Rare earth oxide dispersion strengthened FeCoNiCrMn high entropy alloy coating and preparation method thereof

Abstract

The present invention relates to a rare earth oxide dispersion-strengthened FeCoNiCrMn high-entropy alloy coating and a preparation method thereof. The FeCoNiCrMn high-entropy alloy powder comprises: a molar fraction of Fe of 18-22%, a molar fraction of Co of 18-22%, a molar fraction of Ni of 18-22%, a molar fraction of Cr of 18-22%, and a molar fraction of Mn of 18-22%. The FeCoNiCrMn high-entropy alloy powder and rare earth oxide particles are mixed in any reasonable mass ratio. The present invention primarily increases component supercooling by adding rare earth elements, thereby increasing the internal nucleation rate of the coating and achieving grain refinement under laser cladding technology, ultimately enhancing the mechanical properties of the high-entropy alloy composite coating, including hardness, wear resistance, and corrosion resistance. When the Sm2O3 mass content is 2%, the hardness of the composite coating is the highest, which is 15.85% higher than that of the high-entropy alloy coating; with the increase of Sm2O3 mass content, the wear resistance and corrosion resistance of the composite coating tend to first increase and then decrease. When the Sm2O3 mass content is 2%, its wear resistance and corrosion resistance reach the maximum.

Description

Technical Field

[0001] The present invention belongs to the field of electric power technology, and in particular relates to a rare earth oxide dispersion strengthened FeCoNiCrMn high entropy alloy coating and a preparation method thereof. Background Art

[0002] High-entropy alloys (HEAs), as an emerging alloy system, are composed of five or more elements, with the molar content of each element ranging from 5wt% to 35wt%. The emergence of HEAs has disrupted traditional alloy systems and proposed new directions for alloy design. HEAs are usually composed of precious metals, and if the entire part is made of HEAs, the cost is high. Therefore, preparing HEAs coatings on the surfaces of mechanical parts is a good way to both extend the life of the parts and reduce costs. As an advanced surface strengthening technology, laser cladding technology has the characteristics of fast processing speed, small heat-affected zone, small deformation, and outstanding metallurgical bonding. Therefore, laser cladding technology is considered an ideal method for preparing HEAs coatings.

[0003] High-entropy alloy coatings can achieve surface modification and are commonly used on critical components such as aircraft engines and cutting tools. Due to the relatively harsh operating environments of these components, high-entropy alloy coatings require excellent properties such as hardness, toughness, wear resistance, and corrosion resistance. However, if the precipitation and solid solution strengthening mechanisms within the alloy fail during the preparation of the high-entropy alloy coating, its hardness, wear resistance, and corrosion resistance cannot be guaranteed, and cracks can easily form within the coating during the laser cladding process.

[0004] To this end, in response to the above technical problems, it is necessary to provide a rare earth oxide dispersion strengthened FeCoNiCrMn high entropy alloy coating and a preparation method thereof. Summary of the Invention

[0005] The present invention provides a rare earth oxide dispersion-strengthened FeCoNiCrMn high-entropy alloy coating and a preparation method thereof, in order to solve the technical problem in the prior art that, during the preparation of the high-entropy alloy coating, the precipitation strengthening and solid solution strengthening mechanisms in the alloy fail, the hardness, wear resistance and corrosion resistance cannot be guaranteed, and cracks are easily formed inside the coating during the laser cladding process.

[0006] The first aspect of the present invention provides a rare earth oxide dispersion-strengthened FeCoNiCrMn high-entropy alloy coating, comprising: alloy coating raw materials are FeCoNiCrMn high-entropy alloy powder and rare earth oxide particles; the FeCoNiCrMn high-entropy alloy powder has a molar fraction of Fe of 18 to 22%, a molar fraction of Co of 18 to 22%, a molar fraction of Ni of 18 to 22%, a molar fraction of Cr of 18 to 22%, and a molar fraction of Mn of 18 to 22%, and the FeCoNiCrMn high-entropy alloy powder and the rare earth oxide particles are mixed according to any reasonable mass ratio.

[0007] Optionally, the rare earth oxide particles are Sm2O3 particles, with a mass fraction of 1 to 3% and a size of 3 to 5 μm.

