A bulk high-entropy alloy with high wear resistance, its preparation method and application

Abstract

The present invention belongs to the technical field of design and preparation of novel alloy materials, and particularly relates to a high-wear-resistance bulk high-entropy alloy, a preparation method thereof, and an application thereof. The chemical components of the high-wear-resistance bulk high-entropy alloy and the corresponding mass percentages are as follows: Ti: 10.5-12.5 wt.%, B: 0.5-1.5 wt.%, Cr: 21.5-23.5 wt.%, Ni: 38-40 wt.%, Al: 0-12.5 wt.%, and the balance is Fe and some inevitable impurities. At the same time, it is necessary to ensure that 10 ≤ Ti + B ≤ 15 (wt.%), 55 ≤ Cr + Ni ≤ 65 (wt.%), 0.5 ≤ Fe / Ti ≤ 2.5, and ensure that the sum of the mass percentages of each component is 100%. The purity of all the element raw materials involved shall not be lower than 99.99%. The high-entropy alloy prepared by the present invention has the characteristics of uniform composition distribution, high stability, high hardness, excellent wear resistance, etc. Compared with the traditional wear-resistant material NM500, its wear resistance is increased by 3-4 times, and the hardness can reach 900-1100 HV.

Description

Technical Field

[0001] The present invention belongs to the technical field of the design and preparation of new alloy materials, and particularly relates to a high-wear-resistant bulk high-entropy alloy, a preparation method thereof, and an application thereof. Background Art

[0002] With the phased development of steel materials, certain progress has been made to a certain extent in wear-resistant steel materials. Existing traditional wear-resistant steels include austenitic manganese steel and martensitic wear-resistant steel that improve wear resistance through matrix strengthening, and representative wear-resistant materials such as high-chromium cast iron that improve wear resistance through second-phase strengthening. The process of improving the wear resistance of alloys by a single method has become mature and cannot further meet the needs of changing and harsh working conditions. High-entropy alloy materials prepared by fusing multiple elemental metals have both matrix and second-phase strengthening effects and have an important impact on the research of improving the wear resistance of alloys.

[0003] A high-entropy alloy is an alloy composed of 5 or more main elements, which has high strength, high hardness, high plasticity, good wear resistance, corrosion resistance, high-temperature softening resistance, low-temperature embrittlement resistance, and radiation resistance superior to traditional alloys. It is a high-performance structural material alloy with high stress potential. Therefore, the properties of the alloy cannot be predicted by simply adding the properties of each element in the design of the alloy. The friction and wear of mechanical parts mainly occur on the material surface, and about 80% of the part working failures are caused by surface wear. The high-entropy alloy has a series of excellent properties superior to traditional alloys, such as high hardness, wear resistance, corrosion resistance, and high temperature resistance, making it have good development potential and broad application prospects.

[0004] Alloying is an effective method to improve the properties of alloys. By adding alloying elements with large differences in atomic radii for compounding, the lattice distortion can be increased, thereby improving the solid solution strengthening effect and obtaining high-entropy alloy materials with better hardness and wear resistance.

[0005] For the patented technology of "A High-Temperature Wear-Resistant High-Entropy Alloy and Its Preparation Method and Application" (CN115404387A), the mass percentages of each element in the high-entropy alloy ingot are as follows: Al: 2 - 6 at%, Co: 28 - 33 at%, Cr: 16 - 22 at%, Ni: 25 - 35 at%, Ti: 5 - 15 at%, Mo: 1 - 10 at%. This invention reduces the consumption of the strategic resource Co element by 50%. At a temperature of 400 - 900 °C, the wear resistance is increased by 10 - 40 times compared with traditional high-temperature wear-resistant steels. Although this technology significantly improves the wear resistance of high-entropy alloys, the alloy cost used is still very high, and the wear resistance at different temperatures varies greatly, lacking universality.

