Method for regulating and controlling phase change and defect repair of FeCoCrNiAlTi high-entropy alloy coating through carbon

Abstract

The invention belongs to the technical field of preparation of high-entropy alloy coatings, and particularly discloses a method for phase change and defect repair of a FeCoCrNiAlTi high-entropy alloy coating through carbon regulation and control, and the method comprises the following steps: S1, preparing alloy powder; and S2, a laser cladding process is adopted, and the FeCoCrNiAlTi high-entropy alloy coating is regulated and controlled through carbon for phase change induction and defect repair. According to the method for regulating and controlling the phase change and defect repair of the FeCoCrNiAlTi high-entropy alloy coating through carbon, the phase change behavior of the FeCoCrNi-based high-entropy alloy coating is regulated and controlled through cooperation of carbon elements and Al and Ti elements, and the method for synchronously repairing point defects and body defects is achieved, so that the comprehensive mechanical property of the coating is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of high entropy alloy coating preparation, and particularly relates to a method for carbon-regulated phase transformation and defect repair of a FeCoCrNiAlTi high entropy alloy coating. Background Art

[0002] High-entropy alloys (HEAs), composed of five or more main elements with nearly equal atomic fractions, have been a hot topic in international metallurgical research over the past decade. These alloys have attracted much attention due to their unique ability to achieve a balance between hardness, wear resistance and ductility, properties that are usually mutually exclusive in traditional materials. HEAs can be prepared by various methods, including induction melting, laser, sputtering, mechanical alloying and vacuum arc melting. Among them, HEAs prepared by laser cladding through a rapid heating and cooling process exhibit excellent mechanical properties, good fatigue resistance, oxidation resistance and corrosion resistance, as well as unique electrical and magnetic properties. By utilizing the high entropy effect, cocktail effect, hysteresis diffusion characteristics and lattice distortion effects of multi-principal element alloys, a leap forward in the performance of HEAs can be achieved.

[0003] However, high-entropy alloys (HEAs) are prone to forming brittle intermetallic compounds during solidification and are often characterized by numerous point and bulk defects, leading to a significant strength-ductility trade-off. While existing technologies, such as doping with elements like Al and Ti, can promote the formation of strengthening phases, they struggle to effectively address the performance degradation caused by lattice defects.

[0004] Carbon (C) is a common impurity element, and the interaction between carbon (C) and metals plays a wide range of roles in materials science. Above the solubility limit of C, carbides are easily formed. This is very useful for improving the strength and hardness of metals. The impurity C element has a significant impact on the mechanical properties of the material. A small amount of C (such as 30 wt ppm) can increase the yield strength of NiAl alloy by 30%. C causes NiAl alloys to reduce brittleness and increase ductility. At the same time, carbon can fill vacancies and interstitial positions in high-entropy alloys, stabilize the crystal structure, and reduce the number of point defects.

[0005] Therefore, a method for carbon-regulated phase transformation and defect repair of FeCoCrNiAlTi high-entropy alloy coatings needs to be developed in this field to effectively solve the above problems. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for carbon-regulated phase transformation and defect repair of FeCoCrNiAlTi high-entropy alloy coatings. This method regulates the phase transformation behavior of FeCoCrNi-based high-entropy alloy coatings by carbon elements in collaboration with Al and Ti elements, and realizes a method for synchronously repairing point defects and body defects, thereby improving the comprehensive mechanical properties of the coating.

[0007] To achieve the above objectives, the present invention provides a method for carbon-regulated phase transformation and defect repair of FeCoCrNiAlTi high-entropy alloy coatings, comprising the following steps:

[0008] Step S1, preparing alloy powder;

[0009] Step S2: using a laser cladding process, carbon-controlled FeCoCrNiAlTi high-entropy alloy coating to induce phase change and repair defects.

[0010] Preferably, step S1 is specifically as follows:

[0011] Step S11, melting the metal raw material into a uniform melt in a vacuum / controlled atmosphere to obtain molten metal;

[0012] Among them, the metal raw materials include Fe, Co, Cr, Ni, Al, and Ti metals;

[0013] Step S12: When the molten metal flows out of the guide nozzle, it interacts with the high-pressure inert gas, breaking it into micron-sized droplets and rapidly solidifying them to form spherical particles;

[0014] Step S13: obtaining alloy powder with controllable particle size through screening.

[0015] Preferably, in step S11, the purity of Fe, Co, Cr, Ni, Al, and Ti metals is ≥99.9wt%;

[0016] In step S12, the size of the micron-sized droplets is 45-105 μm.

