Patent Grant
9540722
This application is a §371 National Stage Application of PCT International Application No. PCT/EP2013/054477 filed Mar. 6, 2013 claiming priority of EP Application No. 12158433.8, filed Mar. 7, 2012.
The present invention relates to a hard and wear resistant coating for a body, the coating comprising at least one Zr-based nitride layer. The invention also relates to a method for coating the body and the use thereof.
TiN has been widely used as hard layer on cutting tools. However, due to its relatively poor oxidation resistance at elevated temperatures, the focus has shifted towards more complex ternary and quaternary compounds, e.g. Ti—Al—N, Ti—Al—Si—N and Ti—Cr—Al—N with improved high temperature performance. For example, Ti—Al—Si—N has been reported as super hard, H>40 GPa, explained in terms of a two phase structure consisting of crystalline phase of NaCl-type in combination with x-ray amorphous Si3N4 or SiINx.
EP 0588350 discloses a hard layer of Ti—Si—N composite material deposited on a body using an evaporation technique resulting in layers with a composition of TiaSib where a is between 75 at % and 85 at % and b is between 15 at % and 25 at %.
JP 2004-338058 discloses a hard coating comprising a compound nitride layer of Ti, Si and Y. The layer has a layered structure composed of gradient layers wherein each layer has a maximum Si content and a minimum Si content. JP 2004-338008 and JP 2004-322279 disclose similar hard coatings comprising a compound (Ti,Si,Cr)N layer and (Ti, Si, Zr)N, respectively.
CN 101338411 discloses Zr—Si—N layers grown by co-sputtering of pure Zr and pure Si targets in a mixed argon and nitrogen discharge on substrates to a total thickness of 2 to 3 μm.
EP 1736565 discloses a cutting tool insert, solid end mill, or drill, comprising a body and a coating composed of one or more layers of refractory compounds of which at least one layer comprises a cubic (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.
WO2005100635A1 discloses an AlxSiyMezN coating, 0.001≦z≦0.08 where Me is a metal dopant element, for example Zr.
Today industry continuously seeks solutions for economic and high productivity/feed-through manufacturing. To meet these demands there is a need for new materials with advanced properties to improve tool life during operation. Within the metal cutting tool industry, a major part of this effort is focused to improve the wear behavior of the cutting tools by designing the properties of the coating material used in the application. Typically, a high productivity/feed-through cutting process results in a dramatic increase of the tool temperature and hence a coating material with a high temperature wear resistance is essential.
It is an object of the present invention to provide a coating material with improved high temperature performance.
It is further an object of the present invention to provide a method for making the same.
According to a first aspect of the invention the object is achieved by a hard and wear resistant coating for a body, the coating comprises at least one metal based nitride layer, wherein said layer is (Zr1-x-zSixMez)Ny with 0<x<0.30, 0.90<y<1.20, 0≦z<0.25, and Me is one or more of the elements Y, Ti, Nb, Ta, Cr, Mo, W and Al, the layer comprises a single cubic phase or a single hexagonal phase or a mixture thereof, preferably a cubic phase of a sodium chloride structure, and the layer has a thickness between 0.5 μm and 15 μm. Thereby a hard and wear resistant coating with high temperature wear resistance is achieved. The enhanced temperature properties of the coating are, for example, observed as an improved crater wear resistance in metal machining by chip removal generating high temperature performance.
According to one embodiment of the invention 0<x<0.15, preferably 0<x<0.085.
According to one embodiment of the invention 0<z<0.15, preferably 0<z<0.10. By the addition of small amounts of one or more of the elements Me: Y, Ti, Nb, Ta, Cr, Mo, W and/or Al excellent high temperature resistance is achieved.
According to one embodiment of the invention Me is one or more of the elements Ta, Ti, Nb, Cr and Al.
