Method for preparing refractory high-entropy alloy coating with ultrahigh hardness

Abstract

The invention belongs to the field of hard alloy coatings, and particularly relates to a method for preparing a refractory high-entropy alloy coating with ultrahigh hardness. A direct current magnetron sputtering method is adopted, a MoNbTaVW refractory high-entropy alloy target material is selected, a MoNbTaVW refractory high-entropy alloy coating is deposited on a substrate, and the structure and performance of the obtained coating are optimized by adjusting technological parameters of direct current magnetron sputtering. According to the preparation method, the refractory high-entropy alloy coating with ultrahigh hardness can be obtained, and all elements are uniformly distributed.

Description

Technical Field

[0001] The invention belongs to the technical field of coating preparation, and specifically relates to a method for preparing a refractory high-entropy alloy coating with ultra-high hardness. Background Art

[0002] The service environment in key fields such as aerospace, cutting-edge equipment, and mechanical processing is becoming increasingly harsh, and the service life requirements for key components serving in them are getting higher and higher. The three main failure modes of engineering components and mechanical parts are friction wear, corrosion, and fatigue fracture, and most of these failure phenomena occur on the surface of the material. Therefore, the service life of the material is determined by the use time of the material surface. Protective coating is currently the most effective means of protecting the surface of the material. Among them, Cr coating and Ta coating are the two most commonly used protective coatings. However, the hardness of the existing Cr coating and Ta coating is relatively low (~12GPa) and can no longer meet the use requirements, and the preparation process of the Cr coating will cause great harm to the environment; the Ta coating is prone to produce β-Ta during the preparation process, which seriously affects its strength.

[0003] Refractory high entropy alloy coating, also known as refractory metal multi-principal alloy coating, is a new high entropy material based on refractory high entropy alloy. Due to the characteristics of high mixed entropy, it exhibits a variety of excellent properties. Compared with traditional metal coatings, it shows obvious advantages in mechanics, corrosion resistance, friction and wear resistance and other aspects. Among many refractory high entropy alloy systems, MoNbTaVW has attracted widespread attention due to its stable single-phase BCC structure and excellent mechanical properties. Literature "Dong Yinghui et al., Fretting Wear Performance of Laser Cladding MoNbTaVW Refractory High Entropy Alloy Coating, Materials Guide, 2024": MoNbTaVW refractory high entropy alloy coating was prepared by laser cladding, but because the base elements will diffuse during the laser cladding process, a single-phase and uniform MoNbTaVW refractory high entropy alloy coating is not formed. Patent "A fully ceramic-based high-temperature solar energy absorption coating and its preparation method, CN201910965109): MoNbTaVWN and MoNbTaVWNO were prepared by magnetron sputtering, but it introduced covalent bonds and no longer belongs to the category of alloy coating.

[0004] Therefore, in order to meet the needs of practical applications, it is urgently necessary to develop a refractory high-entropy alloy coating and its preparation method with simple and efficient preparation process, accurate stoichiometric ratio and ultra-high hardness. Summary of the invention

[0005] In order to solve at least one of the above problems, the present invention provides a method for preparing a refractory high entropy coating with ultra-high hardness, comprising:

[0006] S1. Place the refractory high entropy alloy target and substrate into the chamber of the deposition equipment, evacuate the chamber to below the background vacuum, heat the substrate to the deposition temperature, introduce inert gas, and use a pressure control valve to adjust the deposition working pressure;

[0007] S2, adjusting magnetron sputtering parameters to coat the substrate to obtain the refractory high entropy alloy coating,

[0008] in,

[0009] The refractory high entropy alloy target is MoNbTaVW, in which the atomic ratio of Mo element is 18-22at%, the atomic ratio of Nb element is 18-22at%, the atomic ratio of Ta element is 18-22at%, the atomic ratio of V element is 18-22at%, and the atomic ratio of W element is 18-22at%.

[0010] According to a specific embodiment of the present invention, in step S1, the deposition temperature is not less than 500°C. When the deposition temperature is lower than this temperature, the hardness of the prepared coating is lower than 25 GPa.

