PVD COATINGS COMPRISING MULTI-ANION HIGH ENTROPY ALLOY OXY-NITRIDES

Abstract

Method for producing a coating comprising at least one PVD coating layer, wherein for the production of the at least one PVD coating layer materials from one or more targets are evaporated by using a PVD technique in a coating chamber comprising oxygen and nitrogen as reactive gases, wherein during deposition of the at least one PVD coating layer a multi-anion HEA-oxynitride structure is formed, which comprises a cation lattice formed of five or more elements and an anion lattice formed of two or more elements, wherein if only two elements are present in the anion lattice, they are oxygen and nitrogen.

Claims

1. A method for producing a coating comprising at least one PVD coating layer, wherein for the production of the at least one PVD coating layer: materials from one or more targets are evaporated by using a PVD technique in a coating chamber comprising oxygen and nitrogen as reactive gases, wherein: during deposition of the at least one PVD coating layer a multi-anion HEA-oxynitride structure is formed, which comprises a cation lattice formed of five or more elements and an anion lattice formed of two or more elements, wherein if only two elements are present in the anion lattice, they are oxygen and nitrogen.

2. The method according to claim 1, wherein the PVD technique is a magnetron sputtering technique.

3. The method according to claim 1, wherein the material of the one or more targets is selected comprising the five or more elements that are to be present in the cation lattice.

4. The method according to claim 1, wherein the material of the one or more targets comprises at least one transition metal of the 4th, 5th or 6th group of the periodic table of the elements and at least one of the elements Al, Si, B.

5. The method according to claim 1, wherein the coating is deposited on a substrate by applying a negative bias voltage to the substrate during the coating process, wherein the bias voltage being <200 V.

6. The method according to claim 1, wherein at least three targets are evaporated and deposited on the substrate.

7. The method according to one of the preceding claim 1, wherein the evaporated and deposited target material comprises at least a sum of five elements of a transition metal of the 4th, 5th or 6th group of the periodic table of the elements and the elements Al, Si, B.

8. The method according to claim 1, wherein the substrate temperature during the production of the coating is between 100° C. and 400° C.

9. A coating, obtainable by using a method for producing a coating comprising at least one PVD coating layer, wherein for the production of the at least one PVD coating layer: materials from one or more targets are evaporated by using a PVD technique in a coating chamber comprising oxygen and nitrogen as reactive gases, wherein: during deposition of the at least one PVD coating layer a multi-anion HEA-oxynitride structure is formed, which comprises a cation lattice formed of five or more elements and an anion lattice formed of two or more elements, wherein if only two elements are present in the anion lattice, they are oxygen and nitrogen, comprising: a multi-anion HEA-oxynitride structure, wherein the High Entropy Alloy in the HEA-oxynitride structure comprise at least one transition metal of the of the 4th, 5th or 6th group of the periodic table of the elements and at least one of the elements Al, Si, B.

10. The coating according to claim 9, wherein the High Entropy Alloy in the HEA-oxynitride structure comprises at least in total at least five elements of a transition metal of the 4th, 5th or 6th group of the periodic table of the elements and one of the elements Al, Si, B.

11. The coating according to claim 9, wherein the anion sublattice comprises more than two atoms.

12. The coating according to claim 9, wherein the multi-anion HEA-oxynitride structure is phase stable up to a temperature of 1100° C.

13. The coating according to claim 9, wherein the HEA elements of the cation sublattice are selected such that the structure has a lattice distortion of at least 5%.

14. The coating according to claim 9, wherein the layer thickness of the coating structure is less than 8 μm and more than 500 nm.

15. The coating according to claim 9, wherein the coating structure is formed in the form of a multi-layer coating, wherein the total thickness of the multi-layer coating is more than 1 μm.

16. A use of coating obtainable by using a method for producing a coating comprising at least one PVD coating layer, wherein for the production of the at least one PVD coating layer: materials from one or more targets are evaporated by using a PVD technique in a coating chamber comprising oxygen and nitrogen as reactive gases, wherein: during deposition of the at least one PVD coating layer a multi-anion HEA-oxynitride structure is formed, which comprises a cation lattice formed of five or more elements and an anion lattice formed of two or more elements, wherein if only two elements are present in the anion lattice, they are oxygen and nitrogen, comprising: a multi-anion HEA-oxynitride structure, wherein the High Entropy Alloy in the HEA-oxynitride structure comprise at least one transition metal of the of the 4th, 5th or 6th group of the periodic table of the elements and at least one of the elements Al, Si, B as functional coating.

