Cutting tool

Abstract

A cutting tool includes a base body and a coating applied thereto. For providing a cutting tool, having both a hard coating that also exhibits fracture toughness, the coating includes at least one oxide layer deposited in the PVD process, consisting of at least 10 alternating single coats of Al.sub.2O.sub.3 and (Al.sub.x, Me.sub.1-x).sub.2O.sub.3, where 0<x<1, wherein Me is selected from one or more of the group of Si, Ti, V, Zr, Mg, Fe, B, Gd, La and Cr.

Claims

1. A cutting tool having a base body and a coating applied thereto, wherein the coating comprises at least one oxide layer deposited in the PVD process, consisting of at least 100 alternating single coats of Al.sub.2O.sub.3 and (Al.sub.x, Me.sub.1-x).sub.2O.sub.3 where 0<x<1, wherein Me is selected from one or more of the group of Si, Ti, V, Zr, Mg, Fe, B, Gd, La and Cr, wherein the crystal structure of the single coats consisting of (Al.sub.x, Me.sub.1-x).sub.2O.sub.3 has the same crystal structure as the single coats of Al.sub.2O.sub.3.

2. The cutting tool according to claim 1, wherein the single coats of (Al.sub.x, Me.sub.1-x).sub.2O.sub.3 of the oxide layer consisting of single coats are single phase.

3. The cutting tool according to claim 1, wherein the single coats of Al.sub.2O.sub.3 of the oxide layer consisting of single coats have a γ crystal structure.

4. The cutting tool according to claim 1, wherein the single coats of Al.sub.2O.sub.3 of the oxide layer consisting of single coats have a γ crystal structure and the crystal structure of the single coats consisting of (Al.sub.x, Me.sub.1-x).sub.2O.sub.3 has the same crystal structure as the single coats of Al.sub.2O.sub.3.

5. The cutting tool according to claim 1, wherein the thickness of the single coats is 2 nm to 200 nm.

6. The cutting tool according to claim 1, wherein the oxide layer consists of 100 to 1000 single coats.

7. The cutting tool according to claim 1, wherein the overall layer thickness of the oxide layer consisting of the single coats is from 0.1 μm to 8 μm.

8. The cutting tool according to claim 1, wherein the fraction of Me in the oxide layer consisting of the single coats is in the range of from 1.3 at. % to 2.0 at. %.

9. The cutting tool according to claim 1, wherein Me is selected from Si, Ti, V, Zr, Mg, Fe, Cr, and B.

10. The cutting tool according to claim 1, wherein the oxide layer consisting of the single coats is produced by means selected from sputtering, dual magnetron sputtering and HIPIMS (high power impulse magnetron sputtering).

11. The cutting tool according to claim 1, wherein for the manufacture of the oxide layer consisting of the single coats at least one Al target and at least one AlMe target are used.

12. The cutting tool according to claim 1, wherein the AlMe target contains from 1 at. % Me to 16 at. % Me and from 99 at. % Al to 84 at. % Al.

13. The cutting tool according to claim 1, wherein between the base body and the oxide layer consisting of the single coats at least one further layer is present, being or comprising a nitride selected from TiN, TiCN, TiAlN, AlCrN, TiSiN, TiAlSiN, and TiAlCrN.

14. The cutting tool according to claim 1, wherein the oxide layer consisting of the single coats has a Vickers hardness in the range of from 1800 HV to 4000 HV.

15. A cutting tool having a base body and a coating applied thereto, wherein the coating comprises at least one oxide layer deposited in the PVD process, consisting of at least 10 alternating single coats of Al.sub.2O.sub.3 and (Al.sub.x, Me.sub.1-x).sub.2O.sub.3 where 0<x<1, a thickness of the single coats being 2 nm to 200 nm, and wherein Me is selected from one or more of the group of Si, Ti, V, Zr, Mg, Fe, B, Gd, La and Cr, wherein the crystal structure of the single coats consisting of (Al.sub.x, Me.sub.1-x).sub.2O.sub.3 has the same crystal structure as the single coats of Al.sub.2O.sub.3.

16. A cutting tool having a base body and a coating applied thereto, wherein the coating comprises at least one oxide layer deposited in the PVD process, consisting of at least 10 alternating single coats of Al.sub.2O.sub.3 and (Al.sub.x, Me.sub.1-x).sub.2O.sub.3 where 0<x<1, an overall layer thickness of the oxide layer consisting of the single coats being from 0.1 μm to 8 μm, and wherein Me is selected from one or more of the group of Si, Ti, V, Zr, Mg, Fe, B, Gd, La and Cr, wherein the crystal structure of the single coats consisting of (Al.sub.x, Me.sub.1-x).sub.2O.sub.3 has the same crystal structure as the single coats of Al.sub.2O.sub.3.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a cross-section of the cutting tool according to the present disclosure.

DETAILED DESCRIPTION

(2) Referring to FIG. 1, a cutting tool 10 has base body 12 and a hard coating 14 that also exhibits fracture toughness. The coating includes at least one oxide layer deposited in the PVD process, consisting of at least 10 alternating single coats 16, 18 of either Al.sub.2O.sub.3 and/or (Al.sub.x, Me.sub.1-x).sub.2O.sub.3, wherein 0<x<1, and wherein Me is selected from one or more of the group of Si, Ti, V, Zr, Mg, Fe, B, Gd, La and Cr.

Example 1: Coating of Substrates

(3) For investigating the production of the oxide layers having alternating single coats and in order to compare these with known single layers of Al.sub.2O.sub.3, different coatings were applied to base bodies.