[0008] A second aspect of the present invention provides a method for preparing a rare earth oxide dispersion-strengthened FeCoNiCrMn high-entropy alloy coating, the specific steps of the method comprising:

[0009] Step 1: ball-milling FeCoNiCrMn high entropy alloy powder and rare earth oxide particles to obtain a mixed powder;

[0010] Step 2: Place the mixed powder into a beaker and place it in a drying oven for drying to obtain a dried powder;

[0011] Step 3, pre-treating the substrate surface to obtain a pre-treated substrate;

[0012] Step 4: The dried powder is clad onto the pretreated substrate through a synchronous powder feeding laser cladding device to obtain a rare earth oxide dispersion strengthened FeCoNiCrMn high entropy alloy coating.

[0013] Optionally, in step 1, the mass percentages of FeCoNiCrMn high entropy alloy powder and rare earth oxide particles are: (97-100%): (1-3%), the particle size of FeCoNiCrMn high entropy alloy powder is 45-105 μm; and the particle size of the rare earth oxide particles is 3-5 μm.

[0014] Optionally, in step 1, the mixed powder is stirred in a ball mill at a rotation speed of 200-500 rpm for 12-24 hours, and the mass ratio of the ball-milled ceramic balls to the high entropy alloy powder is 1:1.

[0015] Optionally, in step 2, the operating temperature of the drying oven is 120-150° C., and the drying time is 8-12 hours.

[0016] Optionally, pre-treatment is sandblasting and alcohol cleaning.

[0017] Optionally, the laser cladding process parameters are: laser power of 1200W to 1800W, scanning speed of 600mm / min to 720mm / min, spot diameter of 6mm, powder feeding amount of 0.6g / min to 10g / min, defocusing amount of 36mm, and coating overlap rate of 45%.

[0018] Optionally, in step 4, the thickness of the high entropy alloy coating is 0.4 to 0.8 mm.

[0019] Compared with the prior art, the present invention provides a rare earth oxide dispersion-strengthened FeCoNiCrMn high-entropy alloy coating and a preparation method thereof, which has the following advantages:

[0020] 1. Description of the accompanying drawings The present invention utilizes rare earth oxide dispersion to strengthen the FeCoNiCrMn high entropy alloy coating, which has superior hardness, wear resistance, modulus and other properties compared to ordinary high entropy alloy coatings. By controlling the content of rare earth oxide, the effects of rare earth oxide and high entropy alloy are complementary, and the performance is compatible and synergistic, thereby achieving the preparation of a coating with high strength, high wear resistance and corrosion resistance.

[0021] 2. The rare earth oxide dispersion-strengthened FeCoNiCrMn high-entropy alloy coating of the present invention utilizes a composite powder of Fe, Co, Ni, Cr, Mn, and Sm2O3 particles. This high-entropy alloy exhibits high plasticity and excellent performance due to its simple FCC phase. Controlling the mole fractions of the five elements within the range of 18-22% results in a high mixing entropy, which facilitates the formation of a highly plastic single-phase structure.

[0022] 3. Introducing fine, dispersed Sm2O3 particles can, on the one hand, inhibit dislocation motion and improve material strength; on the other hand, it can inhibit grain growth and achieve better toughness. Too high a Sm2O3 content or too large a particle size can easily lead to brittle material; too low a Sm2O3 content or too small a particle size can lead to insignificant dispersion strengthening.

[0023] 4. The rare earth oxide dispersion-strengthened FeCoNiCrMn high-entropy alloy coating prepared by the preparation method of the present invention has a smooth and uniform morphology, distinct internal interface layers, and uniform tissue growth and distribution, thereby achieving better forming quality and surface continuity of the coating.

[0024] The above and other objects, features and advantages of the exemplary embodiments of the present invention will become readily understood by reading the detailed description below with reference to the accompanying drawings. In the accompanying drawings, several embodiments of the present invention are shown in an exemplary and non-limiting manner, and the same or corresponding reference numerals represent the same or corresponding parts, wherein:

[0025] Figure 1This is a process flow chart of the method for preparing a rare earth oxide dispersion-strengthened FeCoNiCrMn high-entropy alloy coating of the present invention;

[0026] Figure 2 SEM images of spherical composite powders according to the present invention ((a) FeCoNiCrMn powder, (b) Sm2O3 / FeCoNiCrMn powder);

[0027] Figure 3 The microstructure diagrams of the Sm2O3 / HEA composite coatings of Examples 1-3 of the present invention and the HEA coating of Comparative Example 1;

[0028] Figure 4 XRD patterns of the Sm2O3 / HEA composite coatings of Examples 1-3 of the present invention and the HEA coating of Comparative Example 1;