[0011] According to a specific embodiment of the present invention, in step S1, the background vacuum degree is less than 1×10 -3 Pa. If the vacuum degree is not lower than this value, the coating may be oxidized and it is not a pure metal coating.

[0012] According to a specific embodiment of the present invention, in step S1, the inert gas is argon.

[0013] According to a specific embodiment of the present invention, the deposition working pressure is 0.5-2 Pa. When the deposition working pressure is within this range, the hardness of the prepared coating is relatively high.

[0014] According to a specific embodiment of the present invention, in step S2, adjusting the magnetron sputtering parameters includes: adjusting the rotation speed of the substrate, setting the bias voltage, setting the power during DC magnetron sputtering, setting the pre-deposition time and the deposition time.

[0015] More specifically, step S2 includes starting the magnetron sputtering device, adjusting the substrate rotation speed, setting the bias voltage, turning on the DC magnetron sputtering power supply, closing the substrate baffle for pre-deposition for a period of time and then opening the substrate baffle for formal deposition, and cooling to room temperature after deposition for a period of time and taking out.

[0016] According to a specific embodiment of the present invention, the rotation speed of the substrate is 5 to 20 r / min. When the rotation speed of the substrate is within this range, the coating is more evenly distributed.

[0017] According to a specific embodiment of the present invention, the bias voltage is no greater than -100 V. When the bias voltage is greater than -100 V, the hardness of the prepared coating is lower than 25 GPa.

[0018] According to a specific embodiment of the present invention, the power of the DC magnetron sputtering is 50-200W. When the power is out of this range, if it is too large or too small, the hardness of the prepared coating will not meet the standard.

[0019] According to a specific embodiment of the present invention, the pre-deposition time is 20-60 minutes. The pre-deposition is to remove impurities on the surface of the target material. When the pre-deposition time is not less than 20 minutes, the impurities on the surface of the target material have been removed. Too long a time will cause a waste of resources.

[0020] According to a specific embodiment of the present invention, the deposition time is 30 min-120 min. When the deposition time is within this range, the hardness of the prepared coating is relatively high, not less than 25 GPa.

[0021] According to a specific embodiment of the present invention, the substrate includes but is not limited to any one of silicon, gallium arsenide, silicon carbide, stainless steel, and magnesium oxide.

[0022] According to a specific embodiment of the present invention, the atomic ratio between the elements of the high entropy alloy target is Mo:Nb:Ta:V:W is 1:1:1:1:1.

[0023] According to a specific embodiment of the present invention, the hardness of the high entropy alloy coating is not less than 25 GPa, and the elements are evenly distributed, and it is not a mixture of a single or binary alloy coating.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The refractory high entropy alloy coating obtained by the present invention has ultra-high hardness, with a hardness greater than 25GPa, which is significantly better than the existing traditional refractory metal or alloy coating;

[0026] 2. The coating prepared by the present invention is a high entropy alloy coating, having a single BCC phase, not a mixture of pure metals or binary and ternary alloy coatings, and the elements are evenly distributed;

[0027] 3. The preparation process of the present invention is simple, the synthesis cycle is short, the preparation efficiency is high, and it is suitable for large-scale batch production. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 The XRD spectrum of the refractory high entropy alloy coating with ultra-high hardness obtained in Example 1 of the present invention;

[0030] Figure 2 Surface SEM photograph of the refractory high entropy alloy coating with ultra-high hardness obtained in Example 1 of the present invention and the corresponding element distribution diagram. DETAILED DESCRIPTION

[0031] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0032] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. Further, in the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0033] In this document, the terms “contain”, “include” or “comprise” are open expressions, that is, they include the contents specified in the present invention but do not exclude other contents.

[0034] As used herein, the terms "optionally", "optional" or "optionally" generally mean that the subsequently described event or circumstance may but need not occur, and that the description includes instances where the event or circumstance occurs and instances where it does not.

