Patent Grant
8864861
The present invention relates to a cutting tool insert comprising a body of cubic boron nitride compact (PCBN) material and a hard and wear resistant coating comprising a nanolaminated structure based on (Ti,Al)N and (Ti,Si)N layers, respectively. This insert is particularly useful in metal cutting applications generating high temperatures, e.g., high speed machining of steels, cast irons, super alloys, stainless steels and hardened steels. The coating is grown by physical vapour deposition (PVD) and preferably by cathodic arc evaporation.
U.S. Pat. No. 7,056,602 discloses a cutting tool insert coated with a cubic structured (TiyAlxMe1-x-y)N based layer where Me is one of the elements: Zr, Hf, V, Nb, Ta, Cr, Mo, W or Si, and: x is between 0.50 and 0.80; the ratio, x/(x+y), is between 0.50 and 0.85; the sum of the Ti and Al subscripts, x+y, is between 0.7 and 1.0.
EP 1736565 discloses a cutting tool cubic boron nitride based insert coated with a cubic structured (Me,Si)X phase, where Me is one or more of the elements Ti, V, Cr, Zr, Nb, Mo, Hf, Ta and Al, and X is one or more of the elements N, C, O or B.
EP 0588350 discloses a hard layer of Ti—Si—N composite material on a body, the layer being deposited using a source of evaporation possessing a composition of TiaSib with a in the range of 75-85 at % and b 15-25 at %.
Coating optimization has also been obtained by applying different concepts of multilayers as; alternating Ti and Al containing layers (U.S. Pat. No. 6,309,738), oxygen and non-oxygen containing layers (U.S. Pat. No. 6,254,984), one of the layers stacked in the multilayer consists itself of a multilayer (U.S. Pat. No. 6,077,596), alternating nitrogen content (U.S. Pat. No. 5,330,853) or using one metastable compound (U.S. Pat. No. 5,503,912) or as aperiodic multilayer (U.S. Pat. No. 6,103,357).
Further improvements in thermal stability and hardness have been achieved by the introduction of Si into TiN- or TiAlN-based coatings. JP 2000-334607 discloses a coated tool with laminated layers comprising TiSi (layer a) and TiAl (layer b) compounds. The (a) layer is selected among nitride, carbonitride, oxynitride and oxycarbonitride containing 10%<Si<60% with a NaCl type crystalline structure. Layer (b) is selected among nitride, carbonitride, oxynitride and oxycarbonitride containing 40%<Al<75% with a NaCl type crystalline structure. The (a) layer and (b) layers are applied alternately by each one layer or more and the (b) layer is located just above the surface of the base material.
EP 1939327 discloses a cutting tool comprising a hard coating giving improved crater and flank wear resistance, said coating comprising an aperiodic multilayer X+Y+X+Y+ . . . with average layer thickness of X and Y layers of between 0.1 and 100 nm and with average chemical composition AlaTibSicCrdCeN1-e, where 0<a<0.5, 0.1<b<0.9, 0.01<c<0.17, 0≦d<0.06, a+b+c+d=1, and 0≦e<1.
The trends towards dry-work processes for environmental protection, i.e., metal cutting operation without using cutting fluids (lubricants) and accelerated machining speed with improved process put even higher demands on the characteristics of the tool materials due to an increased tool cutting-edge temperature. In particular, coating stability at high temperatures, e.g., oxidation- and wear-resistance have become even more crucial.
It is an object of the present invention to provide a coated cutting tool yielding improved performance in metal cutting applications at elevated temperatures.
It is a further object of the present invention to provide a coated cutting tool with improved edge integrity.
It has been found that combining layers based on (Ti,Si)N and (Ti,Al)N, respectively, in a nanolaminated coating structure onto a cubic boron nitride based cutting tool insert significantly improves the tool life due to increased crater wear resistance, flank wear resistance and edge integrity, especially in high speed machining operations generating high tool temperatures.
According to the present invention, there is provided a cutting tool for machining by chip removal comprising a body of polycrystalline cubic boron nitride compact (PCBN), either as a solid insert or attached to a backing body, onto which is deposited a hard and wear resistant coating comprising a polycrystalline nanolaminated structure of alternating A and B layers with a thickness between 0.5 and 10 μm, preferably between 0.5 and 5 μm, and with an overall columnar structure. The average column width is between 20 and 1000 nm, preferably between 20 and 500 nm, as determined by, e.g., cross section scanning electron microscopy of a middle region of the nanolaminated structure, i.e., in a region within 30 to 70% of the thickness in the growth direction, and said average columnar width is the average from measuring the width of at least ten adjacent columns.
