COATED CUTTING TOOL

Abstract

A coated cutting tool and a process for the production thereof id provided. The coated cutting tool consists of a substrate body of WC-Co based cemented carbide and a coating, the coating including a first (Ti,Al)N multilayer, a first gamma-aluminium oxide layer, and a set of alternating second (Ti,Al)N multilayers and second gamma-aluminium oxide layers.

Claims

1. A coated cutting tool consisting of: a substrate body having a surface; and a coating, the substrate body being a WC-Co based cemented carbide body 5-15 wt % Co, and the coating comprising, in the order from the substrate body surface: a first (Ti,Al)N multilayer having a multilayer of individual alternating (Ti,Al)N sub-layers, wherein an overall atomic ratio of Ti:Al within the first (Ti,Al)N multilayer is from 33:67 to 67:33, wherein a total thickness of the first (Ti,Al)N multilayer is from 1 to 8 μm, wherein each of the individual (Ti,Al)N sub-layers within the first (Ti,Al)N multilayer has a thickness of from 1 to 25 nm, wherein each of the individual (Ti,Al)N sub-layers within the first (Ti,Al)N multilayer being different in respect of the atomic ratio Ti:Al than an immediately adjacent (Ti,Al)N sub-layer, and wherein the first (Ti,Al)N multilayer includes two or more (Ti,Al)N sub-layer stacks arranged immediately on top of each other, wherein within the same (Ti,Al)N sub-layer stack there exists at least two types of individual (Ti,Al)N sub-layers, wherein the at least two types of individual (Ti,Al)N sub-layers have different Ti:Al atomic ratios, and wherein the overall Al content within each of the (Ti,Al)N sub-layer stacks increases from one (Ti,Al)N sub-layer stack to the next (Ti,Al)N sub-layer stack in the direction towards the outer surface of the coating; a first gamma-aluminium oxide layer, wherein a thickness of the first gamma-aluminium oxide layer is from 0.3 to 1.5 μm; a set of alternating second (Ti,Al)N multilayers and second gamma-aluminium oxide layers (10), wherein a number of each of the alternating second (Ti,Al)N multilayers and second gamma-aluminium oxide layers (10) is ≥2, each of the second (Ti,Al)N multilayers being a multilayer of alternating (Ti,Al)N sub-layers, wherein an overall atomic ratio of Ti:Al within the second (Ti,Al)N multilayers is within the range from 33:67 to 67:33, wherein a thickness of each of the second (Ti,Al)N multilayers is from 0.05 to 0.5 μm, wherein each of the individual (Ti,Al)N sub-layers within the second (Ti,Al)N multilayers has a thickness within the range from 1 to 25 nm, each of the individual (Ti,Al)N sub-layers within the second (Ti,Al)N multilayers being different in respect of the atomic ratio Ti:Al than an immediately adjacent (Ti,Al)N sub-layer, wherein a thickness of each of the second gamma-aluminium oxide layers is from 0.05 to 0.5 μm, and wherein a total thickness of the coating of the coated cutting tool is from 3 to 15 μm.

2. The coated cutting tool according to claim 1, wherein a surface zone of the substrate body exhibits a residual compressive stress of at least 0.5 GPa.

3. The coated cutting tool according to claim 1, wherein the atomic ratio Ti:Al of the type of individual (Ti,Al)N sub-layers of the first (Ti,Al)N multilayer having a highest Al content of the types of individual (Ti,Al)N sub-layers is suitably within the range from 20:80 to 60:40.

4. The coated cutting tool according to claim 1, wherein the atomic ratio Ti:Al of the type of individual (Ti,Al)N sub-layers of the first (Ti,Al)N multilayer having a lowest Al content of the types of individual (Ti,Al)N sub-layers is suitably within the range from 35:65 to 80:20.

5. The coated cutting tool according to claim 1, wherein the thickness of each (Ti,Al)N sub-layer stack of the first (Ti,Al)N multilayer is from 0.5 to 5 μm.

6. The coated cutting tool according to claim 1, wherein the first (Ti,Al)N multilayer consists of two to five (Ti,Al)N sub-layer stacks arranged immediately on top of each other.

7. The coated cutting tool according to claim 1, wherein the first (Ti,Al)N multilayer has a Vickers hardness HV0.0015 ≥2800 and/or a reduced Young's modulus >350 GPa.

8. The coated cutting tool according to claim 1, wherein there is a residual compressive stress present within a portion of a thickness of at least 100 nm to at most 1 μm within the first (Ti,Al)N multilayer from an interface of the (Ti,Al)N multilayer arranged in a direction towards the substrate body, the residual compressive stress being from 0.5 to 2 GPa.

9. The coated cutting tool according to claim 1, wherein the Vickers hardness HV(0.0015) of the gamma-aluminium oxide layer is from 3000 to 3500 HV0.0015 and the reduced Young's modulus of the gamma-aluminium oxide layer is from 350 to 390 GPa.

