METHOD FOR PRODUCING A COATED CUTTING TOOL

Abstract

A method for producing a coated cutting tool includes depositing on every flank face and every rake face of the cutting tool an Al.sub.2O.sub.3 layer by a HIPIMS process during two-fold or three-fold rotation of the substrates, at a substrate temperature ≥350° C. but <600° C., the deposited Al.sub.2O.sub.3 layer including α-Al.sub.2O.sub.3.

Claims

1. A method for producing a coated cutting tool having at least one rake face and at least one flank face, the method comprising: providing a cutting tool having a substrate of cemented carbide, cermet, cBN, or ceramic and a coating; depositing on each at least one flank face and each at least one rake face of the cutting tool an Al.sub.2O.sub.3 layer by a HIPIMS process, wherein the process a peak pulse cathode power is ≥500 kW, a value of negative peak pulse voltage is ≥1200 V, a specific target peak pulse power density is ≥350 W/cm.sup.2, a specific average target power density is ≥6 W/cm.sup.2, a pulse time is 20-150 s, a pulse frequency is ≥100 Hz, a peak pulse current is ≥400 A, and wherein there is either a pulsed bias, or DC bias, voltage applied of from 150 to 300 V, negative bias, wherein a peak bias current is ≥100 A and ≤800 A, a specific bias current density is 5-80 mA/cm.sup.2, an oxygen partial pressure is ≥1×10.sup.−4 mbar, and a total pressure is from 0.25 to 3 Pa; charging a PVD reactor chamber, containing at least one Al target and a rotatable substrate holder, with cutting tool blanks, wherein a target size is from 500 to 3000 cm.sup.2; and depositing an Al.sub.2O.sub.3 layer in the HIPIMS process during two-fold or three-fold rotation of the substrates, at a substrate temperature ≥350° C. but <600° C., wherein the deposited Al.sub.2O.sub.3 layer comprises α-Al.sub.2O.sub.3.

2. The method according to claim 1, wherein the substrate temperature during the deposition in the HIPIMS process is ≥400° C. but <580° C.

3. The method according to claim 1, wherein in the HIPIMS process the pulse time is from 30 to 100 μs.

4. The method according to claim 1, wherein in the HIPIMS process the peak pulse cathode power is ≥1 MW.

5. The method according to claim 1, wherein in the HIPIMS process the specific target peak pulse current density is ≥0.25 A/cm.sup.2.

6. The method according to claim 1, wherein in the HIPIMS process the specific target peak pulse power density is ≥650 W/cm.sup.2.

7. The method according to claim 1, wherein in the HIPIMS process the specific bias current density is 10-40 mA/cm.sup.2.

8. The method according to claim 1, wherein the deposited Al.sub.2O.sub.3 layer contains a mixture of α-Al.sub.2O.sub.3 and γ-Al.sub.2O.sub.3.

9. The method according to claim 1, wherein the deposited Al.sub.2O.sub.3 layer in GIXRD (gracing incidence x-ray diffraction) analysis at a 0.5° incidence angle in an 2theta diffractogram, on at least one of the rake face or flank face of a cutting tool, shows: a ratio I(α-Al.sub.2O.sub.3 (113)) to I(γ-Al.sub.2O.sub.3 (400)) being ≥0.5, and/or a ratio I(α-Al.sub.2O.sub.3 (024)) to I(γ-Al.sub.2O.sub.3 (400)) being ≥0.2, and/or a ratio I(α-Al.sub.2O.sub.3 (116)) to I(γ-Al.sub.2O.sub.3 (400)) being ≥0.1.

10. The method according to claim 1, wherein the deposited Al.sub.2O.sub.3 layer is an α-Al.sub.2O.sub.3 layer.

11. A coated cutting tool having at least one rake face and at least one flank face, comprising an Al.sub.2O.sub.3 layer deposited according to the method of claim 1, wherein the deposited Al.sub.2O.sub.3 layer comprises α-Al.sub.2O.sub.3.

12. The coated cutting tool according to claim 11, wherein α-Al.sub.2O.sub.3 is present in the deposited Al.sub.2O.sub.3 layer on each of the at least one rake face and flank face of the cutting tool.

13. The coated cutting tool according to claim 1, wherein the Al.sub.2O.sub.3 layer has a Vickers hardness of ≥2000 HV.

14. The coated cutting tool according to claim 1, wherein the Al.sub.2O.sub.3 layer has a reduced Young's modulus of ≥320 GPa.

