A high-temperature wear-resistant refractory high-entropy alloy and its preparation method

Abstract

The present invention discloses a high-temperature wear-resistant refractory high-entropy alloy and its preparation method, which belongs to the field of high-entropy alloy technology. The purpose is to solve the problem of wear failure of existing high-temperature alloys in high-temperature environments. The alloy is composed of Ti, Zr, Nb, Ta, Al, and the chemical composition expression is Ti 40 Zr 40‑x Nb 10 Ta 10 Al x , where x = 5~10, x is the atomic percentage of Al. The refractory high entropy alloy prepared by the present invention has excellent high-temperature wear resistance. At 800℃, the wear rate is as low as 1.6~9.9×10 ‑5 mm 3 / (N·m). The present invention uses a vacuum arc melting method to prepare the final high-temperature wear-resistant refractory high-entropy alloy. The method is simple to operate and has broad application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of high entropy alloy materials, and in particular relates to a high-temperature wear-resistant refractory high entropy alloy and a preparation method thereof. Background Art

[0002] The alloy design concept of high-entropy alloys was first proposed and reported by Taiwanese scholar Ye Junwei in 2004. Traditional alloy design focuses on mixing enthalpy, using one or two elements as the primary components and adding trace elements to improve performance. High-entropy alloys, on the other hand, focus on configurational entropy, combining four or five elements in equal or nearly equal molar ratios. This design concept overcomes the limitations of traditional alloys, achieving breakthroughs in multiple dimensions, including mechanical properties, wear resistance, and corrosion resistance. Refractory high-entropy alloys are a class of high-entropy alloys primarily composed of the refractory metals W, Ta, Mo, Nb, Hf, Cr, V, Zr, and Ti. The ultra-high melting points of these elements (generally above 1850°C) give the alloys a higher service temperature. This characteristic can overcome the service limits of Ni-based superalloys, enabling the material to exhibit more reliable overall performance in high-temperature environments.

[0003] In recent years, the continuous advancement and development of my country's aerospace technology has made the service environment of aircraft hot-end components and some structural parts more complex and demanding. However, current aerospace high-temperature alloy materials cannot meet the expected use requirements. At higher operating temperatures, high-temperature alloys will melt or even fail, seriously affecting the service life and safety of the aircraft. Therefore, complex operating environments have increasingly stringent requirements for the comprehensive performance of metal alloys, requiring not only high specific strength, fracture toughness, and creep resistance, but also excellent heat resistance and wear resistance.

[0004] Numerous reports have been published on the mechanical properties and tribological properties of high-entropy alloys (HEAs) under conventional working conditions. However, relatively little research has been conducted on the high-temperature tribology of refractory HEAs, and the underlying mechanisms remain relatively in-depth. Currently, refractory HEAs still face challenges with high-temperature wear failure, and their potential as high-temperature wear-resistant materials has yet to be demonstrated in significant engineering applications. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that the current refractory high entropy alloys still have the problem of high temperature wear failure, and thus provide a high temperature wear-resistant refractory high entropy alloy and a preparation method thereof.

[0006] Specifically, the first aspect of the present invention provides a high-temperature wear-resistant refractory high-entropy alloy, the chemical composition of which is expressed as Ti 40 Zr 40-x Nb 10 Ta 10 Al x, where x=5~10, x is the atomic percentage of Al.

[0007] Furthermore, the as-cast structure of the refractory high-entropy alloy is a single-phase BCC structure or a BCC+B2 two-phase structure.

[0008] Furthermore, at 800°C, the wear rate of the refractory high entropy alloy is as low as 1.6~9.9×10 -5 mm 3 / (N·m).

[0009] Furthermore, when x=5, the chemical formula of the alloy is Ti 40 Zr 35 Nb 10 Ta 10 Al5; The as-cast structure of the alloy is a single-phase BCC structure; The wear rate of the alloy at 800℃ is 9.9×10 -5 mm 3 / (N·m).

[0010] Furthermore, when x=8, the chemical formula of the alloy is Ti 40 Zr 32 Nb 10 Ta 10 Al8; The as-cast structure of the alloy is BCC+B2 dual-phase structure; The wear rate of the alloy at 800℃ is 4.2×10 -5 mm 3 / (N·m).

