POLYCRYSTALLINE CUBIC BORON NITRIDE BODY

Abstract

A sintered polycrystalline cubic boron nitride (PCBN) body includes between 40 and 85 vol % of cubic boron nitride (cBN) particles and between 15 and 60 vol % of a binder phase. The binder phase has at least one metal oxide and at least one metal nitride. The metal oxide includes between 20 and 100 vol % of zirconium oxide (ZrO.sub.2) and up to 80 vol % of alumina (Al.sub.2O.sub.3) counted as a volume percentage of the total metal oxide content of the binder phase. The metal nitride includes aluminium nitride (AlN) and at least one metal nitride selected from the group consisting of vanadium nitride (VN), niobium nitride (NbN) and hafnium nitride (HfN). The content of the selected metal nitride selected is at least 10 vol % of the total binder phase, and the content of the metal oxide is at least 10 vol % of the total binder phase.

Claims

1. A sintered polycrystalline cubic boron nitride (PCBN) body having between 40 and 85 vol % of cubic boron nitride (cBN) particles and between 15 and 60 vol % of a binder phase, wherein the binder phase includes at least one metal oxide and at least one metal nitride, wherein the at least one metal oxide includes between 20 and 100 vol % of zirconium oxide (ZrO.sub.2) and up to 80 vol % of alumina (Al.sub.2O.sub.3) counted as a volume percentage of a total metal oxide content of the binder phase, the at least one metal nitride having 1 to 10 vol % aluminium nitride (AlN) based on a total binder phase and at least one metal nitride selected from the group consisting of vanadium nitride (VN), niobium nitride (NbN) and hafnium nitride (HfN), wherein the content of said at least one metal nitride selected from the group consisting of vanadium nitride (VN), niobium nitride (NbN) and hafnium nitride (HfN) is at least 10 vol % of the total binder phase, and wherein the content of said at least one metal oxide is at least 10 vol % of the total binder phase.

2. The PCBN body according to claim 1, wherein the binder phase further comprises at least one metal oxynitride being a reaction product of one of the at least one metal oxides and one of the at least one metal nitrides.

3. The PCBN body according to claim 2, wherein the binder phase includes at least one oxynitride selected from the group consisting of zirconium oxynitride (Zr(O,N)), zirconium vanadium oxynitride ((Zr,V)ON), zirconium niobium oxynitride ((Zr,Nb)ON) and zirconium hafnium oxynitride ((Zr,Hf)ON).

4. The PCBN body according to claim 2 or 3, wherein the binder phase comprises includes at least one oxynitride selected from the group consisting of aluminium oxynitride (Al(O,N)), aluminium vanadium oxynitride (Al, V)ON), aluminium niobium oxynitride ((Al,Nb)ON) and aluminium hafnium oxynitride ((Al,Hf)ON).

5. The PCBN body according to claim 1, wherein the binder phase consists of ZrO.sub.2, Al.sub.2O.sub.3, AlN and at least one metal nitride selected from the group consisting of VN, NbN and HfN.

6. The PCBN body according to claim 1, wherein the metal nitride selected from the group consisting of VN, NbN and HfN constitutes up to 50 vol % of the total binder phase.

7. The PCBN body according to claim 1, wherein the binder phase consists of ZrO.sub.2, Al.sub.2O.sub.3, AlN, at least one metal nitride selected from the group consisting of VN, NbN and HfN, and at least one oxynitride from the group consisting of Zr(O,N), (Zr,V)ON, (Zr,Nb)ON, (Zr,Hf)ON, Al(O,N), (Al,V)ON, (Al,Nb)ON and (Al,Hf)ON.

8. The PCBN body according to claim 2, wherein the oxynitride and metal nitride selected from the group consisting of VN, NbN and HfN are between 10 and 50 vol % of the total binder phase of the PCBN body.

9. The PCBN body according to claim 1, wherein the ZrO.sub.2, is between 20 and 90 vol % of the total metal oxide content of the binder phase.

10. The PCBN body according to claim 1, wherein the Al.sub.2O.sub.3; is between 5 and 25 vol % of the binder phase.

11. The PCBN body according to claim 1, wherein the PCBN body is backed with a backing body of cemented carbide.

12. The PCBN body according to claim 1, wherein the PCBN body is coated with a PVD- or CVD coating having a thickness of between 0.8 ?m and 15 ?m.