15. The coated cutting tool according to claim 1, wherein the Al.sub.2O.sub.3 layer in GIXRD (gracing incidence x-ray diffraction) analysis at 0.5° incidence angle in an 2theta diffractogram, on at least one of the rake face or flank face of a cutting tool, shows: a ratio I(α-Al.sub.2O.sub.3 (113)) to I(γ-Al.sub.2O.sub.3 (400)) in an XRD 2theta diffractogram being ≥0.5, and/or a ratio I(α-Al.sub.2O.sub.3 (024)) to I(γ-Al.sub.2O.sub.3 (400)) in an XRD 2theta diffractogram being ≥0.2, and/or a ratio I(α-Al.sub.2O.sub.3 (116)) to I(γ-Al.sub.2O.sub.3 (400)) in an XRD 2theta diffractogram being ≥0.1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0072] FIG. 1 shows GIXRD measurements on an inventive coating with an incident angle of 1° of a 2f rotated rake face.

[0073] FIG. 2 shows GIXRD measurements on an inventive coating with an incident angle of 1° of a 2f rotated rake face

[0074] FIG. 3 shows GIXRD measurements on an inventive coating with an incident angle of 0.2° of a 2f rotated rake face

[0075] FIG. 4 shows GIXRD measurements on an inventive coating with an incident angle of 0.5° of a 3f rotated flank face

METHODS

[0076] XRD-Phase Analysis:

[0077] The X-ray diffraction patterns concerning the phase analysis were acquired by Grazing incidence mode (GIXRD) on a diffractometer from Panalytical (Empyrean). CuKalpha-radiation with line focus was used for the analysis (high tension 40 kV, current 40 mA). The incident beam was defined by a 2 mm mask and a ⅛° divergence slit in addition with a X-ray mirror producing a parallel X-ray beam. The sideways divergence was controlled by a Soller slit (0.04°). For the diffracted beam path a 0.18° parallel plate collimator in conjunction with a proportional counter (OD-detector) was used. The measurement was done in grazing incidence mode (Omega=1°). The 2Theta range was about 28-45° with a step size of 0.03° and a counting time of 10 s. For the XRD-line-profile analysis a reference measurement (with LaB6-powder) was done with the same parameters as listed above to correct for the instrumental broadening.

[0078] Vickers Hardness:

[0079] 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 (HV 0.0015), 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. Hardness values and values for the reduced Young's modulus, indicated in the examples were each measured on the flank face of the coated tool.

[0080] Reduced Younq's Modulus

[0081] The reduced Young's modulus (reduced modulus of elasticity) was determined by means of nano-indentation (load-depth graph) as described for determining the Vickers hardness.

[0082] Thickness:

[0083] The thickness of the coating layers 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. Measurements of the layer thickness on the rake face (RF) of the cutting tool were carried out at a distance of 2000 μm from the corner, and measurements on the flank face (FF) were carried out in the middle of the flank face.

EXAMPLES

Example 1 (Invention)

[0084] On a WC—Co based cemented carbide substrate, having a Co content of 8 wt % and balance WC, an aluminium oxide coating was deposited in a Hauzer HTC1000 equipment under the following process conditions: [0085] Al target with size 830 mm×170 mm, [0086] TruPlasma Highpulse 4002 generator of Trumpf Huettinger Sp. z o. o., [0087] HIPIMS block shape mode, [0088] average cathode power 15 kW, [0089] total gas pressure approx. 1 Pa, 1260 sccm Ar gasflow, approx. 95 sccm O.sub.2 gasflow, [0090] DC bias voltage 250 V, negative bias [0091] bias current 14.5 A at the end of process, [0092] substrate temperature 550° C., [0093] HIPIMS pulse time approx. 45 μs, [0094] HIPIMS DC charging voltage 2000 V (negative voltage), [0095] power supply peak voltage during pulse approx. 1650 V (negative voltage), [0096] power supply peak current during pulse approx. 680 A, [0097] HIPIMS pulse frequency approx. 680 Hz, [0098] peak pulse cathode power approx. 1150 kW, [0099] coil current approx. 4.0 A, [0100] oxygen partial pressure approx. 5.1×10.sup.4 mbar, [0101] process time 180 minutes

[0102] In 2f rotating mode an aluminium oxide coating having a thickness of 0.75 μm on the rake face and in 3f rotating mode an aluminium oxide coating having a thickness of 0.81 μm on the flank face was made.