[0011] Furthermore, when x=10, the chemical formula of the alloy is Ti 40 Zr 30 Nb 10 Ta 10 Al 10 The as-cast structure of the alloy is BCC+B2 dual-phase structure. The wear rate of the alloy at 800℃ is 1.6×10 -5 mm 3 / (N·m).

[0012] The second aspect of the present invention provides a method for preparing a high-temperature, wear-resistant, refractory high-entropy alloy, comprising: converting the atomic ratio of any one of the above-mentioned refractory high-entropy alloys into a mass ratio and weighing them, and using a vacuum arc melting method to prepare the weighed raw materials to obtain the final high-temperature, wear-resistant, refractory high-entropy alloy.

[0013] Furthermore, the vacuum arc melting process specifically includes: placing the weighed raw materials into a copper mold crucible of a vacuum arc melting furnace, with Al placed at the bottom, Ti and Zr placed in the middle layer, and Nb and Ta placed in the top layer; after vacuuming, filling in high-purity argon gas for melting; and suction-casting the obtained button-shaped ingot into a plate shape. The sample in the furnace is taken out after natural cooling.

[0014] Furthermore, before smelting, the Ti ingot pre-placed in the vacuum furnace is smelted 2 to 3 times to absorb residual oxygen in the furnace.

[0015] Furthermore, during smelting, the smelting current was adjusted to 355-500 A, the smelting time was 3-4 min each time, the magnetic stirring was set to 1.5 A, and after each smelting was completed, the button ingot was turned over and smelted repeatedly for at least 7 times.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects:

[0017] The present invention is achieved by 40 Zr 40 Nb 10 Ta 10 The addition of Al to refractory high entropy alloys makes the alloy lighter. The addition of Al causes the alloy to form a complex oxide composed of Al, Ti, and Ta at high temperatures, which prevents oxygen from further corroding the matrix. 40 Zr 40 Nb 10 Ta 10 Alloy, Ti 40 Zr 40-x Nb 10 Ta 10 Al x At high temperatures, a hard, anti-oxidation oxide layer forms on the alloy surface, significantly improving its high-temperature wear resistance. This makes it promising for development into a new type of high-temperature wear-resistant material that meets the current needs of aviation and aerospace development. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is the XRD pattern of the refractory high entropy alloy prepared in Example 1 of the present invention;

[0019] Figure 2 is a SEM image of the microstructure of the refractory high entropy alloy prepared in Example 1 of the present invention;

[0020] Figure 3 is the XRD pattern of the refractory high entropy alloy prepared in Example 2 of the present invention;

[0021] Figure 4 is a SEM image of the microstructure of the refractory high entropy alloy prepared in Example 2 of the present invention;

[0022] Figure 5 is the XRD pattern of the refractory high entropy alloy prepared in Example 3 of the present invention;

[0023] Figure 6 is a SEM image of the microstructure of the refractory high entropy alloy prepared in Example 3 of the present invention;

[0024] Figure 7 This is the XRD pattern of the refractory high entropy alloy prepared in Comparative Example 1 of the present invention;

[0025] Figure 8 This is a SEM image of the microstructure of the refractory high entropy alloy prepared in Comparative Example 1 of the present invention;

[0026] Figure 9 This is a comparison chart of the wear rates provided by Example 1, Example 2, Example 3, and Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0027] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making creative efforts are within the scope of protection of the present invention.

[0028] The first aspect of the present invention provides a high temperature wear-resistant refractory high entropy alloy, the chemical composition of the refractory high entropy alloy is expressed as Ti 40 Zr 40-x Nb 10 Ta 10 Al x , where x=5~10, x is the atomic percentage of Al.

