COATED CUTTING TOOL AND A PROCESS FOR ITS MANUFACTURE

Abstract

A coated cutting tool and a process for manufacturing a coated cutting tool consisting of a substrate and a single-layer or multi-layer hard material coating. The substrate is selected from cemented carbide, cermet, ceramics, cubic boron nitride, polycrystalline diamond or high-speed steel. The hard coating includes at least one layer of Al.sub.aCr.sub.bMe.sub.cO.sub.dN.sub.e, wherein a+b+c+d+e=1, a, b, d and e each are >0, c=0 or c>0, ab, c/(a+b+c)0.1, wherein Me is at least one element selected from the group consisting of Ti, Zr, Ta, Nb, Hf, Si, and V, and wherein the Al.sub.aCr.sub.bMe.sub.cO.sub.dN.sub.e layer is deposited by an arc vapor deposition process (Arc-PVD) using targets containing Al and Cr with an Al:Cr atomic ratio in the range of 95:5 to 50:50.

Claims

1. A process for manufacturing a coated cutting tool comprising a substrate and a single-layer or multi-layer hard material coating, the substrate being selected from cemented carbide, cermet, ceramics, cubic boron nitride, polycrystalline diamond or high-speed steel, the hard coating comprising at least one layer of Al.sub.aCr.sub.bMe.sub.cO.sub.dN.sub.e, wherein a, b, c, d, and e are atomic ratios, and wherein a+b+c+d+e=1, a, b, d and e each are >0, c=0 or c>0, a>b, c/(a+b+c)0.1, preferably 0.05 0.1d/(d+e)0.5, wherein Me is at least one element selected from the group consisting of Ti, Zr, Ta, Nb, Hf, Si, and V, and wherein the Al.sub.aCr.sub.bMe.sub.cO.sub.dN.sub.e layer is deposited by an arc vapor deposition process using targets containing Al and Cr with an Al:Cr atomic ratio in the range of 95:5 to 50:50, and wherein the reaction gas mixture contains O.sub.2 gas and N.sub.2 gas, wherein optionally a portion or all of the O.sub.2 gas and a portion of the N.sub.2 gas is replaced by a nitrogen and oxygen containing gas, selected from nitrous oxide, N.sub.2O, nitric oxide, NO, nitrogen dioxide, NO.sub.2, and dinitrogen tetroxide, N.sub.2O.sub.4, wherein the reaction gas mixture optionally contains one or more inert gases, wherein the total gas pressure is within the range from 7 Pa to 20 Pa, wherein the O.sub.2 partial pressure is from 0.001 Pa to 0.1 Pa, wherein 0.002(flow rate (O.sub.2)/flow rate (N.sub.2)0.02, and wherein a (flow rate (O.sub.2)+flow rate (N.sub.2))/flow rate (inert gas)4.

2. The process according to claim 1, wherein the Al:Cr atomic ratio in the target(s) is in the range of 90:10 to 50:50.

3. The process according to claim 1, wherein the total gas pressure is 8 Pa and/or the total gas pressure is 15 Pa.

4. The process according to claim 1, wherein (flow rate (O.sub.2)+flow rate (N.sub.2))/flow rate (inert gas)5 or the reaction gas mixture contains no inert gas.

5. The process according to claim 1, wherein a ratio of overall evaporator current (measured in Ampere [A]) to O.sub.2 flow (measured in sccm) is in the range of 15:1 to 6:1.

6. The process according to claim 1, wherein the bias voltage is in the range of 20 to 100 V.

7. The process according to claim 1, wherein the O.sub.2 partial pressure is in the range of 0.01 to 0.1 Pa.

8. A coated cutting tool comprising: a substrate; and a single-layer or multi-layer hard material coating, the substrate being selected from cemented carbide, cermet, ceramics, cubic boron nitride (cBN), polycrystalline diamond (PCD) or high-speed steel, wherein the hard material coating includes at least one layer of Al.sub.aCr.sub.bMe.sub.cO.sub.dN.sub.e, wherein a, b, c, d, and e are atomic ratio and wherein i) a+b+c+d+e=1, ii) a, b, d and e each are 0, iii) c=0 or c0, iv) ab, v) c/(a+b+c)0.1 vi) 0.1d/(d+e)0.5, wherein Me is at least one element selected from the group consisting of Ti, Zr, Ta, Nb, Hf, Si, and V and the Al.sub.aCr.sub.bMe.sub.cO.sub.dN.sub.e layer further having the following characteristics of a Vickers hardness HV 0.0153000 and a reduced Young's modulus E400 GPa.