[0103] The hardness was 2887 HV and the red. Young's modulus was 384 GPa.

Examples 2-7

[0104] Further Examples 2-7, using the same equipment as in Example 1, providing aluminium oxide coatings according to the invention were made where the process conditions had been varied according to Tables 1-4. Both 2f rotating and 3f rotating samples were produced.

TABLE-US-00001 TABLE 1 Process conditions O2 in O2 in O2 sccm sccm partial Tem- Example at after pressure Ar in perature no. begin 30 min in mbar sccm in ° C. 1 100 95 5.1 × 10{circumflex over ( )} − 4 1260 550 2 100 95 5.0 × 10{circumflex over ( )} − 4 1260 550 3 100 90 3.3 × 10{circumflex over ( )} − 4 1260 550 4 95 95 3.5 × 10{circumflex over ( )} − 4 1260 550 5 100 90 3.4 × 10{circumflex over ( )} − 4 1260 550 6 100 95 3.8 × 10{circumflex over ( )} − 4 1260 550 7 95 95 3.4 × 10{circumflex over ( )} − 4 1260 550

TABLE-US-00002 TABLE 2 Process conditions cont. Ex- DC bias Bias Bias Pulse ample Pressure Coil voltage in A in A length no. in Pa in A in V at begin at end in μs 1 1.0 4.0 −250 24.0 14.5 45 2 1.0 4.0 −250 27.0 16.0 45 3 1.0 4.0 −250 24.0 14.5 45 4 1.0 4.0 −250 22.0 0.1 48 5 1.0 4.0 −250 20.6 12.3 45 6 1.0 3.6 −300 19.1 3.8 45 7 1.0 4.0 −250 20.0 13.0 45

TABLE-US-00003 TABLE 3 Process conditions cont. Ex- DC DC ample Voltage* Current Power Frequency voltage** current no. in V in A in kW in Hz in V in A 1 −1650 680 15 680 −2000 8.0 2 −1655 627 15 742 −2000 8.0 3 −1640 700 15 670 −2000 8.5 4 −1670 650 15 650 −2000 8.5 5 −1615 768 15 617 −2000 8.4 6 −1600 850 15 566 −2000 8.7 7 −1420 620 15 850 −1750 9.6 *used in the pulse **charged voltage

TABLE-US-00004 TABLE 4 Proces conditions cont. Example Duty Time U.sub.PeakMax I.sub.PeakMax P.sub.PeakMax no. in % in min. in V in A in kW 1 3.0 180 −2000 680 1150 2 3.3 120 −1990 626 1000 3 3.0 180 −2005 720 1150 4 3.2 150 −2000 650 1080 5 2.8 270 −2000 768 1241 6 2.6 250 −1995 860 1400 7 3.9 140 −1670 605 840

[0105] Aluminium oxide coatings with thicknesses, hardnesses and red. Young's modulus according to Table 5 resulted from the depositions.

TABLE-US-00005 TABLE 5 Thick- Hard- Red. Thick- Hard- red. Young's Ex- ness 2f ness 2f Young's ness 3f ness 3f modulus ample rake in rake in modulus 2f flank in flank in 3f flank no. μm HV in GPa μm HV in GPa 1 0.75 2887 384 0.81 2346 373 2 0.30 2443 412 0.45 2442 412 3 0.75 2857 401 0.66 2640 419 4 0.60 2691 386 0.62 2220 392 5 1.20 2641 351 1.16 2465 355 6 0.75 2519 359 0.85 2650 370 7 0.65 2496 370 0.46 2340 387

[0106] Grazing Incidence XRD (GIXRD) Measurements:

[0107] GIXRD measurements in the 2theta range 35 to 60° of inventive examples no. 1-7 were made under an angle of 0.5° of a 3f rotated flank. The XRD diffractograms all show clearly α-Al.sub.2O.sub.3 (113), (024) and (116) peaks (43.363°, 52.559° and 57.504°, respectively, in PDF no. 42-1468 of the ICDD database). All diffractograms were found to show peaks of α-Al.sub.2O.sub.3 (113), (024) and (116).

[0108] Inventive example No. 1 was investigated further.