10. The coated cutting tool according to claim 1, wherein the coating includes an outermost layer of a metal nitride layer, the metal belonging to group 4, 5, or 6, of the periodic table of elements.

11. The coated cutting tool according to claim 1, wherein the cutting tool is a cutting insert for milling, a cutting insert for turning, a cutting insert for drilling, a drill or an endmill.

12. A process for the production of a coated cutting tool consisting of a substrate body and a deposited coating, comprising the steps of: providing a substrate body, the substrate body being a WC-Co based cemented carbide body including from 5 to 15 wt % Co; subjecting a surface of the substrate body to a pre-treatment, the pre-treatment being an ion etching procedure, so that at least a 0.5 μm thickness of the substrate body is removed; depositing a 1 to 8 μm thick layer of a first TiAlN multilayer by a cathodic arc evaporation PVD process using at least two TiAl targets different in a Ti:Al atomic ratio in a chamber including nitrogen gas at a pressure of from 5 to 15 Pa, using a bias voltage of from −20 to −80 V, and at an applied arc current of from 50 to 200 A, the (Ti,Al)N multilayer being a multilayer of alternating (Ti,Al)N sub-layers, wherein the atomic Ti:Al ratio of the at least two TiAl targets is chosen so that an overall atomic ratio of Ti:Al is from 33:67 to 67:33, wherein each of the individual (Ti,Al)N sub-layers has a thickness within the range from 1 to 25 nm, each of the individual (Ti,Al)N sub-layers being different in respect of the atomic ratio Ti:Al than an immediately adjacent (Ti,Al)N sub-layer, wherein the (Ti,Al)N multilayer is deposited in a manner so that it includes two or more (Ti,Al)N sub-layer stacks arranged immediately on top of each other, wherein within the same (Ti,Al)N sub-layer stack there exists at least two types of individual (Ti,Al)N sub-layers, wherein the at least two types of individual (Ti,Al)N sub-layers have different Ti:Al atomic ratios, and wherein the overall Al content within each of the (Ti,Al)N sub-layer stacks increases from one (Ti,Al)N sub-layer stack to the next (Ti,Al)N sub-layer stack in the direction towards the outer surface of the first (Ti,Al)N multilayer; depositing a 0.3 to 1.5 μm thick layer of a first gamma-aluminium oxide layer by a reactive magnetron sputtering PVD process using at least one Al target in an oxygen containing gas volume at a total gas pressure of from 1 to 5 Pa, an oxygen partial pressure of from 0.001 to 0.1 Pa, at a temperature of from 400 to 600° C., using a power density at the magnetron of from 4 to 20 W/cm.sup.2, a bias voltage of from 80 to 200 V and a pulsed bias current of from 20 to 60 A; depositing a set of alternating layers of second (Ti,Al)N multilayers and second gamma-aluminium oxide layers, the second (Ti,Al)N multilayers and the second gamma-aluminium oxide layers are deposited using the same process conditions as when depositing the first (Ti,Al)N multilayer and the first gamma-aluminium oxide layer, respectively, wherein the number of each of second (Ti,Al)N multilayers and second gamma-aluminium oxide layers is ≥2, each of the second (Ti,Al)N multilayers being a multilayer of alternating (Ti,Al)N sub-layers, the overall atomic ratio of Ti:Al within the second (Ti,Al)N multilayers is from 33:67 to 67:33, the thickness of the second (Ti,Al)N multilayers is from 0.05 to 0.5 μm, each of the individual (Ti,Al)N sub-layers within the second (Ti,Al)N multilayers has a thickness of from 1 to 25 nm, each of the individual (Ti,Al)N sub-layers within the second (Ti,Al)N multilayers being different in respect of the atomic ratio Ti:Al than an immediately adjacent (Ti,Al)N sub-layer, the thickness of the second gamma-aluminium oxide layers is from 0.05 to 0.5 μm, wherein a total thickness of the deposited coating of the coated cutting tool is from 3 to 15 μm; subjecting the deposited coating to a first post-treatment procedure including shot peening using beads of a zirconium oxide based ceramic so that a compressive stress of at least 0.5 GPa is induced in the surface zone of the substrate body; and subjecting the deposited coating to a second post-treatment procedure by wet blasting with a slurry of aluminium oxide particles.

13. The process according to claim 12, wherein an outermost layer is deposited after the depositing of the set of alternating layers of second (Ti,Al)N multilayers and second gamma-aluminium oxide layers, but prior to the first post-treatment procedure, the outermost layer being a metal nitride layer, the metal belonging to group 4, 5, or 6, of the periodic table of elements.

14. The process according to claim 12, wherein the beads used in the shot peening are within a size ranging from 70 to 125 μm, the shot peening is performed using a blasting pressure of from 3 to 6 bar, a working time in the shot peening is from 2 to 10 seconds, a distance between the blasting nozzle and the surface of the coated cutting tool is from 75 to 150 mm, and the shot peening is performed in a shot direction substantially perpendicular to the surface of the coated cutting tool.

