic cross-sectional illustration of a coated cutting tool according to some embodiments. DETAILED DESCRIPTION

[0011] Embodiments described herein will be more readily understood from the following detailed description and examples, and from their preceding and following descriptions. However, elements, devices, and methods described herein are not limited to the specific embodiments presented in the detailed description and examples. It should be understood that these embodiments merely illustrate the principles of the present invention. Numerous modifications and adaptations will be readily apparent to those skilled in the art without departing from the spirit and scope of the invention.

[0012] In one aspect, a coated cutting tool comprises a substrate and a coating comprising a refractory layer deposited by physical vapor deposition and adhered to the substrate, wherein the refractory layer comprises a plurality of sublayer groups, wherein one sublayer group comprises a titanium aluminum nitride sublayer and an adjacent composite sublayer comprising alternating nanolayers of titanium silicon nitride and titanium aluminum nitride, and wherein the titanium aluminum nitride sublayer has the formula Ti 1-x Al x N, where 0.72 ≤ x ≤ 0.9.

[0013] Now considering specific components, coated cutting tools described herein include a substrate. A coated cutting tool may include any substrate not inconsistent with the objectives of the present invention. In some embodiments, a substrate is an end mill, a drill, or an indexable insert. Indexable inserts may have any desired ANSI standard or non-standard geometry for milling, hole drilling, or turning applications. Substrates of cutting tools described herein may be formed from cemented carbide, carbide, ceramic, cermet, or steel. A cemented carbide substrate, in some embodiments, comprises tungsten carbide (WC). WC may be present in a cutting tool substrate in an amount of at least about 80 weight percent or in an amount of at least about 85 weight percent. Additionally, metallic binders of cemented carbide may include cobalt or a cobalt alloy.For example, cobalt may be present in a cemented carbide substrate in an amount ranging from 3 weight percent to 15 weight percent. In some embodiments, cobalt is present in a cemented carbide substrate in an amount ranging from 5 to 12 weight percent or from 6 to 10 weight percent.

[0014] Furthermore, a cemented carbide substrate may have a binder-enriched zone that begins at the surface of the substrate and extends inward from the surface of the substrate.

[0015] Cemented carbide cutting tool substrates may further comprise one or more additives, such as one or more of the following elements and / or their compounds: titanium, niobium, vanadium, tantalum, chromium, zirconium, and / or hafnium. In some embodiments, titanium, niobium, vanadium, tantalum, chromium, zirconium, and / or hafnium form solid solution carbides with the WC of the substrate. In these embodiments, the substrate may comprise one or more solid solution carbides in an amount of 0.1 to 5 weight percent. Furthermore, a cemented carbide substrate may comprise nitrogen.

[0016] A cutting tool substrate may include one or more cutting edges formed at the junction between a rake face and flank surface(s) of the substrate. Fig. 1 illustrates a cutting tool substrate according to an embodiment described herein. As in Fig.As illustrated in Figure 1, the substrate (10) has cutting edges (12) formed at the junctions between the substrate chip surface (14) and flank surfaces (16). The substrate (10) further includes an opening (18) for securing the substrate (10) to a tool holder.

[0017] As described herein, a coating adhered to the substrate comprises a refractory layer deposited by PVD. The PVD refractory layer comprises a plurality of sublayer groups, wherein one sublayer group comprises a titanium aluminum nitride sublayer and an adjacent composite sublayer comprising alternating nanolayers of titanium silicon nitride and titanium aluminum nitride. In some embodiments, the titanium aluminum nitride sublayer has the formula Ti 1-x Al x N, where 0.72 ≤ x ≤ 0.9. In some embodiments, x in the Ti 1-x Al xN sub-layer has a value selected from Table I. Table 1 - Al content of the Ti1-xAlxN underlayer (at%) Value of x in Ti 1-x Al x N ≥ 0,75 ≥ 0,8 0,72-0,9 0,75-0,9 0,8-0,9

[0018] Titanium aluminum nitride sublayers may generally have a uniform aluminum content between sublayer groups. Alternatively, the aluminum content of the titanium aluminum nitride sublayers may vary between sublayer groups. For example, the aluminum content of titanium aluminum nitride sublayers may vary periodically or aperiodically across the thickness of the refractory layer. In some embodiments, the aluminum content in titanium aluminum nitride sublayers increases in a direction away from the substrate. In other embodiments, the aluminum content in titanium aluminum nitride sublayers decreases in a direction away from the substrate.

