Body with a metal based nitride layer and a method for coating the body

Abstract

A hard and wear resistant coating for a body includes at least one metal based nitride layer having improved high temperature performance. The layer is (Zr1-x-zSixMez)Ny with 0<x<0.30, 0.90<y<1.20, 0z<0.25, and Me is one or more of the elements Y, Ti, Nb, Ta, Cr, Mo, W and Al, comprised of a single cubic phase, a single hexagonal phase or a mixture thereof, with a cubic phase of a sodium chloride structure and a thickness between 0.5 m and 15 m. The layer is deposited using cathodic arc evaporation and is useful for metal cutting applications generating high temperatures.

Claims

1. A hard and wear resistant coating for a body, the coating comprising: at least one metal based nitride layer deposited on the body by cathodic arc evaporation, wherein said at least one metal based nitride layer is (Zr.sub.1xzSi.sub.xMe.sub.z)N.sub.y with 0<x<0.15, 0.90<y <1.10, 0z<0.25, and Me is one or more of the elements Y, Ti, Nb, Ta, Cr, Mo and W, the at least one metal based nitride layer being selected from the group of a cubic phase of a sodium chloride structure, a single cubic phase, a single hexagonal phase, and a mixture thereof, the at least one metal based nitride layer having a thickness between 0.5 m and 15 m, and TC(200)>1.5 and simultaneously TC(111), TC(220) and TC(311) all being <1.5 wherein TC(hkl) is determined from XRD data as follows: ${\mathrm{TC}}_{\mathrm{meas}}\left(\mathrm{hkl}\right)={\frac{I_{\mathrm{meas}}\left(\mathrm{hkl}\right)}{I_0\left(\mathrm{hkl}\right)}\left[\frac{1}{n}\underset{n=1}{\overset{n}{.Math.}}\frac{I_{\mathrm{meas}}\left(\mathrm{hkl}\right)}{I_0\left(\mathrm{hkl}\right)}\right]}^{-1}$ wherein I.sub.meas(hkl) is a measured intensity of the (hkl) reflection and I.sub.o(hkl) a standard intensity according to JCPDS card no. 035-0753, and n=4 is the number of (hkl) reflections used in the calculations.

2. The hard and wear resistant coating according to claim 1, wherein 0<x<0.15.

3. The hard and wear resistant coating according to claim 2, wherein 0<x<0.085.

4. The hard and wear resistant coating according to claim 1, wherein 0<z<0.15.

5. The hard and wear resistant coating according to claim 4, wherein 0<z<0.10.

6. The hard and wear resistant coating according to claim 1, wherein Me is one or more of the elements Ta, Ti, Nb, and Cr.

7. The hard and wear resistant coating according to claim 1, wherein TC(200)>2.0.

8. The hard and wear resistant coating according to claim 1, wherein said at least one metal based nitride layer has a thickness between 0.5 m and 10 m.

9. The hard and wear resistant coating according to claim 1, wherein said at least one metal based nitride layer has a nanohardness>20 GPa.

10. The hard and wear resistant coating according to claim 9, wherein said at least one metal based nitride layer has a nanohardness between 25 GPa and 40 GPa.

11. The hard and wear resistant coating according to claim 1, wherein said coating comprises at least one innermost layer selected from the group of TiN, TiC, Ti(C,N) or (Ti,Al)N, followed by said (Zr,Si,Me)N layer and at least one outer layer selected from the group of TiN, TiC, Ti(C,N) or (Ti,Al)N, the coating having a total coating thickness between 1 m and 20 m.

12. The hard and wear resistant coating according to claim 11, wherein the at least one innermost layer is a single layer of (Ti,Al)N.

13. The hard and wear resistant coating according to claim 11, wherein the at least one innermost layer is a plurality of layers selected from the group of TiN, TiC, Ti(C,N) or (Ti,Al)N.

14. The hard and wear resistant coating according to claim 11, wherein the at least one outer layer is a single layer of TiN.

15. The hard and wear resistant coating according to claim 11, wherein the at least one outer layer is a plurality of layers selected from the group of TiN, TiC, Ti(C,N) or (Ti,Al)N.

16. The hard and wear resistant coating according to claim 11, wherein the total coating thickness is between 1 m and 15 m.

17. The hard and wear resistant coating according to claim 11, wherein the total coating thickness is between 1 m and 7 m.