[0006] The patented technology of "A High-Strength, High-Ductility, Wear-Resistant High-Entropy Alloy and Its Preparation Method" (CN110499451A), the high-entropy alloy ingot and the molar percentages of each element are as follows: Fe: 54.0 - 56.0 at%, Co: 9.0 - 11.0 at%, Ni: 9.0 - 11.0 at%, Cr: 9.0 - 11.0 at%, Mo: 4.0 - 6.0 at%, V: 4.0 - 6.0 at% and C: 4.0 - 6.0 at%. The high-strength, high-ductility, wear-resistant high-entropy alloy provided by the present invention has a tensile yield strength of 1130 MPa, a tensile strength of 1380 MPa, and an elongation of 92%; the wear resistance at room temperature reaches 80% of that of M2 high-speed steel. Although this technology has greatly improved the strength and plastic toughness of the alloy, there are certain limitations in improving the wear resistance, and the heat treatment process of this technology is relatively complex, which is not conducive to high-efficiency large-scale industrial production.

[0007] There has been relatively little research on the preparation process of bulk high-entropy alloys, and high-entropy alloy coatings are widely used. For example, in "A Wear-Resistant High-Entropy Alloy Coating and Its Preparation Method and Application" (CN114990409A), the FeCrMnVAlx high-entropy alloy coating obtained by this technology has a lower friction coefficient and wear rate relative to the 1Cr13 martensitic stainless steel substrate. However, this high-entropy alloy coating is only applicable to low-load wear conditions of 4 - 8 N, and it is prone to delamination wear and surface failure under higher loads, with poor practicality.

[0008] Therefore, in order to simultaneously consider improving the hardness and wear resistance of high-entropy alloys and controlling the economic cost to ensure large-scale production, it is urgent to develop a new type of high-entropy alloy with different components and ratios. Summary of the Invention

[0009] To solve the deficiencies of the existing technology, the present invention provides a bulk high-entropy alloy with high wear resistance, its preparation method and application.

[0010] The technical solution provided by the present invention is as follows:

[0011] A bulk high-entropy alloy with high wear resistance, its chemical composition and corresponding mass percentages are: Ti: 10.5 - 12.5 wt.%, B: 0.5 - 1.5 wt.%, Cr: 21.5 - 23.5 wt.%, Ni: 38 - 40 wt.%, Al: 0 - 12.5 wt.%, and the rest is Fe and some inevitable impurities. At the same time, it is necessary to ensure that 10 ≤ Ti + B ≤ 15 (wt.%), 55 ≤ Cr + Ni ≤ 65 (wt.%), 0.5 ≤ Fe / Ti ≤ 2.5 (mass percentage ratio), and ensure that the total mass percentage of each component is 100%. The purity of all element raw materials involved shall not be less than 99.99%.

[0012] In the above technical solution:

[0013] A base high-entropy alloy system is established with five base components of Fe, Ti, B, Cr, and Ni. The advantages of this alloy system itself are: it has relatively excellent high hardness and wear resistance, while maintaining the characteristic of low cost and can be used for large-scale production.

[0014] Furthermore, taking Al as the optimized component, the aluminum element itself has an FCC structure, but at the same time it is an element that promotes the formation of the BCC phase in this high-entropy alloy system. Adding an appropriate amount of aluminum element makes the proportion of the BCC phase structure in the alloy system larger, improving the overall strength, hardness, and wear resistance of the alloy. The aluminum element has an obvious regulating effect on the performance of the duplex high-entropy alloy, promoting the formation of a duplex structure tissue inside the alloy with better performance than the single-phase structure. Aluminum belongs to light metal elements, with an atomic radius of 0.143 nm. Adding aluminum can distort the original lattice structure, reduce the free energy of the system, and play a role in solid solution strengthening. At the same time, aluminum can also make a dense oxide film form on the surface of the alloy, improving the high-temperature oxidation resistance and wear resistance of the alloy.

[0015] The high-entropy alloy prepared by the present invention has the characteristics of uniform composition distribution, high stability, high hardness, and excellent wear resistance. Compared with the traditional wear-resistant material NM500, its wear resistance is increased by 3 to 4 times, and the hardness can reach 900 - 1100 HV.

[0016] Specifically, the total molar percentage of the base components is 80 - 90%, and the molar percentage of the optimized component is 10 - 20%.

