High-hardness corrosion-resistant iron-based amorphous alloy and preparation method thereof

Abstract

The invention discloses a high-hardness corrosion-resistant iron-based amorphous alloy and a preparation method thereof, and belongs to the technical field of amorphous alloy materials. The iron-based amorphous alloy comprises the following components in percentage by mass: 20%-24% of Cr, 3%-7% of Mo, 3.6%-4.0% of B, 0.3%-0.7% of C, 1.0%-1.4% of Si, 1%-5% of Al, 1%-3% of Nb and the balance of Fe. The corrosion resistance is enhanced through the synergistic effect of Mo and Cr; b is a core amorphous forming element; c is used as a metalloid small atom, so that the amorphous forming ability of an alloy system is improved; si and B synergistically improve the amorphous forming ability and participate in formation of a Si-O passivation film at the same time; al optimizes the flowability of the alloy melt; nb is used as a large atom to improve the atom mismatch degree of a system and improve the amorphous forming ability; by accurately regulating and controlling the mass ratio of Fe, Cr, Mo, B, C, Si, Al and Nb, collaborative optimization of amorphous forming ability, hardness, corrosion resistance and forming stability is realized, meanwhile, the preparation process is simplified, and the production cost is reduced.

Description

Technical Field

[0001] This invention belongs to the field of amorphous alloy materials technology, specifically relating to a high-hardness, corrosion-resistant iron-based amorphous alloy and its preparation method, which is particularly suitable for wear-resistant protective coatings, precision mechanical parts, and other scenarios in highly corrosive environments such as marine and chemical industries. Background Technology

[0002] Due to their unique structure of short-range ordered and long-range disordered atomic arrangement, iron-based amorphous alloys possess high hardness, high strength, excellent corrosion resistance, and soft magnetic properties. They have irreplaceable advantages in fields such as power electronics, chemical corrosion protection, and mechanical wear resistance, and have become a research hotspot in the field of new functional and structural materials.

[0003] While current performance optimization of iron-based amorphous alloys focuses on the proportioning and control of key elements such as Cr, Mo, B, C, and Si, it has long faced challenges such as the contradiction between composition design and performance synergy, and the mutual constraints between amorphous formation ability and corrosion / wear resistance. For example, iron-based alloy systems with high Cr content typically exhibit strong corrosion resistance but weak amorphous formation ability. Furthermore, the preparation of iron-based amorphous coatings still faces difficulties such as complex processes, high costs, and poor forming stability, which restricts their large-scale application in practical engineering scenarios.

[0004] Specifically, the limitations of existing technologies include: CN117363996A discloses a design and laser cladding coating preparation process for iron-based amorphous alloys with high Mo content (35-40 at.%). Although a high amorphous ratio is achieved, this method has strict requirements on powder particle size, and the high Mo content leads to a significant increase in raw material costs, which is not conducive to large-scale industrial applications. CN107470641A attempts to prepare iron-based amorphous powders through atomization to reduce costs, but the introduction of sulfur (S) into the composition has an adverse effect on the toughness and corrosion resistance of the coating. CN115608977A introduces a wear-resistant amorphous coating based on the Fe-Si-BPY system, using vacuum atomization and supersonic flame spraying processes. Although the cost is controlled, the P content in the composition needs to be strictly controlled, otherwise it is easy to cause local crystallization of the coating. Moreover, this coating focuses more on wear resistance, and its corrosion resistance in highly corrosive environments is not fully optimized, so its overall performance is still limited. CN112575280A proposes a method of using plasma spraying combined with water-soluble Al2O3 or SiO2 for sealing to improve the seawater corrosion resistance of iron-based amorphous coatings. However, plasma spraying itself has a low energy density and insufficient droplet cooling rate. The amorphous phase content in the coating is usually ≤80%, and the sealing process increases production steps and time costs. The interface between the sealing layer and the coating is prone to becoming the starting point for peeling, resulting in poor long-term service reliability.

[0005] Currently, most iron-based amorphous alloys struggle to simultaneously achieve amorphous forming ability, high hardness, strong corrosion resistance, and forming stability, or suffer from limited performance due to unreasonable compositional design, failing to meet the demands of complex service environments. Therefore, developing an iron-based amorphous alloy with strong amorphous forming ability, excellent comprehensive performance, and stable manufacturing process has significant practical value. Summary of the Invention

[0006] To address the technical problems of existing iron-based amorphous alloys, such as the difficulty in balancing amorphous formation capability and comprehensive performance (hardness, corrosion resistance), and the susceptibility to crystallization and inclusion defects during preparation, this invention provides a high-hardness, corrosion-resistant iron-based amorphous alloy and its preparation method. By precisely controlling the mass ratio of Fe, Cr, Mo, B, C, Si, Al, and Nb, the amorphous formation capability, hardness, corrosion resistance, and forming stability are synergistically optimized, while simplifying the preparation process and reducing production costs.