18. The hard and wear resistant coating according to claim 1, wherein said at least one metal based nitride layer is deposited onto a cutting tool insert for machining by chip removal, said insert comprising a body of a hard alloy selected from the group of cemented carbide, cermet, ceramics, cubic boron nitride based material or high speed steel.

19. A method of using a cutting tool insert for machining by chip removal, comprising the steps of: providing a cutting tool insert, the insert including a body of a hard alloy selected from the group of cemented carbide, cermet, ceramics, cubic boron nitride based material or high speed steel and depositing at least one metal based nitride layer onto the cutting tool insert by cathodic arc evaporation, wherein said at least one metal based nitride layer is (Zr.sub.1xzSi.sub.xMe.sub.z)N.sub.y with 0<x<0.15, 0.90<y<1.10, 0z<0.25, and Me is one or more of the elements Y, Ti, Nb, Ta, Cr, Mo and W, the at least one metal based nitride layer being selected from the group of a cubic phase of a sodium chloride structure, a single cubic phase, a single hexagonal phase, and a mixture thereof, the at least one metal based nitride layer having a thickness between 0.5 m and 15 m, and TC(200)>1.5 and simultaneously TC(111), TC(220) and TC(311) all being<1.5 wherein TC(hkl) is determined from XRD data as follows: ${\mathrm{TC}}_{\mathrm{meas}}\left(\mathrm{hkl}\right)={\frac{I_{\mathrm{meas}}\left(\mathrm{hkl}\right)}{I_0\left(\mathrm{hkl}\right)}\left[\frac{1}{n}\underset{n=1}{\overset{n}{.Math.}}\frac{I_{\mathrm{meas}}\left(\mathrm{hkl}\right)}{I_0\left(\mathrm{hkl}\right)}\right]}^{-1}$ wherein I.sub.meas(hkl) is a measured intensity of the (hkl) reflection and I.sub.o(hkl) a standard intensity according to JCPDS card no. 035-0753, and n=4 is the number of (hkl) reflections used in the calculations; and specifically generating high temperatures, at cutting speeds of 50-400 m/min, with an average feed, per tooth in the case of milling, of 0.08-0.5 mm, depending on cutting speed and insert geometry.

20. The method of claim 19, wherein the reactive atmosphere includes a carrier gas of Ar.

21. The method of claim 19, wherein the total gas pressure is between 1.5 Pa and 4.0 Pa.

22. The method of claim 19, wherein the negative substrate bias is between 10 V and 150 V.

23. The method of claim 19, wherein the temperature is between 300 C. and 600 C.

24. The method of claim 19, wherein the cutting speed is 75-300m/min.

25. The method of claim 19, wherein average feed, per tooth is 0.1-0.4 mm.

26. A cutting tool insert comprising: a body; and a hard and wear resistant coating deposited on the body by cathodic arc evaporation , the coating including at least one metal based nitride layer, wherein said at least one metal based nitride layer is (Zr.sub.1xzSi.sub.xMe.sub.z)N.sub.y with 0<x<0.15, 0.90<y<1.10, 0z<0.25, and Me is one or more of the elements Y, Ti, Nb, Ta, Cr, Mo and W, the at least one metal based nitride layer being selected from the group of a cubic phase of a sodium chloride structure, a single cubic phase, a single hexagonal phase, and a mixture thereof, the at least one metal based nitride layer having a thickness between 0.5 m and 15 m, and TC(200)>1.5 and simultaneously TC(111), TC(220) and TC(311) all being<1.5 wherein TC(hkl) is determined from XRD data as follows: ${\mathrm{TC}}_{\mathrm{meas}}\left(\mathrm{hkl}\right)={\frac{I_{\mathrm{meas}}\left(\mathrm{hkl}\right)}{I_0\left(\mathrm{hkl}\right)}\left[\frac{1}{n}\underset{n=1}{\overset{n}{.Math.}}\frac{I_{\mathrm{meas}}\left(\mathrm{hkl}\right)}{I_0\left(\mathrm{hkl}\right)}\right]}^{-1}$ wherein I.sub.meas(hkl) is a measured intensity of the (hkl) reflection and I.sub.o(hkl) a standard intensity according to JCPDS card no. 035-0753, and n=4 is the number of (hkl) reflections used in the calculations.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a SEM micrograph of a fractured cross section (Zr.sub.0.963Si.sub.0.037)N.sub.102 layer, marked with I, deposited on a cemented carbide insert, marked with II.