[0035] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention provides drawings, which are part of the disclosure of the present invention. They are mainly used to illustrate the embodiments and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. By referring to these contents, ordinary technicians in this field should be able to understand other possible implementation methods and advantages of the present invention.

[0036] In view of this, the invention provides a method for preparing a refractory high entropy alloy coating with ultra-high hardness, comprising the following steps:

[0037] S1. Under normal temperature conditions, place the refractory high entropy alloy target and substrate into the chamber of the deposition equipment, evacuate the chamber to below the background vacuum, heat the substrate, and after reaching the deposition temperature, introduce high-purity argon gas, and use a pressure control valve to adjust the deposition working pressure;

[0038] S2. Start the magnetron sputtering device, adjust the substrate rotation speed, set the bias voltage, turn on the DC magnetron sputtering power supply, close the substrate baffle for pre-deposition for a period of time, then open the substrate baffle for formal deposition, and after deposition for a period of time, cool to room temperature and take out.

[0039] Preferably, the refractory high entropy alloy target is a MoNbTaVW refractory high entropy alloy target, wherein the elements are in nearly equal atomic ratios: Mo 18-22at%, Nb 18-22at%, Ta 18-22at%, V 18-22at%, and W 18-22at%.

[0040] Preferably, the background vacuum is less than 1×10 -3 Pa.

[0041] Preferably, the deposition temperature is higher than 500°C.

[0042] Preferably, the deposition working pressure is 0.5-2Pa.

[0043] Preferably, the substrate rotates at a speed of 5 to 20 r / min.

[0044] Preferably, the bias voltage is ≤-100V.

[0045] Preferably, the DC magnetron sputtering deposition power is 50-200W.

[0046] Preferably, the pre-deposition time is >20 min

[0047] Preferably, the deposition time is 0.5 to 2 hours.

[0048] The present invention provides a refractory high-entropy alloy coating with ultra-high hardness. The refractory high-entropy alloy coating has ultra-high hardness, a hardness greater than 25 GPa, and uniform distribution of various elements, and is not a mixture of a mono- or binary alloy coating.

[0049] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] Example 1

[0051] A MoNbTaVW refractory high entropy alloy coating with ultra-high hardness is prepared by the following steps:

[0052] S1. At room temperature, place the refractory high entropy alloy target (Mo, Nb, Ta, V, W in equal atomic ratios), 316L stainless steel and silicon substrate into the deposition chamber, and evacuate the chamber to 1×10 -3 Pa, the substrate is heated to 500 ° C. After reaching the deposition temperature, high-purity argon gas is introduced, and the working pressure is maintained at 0.5 Pa using a pressure control valve;

[0053] S2. Start the magnetron sputtering device, adjust the substrate rotation speed to 10r / min, set the bias voltage to -100V, turn on the DC magnetron sputtering power supply, set the power to 100W, close the substrate baffle for pre-deposition for 20min, open the substrate baffle for deposition for 1h, and then cool to room temperature and take out;

[0054] The XRD spectrum of the refractory high entropy alloy coating obtained in this example is as follows: Figure 1 As shown, the physical phase is a single BCC structure without any second phase or impurity phase.

[0055] The cross-sectional SEM photograph of the refractory high entropy alloy coating obtained in this embodiment is shown in FIG. Figure 2 As shown, it can be seen that the five elements Mo, Nb, Ta, V, and W are evenly distributed.

[0056] The hardness of the coating was measured by nanoindentation with an indentation force of 2 mN and was found to be 25.16 GPa.