[0029] The present invention first designs the basic alloy component Ti based on the d electron theory 40 Zr 40 Nb 10 Ta 10 At the beginning of the design, in order to balance the mechanical properties of the alloy, the alloy was made to undergo phase transformation during deformation, thus having a better match between strength and plasticity. 40 Zr 40 Nb 10 Ta 10 The addition of Al to refractory high entropy alloys makes the alloy lighter. The addition of Al causes the alloy to form a complex oxide composed of Al, Ti, and Ta at high temperatures, which prevents oxygen from further corroding the matrix. 40 Zr 40 Nb 10Ta 10 Alloy, Ti 40 Zr 40-x Nb 10 Ta 10 Al x A hard, anti-oxidation oxide layer is formed on the surface of the alloy at high temperatures, which significantly improves the high-temperature wear resistance of the alloy.

[0030] The addition of Al element cannot be too much, otherwise, it will seriously reduce the plastic toughness of the material, causing severe three-body wear of the alloy during the friction and wear process, thereby reducing the wear resistance of the alloy. Moreover, the introduction of Al element also needs to consider the coordinated regulation of Zr element, that is, when introducing Al element, it is necessary to reduce the Zr content in a coordinated manner. Since Zr element is a β-Ti stabilizing element, and Al element is an α-Ti stabilizing element, Ti 40 Zr 40 Nb 10 Ta 10 Located in the β region of the Bo-Md curve, reducing the Zr content and increasing the Al content can make the alloy close to the phase transition line, making it easier for phase transition to occur during deformation. After a large number of experimental verifications, the applicant team designed the final chemical composition expression of the refractory high entropy alloy as Ti 40 Zr 40- x Nb 10 Ta 10 Al x , where x=5~10, x is the atomic percentage of Al.

[0031] Specifically, when x=5, the chemical formula of the alloy is Ti 40 Zr 35 Nb 10 Ta 10 Al5; The as-cast structure of the alloy is a single-phase BCC structure; The wear rate of the alloy at 800℃ is 9.9×10 -5 mm 3 / (N·m). When x=8, the chemical formula of the alloy is Ti 40 Zr 32 Nb 10 Ta 10 Al8; The as-cast structure of the alloy is BCC+B2 dual-phase structure; The wear rate of the alloy at 800℃ is 4.2×10 -5 mm 3 / (N·m). When x=10, the chemical formula of the alloy is Ti 40 Zr 30 Nb 10 Ta 10 Al 10The as-cast structure of the alloy is BCC+B2 dual-phase structure. The wear rate of the alloy at 800℃ is 1.6×10 -5 mm 3 / (N·m).

[0032] The preparation method of the above-mentioned high-temperature wear-resistant refractory high-entropy alloy includes: converting the atomic ratio of the above-mentioned refractory high-entropy alloy into a mass ratio and weighing it, and using the weighed raw materials to prepare the final high-temperature wear-resistant refractory high-entropy alloy by a vacuum arc melting method.

[0033] Before smelting, the metal raw materials need to be surface treated, that is, an appropriate amount of Ti, Zr, Nb, Ta and Al bulk elements are selected as raw materials, their surfaces are polished to remove the oxide scale, and then ultrasonically cleaned and dried, and then converted into mass ratio according to the designed atomic ratio and weighed.

[0034] The vacuum arc melting process specifically includes: placing the weighed raw materials into the copper mold crucible of the vacuum arc melting furnace, with Al placed at the bottom, Ti and Zr placed in the middle layer, and Nb and Ta placed on the top layer. After vacuuming, high-purity argon gas is filled in for melting, and the obtained button-shaped ingot is suction-cast into a plate shape. The sample in the furnace is taken out after natural cooling.

[0035] Preferably, before smelting, the Ti ingot, previously placed in a vacuum furnace, is melted two to three times to absorb residual oxygen in the furnace. During smelting, the melting current is adjusted to 355 to 500 A, for example, 355 A, 375 A, 400 A, 425 A, 450 A, 475 A, 500 A, etc. Each melting time is 3 to 4 minutes. A magnetic stirring current of 1.5 A is set to ensure a more uniform distribution of alloying elements. After each melting, the button ingot is flipped and the melting process is repeated at least seven times. The natural cooling time is 15 to 20 minutes.

