A wear-resistant and corrosion-resistant Ti5Si3 precipitate phase reinforced high-entropy alloy coating

Abstract

The application discloses a wear-resistant and corrosion-resistant Ti5Si3 precipitated phase reinforced high-entropy alloy coating. 0.5 CoCrFeNiTi 0.5 ) 100‑x Si x , wherein 10at.%<=x<=25at.%. The high-entropy alloy coating is prepared by adopting a laser melting deposition technology, combining a substrate preheating method, and printing the high-entropy alloy coating on the surface of a TA15 titanium alloy substrate in a serpentine reciprocating single-layer printing mode with a mixture of high-entropy alloy powder and Si elemental powder as a powder raw material in an atomic ratio. 0.5 CoCrFeNiTi 0.5 The high-entropy alloy coating prepared by the application has high hardness, no cracks, pores and other defects, and is well metallurgically combined with the substrate, and the addition of the Si element promotes the precipitation of the Ti5Si3 phase, so that the wear resistance and corrosion resistance of the high-entropy alloy coating can be effectively enhanced.

Description

Technical Field

[0001] This invention relates to a wear-resistant and corrosion-resistant Ti5Si3 precipitate-reinforced high-entropy alloy coating, specifically belonging to the field of laser additive manufacturing technology. Background Technology

[0002] High-entropy alloys, as a novel type of multi-component metallic material, have attracted widespread attention due to their unique composition and microstructure. High-entropy alloys are composed of at least five elements in equimolar or near-equimolar proportions. The high-entropy effect leads to the formation of simple solid solution phases rather than intermetallic compounds. Furthermore, lattice distortion, hysteresis diffusion, and cocktail effects endow them with excellent physicochemical and mechanical properties. Currently, high-entropy alloys are also gaining significant attention due to their unique properties. Compared to traditional alloys, high-entropy alloys exhibit superior comprehensive properties, such as high strength, high hardness, good wear resistance, excellent corrosion resistance, and high-temperature stability, making them more suitable as coating materials. For example, many researchers have prepared high-entropy alloy coatings with excellent wear and corrosion resistance by incorporating Al and Ti elements.

[0003] Studies have found that adding small-atomic-radius silicon (Si) can simultaneously improve the hardness and toughness of high-entropy alloy coatings. The addition of Si can inhibit grain growth, thus refining the grain size. Furthermore, Si atoms can also exist in the alloy as interstitial solid solutions, increasing the alloy's lattice constant and resulting in solid solution strengthening, thereby improving both hardness and wear resistance. Therefore, compared to adding large-atomic-radius substitutional atoms (such as Al and Ti), adding small-atomic-radius interstitial atoms not only improves the hardness of multi-principal-element alloy solid solutions but also significantly enhances their fracture toughness. In addition, adding Si can also improve the corrosion resistance of high-entropy alloy coatings.

[0004] Laser melting deposition (LMD), a typical laser additive manufacturing 3D printing technology, manufactures metal products by layering materials from top to bottom. LMD involves rapid melting and cooling of powder, resulting in coatings with advantages such as a small heat-affected zone, fine grains, and good metallurgical bonding with the substrate. Due to its unique and superior characteristics, LMD has been widely used in coating production. Also known as laser cladding technology, LMD can prepare coatings with excellent wear resistance and corrosion resistance on metal alloy surfaces. Summary of the Invention

[0005] This invention proposes a method for preparing a wear-resistant and corrosion-resistant high-entropy alloy coating reinforced with Ti5Si3 precipitates. The specific chemical composition of the high-entropy alloy is: (Al 0.5 CoCrFeNiTi 0.5 ) 100-x Si xThe content is 10 at.% ≤ x ≤ 25 at.%. By adding an appropriate amount of Si element to promote the precipitation of Ti5Si3 phase in the high-entropy alloy coating, a high-entropy alloy coating with high hardness, good wear resistance and corrosion resistance can be obtained.

[0006] The chemical composition of the wear-resistant and corrosion-resistant Ti5Si3 precipitate-reinforced high-entropy alloy coating of this invention is as follows: (Al 0.5 CoCrFeNiTi 0.5 ) 100-x Si x Where 10 at.% ≤ x ≤ 25 at.%

[0007] The specific preparation process of the Ti5Si3 precipitate-reinforced high-entropy alloy coating is as follows:

[0008] Step 1: Mixing of powdered raw materials

[0009] Al 0.5 CoCrFeNiTi 0.5 High-entropy alloy powder and Si elemental powder are mechanically mixed uniformly according to atomic ratio, and then vacuum dried at 130-150℃ for 2-4 hours to obtain mixed high-entropy alloy powder.