13. The PCBN body according to claim 1, wherein the PCBN body is a cutting tool or is a cutting tip of a cutting tool.

14. A method of manufacturing a PCBN body according to claim 1, comprising the steps of: providing a cubic boron nitride (cBN) powder having an average particle size between 0.5 ?m and 15 ?m; providing binder constituents comprising ZrO.sub.2, or a mixture of ZrO.sub.2 and Al.sub.2O.sub.3, at least one metal nitride selected from the group consisting of: VN, NbN and HfN constituting at least 10% by volume of the binder mixture, and metallic aluminium; admixing the binder constituents with the cBN powder to a powder mixture; milling the powder mixture; forming a green body of the powder mixture; heat treating the green body at a temperature above 600? C. under vacuum to ensure sufficient degassing and removal of absorbed species; and sintering the green body at a temperature of at least 1200? C. and at a pressure of at least 4 GPa to form a solid sintered PCBN compact from which the PCBN body is formed.

15. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The invention will now be explained more closely by the description of different embodiments of the invention and with reference to the appended figures.

[0047] FIG. 1 shows an example of a solid PCBN body.

[0048] FIG. 2 shows another example of a PCBN body with a carbide backing body that is brazed to a cemented carbide insert carrier.

[0049] FIG. 3 shows an optical microscopy image of flank wear on a PCBN body according to an embodiment of the invention.

[0050] FIG. 4 shows an optical microscopy image of flank wear on a first comparative PCBN body.

[0051] FIG. 5 shows an optical microscopy image of flank wear on a second comparative PCBN body.

[0052] FIG. 6 shows an optical microscopy image of notch wear on a PCBN body according to an embodiment of the invention.

[0053] FIG. 7 shows an optical microscopy image of notch wear on a first comparative PCBN body.

[0054] FIG. 8 shows an optical microscopy image of notch wear on a second comparative PCBN body.

[0055] FIG. 9 shows a block diagram of an example method of manufacturing the PCBN body.

[0056] FIG. 10 shows a SEM image and XEDS mapping of different elements in a PCBN body according to an embodiment of the invention.

[0057] FIG. 11 shows an X-Ray ?-2? diffractogram of the PCBN body according to an embodiment of the invention.

DETAILED DESCRIPTION

[0058] Aspects of the present disclosure will be described more fully hereinafter with reference to the accompanying drawings. The device and method disclosed herein can, however, be realized in many different forms and should not be construed as being limited to the aspects set forth herein. Like numbers in the drawings refer to like elements throughout.

[0059] The terminology used herein is for the purpose of describing particular aspects of the disclosure only and is not intended to limit the invention. As used herein, the singular forms a, an and the are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0060] The term cutting tool, as used herein, is intended to denote cutting tools suitable for metal cutting by chip removal, such as turning, milling or drilling. Examples of cutting tools are indexable cutting inserts, solid drills and end mills.

[0061] Unless otherwise defined, all terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0062] Common for cutting tools inserts is that they may be a solid body or a body comprising a backing body onto which an additional material is placed, either over the cutting edge on the rake face, a so-called tipped body, or such that it covers the full rake, a so-called full-face body.

[0063] FIG. 1 shows an example of a sintered PCBN body 1. The PCBN body in FIG. 1 is a solid body. The solid sintered PCBN body 1 in FIG. 1 can in itself be a cutting tool insert or can be cut into smaller pieces that are used as, for example, cutting tips of a cutting tool insert. FIG. 2 shows an example of a cutting tool insert 3 comprising a backing body 4 and a cutting tip in the form of a sintered PCBN body 2 according to the present disclosure. The PCBN body 2 is integrally bonded to the backing body 4 made of, for example, cemented carbide.

[0064] The disclosure provides a sintered PCBN body 1, 2 comprising between 40 and 85 vol % of cubic boron nitride (cBN) particles and between 15 and 60 vol % of a binder phase, wherein the binder phase comprises at least one metal oxide and at least one metal nitride. The at least one metal oxide comprises between 20 and 100 vol % of zirconium oxide (ZrO.sub.2) and up to 80 vol % of alumina (Al.sub.2O.sub.3) counted as a volume percentage of the total metal oxide content of the binder. Further, the at least one metal nitride comprises aluminium nitride (AlN) and at least one of the metal nitrides selected from the group consisting of vanadium nitride (VN), niobium nitride (NbN) and hafnium nitride (HfN). The metal nitride content is at least 10 vol % of the binder phase.