[0036] Example 1

[0037] Provided is a preparation method for a high-temperature wear-resistant refractory high-entropy alloy, wherein the chemical composition of the high-entropy alloy is specifically Ti 40 Zr 35 Nb 10 Ta 10 A15, the method comprises the following steps:

[0038] S1. Surface treatment of raw materials: Select appropriate amounts of Ti, Zr, Nb, Ta and Al bulk elements as raw materials, polish their surfaces to remove oxide scale, then ultrasonically clean and dry them, convert the designed atomic ratio into a mass ratio and weigh them;

[0039] S2. Melting and suction casting of the alloy: Place the raw materials treated in S1 into a copper mold crucible in a vacuum arc melting furnace, with Al at the bottom, Ti and Zr in the middle layer, and Nb and Ta on the top layer. After vacuuming, fill with high-purity argon gas for melting. The obtained button-shaped ingot is suction-cast into a plate shape. The sample in the furnace is taken out after natural cooling.

[0040] Before smelting, the Ti ingot placed in the vacuum furnace was melted three times to absorb the residual oxygen in the furnace. The melting current was adjusted to 450 A, the melting time was 4 min each time, and the magnetic stirring was set to 1.5 A to make the alloy elements more evenly distributed. After each melting, the button ingot was turned over and smelted repeatedly for 8 times. Finally, Ti 40 Zr 35 Nb 10 Ta 10 Al5 high temperature wear-resistant refractory high entropy alloy ingot, the button-shaped ingot is suction cast into a plate, and the sample in the furnace is taken out after natural cooling. The natural cooling time is 15 minutes;

[0041] Figure 1 This is an X-ray diffraction phase analysis of the refractory high entropy alloy of Example 1 performed using an X-ray diffractometer.

[0042] As can be seen from the figure, Example 1 is a single-phase body-centered cubic (BCC) structure, and the alloy does not precipitate a second phase that is potentially harmful to its performance.

[0043] Figure 2 This is the SEM image of the microstructure of Example 1. It can be seen that the microstructure of Example 1 is all dendrites.

[0044] A reciprocating dry friction test was conducted on Example 1 using an Rtec friction and wear tester. The load of the reciprocating dry friction test was 10 N, the friction pair was Si3N4, the sliding frequency was 5 Hz, the wear time was 30 minutes, and the experimental temperature was 800 °C. The experimental results are as follows: Figure 9 As shown in Figure 2, the wear rate of the alloy at 800°C is 9.9×10 -5 mm 3 / (N·m).

[0045] Example 2

[0046] Provided is a high-temperature wear-resistant refractory high-entropy alloy and a preparation method thereof, wherein the chemical composition of the high-entropy alloy is specifically Ti 40 Zr 32 Nb 10 Ta 10 Al8, its preparation method is the same as that in Example 1.

[0047] The Ti obtained in this example40 Zr 32 Nb 10 Ta 10 The test conditions for the microstructure and friction and wear properties of Al8 refractory high entropy alloy are the same as those in Example 1. The test results are shown in Figure 2. Figure 3 、 Figure 4 In this embodiment, Ti 40 Zr 32 Nb 10 Ta 10 The microstructure of Al8 refractory high entropy alloy is BCC+B2 dual phase structure. The microstructure is all dendrites. The wear rate of this alloy at 800℃ is 4.2×10 -5 mm 3 / (N·m).

[0048] Example 3

[0049] Provided is a high-temperature wear-resistant refractory high-entropy alloy and a preparation method thereof, wherein the chemical composition of the high-entropy alloy is specifically Ti 40 Zr 30 Nb 10 Ta 10 Al 10 , and its preparation method is the same as that in Example 1.

[0050] The Ti obtained in this example 40 Zr 30 Nb 10 Ta 10 Al 10 The test conditions for the microstructure and friction and wear properties of the refractory high entropy alloy are the same as those in Example 1. The test results are as follows: Figure 5 、 Figure 6 In this embodiment, Ti 40 Zr 30 Nb 10 Ta 10 Al 10 The microstructure of the refractory high entropy alloy is a BCC+B2 dual-phase structure. The microstructure is all dendrites. The wear rate of the alloy at 800℃ is 1.6×10 -5 mm 3 / (N·m).