(2) FIG. 2 is a X-ray diffraction pattern from (Zr.sub.1-xSi.sub.x)N layers with (A) x=0.012, (B) x=0.037 and (C) x=0.138. S denotes the diffraction peaks for cemented carbide.

(3) FIG. 3 is a diagram of the nanohardness (H) of (Zr.sub.1-xSi.sub.x)N layers as a function of Si content (x).

(4) FIG. 4 is a cross-sectional transmission electron micrograph from a middle part of a (Zr.sub.0.963Si.sub.0.037)N.sub.1.02 layer. The layer has a cubic structure as evident from the electron diffraction pattern (inserted).

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(5) 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 (Zr.sub.1-x-zSi.sub.xMe.sub.z)N.sub.y 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, 0z<0.25, preferably 0z<0.15, most preferably 0z<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 m and 15 m, preferably between 0.5 m and 10 m, most preferably between 0.5 m and 5 m. Additionally, the layer contains a sum of oxygen (O) and carbon (C) concentration between 0 and 2 at %, preferably between 0 and 1 at %.

(6) 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.

(7) 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 (-2 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:

(8) ${\mathrm{TC}}_{\mathrm{meas}}\left(\mathrm{hkl}\right)={\frac{I_{\mathrm{meas}}\left(\mathrm{hkl}\right)}{I_0\left(\mathrm{hkl}\right)}\left[\frac{1}{n}\underset{n=1}{\overset{n}{.Math.}}\frac{I_{\mathrm{meas}}\left(\mathrm{hkl}\right)}{I_0\left(\mathrm{hkl}\right)}\right]}^{-1}$
where

(9) I.sub.meas(hkl) is the measured intensity of the (hkl) reflection and I.sub.o(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 I.sub.o(111)=100, I.sub.o(200)=74, I.sub.o(220)=36 and I.sub.o(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.

(10) 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.

(11) Said layer has a columnar microstructure with an average column width of <1 m, preferably <0.6 m, 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

(12) Said layer has a compressive stress level of 6.0 GPa<<0.5 GPa, preferably of 3.0 GPa<<1.0 GPa. The residual stress is evaluated by XRD using the sin.sup.2 -method with a Poisson's ratio of =0.23 and a Young's modulus of E=379 GPa.

(13) 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.

(14) According to one embodiment of the invention, z=0, and said layer is (Zr.sub.1-xSi.sub.x)N.sub.y 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, 0z<0.25.

(15) 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.

(16) 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 m and 20 m, preferably between 1 m and 15 m, and most preferably between 1 m and 7 m.

(17) 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.

(18) 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.

(19) 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 (Zr.sub.1-x-zSi.sub.xMe.sub.z)N.sub.y with 0<x<0.30, 0.90<y<1.20, 0z<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 N.sub.2 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.

(20) 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/cm.sup.2 and 15 W/cm.sup.2, preferably between 1 W/cm.sup.2 and 5 W/cm.sup.2, 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 N.sub.2 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.

(21) 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.

EXAMPLE 1

(22) Cemented carbide inserts with composition 94 wt % WC-6 wt % Co were used as a body for the layer depositions by cathodic arc evaporation.

(23) 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 2.010.sup.3 Pa, after which the inserts were sputter cleaned with Ar ions. (Zr.sub.1-x-zSi.sub.xMe.sub.z)N.sub.y layers, 0.004x0.234, z=0, coatings 1-8 in Table 1, were grown using (Zr.sub.1-aSi.sub.a) 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 N.sub.2 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 m.

(24) TABLE-US-00001 TABLE 1 (Zr.sub.1abSi.sub.aMe.sub.b) Cathode (Zr.sub.1xzSi.sub.xMe.sub.z)N.sub.y Layer Coat- Composition Composition ing Description a b x z y 1 ZrSiN 0.01 0.004 1.00 2 ZrSiN 0.02 0.012 1.01 3 0.03 0.027 1.02 4 ZrSiN 0.04 0.037 1.02 5 ZrSiN 0.05 0.041 1.02 6 ZrSiN 0.10 0.093 1.06 7 ZrSiN 0.15 0.138 1.08 8 ZrSiN 0.25 0.234 1.09 9 ZrSiTaN 0.04 0.04 0.039 0.035 1.00 10 ZrSiTiN 0.04 0.04 0.026 0.042 1.00 11 ZrSiTiN 0.07 0.14 0.062 0.131 1.04 12 ZrSiNbN 0.10 0.10 0.086 0.090 1.06 13 ZrSiCrN 0.05 0.05 0.045 0.033 1.01 14 ZrSiCrN 0.10 0.05 0.084 0.054 1.03 15 ZrSiCrN 0.05 0.15 0.043 0.145 1.00

EXAMPLE 2

(25) Example 1 was repeated using (Zr.sub.1-a-bSi.sub.aMe.sub.b) cathodes for the deposition of the (Zr.sub.1-x-zSi.sub.xMe.sub.z)N.sub.y layers, coatings 9-15 in Table 1.

