PVD coating with HEA ceramic matrix having a controlled precipitate structure

Abstract

The present invention discloses a PVD coating process for producing a multi-functional coating structure, comprising the steps of producing an HEA ceramic matrix on a substrate and targeting a controlled precipitate structure into the HEA ceramic matrix to produce specific desired properties of the coating structure.

Description

[Technical Field]

[0001] The present invention relates to the creation of a multifunctional coating structure comprising a high-entropy alloy (HEA) ceramic matrix and a controlled precipitate structure located within the HEA ceramic matrix, and to a corresponding multifunctional coating structure. [Background technology]

[0002] Current technology The microstructure design of coatings synthesized by PVD processes such as arc deposition and sputter deposition is already known.

[0003] However, the current microstructure of PVD coatings generally consists of one of the following: (a) cylindrical alloys, (b) multilayer alloys, (c) nanocomposite alloys, and (d) amorphous alloys. This microstructure is generally composed of a similar host material, namely nitrides or carbides, or borides, or combinations thereof, as a solid solution rather than as individual phases.

[0004] One example may be a coating comprising a nitride host and oxide precipitates. This type of microstructure offers multifunctional purposes, namely a combination of high hardness derived from the nitride and high-temperature lubrication derived from a suitable oxide selected from among others (e.g., V2O5).

[0005] Another example is hexagonal-BN precipitates in a carbide host. Here, the host provides the necessary structural stability and high-temperature properties, while H-BN provides a solid lubricant.

[0006] The matrix is ​​generally composed of metastable phases such as TM-Al-N or TM-Si-N, where TM stands for transition metal. At high temperatures, these metastable phases undergo phase transitions at temperatures >900C through the following reactions.

[0007]

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[0008] These structural changes are generally associated with undesirable volume changes and are at the same time associated with a reduction in mechanical properties, and are thus undesirable. SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] Objective of the present invention An object of the present invention is to reduce or overcome one or more problems associated with the prior art. In particular, an object of the present invention is to provide a PVD coating process that enables the generation of a phase-stable and designable multifunctional coating structure. MEANS FOR SOLVING THE PROBLEMS

[0010] Description of the present invention To overcome these problems, a method has been invented that comprises the following two steps: The first step: a step of generating a high-entropy alloy base material, The second step: a step of growing a preferably semi-coherent and controlled precipitate structure on the base material.

[0011] Thus, in a first aspect of the present invention, there is provided a PVD coating process for generating a multifunctional coating structure, a step of generating a HEA ceramic base material on a substrate, and a step of target-introducing a controlled precipitate structure into the HEA ceramic base material to produce desired specific properties of the coating structure, is disclosed.

[0012] This allows the HEA ceramic matrix to be deposited onto a suitable substrate, preferably by a PVD coating process, which is formed at least in part from a metal compound. Preferably, according to the present invention, multiple, particularly numerous, precipitate structures are formed. In the context of the present invention, the term “high-entropy alloy (HEA)” is preferably used to describe a material species composed of at least five components, in particular, each component present at a concentration of 10 to 30 atomic percent, and the corresponding material exhibits an estimated configurational entropy of Sconf. > 1.4R.

[0013] In another example of the first phase, the selective introduction of a controlled precipitate structure is carried out by heat treatment, wherein the HEA ceramic matrix is ​​preferably heated to a temperature of 1000°C, particularly above 1000°C, during the heat treatment.

[0014] In another example of the first phase, the selective introduction of a controlled precipitate structure is modified by changing the processing time and / or processing temperature.

[0015] In another example of the first phase, in the HEA ceramic matrix layer, only a few nanometers, preferably less than 50 nanometers, and especially less than 10 nanometers, are directly heated by the heat treatment.

[0016] In another example of the first phase, the targeted introduction of the controlled precipitate structure into the HEA ceramic matrix is ​​performed in situ during the formation of the HEA ceramic matrix. This allows the controlled precipitate structure to be introduced into the HEA ceramic matrix by an instantaneous heating source to heat the surface of the HEA ceramic matrix to a temperature of 900-1000°C within a few seconds, the instantaneous heating source being preferably in the form of a laser, particularly a nanosecond laser.

[0017] Therefore, in the context of the present invention, surface heating is understood to mean heating to a penetration depth of several nanometers, preferably less than 100 nm. Furthermore, the instantaneous heating source can be formed so that only an area of ​​several nanometers, preferably less than 100 nm, is heated during the heating process. Instead of a laser, the instantaneous heating source may be formed in the form of a filament, particularly a heating filament.

[0018] In another example of the first phase, the targeted introduction of the controlled precipitate structure into the HEA ceramic matrix is ​​carried out after the formation of the HEA ceramic matrix, preferably by post-annealing on a post-annealing line.