Said layer A is (Ti1-x-pAlxMe1p)Na, where 0.3<x<0.95, preferably 0.45<x<0.75, and 0.90<a<1.10, preferably 0.96<a<1.04, 0≦p<0.15, and Me1 is one or more of the metal elements from group 3, 4, 5 or 6 in the periodic table, preferably one or more of Zr, Y, V, Nb, Mo and W, most preferably one or more of Zr, Y, V and Nb. Said layer B is (Ti1-y-zSiyMe2z)Nb, where 0.05<y≦0.25 preferably 0.05<y<0.18, 0≦z<0.4, 0.9<b<1.1, preferably 0.96<b<1.04, and Me2 is one or more of the metal elements from group 3, 4, 5 or 6 in the periodic table including Al, preferably one or more of Y, V, Nb, Mo, W and Al, most preferably one or more of Y, V, Nb and Al. Layers A and B have an average individual layer thickness between 1 nm and 50 nm, as measured by, e.g., cross sectional transmission electron microscopy of a middle region of the nanolaminated structure, i.e., a region within 30 to 70% of the thickness in the growth direction, and said average layer thickness is the average from measuring the thickness of at least ten adjacent layers. Said nanolaminated structure comprises a phase mixture of cubic and hexagonal phases, preferably only cubic phases, as determined by X-ray diffraction.
In a first preferred embodiment z=p=0.
In a second preferred embodiment Me1 is one or more of Zr, Y, V and Nb with 0<p<0.05.
In a third preferred embodiment Me2 is Y, 0<z<0.15.
In a fourth preferred embodiment Me2 is one or both of V and Nb with 0<z<0.3.
In a fifth preferred embodiment Me2 is Al, 0.2<z<0.4.
The average composition of said nanolaminated structure is 45 at %<Ti+Al+Si+Y+V+Nb+Mo+W+Zr<55 at %, preferably 48 at %<Ti+Al+Si+Y+V+Nb+Mo+W+Zr<52 at % and rest N as determined by, e.g., EDS or WDS techniques.
Said coating may comprise an inner single- and/or multilayer coating of TiN, TiC, Ti(C,N) or (Ti,Al)N, preferably (Ti,Al)N, and/or an outer single- and/or multilayer coating of TiN, TiC, Ti(C,N), (Ti,Si)N or (Ti,Al)N, preferably (Ti,Si)N or (Ti,Al)N, according to known art, to a total coating thickness, including the thickness of the nanolaminated structure, of between 0.5 and 20 μm, preferably between 0.5 and 10 μm, and most preferably between 0.5 and 7 μm.
Said PCBN body contains at least 30 vol % of cubic phase boron nitride (cBN) in a binder. The binder contains at least one compound selected from a group consisting of nitrides, borides, oxides, carbides and carbonitrides of one or more of the elements belonging to the groups 4, 5 and 6 of the periodic table and Al, e.g., Ti(C,N) and AlN.
In a sixth preferred embodiment, said PCBN body contains 30 vol %<cBN<70 vol %, preferably 40 vol %<cBN<65 vol %, with an average cBN grain size between 0.5 μm and 4 μm. The binder contains 80 wt %<Ti(C,N)<95 wt % and rest containing mainly other compounds comprising two or more of the elements Ti, N, B, Ni, Cr, Mo, Nb, Fe, Al and/or O, e.g., TiB2 and Al2O3.
In a seventh preferred embodiment, said PCBN body contains 45 vol %<cBN<70 vol %, preferably 55 vol %<cBN<65 vol %, with an average cBN grain size between 0.5 μm and 4 μm, preferably between 1 μm and 3 μm. The binder contains 80 wt %<Ti(C,N)<90 wt %, 1 wt. %<alloy containing one or more of the elements Ni, Co, Cr and/or Mo<10 wt %, and rest containing mainly TiB2 and Al2O3.
In an eighth preferred embodiment, said PCBN body contains 70 vol %<cBN, preferably 80 vol %<cBN<95 vol %, with an average cBN grain size either between 0.5 μm and 10 μm, preferably between 1 μm and 6 μm, or between 10 μm and 25 μm, preferably between 15 μm and 25 μm. The binder contains compounds of two or more of the elements Al, B, N, W, Co, Ni, Fe, Al and/or O.
The deposition method for the coatings of the present invention is based on cathodic arc evaporation of an alloy or composite cathode under the following conditions; (Ti,Al,Me1)N and (Ti,Si,Me2)N layers are grown from cathodes yielding the desired layer composition. The evaporation current is between 50 A and 200 A. The layers are grown in an Ar+N2 atmosphere, preferably in a pure N2 atmosphere, at a total pressure of 0.5 Pa to 9.0 Pa, preferably 1.5 Pa to 5.0 Pa. The bias is −10 V to −300 V, preferably −20 V to −200 V. The deposition temperature is between 350° C. and 700° C., preferably between 400° C. and 650° C.
The invention also relates to the use of cutting tool inserts according to the above for machining of steels, cast irons, super alloys and hardened steels at cutting speeds of 50-2000 m/min, preferably 50-1500 m/min, with an average feed of 0.01-1.0 mm/rev, preferably 0.01-0.6 mm, depending on the cutting operation.
The coatings of Table 1 were deposited by cathodic arc evaporation onto the following PCBN inserts:
S5 with 90 vol % cBN, an average cBN grain size of about 20 μm and a binder containing mainly AlN and rest containing mainly AlB2.
