High-strength high-entropy alloy and application thereof in metallurgical coating

Abstract

The invention discloses a high-strength high-entropy alloy and application thereof in a metallurgical coating. The high-strength high-entropy alloy is composed of the following elements in atomic percent: 4%-6% of Ti, 9%-12% of Co, 18%-23% of Nb, 28%-32% of Mn, 12%-15% of V and 18%-24% of Cr. The structure is a simple solid solution structure. When laser cladding is carried out, formed coating metal is a high-entropy alloy mainly comprising Ti-Fe-Nb-Ni-V-Cu, generation of brittle and hard intermetallic compounds can be inhibited in the coating, the tendency of cracking and stripping of the metallurgical coating is reduced, and the metallurgical coating has better strength, toughness and wear resistance and has high comprehensive mechanical properties.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of high-entropy alloy material laser additive technology, and particularly relates to a high-strength high-entropy alloy and application thereof in metallurgical coating. BACKGROUND

[0002] High-entropy alloy is a new type of alloy material obtained by introducing "chemical disorder" through multi-component mixing, and its main feature is no dominant element. In recent years, it has been found that high-entropy alloy still has high fracture toughness at low temperature, is stronger than traditional alloy materials in resisting high-temperature softening, and has a wider service temperature range between the ductile-brittle transition temperature and the alloy softening temperature, thereby showing the characteristics of wide temperature range service. At the same time, traditional alloys face many challenges in the fields requiring special properties such as corrosion resistance and high-temperature resistance, and the emergence of high-entropy alloy opens up a new method.

[0003] The coating of the alloy is divided into mechanical bonding coating and metallurgical bonding coating. The mechanical bonding coating is simple to prepare and is widely used in chemical industry, aerospace, marine equipment and other fields, but the adhesion of the mechanical bonding coating is poor, the bonding with the substrate cannot meet the use standard in special environment, and peeling, falling off and other situations easily occur during the service of the equipment, thereby causing serious corrosion of the substrate and affecting the service period. The metallurgical bonding coating has strong bonding with the substrate and is not prone to peeling and other defects, and has been widely used in recent years. The single alloy metallurgical bonding coating has played a great advantage in corrosion resistance, wear resistance and other aspects in some specific environments, and has made great progress in recent years, but its comprehensive performance is poor, and it cannot meet the working requirements in special working environments, and is prone to failure, thereby affecting the performance of the equipment.

[0004] Laser deposition technology includes laser cladding technology (LC), laser surface alloying technology (LSA) and laser surface remelting technology (LSR), which is a modern technology for surface modification by HEAs. Among them, the alloy deposited by laser cladding technology has better performance than traditional alloys.

[0005] Laser cladding, also known as laser coating or laser cladding, is a method of adding cladding material on the surface of the substrate, and using high-energy density laser beam to make it melt together with the thin layer on the surface of the substrate, so as to form a cladding layer on the surface of the substrate. The quality of laser products depends on the quality of the coating, and the quality of the coating depends on the cladding process and cladding powder. High-entropy alloy powder has become a hot spot in the research of cladding powder because it has some excellent properties that traditional alloys cannot match, such as high strength, high hardness, high wear and corrosion resistance, high thermal resistance, high electrical resistance, etc.

[0006] Compared with single metal, multi-principal element alloy can play the advantages of different metal elements, and has better comprehensive performance, and can have performance that single alloy cannot achieve in special environment. As a new type of multi-principal element alloy material, high-entropy alloy has higher mixing entropy, higher compatibility between each component, and can inhibit the generation of intermetallic compounds or intergranular solid solution caused by phase separation to a certain extent, and has the characteristics of high-entropy effect, lattice distortion effect, slow diffusion effect and "cocktail" effect. Compared with the single element metal cladding coating, the high-entropy alloy used as the cladding coating can easily form simple solid solution structures such as FCC, BCC and HCP during the cladding process, can inhibit the generation of brittle intermetallic compounds, and can reduce the tendency of corrosion and cracking of the surface metal, so that the coating has better strength, toughness and wear resistance.