[0019] The thickness of a titanium aluminum nitride underlayer can be selected according to various considerations, including the desired overall thickness of the refractory layer, the number of underlayer groups, and the thickness of the adjacent composite underlayer comprising alternating nanolayers of titanium silicon nitride and titanium aluminum nitride. In some embodiments, a titanium aluminum nitride underlayer has a thickness of less than 100 nm. A titanium aluminum nitride underlayer of a sublayer group can also have a thickness selected from Table II. Table II - Thickness of the titanium aluminum nitride underlayer (nm) 5 to 100 10 to 100 20 to 100 20 to 90 20 to 60

[0020] Titanium aluminum nitride sublayers may have a generally uniform thickness between sublayer groups. Alternatively, the thickness of the titanium aluminum nitride sublayers may vary between sublayer groups. For example, the thickness of titanium aluminum nitride sublayers may vary periodically or aperiodically across the thickness of the refractory layer. In some embodiments, the thickness of the titanium aluminum nitride sublayer increases in a direction away from the substrate. In other embodiments, the thickness of the titanium aluminum nitride sublayer decreases in a direction away from the substrate.

[0021] A sublayer group also includes a composite sublayer adjacent to the titanium aluminum nitride sublayer. The composite sublayer includes alternating nanolayers of titanium silicon nitride (TiSiN) and titanium aluminum nitride. In some embodiments, the titanium silicon nitride has the formula Ti1-p Si p N, where 0.05 ≤ p ≤ 0.3. In some embodiments, p in the Ti 1-p Si p N sub-layer has a value selected from Table III. Table III - Si content of the Ti1-pSipN nanolayer (at%) Value of p in Ti 1-p Si p N 0,05-0,25 0,05-0,20 0,05-0,15 0,1-0,2 0,1-0,15

[0022] TiSiN nanolayers may have a generally uniform silicon content between sublayer groups or within a sublayer group. Alternatively, the silicon content of TiSiN nanolayers may vary between sublayer groups or within a sublayer group. For example, the silicon content of TiSiN nanolayers may vary periodically or aperiodically across the thickness of the refractory layer. In some embodiments, the silicon content in TiSiN nanolayers increases in a direction away from the substrate. In other embodiments, the silicon content in TiSiN nanolayers decreases in a direction away from the substrate.

[0023] The thickness of the TiSiN nanolayers of a sublayer group can be selected according to various considerations, including the number of TiSiN nanolayers of a single sublayer group, the thickness and / or number of alternating titanium aluminum nitride nanolayers, the desired overall thickness of the refractory layer, and the thickness of the adjacent titanium aluminum nitride sublayer. In some embodiments, a TiSiN nanolayer has a thickness of less than 10 nm. For example, the TiSiN nanolayer may have a thickness of 1 to 7 nm, 1 to 5 nm, or 1 to 3 nm.

[0024] A composite sublayer also includes titanium aluminum nitride sublayers alternating with the TiSiN sublayers. In some embodiments, the titanium aluminum nitride sublayers have the formula Ti 1-y Al yN where y ≥ 0.68. In some embodiments, y in the Ti 1-y Aly N sublayer has a value selected from Table I above. Titanium aluminum nitride nanosheets may have a generally uniform aluminum content between sublayer groups or within a sublayer group. Alternatively, the aluminum content of titanium aluminum nitride nanosheets may vary between sublayer groups or within a sublayer group. For example, the aluminum content of titanium aluminum nitride nanosheets may vary periodically or aperiodically across the thickness of the refractory layer. In some embodiments, the aluminum content in titanium aluminum nitride nanosheets increases in a direction away from the substrate. In other embodiments, the aluminum content in titanium aluminum nitride nanosheets decreases in a direction away from the substrate.