According to one embodiment of the invention TC(200)>1.5 and simultaneously TC(111), TC(220) and TC(311) should all be <1.5 where
TC(hkl) is determined from the XRD data as follows:
where
Imeas(hkl) is the measured intensity of the (111(1) reflection and Io(hkl) the standard intensity according to the JCPDS card no. 035-0753, and n=4 is the number of (hkl) reflections used in the calculations.
According to one embodiment of the invention TC(200)>2.0.
According to one embodiment of the invention the at least one metal based nitride layer has a thickness between 0.5 μm and 10 μm.
According to one embodiment of the invention the at least one metal based nitride layer has a nanohardness >20 GPa, preferably the nanohardness is between 25 GPa and 40 GPa.
According to one embodiment of the invention the coating consists of an innermost single layer and/or multilayer comprising, e.g., TiN, TiC, Ti(C,N) or (Ti,Al)N, preferably a single layer of (Ti,Al)N, followed by said (Zr,Si,Me)N layer and an outer single layer and/or multilayer comprising, e.g., TiN, TiC, Ti(C,N) or (Ti,Al)N, preferably a single layer of TiN, to a total coating thickness between 1 μm and 20 μm, preferably between 1 μm and 15 μm, and most preferably between 1 μm and 7 μm.
According to one embodiment of the invention the at least one layer is deposited onto a cutting tool insert for machining by chip removal, said insert comprises a body of a hard alloy of cemented carbide, cermet, ceramics, cubic boron nitride based material or high speed steel. According to a second aspect of the invention the object is achieved by a method for making a hard and wear resistant coating by growing a metal based nitride layer by cathodic arc evaporation with an evaporation current between 50 A and 200 A using composite and/or alloyed cathodes, wherein said layer is (Zr1-x-zSixMez)Ny with 0<x<0.30, 0.90<y<1.20, 0≦z<0.25, where Me is one or more of the elements: Y, Ti, Nb, Ta, Cr, Mo, W or Al, in a reactive atmosphere containing N2 and optionally with a carrier gas such as, e.g. Ar, at a total gas pressure between 1.0 Pa and 7.0 Pa, preferably between 1.5 Pa and 4.0 Pa, with a negative substrate bias between 0 V and 300 V, preferably between 10 V and 150 V, at a temperature between 200° C. and 800° C., preferably between 300° C. and 600° C.
According to a third aspect of the invention the object is achieved by use of a cutting tool insert for machining by chip removal, specifically generating high temperatures, at cutting speeds of 50-400 m/min, preferably 75-300 m/min, with an average feed, per tooth in the case of milling, of 0.08-0.5 mm, preferably 0.1-0.4 mm, depending on cutting speed and insert geometry.
According to one embodiment of the present invention, there is provided a body onto which a hard and wear resistant coating is deposited comprising at least one layer of (Zr1-x-zSixMez)Ny with 0<x<0.30, preferably 0<x<0.15, most preferably 0<x<0.085, 0.90<y<1.20, preferably 0.90<y<1.10, 0≦z<0.25, preferably 0≦z<0.15, most preferably 0≦z<0.10, and Me is one or more of the elements Y, Ti, Nb, Ta, Cr, Mo, W and Al, preferably one or more of the elements Ta, Ti, Nb, Cr and Al, most preferably one or more of the elements Ta and Cr, comprising a single cubic phase or a single hexagonal phase or a mixture thereof, preferably with a cubic phase of a sodium chloride structure, as determined by X-ray diffraction with a thickness between 0.5 μm and 15 μm, preferably between 0.5 μm and 10 μm, most preferably between 0.5 μm and 5 μm. Additionally, the layer contains a sum of oxygen (O) and carbon (C) concentration between 0 and 2 at %, preferably between 0 and 1 at %.
The elemental composition of said layer, x, y and z including O and C, is estimated from measurements by, e.g., EDS or WDS techniques and is, within the measurement accuracy, essentially constant all through the layer thickness with a variation less than 10%, including the influence of normal process variations such as, e.g., rotation of the inserts during growth.