15. The process according to claim 12, wherein the second post-treatment procedure includes wet blasting using a blasting pressure of from 1.5 to 2 bar, a concentration of aluminium oxide particles in a slurry is from 15 to 20 vol-%, the aluminium oxide particles used in the wet blasting belong to one or more of FEPA designations F240, F280 and F320, a blasting time in the wet blasting is from 2 to 60 seconds, a distance between a blasting gun nozzle and the surface of the coated cutting tool is from 50 to 200 mm, and the wet blasting is performed in a blasting direction having an angle to the surface of the coated cutting tool being from 60 to 90°.

16. The process according to claim 15, wherein the wet blasting is done until a residual compressive stress of at least 0.2 GPa, as averaged over the thickness of the coating, is induced within the coating.

17. The coated cutting tool according to claim 10, wherein the metal is Zr, Ti or Cr.

18. The process according to claim 13, wherein the metal is Zr, Ti or Cr.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0110] FIG. 1 shows a schematic view of one embodiment of a cutting tool being a milling insert.

[0111] FIG. 2 shows a schematic view of a cross section of an embodiment of the coated cutting tool of the present invention showing a substrate and a coating comprising different layers.

DETAILED DESCRIPTION OF EMBODIMENTS IN DRAWINGS

[0112] FIG. 1 shows a schematic view of one embodiment of a cutting tool (1) having a rake face (2) and flank faces (3) and a cutting edge (4). The cutting tool (1) is in this embodiment a milling insert. FIG. 2 shows a schematic view of a cross section of an embodiment of the coated cutting tool of the present invention having a substrate body (5) and a coating (6). The coating consisting of a first (Ti,Al)N multilayer (7), a first gamma aluminium oxide layer (8), a set of alternating second (Ti,Al)N multilayers (9) and second gamma aluminium oxide layers (10) and an outermost layer (11) being a ZrN layer.

EXAMPLES

Example 1: Manufacturing of Samples According to the Invention

[0113] As a substrate was used cutting tool bodies (called “blanks”) being insert having a geometry ADMT160608R-F56, ODHT050408-F57 and P2808.1 which are all geometries used in milling operations.

[0114] For samples S1 to S4, the cutting tool body was made out of a cemented carbide of the composition 88 wt % WC, 1.5 wt % (Ta, Nb)C and a binder phase of 10.5 wt % Co. The average WC grain size dWC was 0.8 μm.

[0115] For samples S5 and S6, the cutting tool body was made out of a cemented carbide of the composition 87.5 wt % WC, 0.5 wt % Cr and a binder phase of 12.5 wt % Co. The average WC grain size dWC was 0.4 μm.

[0116] Prior to the deposition, the substrate bodies were pretreated by ultrasonic cleaning in a water-based medium.

[0117] The PVD reactor was evacuated to 8×10.sup.−5 mbar, and the substrate was pre-treated at 550° C. The pre-treatment included an Ar ion etching procedure conducted removing about 0.8 μm thickness of the substrate so that all carbide grains that had been damaged (cracked) during earlier treatments of the blank, such as edge rounding, were removed.

[0118] The coating equipment used for depositing the coating according to the invention was a Hauzer HTC1000 (IHI Hauzer Techno Coating B.V., The Netherlands) with a chamber size of 1 m.sup.3.

Deposition of the First (Ti,Al)N Multilayer

[0119] In the deposition of the first (Ti,Al)N multilayer cathodic arc evaporation was used. In the Hauzer HTC1000 equipment used a circular Arc-PVD technology (CARC+) using constant magnetic field configuration was applied during deposition.

[0120] For the deposition of the first (Ti,Al)N multilayer, two types of TiAl-targets with different atomic ratios Ti:Al were used to produce alternating (Ti,Al)N sub-layers. The Ti:Al atomic ratios in the two types of TiAl-targets, respectively, were “Ti50Al50” (Ti:Al=50:50) and “Ti33Al67” (Ti:Al=33:67).

[0121] If reference is herein made to a target of a particular composition, this means that, due to the layout of the used PVD reactor, a line of four targets of the same composition were vertically arranged to allow for a homogeneous deposition throughout the height of the reactor.

[0122] The targets had a diameter of 100 mm. The reactive gas for the nitride deposition was N.sub.2. Two types of (Ti,Al)N sub-layer stacks, L1 and L2, were produced. To produce the inventive coating, L1 was deposited immediately on the substrate surface, and L2 was deposited immediately on top of L1. However, to investigate the (Ti,Al)N sub-layer stacks L1 and L2 independent from each other, samples wherein only L1 was deposited immediately on the substrate surface and samples wherein only L2 was deposited immediately on the substrate surface were produced. For the deposition of L1, two targets were used: 1x “Ti50Al50”+1x “Ti33Al67”. To achieve a lower Ti content and a higher Al content in L2, for the deposition of L2 three targets were used: 1x “Ti50Al50”+2x “Ti33Al67”. The depositions were carried out at an arc current at each target of about 150 A. Different samples were made using different bias levels, −40 V and −60 V, respectively, for L1 and −40 V and −50 V, respectively, for L2. The further process parameters for the deposition of different layers are given in table 1.