17. The method according to claim 2, wherein the PVD technique is HiPIMS or a cathodic ARC PVD technique.

18. The method according to claim 4, wherein Al and Si are included.

19. The method according to claim 6, wherein at least three targets simultaneously evaporated and deposited.

20. The coating according to claim 12, wherein the multi-anion HEA-oxynitride structure is phase stable up to a temperature beyond 1100° C.

Description

DETAILED DESCRIPTION

[0044] FIG. 1 shows the calculated configurational entropy of mixing (at 1000 K), as a function of number of components in an equimolar alloy,

[0045] FIG. 2 shows the graphical representation of formation of cubic phase consisting of TMN, AlN, and Si.sub.3N.sub.4, enabled by entropy stabilization,

[0046] FIG. 3 shows the estimated S/R values for alloys consisting of one anion, and two anion sub lattice with two and five elements in the metallic sub lattice,

[0047] FIG. 4 shows the estimated ΔH.sub.mix, and ΔT.sub.s mix for the (AlTaSiCrTi)N alloy with respect to their binaries,

[0048] FIG. 5a shows the schematic set up used to grow HEA nitrides and oxi-nitrides using industrial scale reactive arc deposition system,

[0049] FIG. 5b shows SEM image of fractured-cross section of coating at bottom (R2), middle (R10), and top (R18) positions,

[0050] FIG. 5c shows hardness evolution as a function of substrate position,

[0051] FIG. 6a shows XRD pattern of (Al.sub.19Ta.sub.21Si.sub.11Cr.sub.11Ti.sub.38)N of As-deposited (AD), and after elevated temperature anneals,

[0052] FIG. 6b shows H evolution of the (Al.sub.19Ta.sub.21Si.sub.11Cr.sub.11Ti.sub.38)N as a function of annealing temperature, and compared to bench marked Al.sub.67Ti.sub.33N coating,

[0053] FIG. 7a shows XRD pattern of (Al.sub.21Ta.sub.21Si.sub.9Cr.sub.13Ti.sub.36)O.sub.20N.sub.35 of As-deposited (AD), and after elevated temperature anneals,

[0054] FIG. 7b shows H evolution of the (Al.sub.21Ta.sub.21Si.sub.9Cr.sub.13Ti.sub.36)O.sub.20N.sub.35 as a function of annealing temperature, and compared to bench marked Al.sub.67Ti.sub.33N coating,

[0055] FIG. 8 shows a cross-sectional SEM image of the coated substrate after subjecting to oxidation at 900° C. for 2 Hrs in ambient atmosphere.

[0056] FIG. 1 shows the calculated configurational entropy of mixing (at 1000 K), as a function of number of components in an equimolar alloy. The above equation indicates that the configurational entropy scales with the number of constituents.

[0057] FIG. 2 shows a graphical representation of formation of cubic phase consisting of TMN, AlN, and Si.sub.3N.sub.4, enabled by entropy stabilization. As already mentioned above, an objective of the present invention is to provide new materials that can preferably be produced as coating materials (more preferably as PVD coatings). These coatings may also comprise alloys of TMN, AlN, and Si.sub.3N.sub.4 formed in cubic phase that can retain its phase stability after elevated temperature annealing up to 1100° C., enabled by entropy stabilization, as graphically shown in FIG. 2. This example indicates that the previously mentioned entropy stabilization effect, there by retaining the cubic solid solution consisting of non-iso structural components under thermodynamic equilibrium conditions such as elevated temperature anneals of 1100° C. may not achieved by random choice of alloying elements.

[0058] In a further aspect of the invention, due to entropy stabilization, the inventive alloy design also considers choice of elements with a high difference in the atomic sizes, thereby to induce a lattice distortion as shown in FIG. 2. The induced lattice distortion strengthens the alloy, and hampers the diffusivity of the alloy e.g. in the inventive alloy, mixture of Ta with an ionic radius of 170 pm, and Si with an ionic radius of 111 pm creates a lattice distortion approximately about 20% distortion in the lattice very locally.