[0025] The thickness of the titanium aluminum nitride nanolayers of a sublayer group can be selected according to various considerations, including the number of titanium aluminum nitride nanolayers of a single sublayer group, the thickness and / or number of alternating TiSiN nanolayers, the desired overall thickness of the refractory layer, and the thickness of the adjacent titanium aluminum nitride sublayer. In some embodiments, a titanium aluminum nitride nanolayer has a thickness of less than 10 nm. For example, the titanium aluminum nitride nanolayer may have a thickness of 1 to 7 nm, 1 to 5 nm, or 1 to 3 nm.

[0026] A group of composite sublayers may comprise any desired number of alternating nanolayers of TiSiN and titanium aluminum nitride. In some embodiments, a composite sublayer comprises up to 30 or up to 20 combined nanolayers of TiSiN and titanium aluminum nitride. The thickness of a composite sublayer depends on the number of alternating TiSiN and titanium aluminum nitride nanolayers that comprise the composite sublayer. In some embodiments, a thickness of a composite sublayer has a value selected from Table II above. In addition, a thickness ratio between a composite sublayer and an adjacent sublayer of titanium aluminum nitride (e.g., a Ti 1-x Al xN-sublayer) in some embodiments in the range of 0.5 to 5. In some embodiments, the thickness ratio between a composite sublayer and an adjacent titanium aluminum nitride sublayer is in the range of 1.5 to 5 or 2 to 4.

[0027] Furthermore, the thickness of the composite sublayer may be generally uniform throughout the refractory layer. Alternatively, the thickness of the composite sublayer may vary between sublayer groups. For example, the thickness of the composite sublayer may vary periodically or aperiodically across the thickness of the refractory layer. In some embodiments, the thickness of the composite sublayer increases in a direction away from the substrate. In other embodiments, the thickness of the composite sublayer decreases in a direction away from the substrate.

[0028] A number of sublayer groups can be deposited by PVD to provide a refractory layer of the desired thickness. In some embodiments, a refractory element comprising the sublayer group has a thickness of less than 1 µm. A refractory layer comprising the sublayer groups can also have a thickness selected from Table IV. Table IV - Thickness of the PVD refractory layer (µm) 0,1-1 0,2-0,8 0,1-0,6 ≤ 0,5 0,1-0,5

[0029] As described herein, a titanium aluminum nitride in the refractory layer may have a high aluminum content. Ti 1-x Al x N sublayers and Ti 1-y Al yN-nanolayers of sublayers of a composite layer may exhibit aluminum contents where x is greater than 0.72 and y is greater than 0.68. In some embodiments, both x and y have a value selected from Table I above. In such high-aluminum-content embodiments, the PVD refractory layer may exhibit less than 35 weight percent hexagonal phase. In some embodiments, the PVD refractory layer may exhibit a hexagonal phase with a value selected from Table V. Table V - Content of the hexagonal phase of the refractory layer Hexagonal phase of the refractory layer (wt%) 0-35 3-30 20-35 25-35 20-30 1-10 1-5

[0030] In some embodiments, the PVD refractory layer does not comprise a hexagonal phase. Furthermore, the PVD refractory layer may also comprise one or more silicon nitride phases, such as Si3N4. In some embodiments, the PVD refractory layer comprises an amorphous phase in addition to TiSiN and / or titanium aluminum nitride phases.

[0031] Phase determination of refractory coatings described herein, including determination of the hexagonal phase, is performed using X-ray diffraction (XRD) techniques and the Rietveld refinement method. The measured specimen profile and a calculated profile are compared. By varying several parameters known to those skilled in the art, the difference between the two profiles is minimized. All phases present in a coating layer under analysis are taken into account to perform proper Rietveld refinement.

[0032] A cutting tool comprising a coating including a PVD refractory layer described herein can be analyzed by XRD using a grazing incidence technique that requires a flat surface. The rake face or flank face of the cutting tool can be analyzed, depending on the cutting tool geometry. XRD analysis of coatings described herein can be completed using a parallel-beam optical system equipped with a copper X-ray tube. Operating parameters are 45 kV and 40 mA. Typical optics for grazing incidence analysis include an X-ray mirror with a 1 / 16 degree scatter slit and a 2° (0.04 radian) Soller slit. Receiving optics include a flat graphite monochromator, a parallel-plate collimator, and a sealed proportional counter.X-ray diffraction data are acquired at a grazing incidence angle selected to maximize coating peak intensity and eliminate noise from the substrate. Counting times and sampling rates are selected to provide optimal data for Rietveld analysis. Before grazing incidence data are acquired, the specimen height is adjusted using X-ray beam splitting.