[0029] Figure 5 Graph showing the change in friction coefficient over time of the Sm2O3 / HEA composite coatings of Examples 1-3 of the present invention and the HEA coating of Comparative Example 1;

[0030] Figure 6 The wear amount of the Sm2O3 / HEA composite coatings of Examples 1-3 of the present invention and the HEA coating of Comparative Example 1;

[0031] Figure 7 Friction and wear morphologies of the Sm2O3 / HEA composite coatings of Examples 1-3 of the present invention and the HEA coating of Comparative Example 1 ((a) FeCoNiCrMn, (b) FeCoNiCrMn+1% Sm2O3, (c) FeCoNiCrMn+2% Sm2O3, (d) FeCoNiCrMn+3% Sm2O3);

[0032] Figure 8 Vickers hardness of the Sm2O3 / HEA composite coatings of Examples 1-3 of the present invention and the HEA coating of Comparative Example 1;

[0033] Figure 9 Electrochemical corrosion polarization curves of the Sm2O3 / HEA composite coatings of Examples 1-3 of the present invention and the HEA coating of Comparative Example 1;

[0034] Figure 10 These are the corrosion morphologies of the Sm2O3 / HEA composite coatings of Examples 1-3 of the present invention and the HEA coating of Comparative Example 1 ((a) HEA coating, (b) 1% Sm2O3 / HEA coating, (c) 2% Sm2O3 / HEA coating, and (d) 3% Sm2O3 / HEA coating). DETAILED DESCRIPTION

[0035] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art.

[0036] The substrate used in the experiments of this embodiment is 45# steel. Table 1 shows the element ratios of Examples 1 to 3 and Comparative Example 1. Although mixing FeCoNiCrMn high entropy alloy powder and rare earth oxide particles in any reasonable mass ratio can achieve the purpose of this embodiment, the effect is not good. The preferred embodiment scheme is as follows:

[0037] Table 1 Molar ratio of elements in each example

[0038]

[0039] The alloy coatings of Examples 1 to 3 and Comparative Example 1 were prepared respectively by the following preparation methods:

[0040] A method for preparing a rare earth oxide dispersion-strengthened FeCoNiCrMn high-entropy alloy coating, comprising the following steps:

[0041] Powder mixing: Weigh and mix the high entropy alloy powder and Sm2O3 powder of the corresponding molar ratio and put them into a ball mill. Stir the mixed powders at 300 rpm in a ball mill for 24 hours to mix them thoroughly.

[0042] Powder drying: put the mixed powder into a beaker and dry it in a vacuum oven at 150°C for 12 hours;

[0043] Substrate pretreatment: sandblasting the substrate surface to remove dirt and then cleaning the surface with alcohol;

[0044] Laser cladding: The RC-HSLC-6000 ultra-high-speed cladding equipment, manufactured by Nanjing Zhongke Yuchen Co., Ltd. in China, was used. It was equipped with an RFL-C6000 laser unit (maximum power 6000W) from Wuhan Raycus Fiber Laser Technology Co., Ltd. The nozzle employed a coaxial four-way powder feed system, with argon as both the feed and shielding gases. The laser cladding process parameters were: laser power of 1800W, scanning speed of 720mm / min, spot diameter of 6mm, powder feed rate of 10g / min, defocus of 36mm, and coating overlap of 45%.

[0045] Examples 1 to 3 and Comparative Example 1 were tested:

[0046] Phase Composition and Microstructure: The prepared coatings were cut into specimens of various sizes using wire cutting. The cut specimens were mounted and then ground and polished. The mounted specimens were etched with a 3:1 solution of hydrochloric acid:nitric acid for 60 seconds, and the surfaces were immediately cleaned with ethanol. The microstructure and elemental distribution of the coatings were analyzed using an Olympus BX53M optical microscope (OM), an Olympus DSX1000 super-depth microscope, a CIQTEK SEM3100 scanning electron microscope (SEM), and an Oxford Xplore15 energy dispersive spectrometer (EDS). The phase composition of the coatings was analyzed using a Rigaku UltimaIV X-ray diffractometer (XRD).

[0047] Microhardness: The coating's hardness was measured using an HVS-1000 Vickers microhardness tester, with a 0.4 kg load and a 15 second hold time. Each test point was 200 μm apart in the vertical direction of the coating. Five points at the same height were measured, and the average hardness value was taken as the average value.