[0007] Patent document CN109112530A discloses a kind of high-entropy alloy material for laser cladding, including Co, Cr, Al, W, Mn and Nb, and the molar ratio is 1:1:1:1:1:x, x=0.1~1.0;The purity of each component is greater than or equal to 99.9%.However, the high-entropy alloy coating prepared in the document has poor wear resistance of the oxidation film on the surface, and is easy to cause wear of the high-entropy alloy coating after damage.

[0008] Patent document CN110230056A discloses a kind of low-melting-point high-entropy alloy powder for magnesium-lithium alloy laser surface modification, which is composed of 1%~35% of Al, 1%~35% of Sn, 1%~35% of Cu, 1%~35% of Mn, 1%~5% of Mg, 0~10% of adjusting coating melting point material and 0~5% of rare earth oxide according to atomic percentage;High-entropy alloy coating is prepared on the surface of magnesium-lithium alloy by laser cladding.However, the high-entropy alloy metallurgical coating prepared in the document has low tensile strength, and is easy to produce cracks and other defects under stress, which affects the use of magnesium-lithium alloy. SUMMARY

[0009] The purpose of the present application is to provide a kind of high-strength high-entropy alloy and its application in metallurgical coating, to solve the problem of low tensile strength and poor wear resistance of Q235 steel in the prior art.

[0010] In order to achieve the above-mentioned purpose, the technical scheme of the present application is:

[0011] A kind of high-strength high-entropy alloy according to the present application, characterized by the following atomic percentage of elements: Ti is 4%~6%, Co is 9%~12%, Nb is 18%~23%, Mn is 28%~32%, V is 12%~15%, Cr is 18%~24%;The high-strength high-entropy alloy is a simple solid solution structure.

[0012] Preferably, the high-strength high-entropy alloy is composed of the following atomic percentage of elements: Ti is 4%, Co is 9%, Nb is 22%, Mn is 32%, V is 15%, and Cr is 18%; or, Ti is 5%, Co is 10%, Nb is 20%, Mn is 30%, V is 15%, and Cr is 20%; or, Ti is 6%, Co is 12%, Nb is 18%, Mn is 28%, V is 12%, and Cr is 24%.

[0013] The specific composition of the high-entropy alloy is mainly determined according to the solid solubility theory proposed by Hume-Rothery, and factors such as atomic radius difference, system mixing enthalpy, system mixing entropy, characteristic parameter and system Gibbs free energy are comprehensively considered when the solid solution of the multi-principal element alloy is formed. In order to improve the comprehensive mechanical properties of the high-performance metallurgical coating, the chemical composition of the weld metal needs to be in the content range of the principal elements forming the high-entropy alloy. According to the wear resistance and high strength characteristics that the expected coating should meet, the Ti-Co-Nb-Mn-V-Cr six-element system amorphous alloy is selected. In the composition of the high-entropy alloy, the main reasons for determining the composition and content of each element are as follows: ① Ti element can increase the lattice distortion, improve the strength and hardness. ② Co element can improve the plasticity and wear resistance, can be enriched in the interdendritic of the alloy to play the role of adhesive, reduce the brittleness, and prevent the coating from cold cracking. ③ Nb element can greatly enhance the corrosion resistance of the high-entropy alloy. ④ Mn element can reduce the oxidation resistance, promote the formation of the surface oxide film of the high-entropy alloy coating, improve the corrosion resistance of the joint, and reduce the cost. ⑤ Cr element can promote the formation of BCC solid solution and improve the comprehensive mechanical properties. ⑥ V element can refine the alloy organization and improve the strength and hardness.

[0014] The preparation method of the high-strength high-entropy alloy provided by the application has the characteristics that it comprises the following steps: S1, the elemental metal powders are weighed according to the atomic percentage, mixed uniformly, and compacted into a rough blank; S2, the rough blank is placed in a crucible, and under the protection of argon, an electric current is passed to generate an arc for melting to obtain a high-entropy master alloy; S3, the high-entropy master alloy is remelted in a vacuum atmosphere and cast into a mold to obtain a high-entropy alloy plate.