[0017] Preferably, step S2 specifically comprises: in-situ synthesizing a FeCoCrNiAlTi high entropy alloy coating on the surface of a low-carbon steel substrate based on a four-coaxial powder feeding system constructed with a fiber laser and a KUKA six-axis robot.

[0018] Preferably, in step S2, the specific parameters of the laser cladding process are: laser power of 2000 W, spot diameter of 3 mm, scanning speed of 10 mm / s, linear energy density of 200 J / mm, powder feeding rate of 16.8 g / min, and carrier gas flow rate of 1.2 L / min; wherein, 250°C substrate preheating and high-purity Ar atmosphere protection are set, and the O2 concentration is ≤50 ppm.

[0019] Preferably, in the carbon-regulated FeCoCrNiAlTi high-entropy alloy coating, the atomic ratio of metals is Fe:Co:Cr:Ni:Al:Ti=Bal.:22.09:23.98:24.63:2.30:4.31, and the content of C element is ≤0.5wt%.

[0020] The present invention adopts the above-mentioned method of carbon-regulated phase transformation and defect repair of FeCoCrNiAlTi high-entropy alloy coating, and the beneficial effects are as follows:

[0021] (1) The present invention aims to achieve the two important goals of achieving a good combination of strength and ductility and repairing internal defects in high-entropy alloys. Based on the Al-Ti synergistic effect and the significant influence of the introduction of C element impurities on material properties: in the FeCoCrNiAlTi high-entropy alloy system, C atoms spontaneously incorporate into AlNi2 and TiAlNi2 intermetallic compounds to achieve a dual strengthening mechanism. The bonding of C with Al / Ni effectively repairs lattice point defects (such as vacancies and antisite defects) and improves the order of atomic arrangement; secondly, the strong affinity between C and Ti drives the in-situ precipitation of nano-TiC phase, forming a dispersion-strengthened structure, repairing bulk defects and significantly reducing the critical stress required for dislocation movement, thereby improving the mechanical properties of the material.

[0022] (2) The present invention spontaneously incorporates impure C atoms into AlNi2 and TiAlNi2 intermetallic compounds, and achieves a stable state at the Ni substitution position of AlNi2 and the Al-Ni-Ti mixed coordination octahedral interstitial position of TiAlNi2.

[0023] (3) The formation of C-Al bonds in the present invention will weaken the Ni-Al bonds in the AlNi2 intermetallic compound, which will have a negative impact on the mechanical properties of AlNi2; while when C combines with Ti to form C-Ti bonds, it can effectively reduce the breakage of Ni-Al bonds in TiAlNi2. At the same time, C combines with Ti to form TiC, which enhances the hardness and wear resistance of the alloy.

[0024] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The XRD patterns of an embodiment of a method for carbon-regulated phase transformation and defect repair of a FeCoCrNiAlTi high-entropy alloy coating and a comparative example alloy coating of the present invention are shown; wherein (a) is a FeCoCrNiAl alloy coating, and (b) is a FeCoCrNiAlTi alloy coating;

[0026] Figure 2 This is a tribological behavior diagram of an embodiment of a method for carbon-regulated phase transformation and defect repair of a FeCoCrNiAlTi high-entropy alloy coating of the present invention and a comparative alloy coating; wherein (a) is a FeCoCrNiAl alloy coating, and (b) is a FeCoCrNiAlTi alloy coating. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0028] Unless otherwise defined, technical or scientific terms used in the present invention shall have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0029] Example

[0030] A method for carbon-regulated phase transformation and defect repair of a FeCoCrNiAlTi high-entropy alloy coating, comprising the following steps:

[0031] Step S1: preparing high-purity alloy powder by vacuum induction melting (VIM) combined with inert gas atomization technology.

[0032] Step S11: Smelting Fe, Co, Cr, Ni, Al, and Ti metal raw materials into a uniform melt in a controllable atmosphere to obtain molten metal.

[0033] The purity of Fe, Co, Cr, Ni, Al and Ti metals is ≥99.9wt%.

[0034] Step S12: When the molten metal flows out through the guide nozzle, it interacts with the high-pressure inert gas and breaks into micron-sized droplets with a size of 45-105 μm and quickly solidifies to form spherical particles.

[0035] Step S13: obtaining alloy powder with controllable particle size through screening.

[0036] Step S2: using a laser cladding process, carbon-controlled FeCoCrNiAlTi high-entropy alloy coating to induce phase change and repair defects.