[0019] In another example of the first phase, the HEA base material is deposited on the substrate by applying a negative bias voltage to the substrate during the coating process, wherein the bias voltage is <200V, preferably <150V, and particularly <120V.

[0020] In another example of the first aspect, the formation of the HEA ceramic matrix and / or the controlled precipitate structure is carried out in a reactive atmosphere, which preferably contains nitrogen and / or oxygen and / or methane.

[0021] In another example of the first phase, sputtering techniques, particularly HiPIMS or arc PVD processes, are used as the PVD coating process described above.

[0022] In another example of the first phase, the substrate temperature during the formation of the HEA ceramic matrix and / or the controlled precipitate structure is 100°C to 400°C, preferably 150°C to 300°C, and particularly 200°C to 250°C.

[0023] In the second aspect, a multifunctional coating structure is disclosed, which is obtained by the above process, wherein the multifunctional coating structure comprises a HEA ceramic matrix and a precipitate structure disposed within the HEA ceramic matrix to ensure specific properties of the coating structure. According to the second aspect, the precipitate structure may be semi-coherent with respect to the HEA ceramic matrix in particular.

[0024] In another example of the second aspect, the HEA ceramic matrix comprises nitrides and / or carbides and / or oxides and / or borides. According to the second aspect, the HEA ceramic matrix may also comprise silicides or oxynitrides, and may be formed as multi-anionic compounds.

[0025] In another example of the second aspect, the HEA ceramic matrix contains elements from Group IV and / or Group V and / or Group VI of the periodic table, preferably at least one of the elements Ti, Zr, Va, Nb, Ta, Cr, Mo, or W.

[0026] In another example of the second aspect, the HEA ceramic matrix preferably contains Si as the component with the highest atomic weight. According to the second aspect, it has been found that the addition of Si improves the oxidation stability of a given multifunctional coating structure, especially in the case of high-temperature treatment.

[0027] In another example of the second aspect, the HEA ceramic matrix comprises Ti and / or Al and / or Si and / or V. According to the second aspect, the HEA ceramic matrix may also contain other elements, preferably other transition metals.

[0028] In another example of the second aspect, the HEA ceramic matrix comprises Ti, Al, Si, and V, and the HEA ceramic matrix is ​​preferably in the form of TiAlSiVN, particularly Ti 37 Al 34 Si 12 V 17It is formed in the form of N. According to the second aspect, an AlCrNbTaTiSiN matrix may also be provided by adding silicon to an AlCrNbTaTiN matrix.

[0029] In another example of the second phase, the HEA ceramic matrix described above is phase-stable up to a temperature of 1000°C, and preferably up to a temperature of 1100°C.

[0030] In another example of the second phase, the precipitate structure is designed to ensure one of the following specific properties: improved structural stability, improved lubricity, or improved temperature resistance. Furthermore, the precipitate structure can be selected particularly in relation to its compatibility with the HEA ceramic matrix.

[0031] In another example of the second aspect, the precipitate structure described above is formed in the form of oxides and / or carbides and / or borides, particularly in the form of BN and / or Al2O3 and / or VC.

[0032] In another example of the second aspect, the precipitate structure described above has a size of less than 100 nm, preferably less than 50 nm, and particularly less than 10 nm.

[0033] In another example of the second aspect, the layer thickness of the coating structure described above is less than 500 nm, preferably less than 300 nm, and particularly less than 200 nm.

[0034] In the third phase, its use as a functional coating, particularly as an abrasion-resistant coating or a decorative coating, is disclosed.

[0035] Here, the present invention will be described in more detail, based on an example and with the help of the drawings. [Brief explanation of the drawing]

[0036] [Figure 1] This figure shows the structural evolution of various alloys in response to temperature. [Figure 2]Figure 2(a) shows the structural evolution of various alloys according to temperature, Figure 2(b) shows the evolution of T.Sconfig. according to temperature, and Figure 2(c) shows the hardness evolution of various alloys according to annealing temperature. [Figure 3] Figure 3(a) shows the microstructure of the HEA matrix with controlled precipitates according to the present invention, Figure 3(b) shows an x-SEM image at BSE contrast where the proposed structure is formed by thermal annealing, and Figure 3(c) is a schematic diagram of sequential coating deposition and flash heating. [Modes for carrying out the invention]

[0037] Figure 1 shows the structural evolution of various alloys with respect to temperature, and in particular, Figure 1 shows a comparison of the XRD evolution of AlVTiSiN with known metastable alloys c-Ti-Al-N and c-Ti-Si-N.