[0033] A background profile is fitted, and a peak search is performed on the specimen data to identify all peak positions and peak intensities. The peak position and intensity data are used to identify the crystal phase composition of the specimen coating using any commercially available crystal phase database.

[0034] Crystal structure data were entered for each of the crystal phases present in the specimen. Typical Rietveld refinement parameter settings are: Background calculation method: polynomial Test specimen geometry: Flat plate Linear absorption coefficient Calculated from the average test specimen composition Weighting scheme: Against praise Profile function: Pseudo-Voigt Profile base width: Selected per test specimen least squares type Newton-Raphson Polarization coefficient: 1,0

[0035] The Rietveld refinement typically includes: Test specimen displacement: Displacement of the test specimen from X-ray beam alignment Background profile selected to best describe the background profile of the diffraction data Scale function: Scale function of the individual phases B total: Displacement parameter applied to all atoms in the phase Cell parameters: a, b, c and alpha, beta and gamma W parameters: describes peak FWHM

[0036] Any additional parameters to achieve an acceptable “Weighted R-Profile”

[0037] All Rietveld phase analysis results are expressed as weight percentages.

[0038] The PVD refractory layer comprising sublayer groups described herein may have a hardness of at least 22 GPa. Hardness values ​​are determined according to ISO 14577-1:2015. Metallic Materials - Instrumented Indentation Testing for Determining Hardness and Other Material Parameters using a Vickers Indenter with a penetration depth of 0.25 µm. In some embodiments, a PVD refractory layer having a construction described herein has a hardness according to Table VI. Table VI - Hardness of the PVD refractory layer (GPa) ≥ 25 ≥ 27 ≥ 28 25-35 25-30 27-35 28-35 30-35

[0039] In addition to hardness, a refractory layer comprising the sublayer group described herein can withstand a critical load (L c) of at least 588 N (60 kgf). A critical load, which characterizes the adhesion of the refractory layer, is determined according to the following protocol. A Rockwell hardness tester with surface scales is used, with a Rockwell A or C Brale indenter that is free of cracks, chips, defects, and adherent surface contamination. Also used are a spot anvil (0.64 centimeters (0.25 inches) diameter) and a flat anvil (5 centimeters (2 inches) diameter). The appropriate preload (98 N (10 kg)) for the indenter load used is selected. A flat surface of the coated substrate is selected and positioned on the anvil under the Brale indenter, and the set screw is adjusted to the required zero scale position. A notch(s) is (are) applied with the desired superficial load (e.g. 588, 981, 1471 N etc. (60, 100, 150 kgf etc.)).The set screw is loosened and the specimen is positioned laterally to apply the next load. Notches are spaced apart to avoid interference or contributions from neighboring notches. The recommended spacing is 3–5 times the diameter of the notch. Any detached but still adherent refractory layers can be removed by immersing the specimen in an ultrasonic bath for several minutes. Alternatively, an adhesive strip can be used to remove a detached refractory layer. The notched specimens are examined under an optical microscope (10x–100x) for flaking and delamination along the surface edge of the notch. The critical load (L) c ) is specified as the load at which flaking and / or delamination occurs beyond the diameter of the notch. Fig.Figure 2 illustrates non-limiting reference examples of exfoliation of a PVD coating under the present adhesion test. A refractory layer comprising sublayer groups described herein exhibits, in some embodiments, a L c selected from Table VII. Table VII - Critical load (Lc) of an M1-xAlxN refractory layer ≥ 588 N (60 kgf) ≥ 981 N (100 kgf) ≥ 1471 N (150 kgf)

[0040] In some embodiments, the coating adhered to the substrate further comprises one or more intermediate layers between the PVD refractory layer and the substrate. An intermediate layer may, for example, comprise titanium aluminum nitride. The titanium aluminum nitride of the intermediate layer may, for example, have the formula Ti 1-z Al z N, where z ≥ 0.68. In some embodiments, z has a value selected from Table I above. In other embodiments, z may be less than 0.68. A Ti 1-z Al zIn some embodiments, the N-interlayer has less than 5 weight percent hexagonal phase. A Ti 1-z Al z For example, N-interlayer may be free of a hexagonal phase.

