Coated cutting tool and a method for its production

Abstract

A coated cutting tool includes a substrate of cemented carbide, cermet, cBN, ceramics or HSS and a coating of a nitride layer, which is a High Power Impulse Magnetron Sputtering (HIPIMS) deposited layer of a nitride of one or more of Ti, Zr, Hf, V, Ta, Nb, Cr, Si and Al, and a HIPIMS-deposited oxide layer being an (Al.sub.aMe.sub.1−a).sub.2O.sub.3 layer, 0.05≤a≤1, wherein Me is one or more of Ti, Mg, Ag, Zr, Si, V, Fe, Hf, B and Cr. The oxide layer is situated above the nitride layer. Also, a method is disclosed for producing a coated cutting tool having the nitride layer and oxide layer, the nitride layer and the oxide layer being deposited by a HIPIMS process.

Claims

1. A coated cutting tool comprising a substrate of cemented carbide, cermet, cBN, ceramics or HSS, with a coating comprising a nitride layer, which is a High Power Impulse Magnetron Sputtering (HIPIMS)deposited layer of a nitride of one or more of Ti, Zr, Hf, V, Ta, Nb, Cr, Si and Al, and a HIPIMS-deposited oxide layer being an (Al.sub.aMe.sub.1−a).sub.2O.sub.3 layer, 0.05≤a≤1, wherein Me is one or more of Ti, Mg, Ag, Zr, Si, V, Fe, Hf, B and Cr, the oxide layer being situated directly above the nitride layer or there is a 2-200 nm part of (Al,Me,O) between the nitride layer and the oxide layer, the atomic ratio (Al+Me)/O being equal to or greater than 2/3.

2. The coated cutting tool according to claim 1, wherein the nitride layer is a (Ti,Al)N layer of the general formula Ti.sub.bAl.sub.1-bN, wherein 0<b<1.

3. The coated cutting tool according to claim 1, wherein the (Al.sub.aMe.sub.1−a).sub.2O.sub.3 layer is an (Al.sub.aCr.sub.1−a).sub.2O.sub.3 layer.

4. The coated cutting tool according to claim 1, wherein a thickness of the nitride layer is 0.5-5 μm and a thickness of the oxide layer is 0.1-5 μm.

5. The coated cutting tool according to claim 1, wherein in the (Al.sub.aMe.sub.1−a).sub.2O.sub.3 layer 0.1≤a≤1.

6. The coated cutting tool according to claim 1, wherein the substrate is cemented carbide.

7. A method for producing a coated cutting tool comprising depositing a 0.1-5 μm nitride layer, which is a nitride of one or more of Ti, Zr, Hf, V, Ta, Nb, Cr, Si and Al, onto a substrate, followed by depositing a 0.1-3 μm oxide layer being an (Al.sub.aMe.sub.1−a).sub.2O.sub.3 layer, 0.05≤a≤1, wherein Me is one or more of Ti, Mg, Ag, Zr, Si, V, Fe, Hf, B and Cr, the nitride layer and the oxide layer being deposited by a High Power Impulse Magnetron Sputtering (HIPIMS) process.

8. The method according to claim 7, wherein a maximum local peak power density used in the HIPIMS process in the deposition of the nitride layer is more than 100 W.Math.cm.sup.−2.

9. The method according to claim 7, wherein a maximum local peak power density used in the HIPIMS process in the deposition of the oxide layer is more than 50 W.Math.cm.sup.−2.

10. The method according to claim 7, wherein a maximum local peak current density used in the HIPIMS process in the deposition of the nitride layer is more than 0.4 A.Math.cm.sup.−2.

11. The method according to claim 7, wherein a maximum local peak current density used in the HIPIMS process in the deposition of the oxide layer is more than 0.2 A.Math.cm.sup.−2.

12. The method according to claim 7, wherein a pulse length used in the HIPIMS process in both the deposition of the nitride layer and the deposition of the oxide layer is from 2 μs to 200 ms.

13. The method according to claim 7, wherein a substrate temperature during the HIPIMS process in both the deposition of the nitride layer and the deposition of the oxide layer is from 350 to 600° C.

14. The method according to claim 7, wherein the nitride layer is a (Ti,Al)N layer of the general formula Ti.sub.bAl.sub.1−bN, wherein 0<b<1, or 0.1<b<0.9, or 0.2<b<0.7, or 0.3<b<0.6.

15. A method of using a coated cutting tool, comprising: providing a coated cutting tool according to claim 1; and machining ISO-S materials with the coated cutting tool.

16. The coated cutting tool according to claim 1, wherein the nitride layer is a nitride of Al and one or more of Ti and Cr.