[0038] In contrast to metastable alloys, the proposed multi-principal high-entropy alloy Ti 37 Al 34 Si 12 V 17 N does not exhibit any phase transitions. Despite the presence of immiscible components of AlN and Si3N4 in this alloy, a cubic phase solid solution is retained after annealing at 1100°C.

[0039] As is evident from the extensive XRD cubic phase analysis, the alloy c-TiSiN forms nanocrystalline phases in the depositional state shown in Figure 1. However, at high temperatures, the peaks narrow, indicating a particle growth process with the precipitation of undesirable phases, indicated by the arrows.

[0040] In contrast, as seen in the corresponding XRD diffractograms, for example, in the TiAlSiVN alloy, nanocrystalline properties are retained and a cubic solid solution is preserved after annealing at 1100°C.

[0041] Figure 2a is a diagram showing the structural evolution of various alloys according to temperature. The left image of the XRD is a cross-sectional SEM of the cracked coating in BSE mode. As confirmed by the SEM image of the cracked coating, in the as-deposited state, Ti 37 Al 34 Si 12 V 17 N alloys retain the cubic solid solution after annealing to 1100 °C, but it should be noted that this is not the case for Ti 35 Al 65 N. In Figure 2a, the cracked image does not show any structural or contrast changes indicating the phase change of the Ti 37 Al 34 Si 12 V 17 N alloy. In contrast, the cross-sectional view of the SEM image of the TiAlN coating shows a structural change from columnar to fine particle structure, along with local contrast changes corresponding to the phase change.

[0042] Figure 2b evaluates the thermodynamic driving force for cubic phase stabilization by examining the value of H mix(混合のエンタルピ) [](which is the energy penalty for causing mixing) and the energy gain caused by the configurational entropy Sconf.

[0043] In Figure 2b, the evolution of T.S configuration and H mix of various alloys according to temperature was evaluated. For the alloy Ti 37 Al 34 Si 12 V 17 N, the value of T.S conf. overcomes H mix , making the solid solution more energetically favorable compared to their binary nitrides, but it should be noted that this does not apply to TiSiN and AlVN. For the alloys c-Al 65 V 35 N and c-Ti 35 Al 65 ​In N, a cubic phase is formed in the azdepo state, and this alloy decomposes in annealing at 900C, as is evident from the XRD above. c-Al 65 V 35 N and c-Ti 35 Al 65 The evolution of w-AlN in XRD of N exhibits the following degradation pathway.

[0044]

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[0045] Thermodynamic parameters in Figure 2b, i.e., H of the alloy mix This is evaluated using density functional theory calculations, while Sconf. is evaluated by formula theory using the Boltzmann equation, assuming a random solid solution model.

[0046] The above alloy Ti 37 Al 34 Si 12 V 17 N is just one example, and experts in the field recognize that similar entropy-stabilized multiprincipal nitrides can be synthesized from Group IV, V, and VI elements of the periodic table.

[0047] As shown in Figure 2b, the high thermal stability of this alloy is due to the formation of an entropy-stabilized solid solution. Only in alloy c-TiAlSiVN does TΔSconfig.mix have ΔH at temperatures above 1000°C. mix It is larger than that. Therefore, the ΔG of this alloy mix It is lower in solid solutions in relation to those competing phases. T is the temperature, Sconfig. is the configuration entropy, and G mix R is the free energy of mixing, and R is the gas constant.

[0048] Figure 2c shows the hardness evolution of various alloys according to annealing temperature. Thermally stable alloy Ti 37 Al 34 Si 12 V 17It should be noted that N also exhibits relatively stable hardness depending on the annealing temperature. In particular, alloy decomposition occurs at temperatures above 1000C. Furthermore, as shown in Figure 2c, entropy-stabilized Ti 37 Al 34 Si 12 V 17 N alloy exhibits relatively stable hardness up to an annealing temperature of 1100°C.

[0049] A second step of the first aspect of the present invention is schematically shown in Figure 3. The base material may be any high-entropy alloy ceramic of nitrides, carbides, oxides, and borides. The precipitate composition is carefully selected to provide further reinforcement or to produce additional functions such as lubrication. The composition and structure of the precipitate are also selected so as not to produce undesirable stresses.

[0050] The composition and structure of the precipitates (e.g., H-BN in HEA nitride or HEA carbide alloys) may be similar or different. Controlled precipitate structures may be formed in-situ during the azdepo state or via the post-annealing route.

[0051] According to the first example, the proposed microstructure includes two components shown in Figure 3a. The first component is used to form an entropy-stabilized ceramic matrix.