TABLE-US-00001 TABLE 1 (Ti, Al)N Targets “Ti50Al50” + “Ti33Al67” sub-layer Bias −40 V and −60 V stack L1 Pressure (N.sub.2) 10 Pa Arc Current/Target 150 A Rotation Speed 3 rpm Temperature 550° C. (Ti, Al)N Targets “Ti33Al67” + “Ti50Al50” + “Ti33Al67” sub-layer Bias −40 V and −50 V stack L2 Arc Current/Target 150 A Pressure 10 Pa Rotation 3 rpm Temperature 550° C.

[0123] The thicknesses of the sub-layer stacks L1 and L2 for the samples made by using a bias level of −40 V were about 2 μm each, measured at the edge (at the beginning of the edge rounding) on both the rake face and the flank face and calculating an average.

[0124] The thicknesses of the sub-layer stacks L1 and L2 for the samples made by using a bias level of −60 V (L1) and −50 V (L2) were about 1.5 μm each, measured at the edge (at the beginning of the edge rounding) on both the rake face and the flank face and calculating an average. Table 2 summarises the samples made.

TABLE-US-00002 TABLE 2 Sample Insert geometry Substrate Bias L1 L2 S1 ADMT160608R-F56 1 −40 V   2 μm   2 μm S2 ADMT160608R-F56 1 −60 V 1.5 μm 1.5 μm S3 ODHT050408-F57 1 −40 V   2 μm   2 μm S4 ODHT050408-F57 1 −60 V 1.5 μm 1.5 μm S5 P2808.1 2 −40 V   2 μm   2 μm S6 P2808.1 2 −60 V 1.5 μm 1.5 μm S1 ADMT160608R-F56 1 −40 V(L1)   2 μm   2 μm −40 V(L2) S2 ADMT160608R-F56 1 −60 V(L1) 1.5 μm 1.5 μm −50 V(L2) S3 ODHT050408-F57 1 −40 V(L1)   2 μm   2 μm −40 V(L2) S4 ODHT050408-F57 1 −60 V(L1) 1.5 μm 1.5 μm −50 V(L2) S5 P2808.1 2 −40 V(L1)   2 μm   2 μm −40 V(L2) S6 P2808.1 2 −60 V(L1) 1.5 μm 1.5 μm −50 V(L2)

[0125] The deposition time for L1 was 90 minutes when depositing using −40 V (samples S1, S3 and S5). Thus, L1 consisted of about 270 sub-layer periods, approximating an individual sub-layer thickness of about 4 nm.

[0126] When depositing L1 using −60 V (samples S2, S4 and S6) the deposition time for L1 was 63 minutes. Thus, L1 consisted of about 190 sub-layer periods, approximating an individual sub-layer thickness of about 4 nm.

[0127] The deposition time for L2 was 60 minutes when depositing using −40 V (samples S1, S3 and S5). Thus, L2 consisted of about 180 sub-layer periods, approximating an individual sub-layer thickness of about 4 nm for the sub-layer having an approximate composition Ti.sub.0.50Al.sub.0.50N and an individual sub-layer thickness of about 8 nm for the sub-layer having an approximate composition Ti.sub.0.33Al.sub.0.67N.

[0128] When depositing L2 using −50 V (samples S2, S4 and S6) the deposition time for L2 was 42 minutes. Thus, L2 consisted of about 130 sub-layer periods, approximating an individual sub-layer thickness of about 4 nm for the sub-layer having an approximate composition Ti.sub.0.50Al.sub.0.50N and an individual sub-layer thickness of about 8 nm for the sub-layer having an approximate composition Ti.sub.0.33Al.sub.0.67N.

Hardness and Young's Modulus of the first (Ti,Al)N Multilayer

[0129] The hardness and Young's modulus of the (Ti,Al)N sub-layer stacks L1 and L2 deposited in example 1 were measured by depositing L1 and L2 separately, respectively, immediately on a substrate and then perform the measurement. The thicknesses of the sub-layer stacks L1 and L2 were about 2 μm. The results are shown in table 3. As an alternative, it would also have been possible to measure the hardness and Young's modulus of L1 and L2, respectively, on a cross-sectional area of the first (Ti,Al)N multilayer, or measurement on an angled polished sample.

TABLE-US-00003 TABLE 3 Reduced Young's (Ti, Al)N Vickers hardness modulus sub-layer stack* [HV0.0015] [GPa] L1 3071 498 L2 3035 483 *using −40 V bias voltage

Deposition of the First Gamma-aluminium Oxide Layer

[0130] All samples S1 to S6 were provided with a first gamma-aluminium oxide layer onto the first (Ti,Al)N layer.