17. A coated cutting tool comprising a substrate of cemented carbide, cermet, ceramics or HSS, with a coating comprising a nitride layer which is a High Power Impulse Magnetron Sputtering (HIPIMS) deposited layer of a nitride of one or more of Ti, Zr, Hf, V, Ta, Nb, Cr, Si and Al, and a HIPIMS-deposited oxide layer being an (Al.sub.aMe.sub.1−a).sub.2O.sub.3 layer, 0.05≤a≤1, wherein Me is one or more of Ti, Mg, Ag, Zr, Si, V, Fe, Hf, B and Cr, wherein the (Al.sub.aMe.sub.1−a).sub.2O.sub.3 layer is of a gamma crystal phase, the oxide layer being situated above the nitride layer.

18. The coated cutting tool according to claim 17, wherein the nitride layer is a nitride of Al and one or more of Ti and Cr.

Description

EXAMPLES

Example 1 (Invention)

(1) Cemented carbide solid endmill blanks were provided having a composition of 12 wt % Co, 0.46 wt % Cr and balance WC.

(2) The grain size d.sub.wc, determined from coercivity 19 kA/m, was 0.5 μm.

(3) Sample 1:

(4) A (Ti,Al)N layer was deposited by HIPIMS using sequential power pulses provided according to the description in U.S. 2014/0339917A1. An Oerlikon Balzers S3P Ingenia equipment was used. The following process parameters/conditions were used:

(5) Total pressure: 0.61 Pa

(6) Ar-pressure: 0.43 Pa

(7) N.sub.2-pressure: 0.18 Pa

(8) Substrate temperature: 430° C.

(9) Bias voltage: −40 V DC

(10) Bias current: −4.1 A

(11) Power per Ti40Al60 target: 9.06 kW

(12) Target diameter: 160 mm

(13) Estimated max. local peak power

(14) density during pulse: 900 W.Math.cm.sup.−2

(15) Estimated max. local peak current

(16) density during pulse: 1.2 A.Math.cm.sup.−2

(17) On-time of pulse: 7.56 ms

(18) Pulse frequency: 20 Hz

(19) Deposition time: 180 minutes

(20) The layer thickness was measured to 2.8 μm on flank face. The hardness of the deposited (Ti,Al,)N layer was measured to 3300HV0.015. The reduced E-modulus was measured to 450 GPa.

(21) Further, a very thin layer (2-20 nm) metallic (Al,Cr) (minor amounts Cr due to a Cr-containing fringe on the Al-target used) was deposited by HIPIMS using sequential power pulses. The following process parameters/conditions were used:

(22) Ar-pressure: 0.6 Pa (=total pressure)

(23) Substrate temperature: 430° C.

(24) Bias voltage: 100 V unipolar pulsed

(25) Bias current: −0.2 A, +0.3 A

(26) Bias on-time: 10 μs

(27) Bias off-time: 10 μs

(28) Power: 5 kW on 3x Al-targets (with Al50Cr50 fringe)

(29) Target diameter: 160 mm

(30) Average power density: 8.3 W.Math.cm.sup.−2

(31) On-time of pulse: 50 ms

(32) Pulse frequency: 6.67 Hz

(33) Deposition time: 13 s

(34) Further, an Al.sub.2O.sub.3 layer (with slight amount of Cr) was deposited in the same reactor by HIPIMS using sequential power pulses provided according to the description in U.S. 2014/0339917A1. The following process parameters/conditions were used:

(35) Total pressure: 0.72 Pa

(36) Ar-pressure: 0.6 Pa

(37) O.sub.2-pressure: 0.12 Pa

(38) Substrate temperature: 430° C.

(39) Bias voltage: 100 V unipolar pulsed

(40) Bias current: −1.2 A, +1.3 A

(41) Bias-On-time: 10 μs

(42) Bias-Off-time: 10 μs

(43) Power: 10 kW on 3x Al-targets (with Al50Cr50 fringe)

(44) Target diameter: 160 mm

(45) Estimated max. local peak power

(46) density during pulse: 200 W.Math.cm.sup.−2

(47) Estimated max. local peak current

(48) density during pulse: 0.6 A.Math.cm.sup.−2

(49) On-time of pulse: 50 ms

(50) Pulse frequency: 6.67 Hz

(51) Deposition time: 140 minutes

(52) The deposited Al.sub.2O.sub.3 layer contained <1 at. % of Cr.

(53) The deposited Al.sub.2O.sub.3 layer was determined by XRD to be a gamma-Al.sub.2O.sub.3 layer. The layer thickness was measured to 0.65 μm. The hardness of the deposited Al.sub.2O.sub.3 layer was measured to 2800HV0.015. The reduced E-modulus was measured to 370 GPa.