[0057] Example 2

[0058] A MoNbTaVW refractory high entropy alloy coating with ultra-high hardness is prepared by the following steps:

[0059] S1. Under room temperature, place the refractory high entropy alloy target (Mo, Nb, Ta, V, W in equal atomic ratio) and the silicon substrate into the deposition equipment chamber, and evacuate the chamber to 1×10 -3 Pa, the substrate is heated to 500 ° C. After reaching the deposition temperature, high-purity argon gas is introduced, and the working pressure is maintained at 2 Pa using a pressure control valve;

[0060] S2. Start the magnetron sputtering device, adjust the substrate rotation speed to 5r / min, set the bias voltage to -100V, turn on the DC magnetron sputtering power supply, set the power to 200W, close the substrate baffle for pre-deposition for 20min, open the substrate baffle for deposition for 0.5h, and then cool to room temperature and take out;

[0061] A MoNbTaVW refractory high entropy alloy coating with a single BCC phase, uniform element distribution and a hardness of up to 26.57 GPa was obtained.

[0062] Example 3

[0063] A MoNbTaVW refractory high entropy alloy coating with ultra-high hardness is prepared by the following steps:

[0064] S1. Under room temperature, place the refractory high entropy alloy target (Mo, Nb, Ta, V, W in equal atomic ratio) and the alumina substrate into the deposition chamber, and evacuate the chamber to 1×10 -3 Pa, the substrate is heated to 500 ° C. After reaching the deposition temperature, high-purity argon gas is introduced, and the working pressure is maintained at 0.5 Pa using a pressure control valve;

[0065] S2. Start the magnetron sputtering device, adjust the substrate rotation speed to 20r / min, set the bias voltage to -100V, turn on the DC magnetron sputtering power supply, set the power to 50W, close the substrate baffle for pre-deposition for 20min, open the substrate baffle for deposition for 2h, and then cool to room temperature and take out;

[0066] A MoNbTaVW refractory high entropy alloy coating with a single BCC phase, uniform element distribution and a hardness of up to 25.89 GPa was obtained.

[0067] Comparative Example 1

[0068] Compared with Example 1, the difference is that in step S1, the vacuum degree in the cavity is 1.5×10 -3 Pa.

[0069] Comparative Example 2

[0070] Compared with Example 1, the difference is that in step S1, the deposition temperature of the substrate is 400°C.

[0071] Comparative Example 3

[0072] Compared with Example 1, the difference is that in step S2, the bias voltage is -50V.

[0073] Comparative Example 4

[0074] Compared with Example 1, the difference is that in step S2, the power of the DC magnetron sputtering power supply is 45W.

[0075] Comparative Example 5

[0076] Compared with Example 1, the difference is that in step S2, the power of the DC magnetron sputtering power supply is 210W.

[0077] Comparative Example 6

[0078] Compared with Example 1, the difference is that in step S2, the deposition time is 3 hours.

[0079] Comparative Example 7

[0080] Compared with Example 1, the difference is that in step S2, the deposition time is 0.4 h.

[0081] Comparative Example 8

[0082] Compared with Example 1, the difference is that the atomic ratio of each element of the refractory high entropy alloy target material is Mo:Nb:V equal to 1:1:1.

[0083] Comparative Example 9

[0084] Compared with Example 1, the difference is that the atomic ratio of each element in the refractory high entropy alloy target is Mo:Nb:Ta:V:W, which is equal to 1:1.5:1.36:0.8:0.5.

[0085] The hardness of the coatings prepared in Comparative Examples 1-8 was measured using nanoindentation with an indentation force of 2 mN. The results are shown in Table 1, which shows that the refractory high entropy alloy coating of a specific system (equiatomic ratio) and specific process parameters (such as the vacuum degree in the chamber, deposition temperature, bias voltage, power, and deposition time) have an effect on the hardness of the prepared coating, especially the deposition temperature and bias voltage of the substrate, which have the greatest impact on the performance of the coating.