[0131] The Hauzer HTC1000 PVD equipment is set to a mode for deposition by bipolar pulsed magnetron sputtering.

[0132] For the deposition of the aluminium oxide, two Al-targets (800 mm×200 mm×10 mm each) were used and a dual magnetron was applied. The bias power supply was used in a bipolar pulsed mode with 45 kHz and an off-time of 10 ms. The magnetron power supply was pulsed with 60 kHz (±2 kHz), and the pulse form was sinus shape. The cathode voltage at the stabilized stage of the process was 390 V. The deposition was carried out with three-fold rotated substrate. The essential deposition parameters and measurement results (measured on cutting tools to be coated positioned in the middle of the reactor height) are indicated in table 5.

TABLE-US-00004 TABLE 5 Parameter Value Ar flow [sccm] 1220 O.sub.2 flow [sccm] 101 Total pressure [mPa] 1000 O.sub.2 part. press. [mPa] 10.2 Bias current [A] 35.3 Bias voltage [V] −125 Magnetron target 20 power [kW] Magnetron target 6.2 power density [W/cm.sup.2] Coil current [A] 4.5

[0133] 0.6 μm of aluminium oxide was deposited onto the samples S1 to S6.

[0134] XRD measurements showed only gamma phase aluminium oxide peaks.

Hardness and Young's Modulus of the First Gamma-aluminium Oxide Layer

[0135] The hardness and Young's modulus of the first gamma-aluminium oxide layer was measured by further making a deposition of about 1 μm of the gamma-aluminium oxide separately onto a cemented carbide substrate, using the same deposition conditions as used for samples S1 to S6 and then perform the measurement. Table 6 shows the results. As an alternative, it would also have been possible to measure the hardness and Young's modulus on an angled polished sample or on a cross-sectional area of the first gamma-aluminium oxide layer.

TABLE-US-00005 TABLE 6 Vickers Hardness [HV 3100 0.0015] Reduced Young's 380 modulus [GPa]

Deposition of a Set of Alternating Second (Ti,Al)N Multilayers and Second Gamma-aluminium Oxide Layers

[0136] The samples S1 to S6 were further deposited with a set of alternating second (Ti,Al)N multilayers and second gamma-aluminium oxide layers.

[0137] There are three second (Ti,Al)N multilayers and two second gamma-aluminium oxide layers deposited so the layer sequence is (Ti,Al)N-Al.sub.2O.sub.3-(Ti,Al)N-Al.sub.2O.sub.3-(Ti,Al)N.

[0138] The thickness of the first two of the second (Ti,Al)N multilayers and each of the two second gamma-aluminium oxide layers were about 0.1 μm. The third one of the second (Ti,Al)N multilayers was a little bit thicker, about 0.3 μm.

[0139] The second (Ti,Al)N multilayers are deposited in the same manner as when depositing the sub-layer stack L2 of the first (Ti,Al)N multilayer for each of samples S1 to S6, i.e., in the Hauzer HTC1000 equipment used a circular Arc-PVD technology (CARC+) using constant magnetic field configuration was applied during deposition. All other parameters and process conditions were the same as used for making the sub-layer stack L2 of the first (Ti,Al)N multilayer. The bias used for making the second (Ti,Al)N multilayers was −40 V.

[0140] For the deposition of the second (Ti,Al)N multilayers, as for depositing L2 of the first (Ti,Al)N multilayer, three targets were used: 1x “Ti50Al50”+2x “Ti33Al67”. The process parameters are summarised in table 7.

TABLE-US-00006 TABLE 7 second Targets “Ti33Al67” + “Ti50Al50” + (Ti, Al)N multi- “Ti33Al67” layer Bias −40 V Arc Current/Target 150 A Pressure 10 Pa Rotation 3 rpm Temperature 550° C.

[0141] The deposition time for each second (Ti,Al)N multilayer was about 200 s. Since the process conditions for making the second (Ti,Al)N multilayers are the same as for making the sub-layer stack L2 of the first (Ti,Al)N multilayer, a deposition time of 200 s can be estimated to give a layer thickness of a second (Ti,Al)N multilayer to be 0.11 μm. Since the number of sub-layer periods is about 10 for 200 s deposition, an individual sub-layer thickness is approximated to about 4 nm for the sub-layer having an approximate composition Ti.sub.0.50Al.sub.0.50N and an individual sub-layer thickness of about 8 nm for the sub-layer having an approximate composition Ti.sub.0.33Al.sub.0.67N.

[0142] The second gamma-aluminium oxide layers were deposited by bipolar pulsed magnetron sputtering using the same parameters and conditions as for depositing the first gamma-aluminium oxide layer.

[0143] Then, finally the samples an outer about 0.2 μm ZrN layer was deposited for colour and/or wear detection purposes. The deposition of ZrN was made by arc evaporation using an arc current of 150 A per target at 4 Pa nitrogen pressure using a bias voltage of −40 V.