[0017] The present invention also provides a preparation method for a high-wear-resistant bulk high-entropy alloy, which at least includes the following steps: weighing according to the chemical composition and content of the high-wear-resistant bulk high-entropy alloy, melting with a vacuum arc melting furnace, then shaping in a mold, and performing a heat treatment for solutionizing on the obtained high-entropy alloy casting, thus obtaining the high-wear-resistant bulk high-entropy alloy.

[0018] The conditions for melting with the vacuum arc melting furnace are as follows:

[0019] The furnace is evacuated to (2 - 10)×10 -3 Pa, and the materials are discharged from bottom to top in the order of Al, Ni, Fe, Ti, Cr, and B;

[0020] The melting current is 200 - 500 A, the melting time is 40 - 200 min, and the melting is repeated at least 3 times.

[0021] The conditions for the heat treatment for solutionizing are as follows: performing solutionizing treatment in a high-temperature oxidation furnace at 600 - 1500 °C for 60 - 180 min.

[0022] This preparation method may specifically include the following steps:

[0023] 1) Clean the raw materials required for the high-entropy alloy with absolute ethanol and dry them at 50°C, grind off the surface rust layer, and remove the surface oxide layer of the raw materials by pickling;

[0024] 2) In the pre-preparation stage, turn on the circulating water cooling equipment, and the system maintains a constant temperature of 20°C;

[0025] 3) Turn on the melting furnace equipment. After checking its normal operation, turn off the equipment and clean the melting furnace cavity;

[0026] 4) Evacuate the furnace to 2.5×10 -3 Pa, and discharge them from bottom to top in the order of Al, Ni, Fe, Ti, Cr, B. Turn on the melting furnace switch for melting. The melting current is 400A, the melting time is 10 min, and melt repeatedly 3 times;

[0027] 5) After melting is completed, place the as-cast alloy at room temperature for cooling;

[0028] 6) Use wire cutting to cut the high-entropy alloy ingot into small samples with a length, width and height of 3×2×3 cm;

[0029] 7) Ultrasonically clean the small samples: First, place the small samples in acetone solution for 15 min to remove oil stains and impurities on the metal surface; then place the materials in absolute ethanol and ultrasonically clean for 15 min. After cleaning, place them in a drying oven for drying at 50°C;

[0030] 8) Place the processed small samples in a high-temperature oxidation furnace at 800°C for solution treatment for 80 min, and then perform oil quenching treatment;

[0031] 9) Grind the solution-treated samples to 1000 - 1200#, and use polishing paste with a particle size of 2.5 μm to polish the samples until they are shiny. Drop 4% nitric acid alcohol on the alloy surface and stop corrosion when the metal surface turns slightly discolored. Re-clean the corrosion solution with alcohol and dry it according to the previous parameters;

[0032] 10) Conduct metallographic microscopic observation on the qualified small samples.

[0033] Compared with the prior art, the beneficial effects of the present invention are:

[0034] 1) High hardness: The hardness of the high-entropy alloy provided by the present invention can reach 900 - 1100 HV, which is greatly improved compared with the hardness of NM500 of 530 HV.

[0035] 2) High wear resistance: Compared with NM500, its wear resistance is improved by more than 3 times.

[0036] 3) Uniform composition, fine and dispersed metallographic structure, uniform distribution, and stable structure.

[0037] 4) The alloy is prepared by vacuum arc melting to prevent volatilization loss. The prepared alloy has small composition burn - loss, few impurities and high purity, and the composition of the prepared alloy is basically the same as the designed composition.

[0038] 5) The characteristics of elements themselves have a positive effect on improving the properties of the alloy:

[0039] Ti: Titanium is an element with a high melting point. During the process of combining with the alloy, due to its position in the middle transition region of the periodic table, it is easy to form an interstitial solid - solution structure with the alloy. Under the action of solid - solution strengthening, it can improve the comprehensive mechanical properties of the alloy to a certain extent. In addition, titanium has the effect of refining the grain structure of the alloy, and the formed fine and dense tissue structure has a positive effect on improving the strength and toughness of the alloy. During the wear process, titanium elements are easy to oxidize to form an oxide film, which plays a lubricating and protective role during friction, thus achieving the effect of reducing the wear rate of the alloy.