9. The coated cutting tool according to claim 8, wherein 0.05b/(a+b+c)0.5.

10. The coated cutting tool according to claim 8, wherein (a+b+c)/(d+e)1.

11. The coated cutting tool according to claim 8, wherein the Al.sub.aCr.sub.bMe.sub.cO.sub.dN.sub.e layer has a Vickers hardness HV 0.0153200.

12. The coated cutting tool according to claim 8, wherein the Al.sub.aCr.sub.bMe.sub.cO.sub.dN.sub.e layer has a reduced Young's modulus E420 GPa.

13. The coated cutting tool according claim 8, wherein the Al.sub.aCr.sub.bMe.sub.cO.sub.dN.sub.e layer has an average surface roughness Ra, measured over a length of 4.8 mm of 0.5 m.

14. A coated cutting tool made according to the process of claim 1.

Description

FIGURE DESCRIPTION

[0077] FIGS. 1 to 9 show XRD diffractograms of the layer types produced and investigated according to the following examples.

MATERIALS AND METHODS

[0078] For characterizing the deposited layers of the examples and comparative examples described herein, the following methods were used.

[0079] XRD (X-Ray Diffraction)

[0080] XRD measurements were done on a XRD3003 PTS diffractometer of GE Sensing and Inspection Technologies using CuK-radiation. The X-ray tube was run in point focus at 40 kV and 40 mA. A parallel beam optic using a polycapillary collimating lens with a measuring aperture of fixed size was used on the primary side whereby the irradiated area of the sample was defined in such manner that a spill over of the X-ray beam over the coated face of the sample is avoided. On the secondary side a Soller slit with a divergence of 0.4 and a 25 m thick Ni K.sub. filter were used. The measurements were carried out over the range of 15 to 80 2-theta with a step size of 0.03. Grazing-incidence X-ray diffraction technique under 1 incidence angel was employed to study the crystal structure of the layers.

[0081] Vickers Hardness:

[0082] The Vickers hardness was measured by means of nano indentation (load-depth graph) using a Picodentor HM500 of Helmut Fischer GmbH, Sindelfingen, Germany. For the measurement and calculation the Oliver and Pharr evaluation algorithm was applied, wherein a diamond test body according to Vickers was pressed into the layer and the force-path curve was recorded during the measurement. The maximum load used was 15 mN, the time period for load increase and load decrease was 20 seconds each and the holding time (creep time) was 10 seconds. From this curve hardness was calculated.

[0083] Reduced Young's Modulus

[0084] The reduced Young's modulus (modulus of elasticity) was determined by means of nano-indentation (load-depth graph) as described for determining the Vickers hardness.

[0085] Thickness:

[0086] Thickness was determined by calotte grinding. Thereby a steel ball was used having a diameter of 30 mm for grinding the dome shaped recess and further the ring diameters were measured, and the layer thicknesses were calculated therefrom.

[0087] EDX (Energy-Dispersive X-Ray Spectroscopy)

[0088] EDX measurements for atomic content determination within the layer were carried out on a scanning electron microscope Supra 40 VP from Carl Zeiss at 15 kV acceleration voltage with an EDX spectrometer of the type INCA x-act from Oxford Instruments, UK.

[0089] PVD Coating

[0090] For PVD coatings, as described in the examples herein, a Hauzer HTC1000 (IHI Hauzer Techno Coating B.V., The Netherlands) was used applying a circular arc technology (CARC+) using constant magnetic field configuration during deposition.