[0144] Thus, the total thickness of the coating on samples S1, S3 and S5 was about 5.5 μm. Thus, the total thickness of the coating on samples S2, S4 and S6 was about 4.5 μm.

[0145] The layer structure provided is seen in table 8.

TABLE-US-00007 TABLE 8 Layer # Layer (from Thickness (Ti, Al)N sublayer substrate) [μm] Layers composition 1 4 μm first (Ti, Al)N Ti.sub.0.33Al.sub.0.67N/Ti.sub.0.50Al.sub.0.50N (S1, S3, S5) multilayer (two different stacks L1 or and L2) 3 μm (S2, S4, S6) 2 0.6 μm first gamma-Al.sub.2O.sub.3 — 3 0.1 μm second (Ti, Al)N Ti.sub.0.33Al.sub.0.67N/Ti.sub.0.50Al.sub.0.50N multi-layer (as L2) 4 0.1 μm second gamma-Al.sub.2O.sub.3 — 5 0.1 μm second (Ti, Al)N Ti.sub.0.33Al.sub.0.67N/Ti.sub.0.50Al.sub.0.50N multi-layer (as L2) 6 0.1 μm second gamma-Al.sub.2O.sub.3 — 7 0.3 μm second (Ti, Al)N Ti.sub.0.33Al.sub.0.67N/Ti.sub.0.50Al.sub.0.50N multi-layer (as L2) 8 0.2 μm ZrN —

[0146] Thus, the total thickness of the coating on samples S1, S3 and S5 was about 5.5 μm and the total thickness of the coating on samples S2, S4 and S6 was about 4.5 μm.

[0147] The level of residual stress was determined on the cemented carbide substrate of sample S1 with the whole coating deposited but without any post-treatment made. The result was −149 MPa (i.e., 149 MPa residual compressive stress). A value of around −150 MPa is regarded to be typical for all samples S1 to S6.

[0148] The level of residual stress was also determined for the first (Ti,Al)N multilayer close to the substrate surface. Sample S1 was selected. The result was 154 MPa for the sample (i.e., 154 MPa residual tensile stress)

[0149] A further sample S7 was made having a much thinner coating deposited than any of samples S1 to S6. For this sample the bias voltage used during deposition of the first (Ti,Al)N multilayer was −60 V for L1 and −50 V for L2. For the second (Ti,Al)N multilayers −50 V was used (as for L2). This sample had a deposited coating having the same types of layers, and layer sequence, as present in the coating of samples S1 to S6 (see Table 8) but which were in most cases thinner. The total coating thickness was 3.7 μm. Table 9 shows the layer thicknesses. The level of residual stress was determined for the first (Ti,Al)N multilayer close to the substrate surface of this sample as well.

TABLE-US-00008 TABLE 9 Layer # Layer (from Thickness (Ti, Al)N sublayer substrate) [μm] Layers composition 1 2 μm first (Ti, Al)N Ti.sub.0.33Al.sub.0.67N/Ti.sub.0.50Al.sub.0.50N multilayer (two different stacks L1 and L2) 2 0.5 μm first gamma-Al.sub.2O.sub.3 — 3 0.1 μm second (Ti, Al)N multi- Ti.sub.0.33Al.sub.0.67N/Ti.sub.0.50Al.sub.0.50N layer (as L2) 4 0.1 μm second gamma-Al.sub.2O.sub.3 — 5 0.1 μm second (Ti, Al)N multi- Ti.sub.0.33Al.sub.0.67N/Ti.sub.0.50Al.sub.0.50N layer (as L2) 6 0.1 μm second gamma-Al.sub.2O.sub.3 — 7 0.3 μm second (Ti, Al)N multi- Ti.sub.0.33Al.sub.0.67N/Ti.sub.0.50Al.sub.0.50N layer (as L2) 8 0.5 μm ZrN —

[0150] The level of residual stress was determined for the first (Ti,Al)N multilayer close to the substrate surface. The result was −1198 MPa for the sample (i.e., 1198 MPa residual compressive stress)

Post Treatment Operations

[0151] The samples S1 to S6, as well as sample S7 were post treated by shot peening followed by wet blasting. The wet blasting both smoothens the coating surface and imparts a level of average compressive stress in the coating.