[0041] The PVD refractory layer comprising sublayer groups may, in some embodiments, be disposed directly on an intermediate layer comprising Ti 1-z Al z N. Alternatively, one or more intermediate layers with different compositions can be placed between the Ti 1-z Al z N-layer and the PV refractory layer, which comprises a plurality of sub-layers described herein. An intermediate layer(s) may be deposited by PVD and / or chemical vapor deposition (CVD). A Ti 1-z Al z N-interlayer can have any desired thickness. In some embodiments, a Ti 1-z Alz N-interlayer has a thickness of 0.5 µm to 2 µm. In other embodiments, a Ti 1-z Al z N-intermediate layer has a thickness of 2 µm to 10 µm. A Ti 1-z Al z N-interlayer may also have a hardness with a value selected from Table V above.

[0042] Fig. 3 is a schematic cross-sectional view of a coated cutting tool according to some embodiments. As shown in Fig. 3, the coated cutting tool 30 comprises a substrate 31 and a TiAIN intermediate layer 32. In the embodiment of Fig.3, the TiAlN intermediate layer 32 adheres directly to the substrate 31. In other embodiments, one or more inner layers may be positioned between the TiAlN intermediate layer 32 and the substrate 31. A PVD refractory layer 33 comprising a plurality of sublayer groups 33a adheres to the TiAlN intermediate layer 32. A sublayer group 33a comprises a titanium aluminum nitride sublayer (B) and an adjacent composite sublayer (A) comprising alternating nanolayers of TiSiN and TiAlN.

[0043] As in connection with Fig. 3, a coating described herein may further comprise one or more internal layers between the Ti 1-z Al zN-interlayer and the substrate. An inner layer(s) of the coating may comprise one or more metallic elements selected from the group consisting of aluminum and metallic elements of groups IVB, VB and VIB of the periodic table, and one or more non-metallic elements selected from the group consisting of non-metallic elements of groups IIIA, IVA, VA and VIA of the periodic table. For example, in some embodiments, one or more inner layers of TiN, TiC, TiCN or Al2O3 may be disposed between the cutting tool substrate and the Ti 1-z Al z N-intermediate layer. The inner layer(s) may have any desired thickness that is not incompatible with the objectives of the present invention. In some embodiments, an inner layer has a thickness in the range of 100 nm to 5 µm.

[0044] Furthermore, the coating may further comprise one or more outer layers over the PVD refractory layer comprising the plurality of sublayer groups described herein. A refractory outer layer(s) of the coating may comprise one or more metallic elements selected from the group consisting of aluminum and metallic elements of Groups IVB, VB, and VIB of the Periodic Table, and one or more non-metallic elements selected from the group consisting of non-metallic elements of Groups IIIA, IVA, VA, and VIA of the Periodic Table. For example, in some embodiments, one or more refractory outer layers of TiN, AlTiN, TiC, TiCN, or Al2O3 may be positioned over the refractory layer formed from the sublayer groups.The refractory outer layer(s) may have any desired thickness that is not incompatible with the objectives of the present invention. In some embodiments, a refractory outer layer has a thickness in the range of 100 nm to 5 µm. Alternatively, the PVD refractory layer comprising the sublayer groups may be the outermost layer of the coating.

[0045] The sublayers forming the refractory layer can be deposited using any physical vapor deposition technique, including cathodic arc evaporation or magnetron sputtering. Bias voltages used during the deposition of the sublayer groups by cathodic arc evaporation can generally range from -40 V to -210 V. Furthermore, bias voltages can vary between sublayer depositions. In some embodiments, titanium aluminum nitride sublayers and titanium aluminum nitride nanolayers of adjacent composite sublayers are deposited from the same cathode(s). In such embodiments, a titanium aluminum nitride composition can be uniform throughout the thickness of the refractory layer.Alternatively, compositional variation between sublayers and / or within sublayers can be achieved by controlling deposition process parameters and / or by depositing different cathode compositions.