[0037] A FeCoCrNiAlTi high-entropy alloy coating was in situ synthesized on the surface of a mild steel substrate using a four-coaxial powder feeding system constructed using an IPG YLS-4000 fiber laser (wavelength 1070nm) and a KUKA six-axis robot.

[0038] The laser cladding process parameters are: 2000W laser power, 3mm spot diameter, 10mm / s scanning speed, 200J / mm linear energy density, 16.8g / min powder feed rate, and 1.2L / min carrier gas flow rate. The process also includes 250°C substrate preheating, high-purity Ar atmosphere protection, and an O2 concentration of ≤50ppm.

[0039] Among them, in the carbon-regulated FeCoCrNiAlTi high-entropy alloy coating, the atomic ratio of metals is Fe:Co:Cr:Ni:Al:Ti=Bal.:22.09:23.98:24.63:2.30:4.31, and the content of C element is ≤0.5wt%.

[0040] Comparative Example

[0041] A method for carbon-regulated phase transformation and defect repair of a FeCoCrNiAl high-entropy alloy coating, comprising the following steps:

[0042] Step S1: preparing high-purity alloy powder by vacuum induction melting (VIM) combined with inert gas atomization technology.

[0043] Step S11: Smelting Fe, Co, Cr, Ni, and Al metal raw materials into a uniform melt in a controllable atmosphere to obtain molten metal.

[0044] The purity of Fe, Co, Cr, Ni and Al metals is ≥99.9wt%.

[0045] Step S12: When the molten metal flows out through the guide nozzle, it interacts with the high-pressure inert gas and breaks into micron-sized droplets with a size of 45-105 μm and quickly solidifies to form spherical particles.

[0046] Step S13: obtaining alloy powder with controllable particle size through screening.

[0047] Step S2: using a laser cladding process, carbon-controlled FeCoCrNiAl high-entropy alloy coating is used to induce phase change and repair defects.

[0048] A FeCoCrNiAl high-entropy alloy coating was in situ synthesized on the surface of a mild steel substrate using a four-coaxial powder feeding system constructed using an IPG YLS-4000 fiber laser (wavelength 1070 nm) and a KUKA six-axis robot.

[0049] The laser cladding process parameters are: 2000W laser power, 3mm spot diameter, 10mm / s scanning speed, 200J / mm linear energy density, 16.8g / min powder feed rate, and 1.2L / min carrier gas flow rate. The process also includes 250°C substrate preheating, high-purity Ar atmosphere protection, and an O2 concentration of ≤50ppm.

[0050] Among them, in the carbon-regulated FeCoCrNiAl high-entropy alloy coating, the atomic ratio of metals is Fe:Co:Cr:Ni:Al=Bal.:23.14:23.62:26.59:2.29, and the content of C element is ≤0.5wt%.

[0051] The carbon-regulated FeCoCrNiAlTi high-entropy alloy coating in the embodiment and the carbon-regulated FeCoCrNiAl high-entropy alloy coating in the comparative example were subjected to performance tests:

[0052] (1) Microstructure and chemical analysis.

[0053] (1) X-ray diffraction phase structure analysis.

[0054] Cu target Kα irradiation The crystal structures of the two high entropy alloy coatings were characterized by X-ray diffractometer. Figure 1 As shown in Figure 3, the diffraction pattern of the FeCoCrNiAl alloy coating shows characteristic diffraction peaks of a typical face-centered cubic (FCC) structure at 43.3°, 50.4°, and 74.1° (corresponding to the (111), (200), and (220) crystal planes, respectively), indicating that the system forms a single-phase FCC solid solution structure.

[0055] Characteristic peaks of the body-centered cubic (BCC) structure (corresponding to the (110), (200), and (211) crystal planes) were observed in the FeCoCrNiAlTi alloy coating at 44.7°, 65.1°, and 82.3°, confirming that its main phase is a BCC solid solution. Additional diffraction peaks that fully match those of the TiNi2Al intermetallic compound (PDF#04-001-6558) appear at 43.6°, 63.3°, and 80.0°, indicating that the alloy system forms a TiNi2Al second-phase reinforcement structure through the synergistic action of the elements. This dual-phase microstructure helps improve the mechanical properties and high-temperature stability of the coating.

[0056] (2) By selecting six key thermodynamic parameters that determine phase stability, the stable solid solution phase equilibrium conditions of the alloy were analyzed.