Shot Peening Parameters

[0152] Blasting pressure 5 bar

[0153] Blasting Angle 90°, against the surface plane of the coating

[0154] Blasting Distance 10 cm

[0155] Blasting Material ZrO.sub.2 beads (diameter 75-125 μm),

[0156] Blasting time 2 sec

[0157] The ZrO.sub.2 beads used had the following composition:

[0158] ZrO.sub.2: 60-65 wt %

[0159] SiO.sub.2: 25-30 wt %

[0160] Al.sub.2O.sub.3: 2-5 wt %

[0161] the rest being other oxides (CaO, Fe.sub.2O.sub.3, TiO.sub.2)

[0162] Unblasted substrate −80 MPa

[0163] Residual stress in substrate was −1120 MPa

Wet Blasting Parameters

[0164] Blasting pressure: 1.6 to 2 bar

[0165] Blasting Angle: 75°, against the surface plane of the coating

[0166] Blasting Distance: 10 cm

[0167] Blasting Material: Al.sub.2O.sub.3 F220 (FEPA)

[0168] The blasting was made using a set-up provided with 14 blasting guns, the set-up designed for blasting a tray of inserts of about 50-400 cutting tool inserts. A blasting of 40-50 seconds during rotation lead to an estimated blasting time per insert of one to three seconds.

[0169] The level of residual stress was determined on the cemented carbide substrate of sample S1 with the whole coating deposited and after both post-treatments shot peening and wet blasting. The result was −1133 MPa (i.e., 1133 MPa compressive stress).

[0170] The level of residual stress was also determined for the first (Ti,Al)N multilayer close to the substrate surface. Sample S1 and sample S7 were tested which had the whole coating deposited and had been subjected to both post-treatments shot peening and wet blasting. The result was −1258 MPa for sample S1 (i.e., 1258 MPa residual compressive stress) and −1225 MPa for sample S7 (i.e., 1225 MPa residual compressive stress). Thus, the same stress levels were reached for both samples.

[0171] Table 10 summarises the results from all residual stress measurements.

TABLE-US-00009 TABLE 10 Residual stress, Residual lowest part of stress, sub- first (Ti, Al)N strate surface multilayer Sample [MPa] [MPa] S1 with coating, as deposited −149 +154 S1 with coating, after post treatments −1133 −1258 S7 with coating, as deposited — −1198 S7 with coating, after post treatments — −1225

[0172] The post treatment process increases the residual compressive stress (for the thicker coating) in the lowest part of the coating to a level of about 1 GPa. The surface of the substrate at the same time has a residual stress level after the post treatment process at the same level.

Example 2: Manufacturing of Comparative Samples

[0173] A comparative coated cutting tool samples S8 to S10, essentially according to prior art U.S. Pat. No. 8,709,583, were made by depositing a coating onto a cutting tool body being an insert having a geometry ADMT160608R-F56 (for sample S8), ODHT050408-F57 (for sample S9) and P2808.1 (for sample S10), respectively. The cutting tool body was for samples S8 and S9 made out of a cemented carbide of the composition 88 wt % WC, 1.5 wt % (Ta, Nb)C and a binder phase of 10.5 wt % Co. The average WC grain size dWC was 0.8 μm. For sample S10 the cutting tool body was a cemented carbide of the composition 87.5 wt % WC, 0.5 wt % Cr and a binder phase of 12.5 wt % Co. The average WC grain size dWC was 0.4 μm.

[0174] The coating was deposited by using a PVD coating installation Hauzer HTC1000. The coating was made out of a 7-layer coating:

[0175] 1. (Ti,Al)N (ratio Ti:Al of 33:67 atomic %) of a layer thickness of 2 μm deposited by arc evaporation,

[0176] 2. aluminium oxide of a layer thickness of 0.5 μm deposited by reactive magnetron sputtering,

[0177] 3. (Ti,Al)N (ratio Ti:Al of 33:67 atomic %) of a layer thickness of 0.2 μm deposited by arc evaporation,

[0178] 4. aluminium oxide of a layer thickness of 0.15 μm deposited by reactive magnetron sputtering,

[0179] 5. (Ti,Al)N (ratio Ti:Al of 33:67 atomic %) of a layer thickness of 0.2 μm deposited by arc evaporation,

[0180] 6. aluminium oxide of a layer thickness of 0.15μm deposited by reactive magnetron sputtering,

[0181] 7. ZrN of a layer thickness of 0.6 μm deposited by arc evaporation,

[0182] Before the coating operation the substrate was cleaned in alcohol and additionally cleaned by using an Ar ion bombardment prior to deposition of the layers in the vacuum chamber. The Ar ion bombardent was, however, only proceeded that only up to about 0.2 μm of the substrate material was removed.

[0183] Deposition of the layers:

[0184] 1st, 3rd and 5th layers:

[0185] Deposition of (Ti,Al)N was effected by arc evaporation with a 65 A vaporiser current per source at 3 Pa nitrogen and with a bias voltage in the DC mode of −40 V and at a temperature of about 550° C.

[0186] 2nd, 4th and 6th layers:

[0187] Deposition of aluminium oxide was effected by reactive magnetron sputtering with a specific cathode power of about 7 W/cm.sup.2 at 0.5 Pa Ar and oxygen as the reactive gas (flow about 80 sscm), with a bipolarly pulsed bias voltage (70 kHz) of −150 V and a temperature of about 550° C.

[0188] 7th layer:

[0189] ZrN was deposited in an arc with a 150 A vaporiser current per source at 4 Pa nitrogen and a bias voltage in the DC mode of −40 V and a temperature of about 550° C.