[0046] In some embodiments, one or more Ti 1-z Al z N-interlayers deposited by cathode arc evaporation. A Ti 1-z Al z The N-interlayer can be deposited using the same cathode(s) used for the deposition of titanium aluminum nitride of the refractory layer. Furthermore, bias voltages can generally be in the range of -20 V to -100 V. In some embodiments, the bias voltage is adjusted during the deposition of a Ti 1-z Al z N-interlayer increased or decreased.

[0047] These and other embodiments are further illustrated in the following non-limiting examples. EXAMPLE 1 - Coated cutting tool

[0048] A cutting tool was coated with a refractory layer formed from a plurality of sublayer groups, wherein one sublayer group comprises a Ti 1-x Al x N sublayer and an adjacent composite sublayer comprising alternating nanolayers of TiSiN and Ti 1-y Al y N, where 0.72 ≤ x 0.9 and y ≥ 0.68. An intermediate layer of Ti 1-z Al z N (z ≥ 0.68) was used between the substrate and the refractory layer comprising the sublayer groups. The coating was deposited by cathodic arc evaporation on a cemented carbide (WC-6 wt% Co) indexable insert substrate [ANSI standard geometry CNGG432FS] according to the parameters in Table VIII. Table VIII - Cathode arc evaporation parameters layer Step Goal Length of time Preload temperature Pressure thickness TiAIN base layer 1 Al 0.71 Ti 0.29 42 minutes 40 V 530 °C 3.5 Pa(3.5*10 -2 (end) 1,5 µm 2 84 minutes 80 V Top layer 3 You 0.83 Yes 0.13 To the 0.71 You 0.29 5 minutes 120 V 450 °C 5 Pa(5*10 -2 (end) ~64 nm 4 Al 0.71 Ti 0.29 5 minutes 120 V ~36 nm 5 You 0.83 Yes 0.13 To the 0.71 You 0.29 5 minutes 160 V ~64 nm 6 Al 0.71 Ti 0.29 5 minutes 160 V ~36 nm 7 You 0.83 Yes 0.13 To the 0.71 You 0.29 5 minutes 210 V ~64 nm 8 Al 0.71 Ti 0.29 5 minutes 210 V ~36 nm

[0049] Properties of the resulting coating are given in Table IX. The hexagonal phase content and hardness of the refractory top layer were determined according to their respective techniques described herein. Table IX - Refractory layer properties Example Hardness (GPa) Hexagonal phase (wt%) Coating thickness [µm] 1 30,2 0 1,8 EXAMPLE 2 - Metal cutting tests

[0050] Coated inserts (1) with the architecture of Example 1 were subjected to a tool life test relative to coated comparative inserts (2-4). The coated comparative inserts (2-4) exhibited compositional properties shown in Table X. The coatings listed in Table X were deposited by cathodic arc evaporation. Table X - Coated comparison inserts Coated indexable insert Substrat First layer Second layer 2 WC-Co (6 wt%) CNMG432.xx TiAlN (1.1 µm) TiAlSiN (3.5 µm) 3 WC-Co (6 wt%)CNGG432FS The 0.39 Al 0.61 N (3 μm) No 4 WC-Co (6 wt%)CNGG432FS The 0.30 Al 0.6 1N (2.1 μm) No

[0051] Coated inserts 1-4 were subjected to a cutting life test in a continuous Inconel 718 turning chip test. The cutting conditions were as follows: Cutting speed: 91 m / min (300 sfm) Feed per revolution: 0.2 mmpr (0.006 ipr) Axial cutting depth: 0.025 centimeters (0.01 inches) Coolant: Flooding Tool life criteria are given in Table XI. Table XI - Tool life criteria (centimeters (inches)) Even wear 0,02 (0,006) Max. wear 0,02 (0,006) Corner wear 0,02 (0,006) Depth of the cutting notch 0,02 (0,006) trailing edge 0,02 (0,006)

[0052] A total of four repetitions were performed for each insert. The average cutting life is shown in Table XII. Table XII - Service life of coated cutting tools (minutes) Coated indexable insert Average service life 1 13,8 2 2,2 3 2,0 4 5,7

[0053] As indicated in Table XII, cutting tools with coating architectures of Example 1 herein showed significant increases in cutting life relative to the control inserts.