[0040] B: Boron can be used as a modifier in the alloy system, playing the roles of refining grains, reducing the melting point, reducing expansion, and improving the strength, hardness and wear resistance of the alloy. In addition, boron has a certain purification effect on the alloy melting process, which can greatly reduce the accumulation of impurity atoms at the grain boundaries, narrow the grain - boundary width and reduce the hindrance of grain boundaries to dislocations, thus improving the melting effect of the alloy.

[0041] Cr: Chromium is the main element for high - temperature oxidation resistance in common alloy systems. Due to its high melting - point property, it generates Cr2O3 or chromium - containing spinel structures during the wear - heating process, and forms a dense and continuous oxide layer, blocking the further contact between gas and the alloy matrix, and improving the high - temperature oxidation resistance of the material. In addition, chromium is a strong carbide - forming element, which can form a large number of carbides such as CrC6, effectively improving the wear resistance of the alloy. A higher chromium content can enhance the hardenability of the alloy, making the alloy not easy to crack in extreme working conditions such as rapid cooling and heating environments, and extending the service life. An excessive chromium content increases production costs. Therefore, the chromium content in this invention is 21.5 - 23.5 wt.%, ensuring that the prepared high - entropy alloy has good practicability in the working environment of alternating hot and cold, including excellent high - temperature oxidation resistance and good wear resistance. 23 C6 and other carbides, effectively improving the wear resistance of the alloy. A higher chromium content can enhance the hardenability of the alloy, making the alloy not easy to crack in extreme working conditions such as rapid cooling and heating environments, and extending the service life. An excessive chromium content increases production costs. Therefore, the chromium content in this invention is 21.5 - 23.5 wt.%, ensuring that the prepared high - entropy alloy has good practicability in the working environment of alternating hot and cold, including excellent high - temperature oxidation resistance and good wear resistance.

[0042] Ni: Nickel is a hard, ductile and ferromagnetic metal. It can be highly polished and is corrosion - resistant. Nickel belongs to siderophile elements and is easy to combine with iron elements in the alloy system to improve the hardness of the alloy. Nickel is insoluble in water and forms a dense oxide film on the surface in humid air at room temperature, which can prevent the base metal from further oxidation and improve the surface wear resistance of the alloy.

[0043] Al: The aluminum element itself has an FCC structure. However, it is an element that promotes the formation of the BCC phase within the high-entropy alloy system. Adding an appropriate amount of aluminum makes the proportion of the BCC phase structure in the alloy system larger, improving the overall strength, hardness, and wear resistance of the alloy. The aluminum element has an obvious regulatory effect on the performance of the duplex high-entropy alloy, promoting the formation of a duplex structure organization inside the alloy with better performance than the single-phase structure. Aluminum belongs to the light metal element, with an atomic radius of 0.143 nm. Adding aluminum can distort the original lattice structure, reduce the free energy of the system, and play a role in solid solution strengthening. At the same time, aluminum can also make a dense oxide film form on the surface of the alloy, improving the high-temperature oxidation resistance and wear resistance of the alloy.

[0044] In summary, through reasonable control of the ratios and contents of various elements, a high-wear-resistance bulk high-entropy alloy prepared by the present invention obtains a high-entropy alloy ingot with excellent hardness and wear resistance. The high-wear-resistance bulk high-entropy alloy prepared by the present invention is applicable to parts for reciprocating mechanical motion and cutting tools, etc. Brief Description of the Drawings

[0045] Figure 1 It is the SEM image of the high-entropy alloy after solution treatment in Example 1 at 1000 times magnification.

[0046] Figure 2 It is the SEM image of the high-entropy alloy after solution treatment in Example 2 at 1000 times magnification.