[0052] The second component is used to form controlled precipitates within the structure. A schematic representation of the pathway for forming the desired microstructure is shown in Figure 3. The precipitates may be any oxides, carbides, and borides in the HEA ceramic matrix. An example of the pathway for forming this structure is as follows:

[0053] (a) By post-annealing as shown in Figure 3b: Desired phase precipitation is achieved in the HEA matrix by appropriately adjusting the matrix composition for metallic and nonmetallic lattices. The example in Figure 3a shows a WAlTiSiN alloy in which precipitates on the nanometer scale are realized by thermal annealing. The size, chemical properties, and interface structure of the precipitates are controlled by the alloy composition, time, and temperature of the annealing cycle.

[0054] (b) To enable similar precipitates in the asdepot state coating, the deposition chamber is further equipped with an additional heating source capable of instantaneously heating the substrate surface to a depth of several nanometers to a temperature of 900C–100C in several seconds, such heating referred to below as flash heating. The flash heating source may be a nanosecond laser, electron heating by a filament, etc. The energy of the flash heater is adjusted so that only a surface of a few nanometers is heated with each irradiation. The chamber is designed so that the coated substrate is alternately exposed to the coating and flash heating source schematically shown in Figure 3c. When the coated substrate is exposed to the flash heating source, localized heating allows for the decomposition of a given alloy, resulting in a controlled precipitate structure. The composition of the matrix and precipitate is adjusted by the selection of alloy composition, energy input, and flash heating cycle time, according to the thermodynamic rule of free energy minimization combined with the controlled dynamics available during flash heating. Coating growth is continuous through coating deposition and flash heating, sequentially forming the HEA matrix and controlled precipitate structure.

[0055] In the proposed method, the formation of precipitate structures and host matrix materials is induced by the selection of alloys.

[0056] a) Alloying elements that can form entropy-stabilized solid solutions have a lower ΔG for all competing states of the solid solution. mix Close 37 Al 34 Si 12V 17 The screening is performed using a calculation based on the first principle, similar to the example of N.

[0057] b) The precipitate structure is formed by having alloying elements / components such as BN, Al2O3, and V2O5 that do not mix with the HEA matrix as determined by careful thermodynamic studies. The necessary kinetics required to form the precipitate are provided by post-annealing or by flash heating in-situ during coating deposition. Based on the selected alloy and precipitate combination, a reactive atmosphere is created in the chamber as needed, which may contain, for example, nitrogen and / or oxygen and / or CH4 separately or as a mixture thereof.

[0058] Some examples include Ti to enable additional functional properties of the coating. 37 Al 34 Si 12 V 17 These are precipitates of BN, Al2O3, and VC in the N HEA matrix, but are not limited to these.

Claims

1. A PVD coating process for generating a multi-functional coating structure, A step of generating a HEA ceramic base material on a substrate, The method comprises the step of targeting the introduction of a controlled precipitate structure into the HEA ceramic matrix in order to produce a desired specific property of the multifunctional coating structure, wherein the targeted introduction of the controlled precipitate structure into the HEA ceramic matrix is - This is done by post-heat treatment, which involves heating the already produced HEA ceramic base material to a temperature of 900 to 1000°C, or —A PVD coating process performed in-situ by using an instantaneous heating source during the production of the HEA ceramic base material.

2. The PVD coating process according to claim 1, wherein the modification of the targeted introduction of a controlled precipitate structure is performed by changing the processing time and / or processing temperature.

3. The PVD coating process according to claim 1 or 2, wherein in the layer of the HEA ceramic matrix, only a portion less than 50 nm is directly heated by the post-heat treatment.

4. The PVD coating process according to any one of claims 1 to 3, wherein the instantaneous heating source is in the form of a laser for instantaneously heating the surface of the HEA ceramic base material.

5. The PVD coating process according to any one of claims 1 to 4, wherein the targeted introduction of the controlled precipitate structure into the HEA ceramic matrix is ​​performed by post-annealing on a post-annealing line after the formation of the HEA ceramic matrix.

6. The PVD coating process according to any one of claims 1 to 5, wherein the HEA ceramic base material is deposited on the substrate by applying a negative bias voltage to the substrate during the PVD coating process, and the bias voltage is <200V.

7. The PVD coating process according to any one of claims 1 to 6, wherein the formation of the HEA ceramic matrix and / or the controlled precipitate structure is carried out in a reactive atmosphere, the reactive atmosphere comprising nitrogen and / or oxygen and / or methane.

8. A PVD coating process according to any one of claims 1 to 7, wherein sputtering technology is used as the PVD coating process.

9. The PVD coating process according to any one of claims 1 to 8, wherein the substrate temperature during the formation of the HEA ceramic matrix and / or the controlled precipitate structure is 100°C to 400°C.

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