[0190] Table 11 summarises the layer sequence in comparative samples S8 to S10.

TABLE-US-00010 TABLE 11 Layer # Layer Thickness (from substrate) [μm] Layers 1   2 μm Ti.sub.0.33Al.sub.0.67N, single layer 2  0.5 μm gamma-Al.sub.2O.sub.3 3  0.2 μm Ti.sub.0.33Al.sub.0.67N, single layer 4 0.15 μm gamma-Al.sub.2O.sub.3 5  0.2 μm Ti.sub.0.33Al.sub.0.67N, single layer 6 0.15 μm gamma-Al.sub.2O.sub.3 7  0.6 μm ZrN

[0191] It was tested to perform the shot peening post treatment as made for the inventive samples in Example 1 also to the comparative samples. However, the coating flaked off.

Example 3-Cutting Tests

[0192] The performance of the coated cutting tools samples S1 to S6 according to the invention was tested in milling operation along with the comparative samples S8 to S10. See table 12 summarising the samples.

TABLE-US-00011 TABLE 12 Sample Insert geometry Substrate Coating S1 ADMT160608R-F56 1 invention S2 ADMT160608R-F56 1 invention S3 ODHT050408-F57 1 invention S4 ODHT050408-F57 1 invention S5 P2808.1 2 invention S6 P2808.1 2 invention S8 ADMT160608R-F56 1 comparative S9 ODHT050408-F57 1 comparative S10 P2808.1 2 comparative

[0193] Samples S1 and S2 were compared against comparative sample S8.

[0194] Samples S3 and S4 were compared against comparative sample S9.

[0195] Samples S5 and S6 were compared against comparative sample S10.

Test 1

[0196] The metal cutting performance of the coated cutting tool samples S1, S2 and S8 were tested in face milling operations using a face milling cutter type F2010.UB.127.Z08.02R681M (according to DIN4000-88) from Walter AG, Tübingen, Germany, on a Heller FH 120-2 machine under the following conditions.

Cutting Conditions

[0197] Tooth Feed f.sub.z [mm/tooth]: 0.2

[0198] Cutting speed v.sub.c [m/min]: 283

[0199] Axial cutting depth a.sub.p [mm]: 98

[0200] Radial cutting depth a.sub.e [mm]: 3

[0201] Workpiece material: 42CrMo4; tensile strength Rm: 740 N/mm.sup.2

[0202] The cut-off criteria was the maximum wear at the flank faces of the tool, i.e., the deepest crater observed on the flank face of a tool, V.sub.Bmax,reaching 0.3 mm.

[0203] Table 13 shows the results of the cutting tests.

TABLE-US-00012 TABLE 13 Cutting length Sample ID [mm] S1 7200 S2 6400 S8 5600

Test 2

[0204] The metal cutting performance of the coated cutting tool samples S3, S4 and S9 were tested in face milling operations using a face milling cutter type F4081.B.052.Z05.04 (according to DIN4000-88) from Walter AG, Tübingen, Germany, on a Heller FH 120-2 machine under the following conditions.

Cutting Conditions

[0205] Tooth Feed f.sub.z [mm/tooth]: 0.23

[0206] Cutting speed v.sub.c [m/min]: 240

[0207] Axial cutting depth a.sub.p [mm]: 3

[0208] Radial cutting depth a.sub.e [mm]: 40

[0209] Workpiece material: 1.4435 (X2CrNiMo18-14-3); tensile strength Rm: 515 N/mm.sup.2

[0210] The cut-off criteria was the maximum wear at the flank faces of the tool, i.e., the deepest crater observed on the flank face of a tool, V.sub.Bmax,reaching 0.3 mm.

[0211] Table 14 shows the results of the cutting tests.

TABLE-US-00013 TABLE 14 Cutting length Sample ID [mm] S3 15000 S4 14000 S9 10000

Test 3

[0212] The metal cutting performance of the coated cutting tool samples S5, S6 and S10 were tested in face milling operations using a face milling cutter type F2010.UB.127.Z08.02R681M (according to DIN4000-88) from Walter AG, Tübingen, Germany, on a Heller FH 120-2 machine under the following conditions.

Cutting Conditions

[0213] Tooth Feed f.sub.z [mm/tooth]: 0.2

[0214] Cutting speed v.sub.c [m/min]: 150

[0215] Axial cutting depth a.sub.p [mm]: 3

[0216] Radial cutting depth a.sub.e [mm]: 50

[0217] Workpiece material: 1.4301 (X5CrNi18-10)

[0218] The cut-off criteria was the maximum wear at the flank faces of the tool, i.e., the deepest crater observed on the flank face of a tool, V.sub.Bmax, reaching 0.3 mm.

[0219] Table 15 shows the results of the cutting tests.

TABLE-US-00014 TABLE 15 Cutting length Sample ID [mm] S5 4800 S6 4800 S10 3200