[0010] Step 2: Pretreatment of the substrate

[0011] Use 320 grit, 600 grit, and 1000 grit sandpaper to polish the TA15 titanium alloy substrate to a smooth and bright finish, then ultrasonically clean it in anhydrous ethanol solution, and finally dry it for later use.

[0012] Step 3: Laser melting deposition of high-entropy alloy coating

[0013] The TA15 titanium alloy substrate is preheated, and under argon protection, the mixed high-entropy alloy powder is sent to the surface of the TA15 titanium alloy substrate. A serpentine reciprocating single-layer printing method is adopted, and a wear-resistant and corrosion-resistant high-entropy alloy coating is obtained by laser melting deposition.

[0014] The Al 0.5 CoCrFeNiTi 0.5 The particle size of high-entropy alloy powder is less than 25 μm.

[0015] The preheating process of the TA15 titanium alloy substrate is as follows: electromagnetic eddy current heating is adopted, and the preheating temperature of the TA15 titanium alloy substrate is set to 540-580℃. The preheating temperature is maintained during the laser melting deposition process until the laser melting deposition of the high-entropy alloy coating is completed.

[0016] The process parameters for laser melting deposition are as follows: spot diameter is 1.5-2.5 mm, overlap is 0.5-1.0 mm, synchronous powder feeding speed is 0.15-0.25 r / min, powder gas flow rate is 8-12 L / min, scanning speed is 800-1200 mm / min, and laser power is 600-800 W.

[0017] The beneficial effects of this invention are as follows: By designing a reasonable alloy element composition and introducing Si element, this invention promotes the precipitation of Ti5Si3 phase in the high-entropy alloy coating, thereby obtaining a high-entropy alloy coating with high hardness, wear resistance, and corrosion resistance. Because the Ti5Si3 intermetallic compound has both metallic bonds (identical to those found in metals) and covalent bonds (not found in metals), it combines some properties of both metals and ceramics, such as high electrical conductivity, high melting point, high hardness (968±30HV), and excellent corrosion resistance.

[0018] To reduce the possibility of crack initiation, this invention preheats the TA15 titanium alloy substrate and maintains it at a suitable temperature. The coating is obtained by laser melting deposition using a serpentine reciprocating single-layer printing method. After deposition, the high-entropy alloy coating and the substrate are slowly cooled to room temperature by the heating plate. The prepared coating has good metallurgical bonding with the substrate, has a small dilution effect on the substrate and a small heat-affected zone, and the coating is free of defects such as pores and cracks, exhibiting excellent wear and corrosion resistance. Attached Figure Description

[0019] Figure 1 XRD phase analysis spectra of high-entropy alloy coatings with different silicon atom percentages according to this invention;

[0020] Figure 2 : Low-magnification SEM image of the cross-section of the high-entropy alloy coating of this invention;

[0021] Figure 3-1 High-magnification SEM image of the upper layer of the cross-section of the high-entropy alloy coating with a silicon atom percentage of 10 at.% in this invention;

[0022] Figure 3-2 High-magnification SEM image of the upper layer of the cross-section of the high-entropy alloy coating with a silicon atom percentage of 15 at.% in this invention;

[0023] Figure 3-3 High-magnification SEM image of the upper layer of the cross-section of the high-entropy alloy coating with a silicon atom percentage of 20 at.% in this invention;

[0024] Figure 3-4 High-magnification SEM image of the upper layer of the cross-section of the high-entropy alloy coating with a silicon atom percentage of 25 at.% in this invention;

[0025] Figure 4 Comparison of average microhardness of high-entropy alloy coatings with different silicon atom percentages in this invention;

[0026] Figure 5 Two-dimensional contour diagrams of wear trajectories of high-entropy alloy coatings with different silicon atom percentages according to this invention;

[0027] Figure 6 Comparison of specific wear rates of high-entropy alloy coatings with different silicon atom percentages according to this invention;

[0028] Figure 7 Potentiodynamic polarization curves of high-entropy alloy coatings with different silicon atom percentages in this invention. Detailed Implementation

[0029] In this embodiment, the microhardness of the high-entropy alloy coating was measured using an HVD-10AP micro Vickers hardness tester. A load pressure of 1000 gf was applied, and the holding time was 15 s. Therefore, the unit of hardness value was recorded as HV1. Each sample was tested 10 times, and the average value was obtained after removing the maximum and minimum values.