[0015] Further, the high-entropy alloy plate is cleaned, dried, and cut into a thin sheet to obtain a high-entropy alloy thin sheet.

[0016] Further, the cleaning is that the high-entropy alloy plate is placed in alcohol for ultrasonic cleaning to remove surface impurities.

[0017] The high-entropy alloy thin sheet provided by the application is applied to the surface laser cladding coating of Q235 steel.

[0018] Further, the high-entropy alloy flake is finely ground to an optimal size by means of sandpaper or the like, and is then placed in alcohol for ultrasonic cleaning, and is dried and used for laser cladding.

[0019] A preparation method of a laser cladding coating, characterized by comprising the following steps: D1, processing the surface of a Q235 steel substrate to meet the requirements of laser cladding; D2, laser cladding of a high-entropy alloy coating: preheating the substrate to 140-160 DEG C, using the high-entropy alloy flake as cladding material to perform laser cladding on the Q235 steel substrate to form a metallurgical coating.

[0020] The process parameters of the laser cladding are as follows: current is 135-145 A, laser power is 3200-3700 W, defocusing amount is +2 to +5 mm, light wire distance is 2-4 mm, additive speed is 7-9 mm / s, and protective gas flow is 18-23 L / min.

[0021] Compared with the prior art, the present application has the following beneficial effects:

[0022] 1. The mixing enthalpy of the high-entropy alloy is close to zero, which can avoid phase separation and composition segregation, reduce the bonding force between elements, and enable the elements to be randomly distributed in the crystal lattice, thereby obtaining a more stable disordered solid solution. The atomic radius variance between the elements is small, and the crystal lattice is not easy to distort, and the high-entropy alloy has excellent strength, toughness and wear resistance, and can obtain a high-performance cladding coating.

[0023] 2. The high-entropy alloy prepared by melting is a simple solid solution structure. When laser cladding is performed, the formed coating metal is mainly a Ti-Fe-Nb-Ni-V-Cu high-entropy alloy, the generation of brittle intermetallic compounds in the coating can be inhibited, the tendency of the metallurgical coating to crack and peel off is reduced, the metallurgical coating has more excellent strength, toughness and wear resistance, and has strong comprehensive mechanical properties.

[0024] 3. The high-entropy alloy is used for laser cladding, the heat input is small, the influence of excessive heat input on the substrate is avoided, and the metallurgical bonding enables the coating and the substrate to have strong bonding force. DETAILED DESCRIPTION

[0025] Figure 1 It is a schematic view of the thickness direction section of the micro-tension standard sample.

[0026] Figure 2 It is a schematic view of the plane of the micro-tension standard sample.

[0027] Figure 3 It is a micro-tension stress-strain curve of the metallurgical coating of Example 1.

[0028] Figure 4 The friction coefficient of the metallurgical coating of Example 1.

[0029] Figure 5 The micro-tensile stress-strain curve of the metallurgical coating of Example 2.

[0030] Figure 6 The friction coefficient of the metallurgical coating of Example 2.

[0031] Figure 7 The micro-tensile stress-strain curve of the metallurgical coating of Example 3.

[0032] Figure 8 The friction coefficient of the metallurgical coating of Example 3. DETAILED DESCRIPTION

[0033] A person of ordinary skill in the art should recognize that the embodiments are only used to illustrate the present application, and are not used as a limitation to the present application, and as long as the embodiments are changed and modified within the scope of the present application, the changes and modifications are within the scope of the present application.

[0034] Example 1

[0035] A high-strength high-entropy alloy, the atomic percentage composition is as follows: Ti is 4%, Co is 9%, Nb is 22%, Mn is 32%, V is 15%, Cr is 18%;

[0036] A method for preparing a high-strength high-entropy alloy, comprising the following steps:

[0037] S1, convert the atomic percentage to the weight percentage, and weigh the elemental metal powder according to the weight percentage, mix uniformly, and compact into a rough blank;

[0038] S2, vacuum the hearth and fill it with argon to ensure that the impurity gas in the hearth is removed; place the rough blank in the crucible, and under the protection of argon, pass current to arc to carry out smelting, and obtain a high-entropy master alloy;

[0039] S3, re-melt the high-entropy master alloy in a vacuum atmosphere, and use the principle of pressure difference to suction cast the molten alloy into a mold to obtain Ti4Co9Nb 22 Mn 32 V 15 Cr 18 The high-entropy alloy plate is a simple solid solution structure.