[0057] The six key thermodynamic parameters include ΔSmix, ΔHmix, atomic radius mismatch (δ), electronegativity difference (Δχ), valence electron concentration (VEC), and equilibrium parameter (Ω), specifically:

[0058]

[0059]

[0060] Where, is the mixing enthalpy of binary alloys i and j, ΔS mix is the mixing entropy of binary alloys i and j, c i 、c j is the content of high entropy alloy components, χ i The Pauling electronegativity of the i-th element in the high entropy alloy component, is the Pauling charge of the ith element in the HEAs, (VEC) i The valence electron concentration of the i-th element in the high entropy alloy component, r i is the atomic radius of the constituent element, is the average atomic radius, R is the molar gas constant 8.314 JK -1 mol -1 .

[0061] The carbon-regulated FeCoCrNiAlTi high-entropy alloy coating in the embodiment and the carbon-regulated FeCoCrNiAl high-entropy alloy coating in the comparative example were calculated using formulas (1) to (6), as shown in Table 1. The results are:

[0062] Table 1 Thermodynamic parameters of two HEAs coatings

[0063] coating <![CDATA[ΔS mix ]]> <![CDATA[ΔH mix ]]> δ Δχ VEC <![CDATA[T m (K)]]> Ω FeCoCrNiAl 12.157 -5.01 2.793％ 0.100 8.176 1573.038 4.272 FeCoCrNiAlTi 13.135 -8.32 3.027％ 0.114 7.946 1581.960 2.776

[0064] ΔS of FeCoCrNiAlTi mix =13.135R, which is 8% higher than the 12.157R of FeCoCrNiAl. It can be seen that the mixing entropy of FeCoCrNiAlTi is higher, indicating that it is more stable at high temperature and has stronger resistance to phase separation. mix =-8.32kJ / mol, which is 66% lower than that of FeCoCrNiAl alloy. The more negative enthalpy value indicates that a stronger metallic bond network is formed between atoms. Combined with first-principles calculations, it is found that the addition of Ti increases the metallic bond strength, indicating that its formation process is more stable and the interaction between elements is stronger, which improves its stability. The larger atomic radius difference may lead to higher lattice distortion, thereby enhancing the hardness and strength of the alloy. The δ of FeCoCrNiAlTi is 3.027%, which is 8.3% higher than that of the baseline alloy, and it has higher hardness and strength. The electronegativity difference (Δχ) reflects the difference in electron cloud attraction ability between elements in the alloy. The Δχ of FeCoCrNiAlTi is 0.114, which is 14% higher than that of FeCoCrNiAl alloy. The larger electronegativity difference promotes charge transfer and forms a stronger ionic-covalent mixed bond. The larger electronegativity difference leads to stronger chemical bonding, thereby improving the hardness and strength of the alloy. The larger electronegativity difference of FeCoCrNiAlTi indicates that its chemical bonding is stronger, and it has higher hardness and strength. Valence electron concentration (VEC) is one of the key parameters affecting alloy properties. Lower VEC is generally associated with higher hardness and brittleness, while higher VEC may be associated with better toughness and ductility. FeCoCrNiAlTi has a slightly lower VEC, making it harder.

[0065] Therefore, the coordinated optimization of the above parameters enables the FeCoCrNiAlTi alloy coating to significantly surpass the excellent performance of the FeCoCrNiAl alloy coating in terms of mechanical properties and electronic structure characteristics.

[0066] (2) Hardness test.

[0067] Experimental Details: Surface hardness of the samples was characterized using an HV-1000 Vickers hardness tester. Test parameters were set as follows: a diamond indenter loading force of 500 gf (4.903 N) and a dwell time of 10 seconds. To eliminate the influence of local microstructural differences, a matrix sampling method was used, uniformly selecting 5×5 points on the coating surface for a total of 25 test points for indentation testing.

[0068] According to ISO 6507-1, the diagonal length of each point is obtained through an automatic measurement system. The Vickers hardness value (HV) is calculated after geometric correction. Finally, the arithmetic mean is taken as the effective hardness data after eliminating outliers (maximum / minimum values).

[0069] The dry friction behavior was evaluated using an Rtec MFT-5000 multifunctional friction and wear tester equipped with a ball-plane contact module. The experimental parameters were set as follows: 6mm diameter silicon nitride (Si3N4) ceramic ball grinding pair, normal load 10N, sliding stroke 6mm, reciprocating frequency 2Hz, and total test time 30min. To quantify the wear resistance of the coating, a non-contact three-dimensional profiler (accuracy 0.1μm) was used to scan the wear scar profile, and the wear volume was calculated based on the ISO 25262 standard. The experimental repeatability was verified by three independent tests, and the arithmetic mean of the steady-state value of the friction coefficient-time curve and the wear volume were taken as the final evaluation indicators.