[0059] FIG. 3 shows estimated S/R values for alloys consisting of one anion, and two anion sub lattice with two and five elements in the metallic sub lattice.

[0060] As already mentioned, an objective of the present invention is attained by providing new materials produced preferably as PVD coatings comprising or consisting of multi-anion High Entropy Alloy Oxy-Nitrides.

[0061] The new materials produced according to the present invention particularly differ from the state of the art at least in following aspects:

[0062] 1) Design of Multi-principal element alloy with 5 elements in the cation sublattice with 2 or more anion sub-lattice i,e, nitride, and oxide sub-lattice as an example. FIG. 3 compares the variation of S/R value for an alloy with one anion to two anions while having 5 elements in metallic sub-lattice. Further increase in S/R value with more anions.

[0063] 2) Choice of metallic elements includes group 4, 5, and 6 elements with controlled addition of Al, Si, and optionally of B so to make sure that the high ΔH mix value is overtaken by TΔS.sub.mix at finite temperatures of about 900° C.

[0064] FIG. 4 shows an estimated Δ H.sub.mix, and Δ T.sub.s mix for the (AlTaSiCrTi)N alloy with respect to their binaries. Note that entropy overtakes enthalpy component at Temp of about 700° C. (more exactly ca. 650° C. or a values between 600° c. and 700° C.). In particular, FIG. 4 shows an estimated balance for the alloy of (Al.sub.19Ta.sub.21Si.sub.11Cr.sub.11Ti.sub.38)N. ΔH.sub.mix values were taken from published literature, and TΔS.sub.mix values were estimated from the formula 1. The graphic represents only two configurations, i.e cubic solid solution with respect to their binaries. But in principal this consideration should include all other configurations or decomposition path ways. This consideration is a necessary criterion, but not sufficient criterion.

[0065] FIG. 4 indicates that a likely entropy stabilization for (Al.sub.19Ta.sub.21Si.sub.11Cr.sub.11Ti.sub.38)N alloy at Temp above ˜700 C. Also in the consideration only one anion lattice is presented, and from the previously description it is known that 2 anion sublattice alloy i.e. (Al.sub.19Ta.sub.21Si.sub.11Cr.sub.11Ti.sub.38)ON should favor the enhanced entropy stabilization compared to nitride alloy.

[0066] FIG. 5a shows the schematic set up used to grow HEA nitrides and oxi-nitrides using industrial scale reactive arc deposition system. The example coating of (Al.sub.19Ta.sub.21Si.sub.11Cr.sub.11Ti.sub.38)N is grown in combinatorial approach using the targets of Al.sub.56Cr.sub.24Ta.sub.20 at bottom (R2), and Ti.sub.70Si.sub.30 at top (R18).

[0067] FIG. 5b shows a SEM image of fractured-cross section of coating at bottom (R2), middle (R10), and Top (R18) positions. The composition of the coatings measured by EDS is indicated in the annotation of FIG. 5b. The targets are arc discharged in N.sub.2 p.partial pressure of 5 Pa, and the resultant coating compostions measured by EDS and the coating fractured SEM micro graph shown is shown in FIG. 5b. In this configuration a High entropy alloy of (Al.sub.19Ta.sub.21Si.sub.11Cr.sub.11Ti.sub.38)N is synthesized in the middle of the substrate holder at position R10.

[0068] FIG. 5c shows hardness evolution as a function of substrate position.

[0069] Apart from the core of the invention as described above, there are additional technical measures which lead to preferred embodiments of the invention. For example, following additional technical measures:

[0070] 1) Multi-principal element oxy-nitride alloy consisting of AlN, TaN and SiN will display a high oxidation resistance due to sluggish diffusion of the chemical components in the coating.

[0071] 2) Multi-principal element oxy-nitride alloy comprising AlN, and SiN will display a high fracture resistance, as the local atomic distortions causes crack branching.

[0072] 3) Controlled formation of AlN, and SiN is motivated next to enable high oxidation resistance, high temperature properties

[0073] 4) Multi-principal element oxy-nitride alloy comprising AlN, and SiN, with entropically stabilized cubic phase, without causing phase separation at temperatures above 800° C., more preferably of 900° C. or above 900° C., e.g. 1100° C. This high temperature cubic phase stability results in stable hardness up to elevated temperature annealing of 1100° C. and beyond.