[0054] Various embodiments of the invention have been described which achieve the various objects of the invention. It should be understood that these embodiments merely illustrate the principles of the present invention. Numerous modifications and adaptations will be readily apparent to those skilled in the art without departing from the spirit and scope of the claims.

Claims

[1] Coated cutting tool comprising: a substrate and a coating comprising a refractory layer deposited by physical vapor deposition and adhered to the substrate, wherein the refractory layer comprises a plurality of sublayer groups, wherein one sublayer group comprises a titanium aluminum nitride sublayer and an adjacent composite sublayer comprising alternating nanolayers of titanium silicon nitride and titanium aluminum nitride, and wherein the titanium aluminum nitride sublayer has the formula Ti 1-x Al x N, where 0.72 ≤ x ≤ 0.

9. [2] The coated cutting tool according to claim 1, wherein the titanium aluminum nitride nanolayers have the formula Ti 1-y Al y N, where y ≥ 0.

68. [3] A coated cutting tool according to claim 2, wherein y ≥ 0.

69. [4] A coated cutting tool according to claim 2, wherein 0.72 ≤ y ≤ 0.

9. [5] A coated cutting tool according to any one of the preceding claims, wherein the refractory layer has a hardness of at least 22 GPa. [6] A coated cutting tool according to claim 5, wherein the refractory layer has a hardness of 25 to 35 GPa. [7] A coated cutting tool according to any one of the preceding claims, wherein the refractory layer comprises less than 35 weight percent hexagonal phase. [8] A coated cutting tool according to claim 7, wherein the refractory layer has less than 5 weight percent hexagonal phase. [9] Coated cutting tool according to one of the preceding claims, wherein the titanium silicon nitride nanolayers have the formula Ti 1-p Si p N, where 0.05 ≤ p ≤ 0.

3. [10] Coated cutting tool according to one of the preceding claims, wherein the refractory layer has a critical load (L c ) of at least 981 N. [11] A coated cutting tool according to any one of the preceding claims, wherein the refractory layer has a thickness of less than 1 µm. [12] A coated cutting tool according to any one of the preceding claims, further comprising an intermediate layer between the refractory layer and the substrate. [13] A coated cutting tool according to claim 12, wherein the intermediate layer comprises titanium aluminum nitride. [14] A coated cutting tool according to claim 13, wherein an aluminum gradient is present between the intermediate layer and the refractory layer. [15] Coated cutting tool according to claim 13 or 14, wherein the titanium aluminum nitride of the intermediate layer has the formula Ti 1-z Al z N, where z ≥ 0.

68. [16] A coated cutting tool according to claim 15, wherein the intermediate layer comprises less than 5 weight percent hexagonal phase. [17] A coated cutting tool according to claim 15 or 16, wherein the intermediate layer has a hardness of more than 22 GPa. [18] A coated cutting tool according to any one of claims 12-17, wherein the intermediate layer contacts the substrate. [19] A coated cutting tool according to any one of claims 12-18, further comprising an inner layer between the intermediate layer and the substrate. [20] A coated cutting tool according to claim 19, wherein the inner layer comprises one or more metallic elements selected from the group consisting of aluminum and metallic elements of groups IVB, VB and VIB of the periodic table, and one or more non-metallic elements of groups IIIA, IVA, VA and VIA of the periodic table. [21] A coated cutting tool according to any one of the preceding claims, further comprising an outer layer deposited on the refractory layer, the outer layer comprising one or more metallic elements selected from the group consisting of aluminum and metallic elements of groups IVB, VB and VIB of the Periodic Table, and one or more non-metallic elements of groups IIIA, IVA, VA and VIA of the Periodic Table. [22] A coated cutting tool according to any one of the preceding claims, wherein the refractory layer does not comprise a hexagonal phase. [23] A coated cutting tool according to any one of the preceding claims, wherein 0.75 ≤ x ≤ 0.

9. [24] A coated cutting tool according to claim 23, wherein the refractory layer has a hardness of 25 to 35 GPa.

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