[0047] Figure 3 It is the XRD pattern of the high-entropy alloy after solution treatment in Examples 1 and 2. Detailed Embodiments

[0048] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0049] Example 1

[0050] Preparation of an aluminum-free high-wear-resistance bulk high-entropy alloy

[0051] The preparation method described in this example is as follows:

[0052] Using spherical metallic elements of Fe, Ti, B, Cr, Ni, and Al with a purity of not less than 99.99%, the ingredients are prepared according to the following mass percentages: 10.5 wt.% Ti, 0.5 wt.% B, 21.5 wt.% Cr, 38 wt.% Ni, 0 wt.% Al, and 29.5 wt.% Fe. Before ingredient preparation, the surfaces of the raw materials are polished with 600# - 1200# sandpaper to remove surface foreign matters and metal oxides. Subsequently, they are ultrasonically cleaned in water and alcohol. After cleaning, a drying treatment is carried out at 50 °C for 2 h, and the raw materials are reserved for use. A vacuum arc melting furnace is used for high-temperature melting. The reserved metal raw materials are taken out and, in the order of Ni, Fe, Ti, Cr, B, a quantitative amount of metal raw materials is sequentially placed into the water-cooled copper crucible of the arc melting furnace. First, it is evacuated. When the vacuum degree reaches below 2.5×10 -3 Pa, an inert gas is filled to -0.04 MPa for alloy melting. The starting arc current is 250 A, the melting current is 400 A, and the melting time is 60 min. After melting, it is rapidly water-cooled and then subjected to an inverted ingot. After repeated melting 3 times, a high-entropy alloy ingot with a uniform internal microstructure and high wear resistance is obtained. After melting, a high-entropy alloy material ingot is obtained by cooling in a water-cooled copper crucible. Subsequently, the cooled alloy ingot is placed in a high-temperature oxidation furnace at 800 °C for solution treatment for 80 min, and after completion, the alloy is subjected to oil quenching treatment.

[0053] The prepared specimens are subjected to a microhardness test experiment (using an HV-1000 Vickers hardness tester for microhardness testing). The hardness of the sample in Example 1 of the present invention can reach 786 HV1.

[0054] The prepared specimens are subjected to a sliding friction and wear experiment (a Bruker, UMT3, USA wear test prototype). The counter-material is selected as stainless steel. The load is 30 N, the working condition temperature is room temperature, the wear time is 30 min, and the alloy wear mode can be either rotational or reciprocating linear motion. The rotational speed is 200 r / min, and the reciprocating motion speed is 0.1 m / s. The wear resistance index (wear mass) of the high-entropy alloy material of the present invention is obtained, and the wear amount is reduced by 2.6 times compared with the traditional wear-resistant steel NM500.

[0055] Example 2

[0056] Preparation of an aluminum-containing high-wear-resistant bulk high-entropy alloy

[0057] The preparation method described in this example is as follows:

[0058] Using spherical metallic elements of Fe, Ti, B, Cr, Ni, and Al with a purity of not less than 99.99%, the ingredients are prepared according to the following mass percentages: 12.5 wt.% Ti, 1.5 wt.% B, 23.5 wt.% Cr, 40 wt.% Ni, 12.5 wt.% Al, and 10 wt.% Fe. Before batching, first use 600# - 1200# sandpaper to polish the surface of the raw materials to remove surface foreign matters and metal oxides. Subsequently, place them in water and alcohol for ultrasonic cleaning. After cleaning, perform a drying treatment at 50°C for 2 hours, and reserve the raw materials for use. Use a vacuum arc melting furnace for high-temperature melting. Take out the reserved metal raw materials and sequentially put the quantitative metal raw materials into the water-cooled copper crucible of the arc melting furnace in the order of Ni, Fe, Ti, Cr, B. First, evacuate the air. When the vacuum degree reaches below 2.5×10 -3 Pa, then fill it with inert gas to -0.04 MPa for alloy melting. The starting arc current is 250 A, the melting current is 400 A, and the melting time is 180 min. After melting, perform rapid water cooling and then flip the ingot. After repeated melting 3 times, a high-entropy alloy ingot with a uniform internal structure and high wear resistance is obtained. After melting, cool it in the water-cooled copper crucible to obtain a high-entropy alloy material ingot. Subsequently, place the cooled alloy ingot in a high-temperature oxidation furnace at 800°C for solution treatment for 80 min, and then perform oil quenching treatment on the alloy.