[0048] Friction and wear: A reciprocating friction and wear machine was used for the friction and wear test. Before the test, the surface of the specimen was sanded and polished, then placed in an ultrasonic cleaner and cleaned with alcohol, and finally rinsed with deionized water and blown dry. The weight of the specimen was measured using an electronic balance. Each specimen was measured 5 times, and the average value was taken as the specimen weight. The test was carried out at room temperature and dry friction conditions. Friction and wear test conditions: load of 500N, sliding speed of 30mm / s, amplitude of 5mm, frequency of 1Hz, and test time of 30min. After the test, the specimen was cleaned with an ultrasonic cleaner and the weight of the specimen after friction and wear was measured to calculate the wear amount. The morphology and depth of the wear marks were observed using an ultra-depth of field microscope, and the wear morphology of the coating surface was analyzed using a scanning electron microscope (SEM).

[0049] Electrochemical corrosion: The electrochemical corrosion test was conducted using an electrochemical workstation. Before the test, the surface of the specimen was sanded and then polished to ensure that there were no obvious scratches on the coating surface. The non-test surface of the specimen was sealed with epoxy resin, leaving a 0.36 cm 2 The test area was 3.5 wt% NaCl solution was used as the corrosive medium. The polarization curves of the specimens were measured, and the electrochemical parameters of corrosion potential Ecorr and corrosion current density Icorr of each specimen were compared based on the polarization curves. After the polarization curve test was completed, the corroded surface of the specimen was cleaned with an ultrasonic cleaner, and the morphology after corrosion was observed using a scanning electron microscope (SEM).

[0050] Figure 2The microstructures of HEA coating and Sm2O3 / HEA composite coating are shown respectively. According to the structural characteristics of the coating, the coating is divided into three parts: upper, middle and lower. From a3, b3, c3 and d3, it can be seen that no cracks or other defects are found at the junction of the coating and the substrate. The structural transition between the coating and the substrate is good, which shows that the coating and the substrate have good bonding. Figure 2 It can be seen that from the bottom to the top of the coating, its microstructure is planar grains, cellular grains, columnar grains, and equiaxed grains. Figure 2 With the increase of Sm2O3 content, the grain structure of the coating is refined, the number of columnar grains decreases, the number of equiaxed grains and cellular grains increases, and the size of columnar grains also decreases with the increase of Sm2O3 content.

[0051] Figure 3 Shows the XRD patterns of Sm2O3 / HEA composite coatings with different Sm2O3 contents. Figure 3 It can be seen that the HEA coating is mainly composed of the FCC phase. After the addition of Sm2O3, the Sm2O3 / HEA composite coating (Examples 1-3) is composed of the FCC phase and the Co5.24Sm0.97 phase. During the laser cladding process, the Sm2O3 decomposes into Sm atoms, which combine with the Co atoms in the HEA to form a new Co5.24Sm0.97 phase.

[0052] Combine Figure 4 As shown in the curve of the change of friction coefficient (COF) of HEA coatings with different Sm2O3 contents over time, the wear process of parts can be divided into three stages: running-in stage, stable wear stage and severe wear stage. Figure 4 Indicates the running-in phase and the stable wear phase, represented by Figure 4 As can be seen, the COF is initially unstable, indicating the running-in phase. After 100 seconds, the COF stabilizes, marking the stable wear phase. During this phase, the COF increases over time. This is primarily due to the abrasive and adhesive wear characteristics of the coating. During the wear process, a large amount of wear debris is generated, which remains on the wear surface, causing abrasive wear and increasing the friction coefficient.

[0053] like Figure 5 As shown in Figure 2, the friction coefficients of HEA coatings with different Sm2O3 contents are 0.724, 0.667, 0.629, and 0.653, respectively. The larger the friction coefficient, the worse the wear resistance of the coating (e.g. Figure 6 As shown in Figure 3, it can be concluded that the HEA composite coating with 2% Sm2O3 content has the best wear resistance.

[0054] Figure 7The graph shows the change of Vickers hardness values ​​of HEA coatings with different Sm2O3 contents. With the increase of Sm2O3 content, the microhardness of HEA coating increases first and then decreases. When the Sm2O3 content is 2%, the hardness of HEA composite coating reaches a maximum value of 196.44HV 0.4 , while the hardness of HEA coating is only 169.57HV 0.4 , indicating that the appropriate addition of Sm2O3 improves the hardness of the HEA coating.