[0091] Surface Roughness

[0092] Average surface roughness, Ra, was measured with a roughness measuring device P800 type measuring system of the manufacturer JENOPTIK Industrial Metrology Germany GmbH (formerly Hommel-Etamic GmbH) using the evaluation software TURBO WAVE V7.32, determining the waviness according to ISO 11562, TKU300 sensing device and KE590GD test tip with a scan length of 4.8 mm and measured at a speed of 0.5 mm/s.

EXAMPLES

Example 1Deposition of AlCrON Coating Layers According to the Invention and Comparative Coatings

[0093] In the following examples of the preparation of cutting tools according to the present invention and of comparative examples cemented carbide cutting tool substrate bodies (composition: 12 wt-% Co, 1.6 wt-% (Ta, Nb)C, balance WC; WC grain size: 1.5 m geometry: ADMT160608R-F56) were coated in a PVD system as indicated above.

[0094] Prior to the deposition, the installation was evacuated to 810.sup.5 mbar, and the substrate was pretreated at 550 C.

[0095] For the deposition of AlCrON layers in each case 4 targets having an Al:Cr atomic ratio of 70:30, having a diameter of 100 mm and being positioned in the reactor on top of each other were used. The further parameters for the deposition of different layers are given in the following table 1. Thereby, the indicated O.sub.2 partial pressure and the indicated N.sub.2 flow are the ones 10 min after initiation of the deposition process. In the deposition of layer type 5008 no Ar, instead of N.sub.2, was used to obtain the desired total pressure.

TABLE-US-00001 TABLE 1 N.sub.2 O.sub.2 Overall Bias Bias O.sub.2 partial Total flow flow current Time current voltage pressure pressure Layer Type [sccm] [sccm] [A] [min] [A] [V] [Pa] [Pa] 3004 (Comp.) 3950 360 4 150 60 3.9 40 0.11 10 (N.sub.2) 4002 (Comp.) 4090 200 4 150 60 4.9 40 0.11 10 (N.sub.2) 5002 (Comp.) 4180 100 4 150 60 4.9 40 0.047 10 (N.sub.2) 5006 (Inv.) 4180 50 4 150 60 4.8 40 0.017 10 (N.sub.2) 5008 (Comp.) 170 4 150 60 7.7 40 0.11 10 (Ar) 6004 (Comp.) 4210 4 150 60 4.5 40 10 (N.sub.2) 7001 (Comp.) 4080 200 4 150 60 5.8 80 0.11 10 (N.sub.2) 7003 (Comp.) 4050 200 4 150 60 6.3 120 0.12 10 (N.sub.2) 7005 (Inv.) 4170 50 4 150 60 5.5 80 0.017 10 (N.sub.2)

[0096] During the deposition, the O.sub.2 flow was kept constant, while the indicated O.sub.2 partial pressure was reached during the process. The total pressure was kept constant at 10 Pa by adjusting the flow of N.sub.2 or Ar, respectively. In these examples, either N.sub.2 or Ar were used, but no mixtures.

[0097] Table 2 shows the thickness, the Vickers hardness, the reduced Young's modulus and the atomic contents of the deposited layers, measured as described above.

TABLE-US-00002 TABLE 2 reduced Layer Vickers Young's thickness hardness modulus Al Cr O N Layer Type [m] [HV0.015] [GPa] [at. %] [at. %] [at. %] [at. %] 3004 (Comp.) 1.20 2755 354 25.3 12.7 62.1 0.0 4002 (Comp.) 1.40 2828 339 27.2 14.3 54.3 4.3 5002 (Comp.) 1.40 3301 379 27.6 15.1 31.3 26.1 5006 (Inv.) 1.40 3387 433 28.8 15.7 16.7 38.9 5008 (Comp.) 2.00 987 226 29.4 14.3 56.3 0.0 6004 (Comp.) 1.40 2905 460 30.6 17.6 1.7 50.1 7001 (Comp.) 1.60 3010 361 25.7 13.3 52.9 8.0 7003 (Comp.) 1.60 2507 299 24.4 12.8 53.4 9.4 7005 (Inv.) 1.05 3515 421 28.5 16.1 16.7 38.7

[0098] XRD measurements were made on all layer types and are shown in FIGS. 1 to 9. The diffractograms show that each of the AlCrON layers according to the present invention exhibit only one single cubic phase.