[0109] A GIXRD measurement in the 2theta range 20 to 60°, and a fine scan GIXRD measurement in the 2theta range 49 to 61°, were made on inventive example no. 1 with an incident angle of 1° of a 2f rotated rake face are shown in FIG. 1 and FIG. 2. Solid lines mark positions for α-Al.sub.2O.sub.3 and dashed lines mark positions for γ-Al.sub.2O.sub.3, according to PDF no. 42-1468 and PDF no. 10-425 of the ICDD database. The XRD diffractogram in FIG. 1 shows clearly a γ-Al.sub.2O.sub.3 (400) peak (45.863° in PDF no. 10-425 of the ICDD database). Furthermore one sees weak α-Al.sub.2O.sub.3 (024) and (116) peaks (52.559° and 57.504°, respectively, in PDF no. 42-1468 of the ICDD database). FIG. 2 shows an enlarged part of the 2theta range and here the α-Al.sub.2O.sub.3 (024) and (116) peaks are clearly seen.

[0110] A GIXRD measurement in the 2theta range 20 to 70° of inventive example no. 1 was made under an angle of 0.2° of a 2f rotated rake face and is shown in FIG. 3. Solid lines mark positions for α-Al.sub.2O.sub.3 according to PDF no. 42-1468 of the ICDD database. γ-Al.sub.2O.sub.3 peaks are also seen at positions according to PDF no. 10-425 but are not marked in the diffractogram. The smaller angle used in this GIXRD measurement gives a somewhat even more distinct caption of the γ-Al.sub.2O.sub.3 (400) peak (45.863°) but here the 2theta range has been extended so that also the γ-Al.sub.2O.sub.3 (440) peak is clearly seen (67.034° in PDF no. 10-425 of the ICDD database).

[0111] The conclusion of GIXRD of a 2f-rotated rake face of inventive example no. 1 from FIGS. 1-3 is that the aluminium oxide layer contains α-Al.sub.2O.sub.3 in a mixture with γ-Al.sub.2O.sub.3 and the γ-phase dominates.

[0112] A GIXRD measurement in the 2theta range 35 to 62° of inventive example no. 1 was made under an angle of 0.5° of a 3f rotated flank and is shown in FIG. 4. Solid lines mark positions for α-Al.sub.2O.sub.3 and dashed lines mark positions for γ-Al.sub.2O.sub.3, according to PDF no. 42-1468 and PDF no. 10-425 of the ICDD database. The XRD diffractogram shows clearly a γ-Al.sub.2O.sub.3 (400) peak (45.863°) and also a weak γ-Al.sub.2O.sub.3 (222) peak (39.492° in PDF no. 10-425 of the ICDD database). Furthermore one sees strong α-Al.sub.2O.sub.3 (113) and (024) peaks (43.363° and 52.559°, respectively, in PDF no. 42-1468 of the ICDD database).

[0113] The conclusion of GIXRD of a 3f-rotated flank face of inventive example no. 1 from FIG. 4 is that the aluminium oxide layer contains a high amount of α-Al.sub.2O.sub.3 in a mixture with γ-Al.sub.2O.sub.3.

[0114] From FIG. 4 it is also concluded that in the GIXRD measurements of inventive example 1 under an angle of 0.5° of a 3f rotated flank face show that the ratio I(α-Al.sub.2O.sub.3 (113)) to (γ-Al.sub.2O.sub.3 (400)) is about 1.4, the ratio (α-Al.sub.2O.sub.3 (024)) to (γ-Al.sub.2O.sub.3 (400)) is about 0.6 and the ratio I(α-Al.sub.2O.sub.3 (116)) to (γ-Al.sub.2O.sub.3 (400)) is about 0.3.

Example 9 (Comparison)

[0115] On a WC—Co based cemented carbide substrate, having a Co content of 8 wt % and balance WC, an aluminium oxide coating was deposited in a Hauzer HTC1000 equipment using dual magnetron sputtering (DMS) 20 kW. The further process conditions were: [0116] Al target with size 830 mm×170 mm, [0117] approx. 0.47 Pa Ar, [0118] target voltage control mode 480 V, [0119] DMS coil current 6.5 A, [0120] bias current 28.6 A

[0121] In 2f and 3f rotating mode an aluminium oxide coating having a thickness of approx. 1.2 μm was made. The hardness was 2792 HV and the red. Young's modulus was 340 GPa.

[0122] Only γ-Al.sub.2O.sub.3 peaks in XRD analysis were seen.