[0030] In this embodiment, the friction and wear resistance of high-entropy alloy coatings was characterized using an HT-1000 ball-disc wear tester. ZrO2 ceramic balls with a diameter of 5 mm were selected as the friction pair, and the wear time, load, radius, and spindle speed were set to 60 min, 10 N, 5 mm, and 500 r / min, respectively. Each sample was tested three times. The wear cross-sectional profile was analyzed using a JB-5C profilometer, and the wear volume loss was then measured.

[0031] In this example, the electrochemical resistance of the high-entropy alloy coating was characterized using a REF3000-32117 electrochemical workstation. Tests were conducted at room temperature in a 3.5 wt% NaCl solution environment using a classic three-electrode cell. The auxiliary electrode was a 10 mm × 10 mm platinum sheet, the reference electrode was a saturated calomel electrode, and the sample size was 7 mm × 7 mm × 3 mm.

[0032] Example 1

[0033] The specific chemical composition of the Ti5Si3 precipitate-reinforced high-entropy alloy coating of this invention is as follows: (Al 0.5 CoCrFeNiTi 0.5 ) 100-x Si x The selected values ​​for x were 10 at.%, 15 at.%, 20 at.%, and 25 at.%.

[0034] The preparation method of high-entropy alloy coating includes the following steps:

[0035] Step 1: Select commercially available Al with a particle size of less than 25 micrometers. 0.5 CoCrFeNiTi 0.5High-entropy alloy powder and elemental Si powder with a purity greater than 99.9 wt.% were used as powder raw materials; Al was used as the raw material. 0.5 CoCrFeNiTi 0.5 High-entropy alloy powder and Si elemental powder are mechanically mixed uniformly according to the designed atomic ratio. Then, the mixed powder is placed in a vacuum drying oven at 140°C and vacuum dried for 2 hours to obtain mixed high-entropy alloy powder.

[0036] Step 2: Select a TA15 titanium alloy round plate with a diameter of Φ30mm and a thickness of 6mm as the printing substrate. Use 320 grit, 600 grit and 1000 grit sandpaper to polish the TA15 titanium alloy substrate to a smooth and bright finish. Then place it in an anhydrous ethanol solution and use ultrasonic cleaning to clean the surface. Take it out and dry it in an oven for later use.

[0037] Step 3: Before printing, preheat the TA15 titanium alloy substrate to 560℃. Then, using an LDM 8060 powder-feeding metal matrix composite laser rapid prototyping machine, the mixed high-entropy alloy powder is delivered to the surface of the TA15 titanium alloy substrate through protective argon gas. A serpentine reciprocating single-layer printing method is used, where the laser beam directly melts and deposits the wear-resistant and corrosion-resistant high-entropy alloy coating. The preheating temperature is maintained during laser printing until the laser melting and deposition of the high-entropy alloy coating is complete. After printing, the sample is slowly cooled to room temperature along with the heating plate.

[0038] The laser printing parameters are as follows: laser spot diameter is 2.0mm, overlap is 0.6mm, synchronous powder feeding speed is 0.2r / min, powder airflow rate is 10L / min, scanning speed is 1000mm / min, and laser power is 800W.

[0039] Step 4: Use a wire cutting machine to cut the sample prepared in step 3 along the cross-sectional direction of the coating, then grind and polish it with 320-2000 grit metallographic sandpaper, observe the morphology of the coating cross-section, the coating has no obvious defects such as holes and cracks, and it is well bonded to the TA15 titanium alloy substrate.

[0040] The XRD results of the high-entropy alloy coating in this embodiment of the invention are as follows: Figure 1 As shown, (Al) 0.5 CoCrFeNiTi 0.5 ) 90 Si 10 The main constituent phases of the high-entropy alloy coating are FCC (face-centered cubic) and BCC (body-centered cubic) solid solution phases. Due to the high-entropy effect, the precipitation of metal compounds is effectively suppressed, so only a small amount of Ti5Si3 phase precipitates in the coating. As the Si content increases, Ti5Si3 phase gradually precipitates in the high-entropy alloy coating due to the negative enthalpy of mixing between Ti and Si.

[0041] The microstructure of the high-entropy alloy coating cross-section in this embodiment of the invention is as follows: Figure 2 As shown in Figure 3, the scanning electron microscope images of the coating show that with the increase of Si content, the Ti5Si3 phase in the high-entropy alloy coating changes from a blocky structure to a dendritic or petal-like structure, wherein (Al... 0.5 CoCrFeNiTi 0.5 ) 75 Si 25 The Ti5Si3 phase is more uniformly and densely distributed in the high-entropy alloy coating.