[0065] The binder phase of the sintered PCBN body 1 may, for example, comprise at least one metal oxynitride being a reaction product of one of the at least one metal oxides and one of the at least one metal nitrides.

[0066] The binder phase may, for example, comprise at least one oxynitride selected from the group consisting of zirconium oxynitride (Zr(O,N)), zirconium vanadium oxynitride ((Zr,V)ON), zirconium niobium oxynitride ((Zr,Nb)ON) and zirconium hafnium oxynitride ((Zr,Hf)ON).

[0067] As an alternative or additionally, the oxynitride may, for example, comprise at least one oxynitride selected from the group consisting of aluminium oxynitride (Al(O,N)), aluminium vanadium oxynitride ((Al,V)ON), aluminium niobium oxynitride ((Al,Nb)ON) and aluminium hafnium oxynitride ((Al,Hf)ON).

[0068] The oxynitride and metal nitride content of at least one of vanadium nitride (VN), niobium nitride (NbN) and hafnium nitride (HfN) are, for example, between 10 and 50 vol % of the total binder phase.

[0069] FIG. 9 shows a block diagram of an example method of manufacturing the PCBN body 1, 2. According to the example method the following steps are performed. [0070] (a) providing a cubic boron nitride (cBN) powder having an average particle size between 0.5 ?m and 15 ?m, [0071] (b) providing binder constituents comprising ZrO.sub.2, or a mixture of ZrO.sub.2 and Al.sub.2O.sub.3, at least one metal nitride selected from the group consisting of: VN, NbN and HfN, and wherein said at least one metal nitride is at least 10% by volume of the binder mixture, and metallic aluminium, [0072] (c) admixing the binder constituents with the cBN powder to a powder mixture, [0073] (d) milling the powder mixture, [0074] (e) forming a green body of the powder mixture, [0075] (f) heat treating the green body at a temperature above 600? C. under vacuum to ensure sufficient degassing and removal of absorbed species, [0076] (g) sintering the green body at a temperature of at least 1200? C. and at a pressure of at least 4 GPa to form a solid sintered PCBN compact from which the PCBN body (1, 2) is formed.

[0077] According to an alternative example method the following steps are performed for manufacturing the PCBN body: [0078] providing a cubic boron nitride (cBN) powder having an average particle size between 0.5 ?m and 15 ?m from hexagonal boron nitride (hBN) powder. This is done at high temperature and high pressure according to standard practice, [0079] providing a binder mixture of binder constituents comprising ZrO.sub.2, or a mixture of ZrO.sub.2 and Al.sub.2O.sub.3, at least one metal nitride selected from the group consisting of: VN, NbN and HfN, and wherein said metal nitride is at least 10% by volume of the binder mixture, and metallic aluminium. [0080] milling the binder mixture to attain an average particle size of the binder constituents of between 0.5 ?m and 10 ?m, [0081] admixing the milled binder mixture with the cBN powder to a powder mixture, [0082] milling the powder mixture to reduce the average particle size and ensure accurate mixing and dispersion of cBN phase in the binder mixture, [0083] forming a green body of the powder mixture, [0084] heat treating the green body at a temperature above 600? C. under vacuum to ensure sufficient degassing and removal of absorbed species, [0085] sintering the green body at a temperature of at least 1200? C. and at a pressure of at least 4 GPa to form solid sintered PCBN compact from which the PCBN body 1, 2 is formed.

[0086] The solid sintered PCBN compact is, for example, cut into pieces by using EDM or laser. The cut pieces forming PCBN bodies 1, 2 may be brazed to a cemented carbide backing body 4 to form a cutting tool as seen in, for example, FIG. 2.