[0059] Perform a microhardness test experiment on the prepared specimen. The hardness of Example 2 of the present invention can reach 832 HV1.

[0060] Perform a sliding friction and wear experiment on the prepared specimen. Select stainless steel as the counter material, with a load of 30 N, a working condition temperature of room temperature, and a wear time of 30 min. The alloy can be worn by rotation or reciprocating linear motion. The rotation speed is 200 r / min, and the reciprocating motion speed is 0.1 m / s. Obtain the wear resistance index of the high-entropy alloy material of the present invention. Compared with the traditional wear-resistant steel NM500, the wear amount is reduced by 2.8 times.

[0061] Figure 1 This is a 1000-fold SEM image of the high-entropy alloy after solution treatment in Example 1. It can be seen from the figure that there are high contents of dendrites, which makes the high-entropy alloy have significantly improved hardness and wear resistance.

[0062] Figure 2 This is a 1000-fold SEM image of the high-entropy alloy after solution treatment in Example 2. It can be seen from the figure that as the Al content increases, the inter-dendrite structure and strip structure of the alloy increase significantly. Under the combined action of fine grain strengthening and solution strengthening, the alloy thus exhibits stronger hardness and wear resistance.

[0063] Figure 3XRD patterns of the high-entropy alloys after solution treatment in Examples 1-2. It can be seen that the alloy in Example 1 is mainly a single-phase FCC solid solution structure, and the alloy structure has good uniformity and stability. Example 2 is a FCC + BCC duplex solid solution structure. With the increase of the Al element content, a BCC-structured solid solution with higher hardness appears inside the alloy, which improves the overall hardness and wear resistance of the alloy to varying degrees.

[0064] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A bulk high-entropy alloy with high wear resistance, characterized in that Its chemical composition and corresponding mass percentages are as follows: Ti: 10.5 - 12.5 wt.%, B: 0.5 - 1.5 wt.%, Cr: 21.5 - 23.5 wt.%, Ni: 38 - 40 wt.%, Al: 0 - 12.5 wt.%, and the balance is Fe and some inevitable impurities. Among them, 10 ≤ Ti + B ≤ 15 (wt.%), 55 ≤ Cr + Ni ≤ 65 (wt.%), 0.5 ≤ Fe / Ti ≤ 2.5, the sum of the mass percentages of each component is 100%, and the total molar percentage of Fe, Ti, B, Cr, and Ni is 80 - 90%.

2. The high-wear-resistance bulk high-entropy alloy according to claim 1, characterized in that: The molar percentage of Al is 10 - 20%.

3. A method for preparing a high wear-resistant bulk high-entropy alloy according to any one of claims 1 to 2, characterized in that, It includes at least the following steps: Weigh the ingredients according to the chemical composition and content of the high wear-resistant bulk high-entropy alloy, melt them using a vacuum arc melting furnace, then place them in a mold for shaping, and perform a heat treatment for solutionizing on the obtained high-entropy alloy casting, thus obtaining the high wear-resistant bulk high-entropy alloy described above.

4. The preparation method of the high wear-resistant bulk high-entropy alloy according to claim 3, characterized in that, The conditions for melting using the vacuum arc melting furnace are as follows: The inside of the furnace is evacuated to (2~10)×10 -3 Pa, and discharged from bottom to top in the order of Al, Ni, Fe, Ti, Cr, and B; The melting current is 200 - 500 A, the melting time is 40 - 200 min, and it is melted repeatedly 3 - 5 times.

5. The preparation method of the high wear-resistant bulk high-entropy alloy according to claim 3, characterized in that, The conditions for the heat treatment for solutionizing are as follows: Solutionize in a high-temperature oxidation furnace at 600 - 1500 °C for 60 - 180 min.

6. Application of the high wear-resistant bulk high-entropy alloy according to any one of claims 1 to 2, characterized in that: It is used for preparing high wear-resistant cutting tools or dies.

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