[0055] Depend on Figure 8 It can be seen that after adding Sm2O3, the polarization curve of the composite coating has the same trend as that of the HEA coating, and icorr decreases with the increase of Ecorr. Obviously, as the Sm2O3 content increases, Ecorr first increases and then decreases, while icorr first decreases and then increases. Combined with Table 2, it can be seen that the HEA coating has Ecorr = -0.159 V, icorr = 9.61×10 -9 A.cm -2 When an appropriate amount of Sm2O3 is added, Ecorr tends to increase and icorr tends to decrease. When the content of Sm2O3 is 2%, Ecorr reaches a maximum value of -0.184 V and icorr reaches a minimum value of 1.74×10 -10 A.cm -2 , the composite coating has the best corrosion resistance (such as Figure 9 shown).

[0056] Table 2 Corrosion potential (E) of HEA coating and Sm2O3 / HEA composite coating in 3.5% NaCl solution corr ) and current density (i corr )

[0057]

[0058] In summary, the present invention provides a rare earth oxide dispersion-strengthened FeCoNiCrMn high-entropy alloy coating and a preparation method. The process cost of the preparation method is low, and the mechanical properties of the prepared high-entropy alloy composite coating, such as hardness, wear resistance, and corrosion resistance, are good, which effectively increases the application scope of high-entropy alloys in the field of mechanical manufacturing.

[0059] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A rare earth oxide dispersion strengthened FeCoNiCrMn high entropy alloy coating, characterized in that: The alloy coating raw materials are FeCoNiCrMn high entropy alloy powder and rare earth oxide particles; the FeCoNiCrMn high entropy alloy powder has a molar fraction of Fe of 18-22%, a molar fraction of Co of 18-22%, a molar fraction of Ni of 18-22%, a molar fraction of Cr of 18-22%, and a molar fraction of Mn of 18-22%, and the FeCoNiCrMn high entropy alloy powder and the rare earth oxide particles are mixed so that the mass fraction of the rare earth oxide particles is 2%; The particle size of the FeCoNiCrMn high entropy alloy powder is 45-105 μm; the particle size of the rare earth oxide particles is 3-5 μm; The rare earth oxide dispersion strengthened FeCoNiCrMn high entropy alloy coating uses a composite powder of Fe, Co, Ni, Cr, Mn and Sm2O3 particles as the coating material to form a simple FCC phase of the high entropy alloy.

2. A method for preparing the rare earth oxide dispersion-strengthened FeCoNiCrMn high-entropy alloy coating according to claim 1, characterized in that: The specific steps of this method include: Step 1: ball-milling FeCoNiCrMn high entropy alloy powder and rare earth oxide particles to obtain a mixed powder; Step 2: Place the mixed powder into a beaker and place it in a drying oven for drying to obtain a dried powder; Step 3, pre-treating the substrate surface to obtain a pre-treated substrate; Step 4: The dried powder is clad onto the pretreated substrate through a synchronous powder feeding laser cladding device to obtain a rare earth oxide dispersion strengthened FeCoNiCrMn high entropy alloy coating.

3. The method for preparing a rare earth oxide dispersion-strengthened FeCoNiCrMn high-entropy alloy coating according to claim 2, characterized in that: In step 1, the mixed powder is stirred in a ball mill at a rotation speed of 200-500 rpm for 12-24 hours, and the mass ratio of the ball-milled mixed ceramic balls to the high entropy alloy powder is 1:

1.

4. The method for preparing a rare earth oxide dispersion-strengthened FeCoNiCrMn high-entropy alloy coating according to claim 2, characterized in that: In step 2, the operating temperature of the drying oven is 120° C. to 150° C., and the drying time is 8 to 12 hours.

5. The method for preparing a rare earth oxide dispersion-strengthened FeCoNiCrMn high-entropy alloy coating according to claim 2, characterized in that: In step 3, the substrate is pretreated by sandblasting and cleaning with alcohol.

6. The method for preparing a rare earth oxide dispersion-strengthened FeCoNiCrMn high-entropy alloy coating according to claim 2, characterized in that: In step 4, the laser cladding process parameters are: laser power of 1200W~1800W, scanning speed of 600mm / min~720mm / min, spot diameter of 6mm, powder feeding rate of 0.6g / min~10g / min, defocusing amount of 36mm, and coating overlap rate of 45%.

7. The method for preparing a rare earth oxide dispersion-strengthened FeCoNiCrMn high-entropy alloy coating according to claim 2, characterized in that: In step 4, the thickness of the high entropy alloy coating is 0.4-0.8 mm.

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