[0087] According to an example embodiment the PCBN body 1, 2 was manufactured according to the above method and the PCBN body has about 60 vol % of cBN particles and a binder phase comprising ZrO.sub.2 (both cubic and tetragonal), Al.sub.2O.sub.3, AlN, VN and zirconium oxynitride (Zr(O,N)). FIG. 10 shows XEDS mapping of the different elements in the PCBN body and from the XEDS maps it can be seen how the cBN grains comprising B and N are present in a binder phase comprising O, N, Al, V and Zr. FIG. 11 shows the X-ray diffraction (XRD) intensities of cubic BN, ZrO.sub.2 (both cubic and tetragonal), Al.sub.2O.sub.3, AlN, VN and zirconium oxynitride (Zr(O,N)) in the PCBN body as measured using Cu-K? radiation and ?-2? scan. The diffractometer used was STOE STADI MP. For the analysis of the XRD pattern in FIG. 11 the following Crystal Impact Entry (CIE)-cards were used: [0088] Al.sub.2O.sub.3, CIE-card: 96-100-0018 [0089] AlN, CIE-card: 96-152-3096 [0090] BN, CIE-card: 96-035-1365 (cubic) [0091] VN, CIE-card: 96-035-0768 [0092] ZrO.sub.2, CIE-card: 95-050-1089 (tetragonal) [0093] ZrO.sub.2, CIE-card: 96-900-7449 (cubic) [0094] Zr.sub.x(O,N).sub.y, CIE-card: 96-050-1172

Example 1

[0095] PCBN cutting tools according to an embodiment of the present disclosure with a composition corresponding to sample 1 in table 1 were produced according to the above alternative example embodiment of the manufacturing method. First comparative PCBN cutting tools with conventional TiC-binder having a composition according to sample 2 in table 1 and second comparative PCBN cutting tools with conventional TiCN-binder having a composition according to sample 3 in table 1, were produced under identical powder preparation and sintering conditions as sample 1.

[0096] The cutting tools were manufactured in ISO RNGN090300 insert geometry.

TABLE-US-00001 TABLE 1 cBN TiC TiCN Al.sub.2O.sub.3 ZrO.sub.2 AlN VN Zr(O, N) Sample (vol %) (vol %) (vol %) (vol %) (vol %) (vol %) (vol %) (vol %) Sample 1 (invention) 60 6 13 3 15 3 Sample 2 (comparative) 60 31 6 3 Sample 3 (comparative) 60 31 6 6

[0097] Longitudinal turning was performed on Inconel 718 workpiece material supplied in aged condition and having a hardness of HRC 45 with PCBN cutting tools having compositions according to sample 1-3.

[0098] The cutting data used were: [0099] 1. cutting speed v.sub.c=300 m/min at feed f=0.10 mm/rev, [0100] 2. cutting speed v.sub.c=350 m/min at feed f=0.10 mm/rev,

[0101] while depth of cut was a.sub.p=0.3 mm for both cases, corresponding to high-speed finishing conditions. High pressure directed cooling (HPDC) was applied and set for 90 bar coolant pressure at the rake and flank faces of the cutting tool, using 8% oil-water emulsion as coolant medium.

[0102] Flank wear was measured after spiral length of 950 meters which corresponded to the time in cut of 3.2 minutes for cutting speed v.sub.c=300 m/min and 2.7 minutes for cutting speed v.sub.c=350 m/min.

[0103] Flank wear was measured using Olympus SZX7 optical microscope.

[0104] In table 2 the measured flank wear for cutting speeds of 300 and 350 m/min are shown.

TABLE-US-00002 TABLE 2 Flank wear (?m) Flank wear (?m) v.sub.c = 300 m/min; v.sub.c = 350 m/min f = 0.10 mm/rev f = 0.10 mm/rev Sample a.sub.p = 0.3 mm a.sub.p = 0.3 mm Sample 1 (invention) 198 219 Sample 2 (comparative) 335 470 Sample 3 (comparative) 282 328

[0105] The SEM images in FIGS. 3, 4 and 5 show the flank wear on Sample 1-3 after 2.7 minutes for cutting speed 350 m/min, feed f=0.1 mm/rev and depth of cut a.sub.p=0.3 mm.

[0106] From the experimental results and observations related to the example 1 it was concluded that PCBN cutting tool having a composition according to the present invention demonstrated more than 50% improvement in performance compared to the conventional TiC-binder and TiCN-binder.