[0086] Table 1

[0087]

[0088]

[0089] The vacuum degree of Comparative Example 1 is 1.5×10 -3Pa. The inventor speculates that when the vacuum degree is too high, it may cause oxidation of the coating, thereby reducing the hardness of the coating; when the deposition temperature of the substrate in Example 2 is 400°C, the hardness of the coating decreases significantly. The inventor speculates that the temperature reduction causes the mean free path of the sputtered atoms to decrease, and the deposition process diffuses insufficiently, resulting in an uneven structure, which leads to a decrease in hardness; the bias voltage of Example 3 is relatively high. Under this bias voltage, the hardness of the coating is 22.421GPa. The inventor speculates that the reduction in bias voltage causes the kinetic energy of the sputtered atoms to decrease, and the deposition process diffuses insufficiently, resulting in an uneven structure, which leads to a decrease in hardness; in Examples 4 and 5, when the power of the DC magnetron sputtering power supply is low or high, it will affect the hardness of the coating. The inventor speculates that if the power is too low, the number of sputtered atoms per unit time is small, the thickness is low, and if the power is too high, the coating hardness will be affected. If the deposition time is too high, it will lead to too many sputtered atoms per unit time, the coating is not dense, and the coating hardness decreases; in Comparative Examples 6 and 7, too long or too short deposition time will also affect the coating hardness. It is speculated that this is because the coating time is too short, the plated film is thin, and the film thickness does not reach the thickness for optimal performance, while the time is too long, the plated film is thicker, and the coating structure is loose, which leads to a decrease in mechanical properties; in Comparative Examples 8 and 9, the inventors adjusted the elements of the refractory high entropy alloy target and the ratio between the elements of the refractory high entropy alloy target, respectively, and found that only when the specific refractory high entropy alloy target and the elements are in equiatomic ratios, the prepared coating has the best mechanical properties. It is speculated that the unique high entropy effect, lattice distortion effect, hysteresis diffusion effect and cocktail effect of the high entropy alloy improve the coating performance.

[0090] In summary, only the refractory high entropy alloy coating of a specific system (equiatomic ratio) and specific process parameters (deposition temperature not less than 500°C, background vacuum less than 1×10-3Pa, deposition working pressure of 0.5~2Pa, bias voltage not greater than -100V, deposition power of 50~200W, deposition time of 0.5~2h) can produce the best coating hardness.

[0091] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a refractory high entropy alloy coating with ultra-high hardness, characterized in that: include: S1. Place the refractory high entropy alloy target and substrate into the chamber of the deposition equipment, evacuate the chamber to below the background vacuum, heat the substrate to the deposition temperature, introduce inert gas, and use a pressure control valve to adjust the deposition working pressure; S2, adjusting magnetron sputtering parameters to coat the substrate to obtain the refractory high entropy alloy coating, in, The refractory high entropy alloy target is MoNbTaVW, in which the atomic ratio of Mo element is 18-22at%, the atomic ratio of Nb element is 18-22at%, the atomic ratio of Ta element is 18-22at%, the atomic ratio of V element is 18-22at%, and the atomic ratio of W element is 18-22at%.

2. The method according to claim 1, characterized in that In step S1, the deposition temperature is not less than 500°C.

3. The method according to claim 1, characterized in that In step S1, the background vacuum is lower than 1×10 -3 Pa.

4. The method according to claim 1, characterized in that: In step S1, the inert gas is argon; The deposition working pressure is 0.5-2Pa.

5. The method according to claim 1, characterized in that In step S2, adjusting the magnetron sputtering parameters includes: adjusting the rotation speed of the substrate, setting the bias voltage, setting the power during DC magnetron sputtering, setting the pre-deposition time and the deposition time.

6. The method according to claim 5, characterized in that The substrate has a rotation speed of 5 to 20 r / min; The bias voltage is no greater than -100V.

7. The method according to claim 5, characterized in that The power during the DC magnetron sputtering is 50 to 200 W; The pre-deposition time is 20-60 minutes.

8. The method according to claim 5, characterized in that The deposition time is 30 min-120 min.

9. The method according to claim 1, characterized in that: The substrate includes any one of silicon, gallium arsenide, silicon carbide, stainless steel, and magnesium oxide.

10. The method according to claim 1, characterized in that The hardness of the high entropy alloy coating is not less than 25 GPa; In the high entropy alloy coating, the ratios of the elements Mo, Nb, Ta, V, and W in the high entropy alloy target are equiatomic ratios.

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