[0042] The microhardness test results of the high-entropy alloy coating in the embodiments of the present invention are as follows: Figure 4 As shown in the figure. It can be seen from the figure that the hardness of all high-entropy alloys is higher than 800HV1, and (Al... 0.5 CoCrFeNiTi 0.5 ) 75 Si 25 The highest hardness of the high-entropy alloy coating is 900.5±22HV1.

[0043] The two-dimensional profile of the wear trajectory of the high-entropy alloy coating in this embodiment of the invention is as follows: Figure 5 As shown, under the same wear conditions, with the increase of Si addition, the wear track profile of the high-entropy alloy coating becomes lower and narrower, where (Al) 0.5 CoCrFeNiTi 0.5 ) 75 Si 25 The high-entropy alloy coating exhibits the smallest volumetric wear, indicating optimal wear resistance, consistent with the hardness results. It can be seen that the precipitation of the Ti5Si3 phase in the high-entropy alloy coating enhances its overall hardness, thereby strengthening its friction and wear resistance. The friction and wear test results are as follows: Figure 6 As shown. Similarly, (Al) 0.5 CoCrFeNiTi 0.5 ) 75 Si 25 The high-entropy alloy coating achieved the lowest specific wear rate (1.17 × 10⁻⁶). -4 mm 3 / (N·m)) exhibits the best wear resistance.

[0044] The electrochemical corrosion performance test results of the high-entropy alloy coating in the embodiments of the present invention are as follows: Figure 7 As shown in the figure, the potentiodynamic polarization curve of the high-entropy alloy coating shows that the curve directly transitions from the Tafel region to the stable passivation region, indicating that the coating spontaneously passivates under the corrosion potential. Specifically, with the increase of Si content, the self-corrosion potential of the high-entropy alloy coating becomes more positive, and the self-corrosion current density becomes lower, indicating that the addition of Si element improves the electrochemical resistance of the high-entropy alloy coating.

Claims

1. A wear and corrosion resistant Ti5Si3 precipitate phase reinforced high-entropy alloy coating, characterized by: The chemical composition of the Ti5Si3 precipitate phase enhanced high-entropy alloy coating is: (Al 0.5 CoCrFeNiTi 0.5 ) 100-x Si x wherein 10 at.%≤x≤25 at.%. The preparation process of the Ti5Si3 precipitated phase reinforced high-entropy alloy coating is specifically as follows: Step 1: mixing of powder raw materials Al 0.5 CoCrFeNiTi 0.5 The high-entropy alloy powder and the Si elemental powder are mechanically mixed uniformly according to an atomic ratio, and then are vacuum dried at a temperature of 130-150 DEG C for 2-4 h to obtain a mixed high-entropy alloy powder. Step 2: pretreatment of the substrate 320 mesh, 600 mesh and 1000 mesh sandpaper are selected in sequence to polish the TA15 titanium alloy substrate to be flat and bright, and then the substrate is ultrasonically cleaned in anhydrous ethanol solution, and then dried for standby; Step 3: laser melting deposition of the high-entropy alloy coating The TA15 titanium alloy substrate is preheated, the mixed high-entropy alloy powder is sent to the surface of the TA15 titanium alloy substrate under argon protection, the snake-shaped reciprocating single-layer printing mode is adopted, and the laser melting deposition is carried out to obtain the wear-resistant and corrosion-resistant high-entropy alloy coating; The preheating process of the TA15 titanium alloy substrate is as follows: the electromagnetic eddy current heating mode is adopted, the preheating temperature of the TA15 titanium alloy substrate is set to 540-580 DEG C, and the preheating temperature is maintained during the laser melting deposition until the laser melting deposition of the high-entropy alloy coating is completed; The process parameters of the laser melting deposition are as follows: the spot diameter is 1.5-2.5 mm, the overlap amount is 0.5-1.0 mm, the synchronous powder feeding speed is 0.15-0.25 r / min, the powder feeding gas flow rate is 8-12 L / min, the scanning speed is 800-1200 mm / min, and the laser power is 600-800 W.

2. The wear and corrosion resistant Ti5Si3 precipitate phase reinforced high-entropy alloy coating of claim 1, characterized in that: The Al 0.5 CoCrFeNiTi 0.5 The particle size of the high-entropy alloy powder is less than 25 μm.

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