Said layer has a strong (200) texture relation, preferably a fibre texture, with (200) lattice planes oriented parallel to the growth surface and characterized by a strong (200) diffraction peak, measured by XRD (θ-2η configuration), and low intensity of the (111), (220) and (311) diffraction peaks, respectively. The texture coefficients, TC(hkl), are determined from the XRD data as follows:
where
Imeas(hkl) is the measured intensity of the (hkl) reflection and Io(hkl) the standard intensity for the same (hkl) reflection according to literature references. Here are used the standard intensities for cubic ZrN according to the JCPDS card no. 035-0753 where Io(111)=100, Io(200)=74, Io(220)=36 and Io(311)=24, respectively, and n=4, i.e., the number of (hkl) reflections used in the calculations. Only the first order reflections (hkl) are used in the evaluation, i.e., (111), (200), (220) and (311), respectively.
The texture of said layer is defined as TC(200)>1.5, preferably TC(200)>2.0. Simultaneously TC(111), TC(220) and TC(311) should all be <1.5.
Said layer has a columnar microstructure with an average column width of <1 μm, preferably <0.6 μm, as determined by cross sectional transmission electron microscopy of a middle region of the layer, i.e., a region within 30% to 70% of the layer thickness in the growth direction, and said average columnar width is the average of at least 10 adjacent columns
Said layer has a compressive stress level of −6.0 GPa<σ<−0.5 GPa, preferably of −3.0 GPa<σ<−1.0 GPa. The residual stress is evaluated by XRD using the sin2 Ψ-method with a Poisson's ratio of υ=0.23 and a Young's modulus of E=379 GPa.
Said layer has a nanohardness >20 GPa, preferably between 25 GPa and 40 GPa, most preferably between 30 GPa and 40 GPa, as measured by nanoindentation experiments.
According to one embodiment of the invention, z=0, and said layer is (Zr1-xSix)Ny with 0<x<0.30, preferably 0<x<0.15, most preferably 0<x<0.085, 0.90<y<1.20, preferably 0.90<y<1.10, 0≦z<0.25.
It is evident that said (Zr,Si,Me)N layer can be part of a complex coating design and used as an inner, middle and/or an outer layer of said complex coating.
According to one embodiment of the invention, said coating consists of an innermost single layer and/or multilayer comprising, e.g., TiN, TiC, Ti(C,N) or (Ti,Al)N, preferably a single layer of (Ti,Al)N, followed by said (Zr,Si,Me)N layer and an outermost single layer and/or multilayer comprising, e.g., TiN, TiC, Ti(C,N) or (Ti,Al)N, preferably a single layer of TiN, with a total coating thickness between 1 μm and 20 μm, preferably between 1 μm and 15 μm, and most preferably between 1 μm and 7 μm.
According to one embodiment of the invention, said body is a cutting tool insert for machining by chip removal comprising a body of a hard alloy of cemented carbide, cermet, ceramics, cubic boron nitride based material or high speed steel. It is, however, obvious that said body can be other metal cutting tools, e.g., drills and end mills.
The deposition method for said layer is based on PVD techniques, e.g., cathodic arc evaporation or magnetron sputtering using one or more pure, composite and/or alloyed (Zr,Si,Me) cathodes/targets.
In the case of cathodic arc evaporation, the metal based nitride layer is grown with an evaporation current between 50 A and 200 A depending on the cathode size, and said layer is (Zr1-x-zSixMez)Ny with 0<x<0.30, 0.90<y<1.20, 0≦z<0.25. A higher evaporation current is needed for larger cathodes in order to achieve comparable deposition conditions. The layers are grown using one or more composite and/or alloyed cathodes. The desired layer composition is obtained by selecting appropriate composition of the (Zr,Si,Me) cathode and gas atmosphere, where Me, when present in the layer, is one or more of the elements: Y, Ti, Nb, Ta, Cr, Mo, W or Al, in a reactive atmosphere containing N2 and optionally with a carrier gas such as, e.g. Ar, at a total gas pressure between 1.0 Pa and 7.0 Pa, preferably between 1.5 Pa and 4.0 Pa. The negative substrate bias is between 0 V and 300 V, preferably between 10 V and 150 V, most preferably between 15 V and 60 V. The deposition temperature is between 200° C. and 800° C., preferably between 300° C. and 600° C.