Example 2

[0107] Turning of a curved profile with curvature radius of R38.5 mm was performed on Inconel 718 workpiece material supplied in aged condition and having a hardness of HRC 45. PCBN cutting tools having the same composition as in example 1 were used, i.e. compositions according to sample 1-3 in table 1.

[0108] Three different cases of cutting data were used: [0109] 1. cutting speed v.sub.c=350 m/min at feed f=0.10 mm/rev, [0110] 2. cutting speed v.sub.c=420 m/min at feed f=0.08 mm/rev, [0111] 3. cutting speed v.sub.c=420 m/min at feed f=0.10 mm/rev,

[0112] while depth of cut in all three cases was a.sub.p=0.3 mm, corresponding to high-speed finishing conditions. High pressure directed cooling (HPDC) was applied and set for 70 bar coolant pressure at the rake and flank faces of the cutting tool, using 8% oil-water emulsion as coolant medium.

[0113] The cutting tools were manufactured in ISO RNGN090300 insert geometry.

[0114] Flank and notch wear were measured in time intervals of 0.89 minutes ?0.11 minutes and the performance tests were stopped when either maximum flank wear exceeded the criterion of 250 ?m or notch wear exceeded the criterion of 1000 ?m.

[0115] The PCBN cutting tool with TIC as the main binder phase, i.e. sample 2 has rapidly developed a critical notch wear under cutting conditions of cutting speed v.sub.c=420 m/min at feed f=0.08 mm/rev and failed by edge fracture and is therefore not included in table 3 showing the tool wear for example 2.

[0116] Flank and notch wear was measured using Olympus SZX7 optical microscope.

[0117] Table 3 shows the measured flank wear at respective time-in-cut interval when flank or notch wear parameter has reached its limiting criterion for the three different set of cutting data used.

TABLE-US-00003 TABLE 3 v.sub.c = 350 m/min; v.sub.c = 420 m/min v.sub.c = 420 m/min f = 0.10 mm/rev f = 0.08 mm/rev f = 0.10 mm/rev Flank wear (?m) Flank wear Flank wear (?m) Frank wear Flank wear (?m) Frank wear Sample at Time-in-cut (min) rate (?m/min) at Time-in-cut (min) rate (?m/min) at Time in cut (min) rate (?m/min) Sample 1 (invention) 244/7.50 32.5 211/4.11 51.3 241/4.91 49.1 Sample 2 (comparative) 223/3.75 59.47 343/2.01 170.7 Sample 3 (comparative) 239/5.62 42.5 231/3.08 75.0 214/2.89 74.1

[0118] Table 4 shows the measured notch wear for the three different set of cutting data used.

TABLE-US-00004 TABLE 4 Notch wear Notch wear Notch wear (?m) at Time- (?m) at Time- (?m) at Time- in-cut (min) in-cut (min) in-cut (min) v.sub.c = 350 m/min; v.sub.c = 420 m/min v.sub.c = 420 m/min Sample f = 0.10 mm/rev f = 0.08 mm/rev f = 0.10 mm/rev Sample 1 907/7.50 315/4.11 623/4.91 (invention) Sample 2 1239/3.75 539/2.01 (comparative) Sample 3 1479/5.62 430/3.08 813/2.89 (comparative)

[0119] The SEM images in FIGS. 6, 7 and 8 show the notch wear for samples 1, 2 and 3, respectively, for a cutting speed v.sub.c=350 m/min, feed f=0.1 mm/rev and depth of cut a.sub.p=0.3 mm. The result of the notch wear (?m) and time-in-cut (min) for the samples in FIGS. 6, 7 and 8 are also shown in the first column in table 4. As can be seen from table 4, Sample 1 has the longest time-in-cut of 7.50 min, i.e. it cuts two times longer than sample 2 and 33% longer time than sample 3, and at the same time sample 1 still has a lower notch wear than any of samples 2 and 3.

[0120] From the experimental results and observations related to the example 2 it was concluded that Sample 1, i.e. the PCBN cutting tool according to present disclosure, demonstrated more than 31% improvement in performance by flank wear criterion while providing more than 110% improvement by notch wear criterion compared to the conventional TiC-binder and TiCN-binder.

[0121] The present invention is not limited to the embodiments disclosed but may be varied and modified within the scope of the following claims.