[0040] S4, place the high-entropy alloy plate into alcohol for ultrasonic cleaning to remove impurities on the surface of the high-entropy alloy, and clean and dry; use an electric spark cutting machine to cut the high-entropy alloy plate into a high-entropy alloy sheet with a size of 50mmx5mmx1mm, which is used as a cladding material for laser cladding coating.

[0041] A method for preparing a laser cladding coating, comprising the following steps:

[0042] D1, machining the surface of the Q235 steel substrate to meet the requirements of laser cladding: removing the rust layer and oxide film on the surface of the groove to prevent the formation of pores and cracks during laser cladding; using sandpaper to finely grind the surface of the substrate to the optimal size and smoothness, and wiping the surface with alcohol and acetone and drying to remove oil and impurities on the surface;

[0043] D2, laser cladding of high-entropy alloy coating: preheat the Q235 steel substrate to 150°C, use the above-mentioned high-entropy alloy sheet as the cladding material, and laser cladding the Q235 steel substrate. The laser cladding process parameters are: current 140A, laser power 3500W, defocusing amount +4mm, light wire distance 3mm, additive speed 8mm / s, and protective gas flow 20L / min; form a metallurgical coating, the high-entropy alloy sheet is well fused, and there is no crack in the laser cladding area.

[0044] The obtained high-entropy alloy coating is subjected to uniaxial tensile test, the micro-tensile standard sample is as shown in Figures 1-2 , the size is listed in Table 1, and the stress-strain curve is as shown in Figure 3 , the tensile strength of the HEA coating is about 479.662MPa, and the highest yield strength is 383.730Mpa according to the nominal yield strength of 0.2% plastic elongation instead of the yield strength value of the alloy.

[0045] Table 1 Size specification of micro-tensile standard sample

[0046] a b c d e f g α 2 mm 10 mm 39 mm 64 mm 1.5 mm R2 mm R16 mm 20°

[0047] The high-entropy alloy coating is subjected to friction and wear test, and the results are as shown in Figure 4 , the friction frequency is 2Hz, the friction width is 5mm, the initial load is 5N, and the test duration is 30min, and the average friction coefficient is 0.376.

[0048] Example 2

[0049] A high-strength high-entropy alloy, the atomic percentage composition is as follows: Ti is 5%, Co is 10%, Nb is 20%, Mn is 30%, V is 15%, and Cr is 20%;

[0050] According to the method of Example 1, Ti5Co 10 Nb 20 Mn 30 V 15 Cr 20 high-entropy alloy is obtained, and the high-entropy alloy sheet is further processed into a 50mm x 5mm x 1mm high-entropy alloy sheet, which is used as the cladding material for laser cladding coating.

[0051] The laser cladding coating was prepared according to the method of Example 1, the high-entropy alloy sheet was well fused, and the laser cladding area had no cracks.

[0052] The uniaxial tensile test was performed on the high-entropy alloy coating, and the stress-strain curve is shown in Figure 5 The tensile strength of the HEA coating was about 548.053 MPa, and the highest yield strength was 438.442 MPa according to the nominal yield strength of 0.2% plastic elongation instead of the yield strength value of the alloy.

[0053] The friction and wear test was performed on the high-entropy alloy coating, and the results are shown in Figure 6 The average friction coefficient was 0.361, the friction frequency was 2 Hz, the friction width was 5 mm, the initial load was 5 N, and the test duration was 30 min.

[0054] Example 3

[0055] A high-strength high-entropy alloy, the atomic percentage composition is as follows: Ti is 6%, Co is 12%, Nb is 18%, Mn is 28%, V is 12%, and Cr is 24%;

[0056] According to the method of Example 1, Ti6Co 12 Nb 18 Mn 28 V 12 Cr 24 high-entropy alloy was obtained, and the high-entropy alloy sheet with a size of 50 mm x 5 mm x 1 mm was further processed as the cladding material for the laser cladding coating.