In the case of magnetron sputtering, (Zr,Si,Me)N layers may be grown with a power density applied to the sputter target between 0.5 W/cm2 and 15 W/cm2, preferably between 1 W/cm2 and 5 W/cm2, from co-sputtering of pure elemental targets by altering the power to the respective targets (alter the deposition rate for each target) or from a composite and/or alloyed target, where Me, when present, is one or more of the elements: Y, Ti, Nb, Ta, Cr, Mo, W or Al, in a reactive atmosphere containing N2 and optionally with a carrier gas such as, e.g. Ar, at a total pressure between 0.1 Pa and 5.0 Pa, preferably between 0.1 Pa and 2.5 Pa. The desired layer composition is obtained by selecting appropriate composition of the (Zr,Si,Me) target, target power density and gas atmosphere. The negative substrate bias is between 0 V and 300 V, preferably between 10 V and 150 V, most preferably between 10 V and 80 V. The deposition temperature is between 200° C. and 800° C., preferably between 300° C. and 600° C.
The invention also relates to the use of coated cutting tool insert according to the above for machining at cutting speeds of 50-400 m/min, preferably 75-300 m/min, with an average feed, per tooth in the case of milling, of 0.08-0.5 mm, preferably 0.1-0.4 mm, depending on cutting speed and insert geometry.
Cemented carbide inserts with composition 94 wt % WC-6 wt % Co were used as a body for the layer depositions by cathodic arc evaporation.
Before deposition, the inserts were cleaned in ultrasonic baths of an alkali solution and alcohol. The system was evacuated to a pressure of less than 2.0×10−3 Pa, after which the inserts were sputter cleaned with Ar ions. (Zr1-x-zSixMez)Ny layers, 0.004≦x≦0.234, z=0, coatings 1-8 in Table 1, were grown using (Zr1-aSia) cathodes, with a Si content, a, varying between a=0.01 and a=0.25 (see Table 1). The layers were deposited at 450° C. in a pure N2 atmosphere, a process pressure of 3 Pa, a bias of −30 V and an evaporation current of 60 A to a total thickness of about 3 μm.
Example 1 was repeated using (Zr1-a-bSiaMeb) cathodes for the deposition of the (Zr1-x-zSixMez)Ny layers, coatings 9-15 in Table 1.
MgO(001) and Al2O3(0001) single crystals substrates were used as a body for the layer depositions by magnetron sputtering.
Before deposition, the inserts were cleaned in ultrasonic baths of an alkali solution and alcohol. The system was evacuated to a pressure of less than 2.0×10−3 Pa, after which said substrates were heat treated (de-gassed) at 900° C. for 15 min. (Zr1-xSix)Ny layers, 0≦x≦1.00, 1.00≦y≦1.10 were grown by co-sputtering of pure Zr and Si targets, 77 mm in diameter in a lab scale deposition system. Layers were deposited at floating bias conditions, temperatures between 500° C. and 900° C. in mixed Ar+N2 discharge with fixed Ar and N2 partial pressures of 0.5 Pa and 0.07 Pa, respectively, to a total layer thickness between 1 μm and 1.5 μm. The different composition, x, were obtained by altering the power to the respective magnetron sources, and hence the deposition rate of Zr and Si, keeping the total power constant at 250 W.
At optimum growth conditions of 800° C. and x=0.20, said layer is highly (200) textured consisting of ZrN-rich/Si3N4-rich lamellas, 2-5 nm in width with a nanohardness of about 35 GPa. At lower growth temperatures, a polycrystalline microstructure forms with nanohardness close to that measured at the optimum growth conditions and thus offers the possibility for scale-up depositions of (Zr1-xSix)Ny layers onto a body of, e.g., cemented carbide inserts.