[0074] FIG. 6a shows XRD pattern of (Al.sub.19Ta.sub.21Si.sub.11Cr.sub.11Ti.sub.38)N of As-deposited (AD), and after elevated temperature anneals. The SEM images in the back-scattering contrast of the coating in AD, and after annealing to 1100° C. is complemented to XRD. The coating form pos 10 with a composition of (Al.sub.19Ta.sub.21Si.sub.11Cr.sub.11Ti.sub.38)N is subjected to vacuum annealing up to 1100° C. FIG. 6a presents the structural evolution measured by XRD, complemented with fractured cross-section of the coating in SEM back scattered mode.

[0075] XRD image shows that the cubic solid solution of (Al.sub.19Ta.sub.21Si.sub.11Cr.sub.11Ti.sub.38)N is thermally stable up to 1000 C. But at 1100 C, this coating shows precipitation of Cr.sub.2N, and Cr. The decomposition is also clearly visible in the SEM images of the coating after annealing to 1100 C.

[0076] FIG. 6b shows H evolution of the (Al.sub.19Ta.sub.21Si.sub.11Cr.sub.11Ti.sub.38)N as a function of annealing temperature, and compared to bench marked Al.sub.67Ti.sub.33N coating. Note that the coating precipitates Cr.sub.2N, and Cr after annealing to 1100° C. that leads to hardness drop. At temperatures above 1000 C, the alloy (Al.sub.19Ta.sub.21Si.sub.11Cr.sub.11Ti.sub.38)N display a steep hardness drop associated with the phase decomposition.

[0077] Using the above mentioned description of multi-anion entropy stabilization, (Al.sub.21Ta.sub.21Si.sub.9Cr.sub.13Ti.sub.36)O.sub.20N.sub.35 coatings were grown with Oxygen flow of 30 sccm using the similar deposition conditions. The Oxi-nitride coating thermal stability is also investigated as shown in FIG. 7.

[0078] FIG. 7a shows XRD pattern of (Al.sub.21Ta.sub.21Si.sub.9Cr.sub.13Ti.sub.36)O.sub.20N.sub.35 of As-deposited (AD), and after elevated temperature anneals. The SEM images in the back-scattering contrast of the coating in AD, and after annealing to 1100° C. is complemented to XRD.

[0079] FIG. 7b shows H evolution of the (Al.sub.21Ta.sub.21Si.sub.9Cr.sub.13Ti.sub.36)O.sub.20N.sub.35 as a function of annealing temperature, and compared to bench marked Al.sub.67Ti.sub.33N coating. Note that surprisingly this coating shows a thermally stable solid solution at least up to 1100° C., there by a stable solid solution.

[0080] Surprisingly, the XRD shows that the cubic solid solution is stable up to annealing temperatures of 1100° C. which is not the case in Nitride alloy with comparable composition in the metallic sub-lattice. The SEM images shows a similar grey scale image for the as-deposited and after annealing to 1100° C., complementing the XRD results.

[0081] A higher thermal stability, and a stable hardness behavior of the alloy (Al.sub.21Ta.sub.21Si.sub.9Cr.sub.13Ti.sub.36)O.sub.20N.sub.35 is likely by entropy stabilization thus offers as an example to design a thermally stable TM-Al—Si—ON multi-principal alloy in a wide compositional range. The compositional range includes Group 4, 5, and 6 elements with Al, Si, and B

[0082] FIG. 8 shows a cross-sectional SEM image of the coated substrate after subjecting to oxidation at 900° C. for 2 Hrs in ambient atmosphere. The inventive coating oxidation resistance of cubic-(Al.sub.21Ta.sub.21Si.sub.9Cr.sub.13Ti.sub.36)ON is compared with industrial standard coatings of cubic Al.sub.64Ti.sub.36N, and cubic Al.sub.77Ti.sub.23N.

[0083] Surprisingly, even though the inventive alloy has lower Al concentration of 21 at. %, the oxidation resistance is significantly higher the current standard Al-rich AlTiN coatings as shown in FIG. 8. Note that the oxide layer thickness is 3000 nm, 740 nm, and less than 100 nm respectively for cubic Al.sub.64Ti.sub.36N, cubic Al.sub.77Ti.sub.23N and inventive high entropy oxy-nitride alloy.