(4) In all examples the same base bodies were used. These are base bodies having a geometry of S-15 in accordance with ISO naming, having a mirror polished surface as well as a proportion of Co of 10 wt.-% and 90 wt.-% WC.

(5) In order to eliminate effects from underlying layers, with respect to the determination of fracture toughness multi-coat layers have peen applied directly to a base body (substrate) and no further layers have been arranged above or below.

Experiment A: [Al.SUB.2.O.SUB.3.—(AlSi).SUB.2.O.SUB.3.] Oxide Layer

(6) Onto the above described base body the following oxide layer has been applied: [Al.sub.2O.sub.3 (AlSi).sub.2O.sub.3] oxide layer having 360 essentially alternating single coats PVD process: Dual magnetron sputtering (dMS) Targets: Target 1: Al; target size: 800×200 mm Target 2: AlSi where Al:Si is 95:5 (at. %); target size: 800×200 mm Deposition: Temperature: 550° C. 0.43 Pa argon partial pressure Reactive gas: Oxygen (partial pressure: 4×10.sup.−5 mbar) Power (dMs): 30 kW Operating point: 480 V Bias current: 6.5 A Substrate bias voltage: 125 V unipolar (45 kHz, 10 is offtime)

(7) The thickness of the single coats was about 4.4 nm.

(8) The oxide layer of Experiment A was analyzed with XRD and only gamma phase peaks were detected. Both the Al.sub.2O.sub.3 and (AlSi).sub.2O.sub.3 single coats can therefore be concluded to be of single phase gamma structure.

Experiment B: Al.SUB.2.O.SUB.3 .Single Layer

(9) The production was—if not indicated otherwise—under the same conditions as in example A. However, two targets have been used, consisting exclusively of aluminium (Al):

(10) Al.sub.2O.sub.3 single layer PVD process: Dual magnetron sputtering (dMS) Targets: Target 1: Al; target size: 800×200 mm Target 2: Al, target size: 800×200 mm Deposition: Power (DMS): 20 kW Operating point: 510 V Bias current: 5.5 A

Example C: Al.SUB.2.O.SUB.3 .Single Layer by the CVD Process

(11) For this comparative example instead using the PCD process for coating the body of hard metal, a conventional thermal CVD process has been applied.

(12) A summary of the production conditions is provided in the table 1 below.

(13) TABLE-US-00001 TABLE 1 Experiment Target 1 Target 2 Layer Process A Al AlSi (Al.sub.95, Si.sub.5).sub.2O.sub.3 + PVD (95 at. %: Al.sub.2O.sub.3 (dMS) 5 at. %) B Al Al Al.sub.2O.sub.3 PVD (dMS) C — — Al.sub.2O.sub.3 CVD (CVD)

Example 2: Comparison of Properties of the Coatings

(14) For comparing the properties of the coatings the following parameters have been measured:

(15) Fracture Toughness:

(16) Using a Vickers type indenter (a four-sided square-based pyramid having an included angle of) 136° has been pushed onto the surface for 20 s. The (maximum) load for the indentations (test load) was 200 N. The applied load increase and load decrease was 20 N/s without holding time. During the application of the load cracks were formed within the coating. Upon release of the load images were produced by means of scanning electron microscopy and the crack lengths l.sub.1 to l.sub.4 visible on the surface and extending from the four corners of the indentation, were measured.

(17) A HPG 2500/1 apparatus from Gesellschaft für Fertigungstechnik and Entwicklung Schmalkalden mbH was used for producing the indentations.

(18) For each example from 5 to 11 Vickers indentations were produced. The crack length of the single cracks was determined by a commercially available software (AnalySIS docu from Olympus Soft Imaging Solutions GmbH) and the mean crack length (arithmetic average) l.sub.layer was calculated thereof.

(19) The mean crack length l.sub.layer was used as a measure for the resistance against crack propagation of the hard material layer applied by means of PVD.

(20) Vickers Hardness:

(21) The Vickers hardness was determined by means of nano indentation (load-depth graph). The apparatus used was a Helmut Fischer GmbH, Sindelfingen, Germany, Picodentor HM500. The maximum force used was 15 mN, the time period for load increase and load decrease was 20 seconds each and the holding time was 10 seconds. After having applied the load using the Vickers indenter as described above, the length of the diagonal lines d.sub.1 and d.sub.2 of the projected cross-sectional area of the impressions were measured. Using the measures of the diagonal lines and calculating the mean diagonal (arithmetic average) the Vickers hardness was calculated.

(22) Reduced Modulus of Elasticity:

(23) The reduced modulus of elasticity was determined by means of nano indentation (load-depth graph) as described for determining the Vickers hardness.

(24) Thickness:

(25) Determining the thickness was done using the calotte grinding. Thereby a steel ball was used having a diameter of 30 mm for grinding the dome shaped recess and further the ring diameter was measured.

(26) The results of these measurements are summarized in the table 2 below:

(27) TABLE-US-00002 TABLE 2 Reduced Crack Hardness/ modulus Thickness/ length/ Example Layer HV E/GPa μm μm A (Al.sub.95, Si.sub.5).sub.2O.sub.3 + 2837 334 1.6 64.9 Al.sub.2O.sub.3 B Al.sub.2O.sub.3 2847 344 1.3 70.2 C CVD — — 9.5 170

(28) For determining the crack length the test load was set to be 200 N for these examples, as less load would lead to short cracks being difficult to measure and difficult to compare, while greater load caused spalling of the coat.