The composition x, z and y, of the (Zr1-x-zSixMez)Ny layers was estimated by energy dispersive spectroscopy (EDS) analysis using a LEO Ultra 55 scanning electron microscope operated at 10 kV and equipped with a Thermo Noran EDS detector. The data were evaluated using the Noran System Six (NSS ver 2) software.
X-ray diffraction (XRD) patterns of the as-deposited (Zr1-x-zSixMez)Ny layers were obtained using Cu K alpha radiation and a θ-2θ configuration in a Bruker AXS D8 Advance diffractometer.
The residual stresses, σ, of the (Zr1-x-zSixMez)Ny layers were evaluated by XRD measurements using the sin2 Ψ method (see e.g. I. C. Noyan, J. B. Cohen, Residual Stress Measurement by Diffraction and Interpretation, Springer-Verlag, New York, 1987). The measurements were performed using CuKα-radiation on the (311)-reflection. The residual stress values were within −5.0 GPa<σ<−1.0 GPa for the different layers as evaluated using a Poisson's ratio of υ=0.23 and Young's modulus of E=379 GPa.
Hardness data were estimated by the nanoindentation technique of the layers after mechanical polishing of the surface using a UMIS 2000 nanoindentation system with a Berkovich diamond tip with a maximum tip load of 25 mN.
The microstructure of (Zr1-x-zSixMez)Ny layers was studied in cross-section by analytical (scanning) transmission electron microscopy ((S)TEM) using a FEI Technai G2 instrument operated at 200 kV. Samples for TEM were made by conventional mechanical polishing and ion milling until electron translucency.
The coatings from Table 1 (example 1) were tested in a turning operation with the following data:
Geometry: CNMG120408-MF4
Application: Facing
Work piece material: 100Cr6
Cutting speed: 200 m/min
Feed: 0.25 mm/rev.
Depth of cut: 2 mm
Performance criterion: Crater wear resistance
The cutting results are presented in Table 2 clearly indicating an improved crater wear performance of coating 4 of the invention compared to the reference materials according to prior art.
| Number | Date | Country | Kind |
|---|---|---|---|
| 12158433 | Mar 2012 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2013/054477 | 3/6/2013 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2013/131943 | 9/12/2013 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 6274249 | Braendle | Aug 2001 | B1 |
| 7704611 | Coddet | Apr 2010 | B2 |
| 8071211 | Koike | Dec 2011 | B2 |
| 8178220 | Okamura | May 2012 | B2 |
| 8440327 | Palmqvist | May 2013 | B2 |
| Number | Date | Country |
|---|---|---|
| 2000-326107 | Nov 2000 | JP |
| 2008-031517 | Feb 2008 | JP |
| 2008-302474 | Dec 2008 | JP |
| 2011-020194 | Feb 2011 | JP |
| 2005100635 | Oct 2005 | WO |
| Entry |
|---|
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| Yan et al “Microstructures and Mechanical Properties of Zr—Si—N Films Prepared by Reactive Sputtering” Chines Journal of Vacuum Sci & Tech vol. 26, No. 2 (2006) p. 200-203. |
| Liu, et al “Chinese Journal of Vacuum Science and Technology”, vol. 26, No. 3, pp. 200-203. |
| Mei et al. “Effect of Al element on microstructure and mechanical properties of Zr—Si—N composite films”, Heat Treatment of Metals, vol. 34, No. 11, pp. 1-4. |
| Sobol et al “Effect of preparation conditions on the phase composition, structure, and mechanical characteristics of vacuum-arc Zr—Ti—Si—N coatings”, The Physica of Metals and Metallography, vol. 112, No. 2, pp. 188-195. |
| Number | Date | Country | |
|---|---|---|---|
| 20150030406 A1 | Jan 2015 | US |