[0051] Comparative Example 1

[0052] Select Ti, Zr, Nb, and Ta bulk elements with a purity greater than or equal to 99.95 wt% as raw materials. After polishing and cleaning, they are configured into the raw materials required for smelting according to the molar percentage of Ti: Zr: Nb: Ta = 4:4:1:1. The processed raw materials are placed in a copper mold crucible of a vacuum arc melting furnace, with Ti and Zr placed on the lower layer and Nb and Ta placed on the upper layer. After vacuuming, high-purity argon is filled in for smelting. After each smelting is completed, the button ingot is turned over and smelted 8 times, and finally Ti is obtained. 40 Zr 40 Nb 10 Ta 10 The refractory high entropy alloy ingot was cast into a button-shaped plate by suction casting. The sample in the furnace was taken out after natural cooling. The natural cooling time was 15 min.

[0053] The Ti obtained in this comparative example 40 Zr 40 Nb 10 Ta 10 The microstructure of the refractory high entropy alloy is a BCC single phase structure. The microstructure is all dendrites. The test results are as follows Figure 7 、 Figure 8 The plate alloy was subjected to a reciprocating dry friction test with a load of 10 N, a friction pair of Si3N4, a sliding frequency of 5 Hz, a wear time of 30 minutes, and an experimental temperature of 800 ℃. 40 Zr 40 Nb 10 Ta 10 Refractory high-entropy alloys cannot be subjected to friction experiments at 800 °C because they undergo catastrophic oxidation and the samples become powdery.

[0054] It should be noted that, in this document, terms such as "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements that are inherent to such process, method, article or apparatus.

[0055] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a high-temperature wear-resistant refractory high-entropy alloy, characterized in that: include: First, the basic alloy composition Ti was designed based on the d electron theory. 40 Zr 40 Nb 10 Ta 10 , then in the base alloy - Ti 40 Zr 40 Nb 10 Ta 10 The Al element is added to the refractory high entropy alloy, and the Zr content is reduced and the Al content is increased, so that the high entropy alloy is close to the phase transition line, and finally the refractory high entropy alloy is formed. Its chemical composition expression is Ti 40 Zr 40-x Nb 10 Ta 10 Al x , where x=5~10, x is the atomic percentage of Al. When x=5, the as-cast structure of the alloy is a single-phase BCC structure; when x=8, the as-cast structure of the alloy is a BCC+B2 dual-phase structure; when x=10, the as-cast structure of the alloy is a BCC+B2 dual-phase structure; The atomic ratio of the above-mentioned refractory high entropy alloy is converted into a mass ratio and weighed, and the weighed raw materials are prepared by a vacuum arc melting method to obtain the final high-temperature wear-resistant refractory high entropy alloy; The vacuum arc melting process specifically includes: placing the weighed raw materials into the copper mold crucible of the vacuum arc melting furnace, with Al placed at the bottom, Ti and Zr placed in the middle layer, and Nb and Ta placed on the top layer. After vacuuming, high-purity argon gas is filled in for melting. The button-shaped ingot obtained is suction-cast into a plate shape, and the sample in the furnace is taken out after natural cooling.

2. The method for preparing a high-temperature wear-resistant refractory high-entropy alloy according to claim 1, wherein: When x=5, the wear rate of the alloy at 800℃ is 9.9×10 -5 mm 3 / (N·m).

3. The method for preparing a high-temperature wear-resistant refractory high-entropy alloy according to claim 1, wherein: When x=8, the wear rate of the alloy at 800℃ is 4.2×10 -5 mm 3 / (N·m).

4. The method for preparing a high-temperature wear-resistant refractory high-entropy alloy according to claim 1, wherein: When x=10, the wear rate of the alloy at 800℃ is 1.6×10 -5 mm 3 / (N·m).

5. The method for preparing a high-temperature wear-resistant refractory high-entropy alloy according to claim 1, wherein: Before smelting, the Ti ingot pre-placed in the vacuum furnace is smelted 2 to 3 times to absorb the residual oxygen in the furnace.

6. The method for preparing a high-temperature wear-resistant refractory high-entropy alloy according to claim 1, wherein: During smelting, the smelting current was adjusted to 355-500 A, the smelting time was 3-4 min each time, the magnetic stirring was set to 1.5 A, and after each smelting was completed, the button ingot was turned over and smelted repeatedly for at least 7 times.

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