[0099] The surface roughness was measured on an AlCrON layer according to the invention (Layer Type 7005). The average surface roughness Ra, measured over a length of 4.8 mm, was 0.03 m.

Example 2Cutting Tests on Multi-Layer Coated Cutting Tools

[0100] In order to assess the effect of the AlCrON layer according to the invention, compared to conventional coating, with respect to cutting properties, multi-layer coated cutting tools were produced and tested in a milling test. The cemented carbide substrates were the same as used above in example 1. In each case the multi-layer coating structures consisted of a total of seven layers, four of them were conventional TiAlN layers, alternating with inventive AlCrON layers in the tool according to the invention, or with Al.sub.2O.sub.3 layers in the comparative tool. The thicknesses of the layers corresponding to each other were the same in both sequences.

[0101] The TiAlN layers were each deposited in an Arc-PVD process at a total pressure of 10 Pa. The ratio Al/(Al+Ti) in the layers was 0.61 with 50 at. % nitrogen. The deposition conditions were adjusted to achieve the desired layer thicknesses.

[0102] The AlCrON layers in the layer sequence of the tool according to the invention were deposited under the deposition conditions as describe above for layer type 5006, whereby the deposition times were adjusted to achieve the desired layer thicknesses.

[0103] The Al.sub.2O.sub.3 layers in the comparative tool were prepared by dual magnetron sputtering at a 20 kW, a total gas pressure of 0.45 Pa, an Ar flow of 500 sccm, an O.sub.2 flow of about 125 sccm, at a bias voltage of 125 V, pulsed with 40 kHz and 10 s off time and 22 A bias current as well as 480 V cathode voltage after hysteresis (at the operating point).

[0104] The layer structures were as follows:

TABLE-US-00003 Layer Layer # Thickness Layer Composition Layer Composition (from substrate) [m] Inventive Tool Comparative Tool 1 4 m TiAlN 2 0.5 m AlCrNO Al.sub.2O.sub.3 3 0.25 m TiAlN 4 0.1 m AlCrNO Al.sub.2O.sub.3 5 0.25 m TiAlN 6 0.1 m AlCrNO Al.sub.2O.sub.3 7 0.6 m TiAlN

[0105] Cutting tests were performed on a Heller FH 120-2 machine under the following conditions.

[0106] Cutting Conditions: [0107] Tooth Feed f.sub.z [mm/tooth]: 0.2 [0108] Feed v.sub.f [mm/min]: 120 [0109] Cutting speed v.sub.c [m/min]: 235 [0110] Cutting depth a.sub.p [mm]: 3 [0111] Workpiece material: 42CrMo4; tensile strength Rm: 950 N/mm.sup.2

[0112] The following table 3 shows the results of the cutting tests, wherein V.sub.B is the minimum wear at the flank faces of the tool, V.sub.Bmax is the maximum wear, i.e. the deepest crater observed on the flank face of a tool, and V.sub.R is the wear at the cutting edge radius

TABLE-US-00004 TABLE 3 Cutting Inventive Tool Comparative Tool length V.sub.B V.sub.Bmax V.sub.R V.sub.B V.sub.Bmax V.sub.R [mm] [mm] [mm] [mm] [mm] [mm] [mm] 800 0.02 0.02 0.02 0.02 0.03 0.03 1600 0.02 0.02 0.02 0.03 0.04 0.06 2400 0.02 0.02 0.03 0.04 0.06 0.08 3200 0.02 0.03 0.03 0.07 0.10 0.12 4000 0.02 0.03 0.04 0.10 0.12 0.17 4800 0.02 0.06 0.08 0.12 0.35 0.45

[0113] In particular over a longer cutting length, the cutting tool coated with layer sequence, comprising an AlCrON layer according to the invention shows a significant reduction of the wear, both at the flank face and the cutting edge radius, in comparison to a similar layer sequence, comprising Al.sub.2O.sub.3 layers instead of the AlCrON layers according to the invention.