[0057] The laser cladding coating was prepared according to the method of Example 1, the high-entropy alloy sheet was well fused, and the laser cladding area had no cracks.

[0058] The uniaxial tensile test was performed on the high-entropy alloy coating, and the stress-strain curve is shown in Figure 7 The tensile strength of the HEA coating was about 450.682 MPa, and the highest yield strength was 360.546 MPa according to the nominal yield strength of 0.2% plastic elongation instead of the yield strength value of the alloy.

[0059] The friction and wear test was performed on the high-entropy alloy coating, and the results are shown in Figure 8 The average friction coefficient was 0.501, the friction frequency was 2 Hz, the friction width was 5 mm, the initial load was 5 N, and the test duration was 30 min.

[0060] In summary, the high-entropy alloy obtained by the application has excellent strength and wear resistance, and can obtain a high-performance laser cladding coating, wherein the high-entropy alloy coating obtained by example 2 has strong tensile strength and wear resistance, and has good comprehensive performance. The formation of the high-entropy alloy cladding coating can effectively inhibit the generation of intermetallic compounds, and the performance of the cladding coating is significantly improved.

Claims

1. A high-strength, high-entropy alloy, characterized in that, It is composed of the following elements in atomic percentage: Ti 4%–6%, Co 9%–12%, Nb 18%–23%, Mn 28%–32%, V 12%–15%, and Cr 18%–24%; the high-strength high-entropy alloy has a simple solid solution structure.

2. The high-strength, high-entropy alloy according to claim 1, characterized in that, It is composed of the following elements in atomic percentage: 4% Ti, 9% Co, 22% Nb, 32% Mn, 15% V, and 18% Cr; or 5% Ti, 10% Co, 20% Nb, 30% Mn, 15% V, and 20% Cr; or 6% Ti, 12% Co, 18% Nb, 28% Mn, 12% V, and 24% Cr.

3. The high-strength, high-entropy alloy according to claim 1, characterized in that, Laser cladding coating applied to the surface of Q235 steel.

4. The method for preparing the high-strength, high-entropy alloy according to claim 1 or 2, characterized in that, The process includes the following steps: S1, weighing the elemental metal powder according to atomic percentage, mixing it evenly, and compacting it into a rough blank; S2, placing the rough blank in a crucible, melting it under argon protection by passing an electric current to ignite an arc, and obtaining a high-entropy master alloy; S3, remelting the high-entropy master alloy under a vacuum atmosphere and casting it into a mold to obtain a high-entropy alloy plate.

5. The method for preparing the high-strength, high-entropy alloy according to claim 4, characterized in that, The high-entropy alloy sheet is cleaned, dried, and cut into thin slices to obtain high-entropy alloy thin slices.

6. The method for preparing the high-strength, high-entropy alloy according to claim 5, characterized in that, The cleaning process involves immersing the high-entropy alloy plate in alcohol for ultrasonic cleaning.

7. The method for preparing the high-strength, high-entropy alloy according to claim 5, characterized in that, The high-entropy alloy sheet is finely ground to the optimal size, then ultrasonically cleaned in alcohol, and dried before being used for laser cladding.

8. A method for preparing a laser cladding coating, characterized in that, Includes the following steps: D1. Process the surface of the Q235 steel substrate to meet the requirements of laser cladding; D2. Laser cladding of high-entropy alloy coating: The substrate is preheated to 140-160°C, and the high-entropy alloy sheet as described in claim 5 or 7 is used as the cladding material to perform laser cladding on the Q235 steel substrate to form a metallurgical coating.

9. The method for preparing a laser cladding coating according to claim 8, characterized in that, The laser cladding process parameters are as follows: current of 135-145A, laser power of 3200-3700W, defocusing amount of +2-+5mm, filament spacing of 2-4mm, additive speed of 7-9mm / s, and protective gas flow rate of 18-23L / min.

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