(54) Sample 2:

(55) A comparative sample where the same substrate as for Sample 1 has a coating of (Ti,Al)N consisting of a bonding layer next to the substrate of (Ti,Al)N deposited by arc evaporation in an Oerlikon Balzers Innova equipment using two Ti.sub.0.50Al.sub.0.50 targets. The following process parameters/conditions were used:

(56) N.sub.2-pressure: 0.8 Pa

(57) Substrate temperature: 550° C.

(58) Bias voltage: 70 V

(59) Deposition time: 4 minutes

(60) Then a main layer being a nanolayered (Ti,Al)N having an average composition of Ti.sub.0.44Al.sub.0.56N was deposited using two Ti.sub.0.33Al.sub.0.67 targets and four Ti.sub.0.50Al.sub.0.50 targets.

(61) N.sub.2-flow: 1400 sccm

(62) Substrate temperature: 550° C.

(63) Bias voltage: 60 V

(64) Deposition time: 80 minutes

(65) Finally a decorative layer of (Ti,Al)N was deposited using two Ti.sub.0.33Al.sub.0.67 targets. The following process parameters/conditions were used:

(66) N.sub.2-flow: 1400 sccm

(67) Substrate temperature: 550° C.

(68) Bias voltage: 60 V

(69) Deposition time: 5 minutes

(70) The surface rougness of the coating itself was measured on individuals of samples 1 and 2 where the surface of the substrates had been polished prior to the deposition of the coating. This was made in order to minimize the influence of the roughness of the substrate to the measured surface roughness value. Surface roughness Ra were measured with a Hommel-Etamic equipment using software Turbo Wave V 7.32. Stylus sampling length 4.8 mm, 0.5 mm/s. (according to DIN EN ISO 11562/DIN EN ISO 4287). Table 1 shows the results.

(71) TABLE-US-00001 TABLE 1 R.sub.a (μm) Sample 1 0.04 Sample 2 0.09

(72) The coated endmills were then tested in a milling operation in a titanium alloy.

(73) The tool geometry for the solid round endmill was Coromant CoroMill Plura 2S342-1000-100-CMA, diameter 10 mm, 4 flute, corner radius 1 mm. Flute angle of the tool is 42°, one coolant exit per flute. All tools used in this test were from the same production order.

(74) Work piece material: Ti6Al4V, 175×175×50 mm

(75) Machine: Mori Seiki

(76) Liquid cooling, external nozzles, coolant Blasocut B25 (concentration 9%) through external nozzles

(77) Test 1:

(78) a.sub.p=2.5 mm

(79) a.sub.e=2.0 mm

(80) V.sub.c=100 m/min (cutting speed in meters per minute)

(81) f.sub.z=0.04 mm/tooth (feed rate in millimeter per tooth)

(82) Number of passes=230

(83) Milling length=40.25 m

(84) Machining time=79.03 min

(85) Average wear depth at the corner: 0.06 mm, average wear depth at depth of cut (DOC): 0.05 mm. Maximum wear depth at the corner: 0.07 mm, maximum wear depth at DOC: 0.05 mm.

(86) Wear of the comparative sample was (after 160 passes equals 28 m or 54.98 min machining time in the same setup as the invention—example): Average wear depth at the corner: 0.05 mm, average wear depth at DOC: 0.23 mm. Maximum wear depth at the corner: 0.10 mm, maximum wear depth at DOC: 0.30 mm (two edges with a wear of 0.30 mm, two edges with a wear of 0.15 mm).

(87) Test 2 (repeated once):

(88) a.sub.p=2.5 mm

(89) a.sub.e=1.0 mm

(90) V.sub.c=100 m/min (cutting speed in meters per minute)

(91) f.sub.z=0.11 mm/tooth (feed rate in millimeter per tooth)

(92) Number of passes=120 for all tools

(93) Milling length=21 m

(94) Machining time=11.53 min

(95) Average wear depth at the corner: 0.08 mm, average wear depth at DOC: 0.13 mm. Maximum wear depth at the corner: 0.14 mm, maximum wear depth at DOC: 0.23 mm.

(96) Wear of the comparative sample:

(97) Average wear depth at the corner: 0.08 mm, average wear depth at DOC: 0.21 mm. Maximum wear depth at the corner: 0.21 mm, maximum wear depth at DOC: 0.50 mm.

(98) After machining the endmills were inspected by SEM at a magnification of 500× for the rake face and 300× for the flank face.

(99) It was much less smearing of the Ti-based workpiece material on the exposed (Ti,Al)N at the edge of the cutting tool of the invention (Sample 1) than on the (Ti,Al)N at the edge of the cutting tool of the comparison (Sample 2). This was the case both for the rake and flank faces.

(100) Furthermore, It was much less built-up edge on the cutting edge of the cutting tool of the invention (Sample 1) than on the edge of the cutting tool of the comparison (Sample 2). This was the case both for the rake and flank faces.