Before deposition, the inserts were cleaned in ultrasonic baths of an alkali solution and alcohol. The deposition chamber was evacuated to a base pressure of less than 2.0×10−3 Pa, after which the inserts were sputter cleaned with Ar ions. The coatings were deposited from alloy or composite cathodes in 99.995% pure N2 atmosphere at a total pressure of 2-6 Pa, using a bias of −20 to −60 V and an evaporation current of 60-200 A. The cathodes were selected to yield the composition of Layer A and Layer B, respectively, and mounted on opposing sides of the deposition chamber in order to obtain the nanolaminated structure by fixture rotation. The average individual layer thickness was varied by altering the cathode current (60-200 A) and the rotation speed of the fixture (1-5 rpm). The total coating thicknesses were about 2 μm for all inserts and the deposition temperature was 450° C.
The total average composition of the coatings was measured by energy dispersive x-ray spectroscopy (EDS) analysis area using a LEO Ultra 55 scanning electron microscope with a Thermo Noran EDS detector operating at 10 kV. The data were evaluated using a Noran System Six (NSS ver 2) software.
Coatings 1, 3, 6, 40-45 on S1 and S2 inserts were tested under the following conditions:
Geometry: CNGA120408S
Application: Continuous turning
Work piece material: Case hardened steel (16MnCr5)
Cutting speed: 200 m/min
Feed: 0.1 mm/rev
Depth of cut: 0.15 mm
Tool life criteria: Edge failure
The results are shown in Table 2.
Coatings 1-6, 35, 36, 38-42, 44-45 on S3 inserts were tested under the following conditions:
Geometry: RCGN0803MOS
Application: Continuous turning
Work piece material: Case hardened steel (16MnCr5)
Cutting speed: 200 m/min
Feed: 0.1 mm/rev
Depth of cut: 0.15 mm
Tool life criteria: Edge failure
The results are shown in Table 2.
Coatings 6, 37, 40, 41 on S4 inserts were tested under the following conditions:
Geometry: CNMN120412S
Application: Facing
Work piece material: AISI A48-40B
Cutting speed: 1100 m/min
Feed: 0.3 mm/rev
Depth of cut: 1 mm
Tool life criteria: Edge failure
The results are shown in Table 2.
Coatings 6, 40, 41 on S5 inserts were tested under the following conditions:
Geometry: CNMN120412S
Application: Continuous turning
Work piece material: AISI A48-45B
Cutting speed: 1100 m/min
Feed: 0.4 mm/rev
Depth of cut: 2 mm
Tool life criteria: Edge failure
The results are shown in Table 2.
It is obvious from the above examples that the inserts according to the invention show an increased tool performance with improved edge and crater wear characteristics.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0900738 | Jun 2009 | SE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/SE2010/050581 | 5/28/2010 | WO | 00 | 1/24/2012 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2010/140959 | 12/9/2010 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 5330853 | Hofmann et al. | Jul 1994 | A |
| 5503912 | Setoyama et al. | Apr 1996 | A |
| 6077596 | Hashimoto et al. | Jun 2000 | A |
| 6103357 | Selinder et al. | Aug 2000 | A |
| 6254984 | Iyori | Jul 2001 | B1 |
| 6309738 | Sakurai | Oct 2001 | B1 |
| 6316094 | Fukaya et al. | Nov 2001 | B1 |
| 6586122 | Ishikawa et al. | Jul 2003 | B2 |
| 6599062 | Oles et al. | Jul 2003 | B1 |
| 7056602 | Horling et al. | Jun 2006 | B2 |
| 8003232 | Johansson et al. | Aug 2011 | B2 |
| 20050202283 | Gates, Jr. et al. | Sep 2005 | A1 |
| 20060182999 | Yamamoto | Aug 2006 | A1 |
| 20060246320 | Kathrein et al. | Nov 2006 | A1 |
| 20060292399 | Sjolen et al. | Dec 2006 | A1 |
| 20070032369 | Franzen | Feb 2007 | A1 |
| 20080075543 | Zhu et al. | Mar 2008 | A1 |
| Number | Date | Country |
|---|---|---|
| 0588350 | Mar 1994 | EP |
| 0709483 | May 1996 | EP |
| 1736565 | Dec 2006 | EP |
| 1939327 | Jul 2008 | EP |
| 59-097579 | Jun 1984 | JP |
| 08-127862 | May 1996 | JP |
| 08-197306 | Aug 1996 | JP |
| 2000326107 | Nov 2000 | JP |
| 2000-334606 | Dec 2000 | JP |
| 2000334607 | Dec 2000 | JP |
| 3347687 | Nov 2002 | JP |
| 2006-225708 | Aug 2006 | JP |
| 2006-528076 | Dec 2006 | JP |
| 2010076084 | Apr 2010 | JP |
| 2005000518 | Jan 2005 | WO |
| Entry |
|---|
| International Search Report dated Sep. 3, 2010, corresponding to PCT application. |
| Number | Date | Country | |
|---|---|---|---|
| 20120114437 A1 | May 2012 | US |