[0070] Experimental results show that the average Vickers hardness of FeCoCrNiAlTi is 651.222Hv, and the average Vickers hardness of FeCoC rNiAl is 248.144Hv. The average Vickers hardness of FeCoCrNiAlTi is significantly higher than that of FeCoCrNiAl.

[0071] (3) Friction and wear test

[0072] like Figure 2 As shown in the figure, the average friction coefficients of the two high entropy alloy coatings FeCoCrNiAl and FeCoCrNiAlTi are 0.5866 and 0.4084, respectively.

[0073] As shown in Table 2, the volume wear rate of the FeCoCrNiAl coating is 0.0095 mm 3 / min, while the FeCoCrNiAlTi coating reduces this value to 0.0088mm through the TiAlNi2 / TiC composite strengthening mechanism. 3 The mass wear rate showed a significant improvement trend, with the average mass loss of the FeCoCrNiAlTi coating being only 0.010 mg / min, a decrease of 56.5% compared to the 0.023 mg / min of the FeCoCrNiAl coating.

[0074] The difference in mass loss is due to the "double strengthening effect" of the TiC ceramic phase: on the one hand, the ultra-high hardness of the FeCoCrNiAlTi coating effectively resists plastic deformation, reducing the cross-sectional area of ​​the wear track from 7623.28μm 2 Sharply reduced to 3253.685μm 2 On the other hand, the dispersed TiC particles significantly inhibit the adhesion and delamination of the soft metal phase by refining the grains and pinning dislocations.

[0075] Table 2 Wear rate results

[0076]

[0077] Therefore, the present invention adopts the above-mentioned method of carbon-regulated phase transformation and defect repair of FeCoCrNiAlTi high-entropy alloy coating. This method regulates the phase transformation behavior of FeCoCrNi-based high-entropy alloy coating by carbon element in collaboration with Al and Ti elements, and realizes the simultaneous repair of point defects and body defects to improve the comprehensive mechanical properties of the coating.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for carbon-regulated phase transformation and defect repair of FeCoCrNiAlTi high-entropy alloy coatings, characterized in that: The following steps are involved: Step S1, preparing alloy powder; Step S2: using a laser cladding process, carbon-controlled FeCoCrNiAlTi high-entropy alloy coating to induce phase change and repair defects.

2. The method for carbon-regulated phase transformation and defect repair of FeCoCrNiAlTi high-entropy alloy coating according to claim 1, characterized in that: Step S1 is specifically as follows: Step S11, melting the metal raw material into a uniform melt in a vacuum / controlled atmosphere to obtain molten metal; Among them, the metal raw materials include Fe, Co, Cr, Ni, Al, and Ti metals; Step S12: When the molten metal flows out of the guide nozzle, it interacts with the high-pressure inert gas, breaking it into micron-sized droplets and rapidly solidifying them to form spherical particles; Step S13: obtaining alloy powder with controllable particle size through screening.

3. The method for carbon-regulated phase transformation and defect repair of FeCoCrNiAlTi high-entropy alloy coatings according to claim 2, characterized in that: In step S11, the purity of Fe, Co, Cr, Ni, Al, and Ti metals is ≥99.9wt%; In step S12, the size of the micron-sized droplets is 45-105 μm.

4. The method for carbon-regulated phase transformation and defect repair of FeCoCrNiAlTi high-entropy alloy coating according to claim 1, characterized in that: Step S2 specifically includes: in-situ synthesis of a FeCoCrNiAlTi high-entropy alloy coating on the surface of a low-carbon steel substrate using a four-coaxial powder feeding system constructed based on a fiber laser and a KUKA six-axis robot.

5. The method for carbon-regulated phase transformation and defect repair of FeCoCrNiAlTi high-entropy alloy coatings according to claim 4, characterized in that: In step S2, the specific parameters of the laser cladding process are: laser power of 2000 W, spot diameter of 3 mm, scanning speed of 10 mm / s, linear energy density of 200 J / mm, powder feeding rate of 16.8 g / min, and carrier gas flow rate of 1.2 L / min; wherein, 250°C substrate preheating and high-purity Ar atmosphere protection are set, and the O2 concentration is ≤50 ppm.

6. The method of carbon-regulated phase transformation and defect repair of FeCoCrNiAlTi high-entropy alloy coating according to claim 1, characterized in that: In the carbon-regulated FeCoCrNiAlTi high-entropy alloy coating, the atomic ratio of metals is Fe:Co:Cr:Ni:Al:Ti=Bal.:22.09:23.98:24.63:2.30:4.31, and the content of C element is ≤0.5wt%.

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