EXAMPLE 3

(26) MgO(001) and Al.sub.2O.sub.3(0001) single crystals substrates were used as a body for the layer depositions by magnetron sputtering.

(27) 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 2.010.sup.3 Pa, after which said substrates were heat treated (de-gassed) at 900 C. for 15 min. (Zr.sub.1-xSi.sub.x)N.sub.y layers, 0x1.00, 1.00y1.10 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+N.sub.2 discharge with fixed Ar and N.sub.2 partial pressures of 0.5 Pa and 0.07 Pa, respectively, to a total layer thickness between 1 m and 1.5 m. 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.

(28) At optimum growth conditions of 800 C. and x=0.20, said layer is highly (200) textured consisting of ZrN-rich/Si.sub.3N.sub.4-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 (Zr.sub.1-xSi.sub.x)N.sub.y layers onto a body of, e.g., cemented carbide inserts.

EXAMPLE 4

(29) The composition x, z and y, of the (Zr.sub.1-x-zSi.sub.xMe.sub.z)N.sub.y 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.

(30) FIG. 1 shows an SEM micrograph of a fractured cross section (Zr.sub.0.963Si.sub.0.037)N.sub.1.02 layer, marked with I, deposited on a cemented carbide insert, marked with II using a LEO Ultra 55 scanning electron microscope operated at 3 kV.

(31) X-ray diffraction (XRD) patterns of the as-deposited (Zr.sub.1-x-zSi.sub.xMe.sub.z)N.sub.y layers were obtained using Cu K alpha radiation and a -2 configuration in a Bruker AXS D8 Advance diffractometer. FIG. 2 shows X-ray diffraction patterns from (Zr.sub.100-xSi.sub.x)N layers with (A) x=0.012, (B) x=0.037 and (C) x=0.138. S denotes the diffraction peaks for cemented carbide. All layers were indexed with a NaCl structure.

(32) The residual stresses, , of the (Zr.sub.1-x-zSi.sub.xMe.sub.z)N.sub.y layers were evaluated by XRD measurements using the sin.sup.2 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 CuK-radiation on the (311)-reflection. The residual stress values were within 5.0 GPa<<1.0 GPa for the different layers as evaluated using a Poisson's ratio of =0.23 and Young's modulus of E=379 GPa.

(33) 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. FIG. 3 shows the hardness (H) of (Zr.sub.1-xSi.sub.x)N layers as a function of the Si content (x) as obtained at room temperature. Optimum hardness is obtained for the (Zr.sub.1-xSi.sub.x)N layer with x=0.037 corresponding to layer with best performance during metal machining.

(34) The microstructure of (Zr.sub.1-x-zSi.sub.xMe.sub.z)N.sub.y 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. FIG. 4 shows a cross-sectional transmission electron micrograph from a middle part of a (Zr.sub.0.963Si.sub.0.037)N.sub.1.02 layer according to the invention. The layer had a columnar structure with cubic structure as evident from the electron diffraction pattern (inserted). The average column width, as determined from this and similar images, varied between 0.4 m and 1 m as determined from an area close to the middle region of the layer, i.e., a region within 30 to 70% of the layer thickness in the growth direction, taking the average of at least 10 adjacent columns

EXAMPLE 5

(35) The coatings from Table 1 (example 1) were tested in a turning operation with the following data:

(36) Geometry: CNMG120408-MF4

(37) Application: Facing

(38) Work piece material: 100Cr6

(39) Cutting speed: 200 m/min

(40) Feed: 0.25 mm/rev.

(41) Depth of cut: 2 mm

(42) Performance criterion: Crater wear resistance

(43) 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.

(44) TABLE-US-00002 TABLE 2 Coating Relative performance Coatings according to embodiments of the invention Coating 2 100 Coating 3 110 Coating 4 120 Coating 6 110 Reference coatings according prior art Ti.sub.0.34Al.sub.0.66N (ref) 80 Ti.sub.0.93Si.sub.0.07N (ref) 100 TiN (ref) 90