[0007] The high-hardness, corrosion-resistant iron-based amorphous alloy of the present invention is composed of the following components by mass percentage: Cr 20%-24%, Mo 3%-7%, B 3.6%-4.0%, C 0.3%-0.7%, Si 1.0%-1.4%, Al 1%-5%, Nb 1%-3%, with the balance being Fe.

[0008] Preferably, the composition of the high-hardness corrosion-resistant iron-based amorphous alloy by mass percentage is: Cr 22%, Mo 5%, B 3.8%, C 0.5%, Si 1.2%, Al 3%, Nb 2%, with the balance being Fe.

[0009] The preparation method of the high-hardness, corrosion-resistant iron-based amorphous alloy of the present invention includes the following steps: (1) Raw material pretreatment: Select high carbon ferrochrome, iron-carbon ferrochrome, ferromolybdenum, boron carbide, ferrosilicon, electrolytic aluminum, ferroniobium and pure iron as raw materials, weigh them accurately according to the composition ratio, remove the oxide scale and oil stains on the surface of the raw materials, and dry them for later use; (2) Alloy melting: The pretreated raw materials are placed in a vacuum induction melting furnace and vacuumed to a vacuum degree ≤5×10 -3 Pa, introduce inert gas for protection, heat to 1550-1650℃, hold for 20-30 minutes to completely melt and uniformly mix the raw materials, and electromagnetically stir 2-3 times during the process, each stirring time is 3-5 minutes to ensure uniform alloy composition; (3) A gas atomization process is used to atomize the molten alloy liquid into amorphous alloy powder. The atomization pressure is 3-5 MPa and the cooling rate is ≥10. 5 K / s, sieve and collect 50-150μm powder for later use.

[0010] In step (2), the inert gas is nitrogen or argon with a purity of ≥99.99%.

[0011] The core of this invention lies in the optimized design of the composition of iron-based amorphous alloys. The role and proportion of each element are based on the following: Fe, as the matrix element of the alloy, provides the basic framework for the formation of the amorphous structure, ensuring the basic mechanical properties of the alloy; Cr forms a dense oxide passivation film on the alloy surface, significantly improving corrosion resistance, while moderately expanding the amorphous formation range, avoiding excessive addition that would reduce the amorphous formation ability; Mo and Cr work synergistically to enhance corrosion resistance, especially improving the alloy's resistance to pitting corrosion in acidic and salt spray environments, while refining the amorphous structure and assisting in strengthening hardness; B is the core amorphous formation element, lowering the alloy's liquidus temperature and the critical cooling rate of the amorphous alloy, improving the amorphous formation ability, and this ratio can reduce the oxidation loss of boron, ensuring compositional stability; C, as a similar element... Small metallic atoms enhance the atomic mismatch and negative mixing enthalpy of the alloy system, thereby improving its amorphous forming ability. Si and B synergistically enhance amorphous forming ability, lower the alloy melting point, improve melt flowability, and participate in the formation of Si-O passivation film, thus helping to improve corrosion resistance. Al optimizes the melt flowability of the alloy, solves the problem of uneven melt spreading during the forming process, and an appropriate amount of Al can improve the toughness of the alloy. Moreover, this ratio can control the degree of aluminum oxidation, avoiding the formation of a large number of oxide inclusions that lead to forming defects. Nb, as a large atom, improves the atomic mismatch of the system, enhances amorphous forming ability, and can also fix carbon to prevent intergranular corrosion and improve high-temperature stability.

[0012] The application of the high-hardness and corrosion-resistant iron-based amorphous alloy described in this invention in the preparation of wear-resistant and corrosion-resistant iron-based amorphous coatings.

[0013] The application of the high-hardness, corrosion-resistant iron-based amorphous alloy described in this invention in the preparation of wear-resistant and corrosion-resistant iron-based amorphous coatings involves depositing powder and preparing the coating using laser-directed energy deposition (LDED), comprising the following steps: (1) Substrate pretreatment: Grind the surface of the metal substrate to remove oxide scale and surface impurities; (2) Set LDED parameters: laser power is 1300-1500w, powder feeding rate is 20-25 g / min, laser scanning speed is 6-8 mm / s, and the metal substrate is preheated to 300℃; (3) Coating preparation: A molten pool is generated on the surface of the metal substrate by a laser beam. The laser beam and the powder nozzle work together to send the metal powder into the melting area and solidify and deposit it. Argon gas is continuously introduced during the deposition process to prevent oxidation.

[0014] Because the alloy system designed in this invention has excellent amorphous forming ability, a fully amorphous coating can be obtained in one step using the LDED process. Furthermore, by controlling the linear energy density and preheating substrate temperature during the LDED process, process parameter optimization can improve defects such as microcracks in the coating.

[0015] The beneficial effects of this invention are as follows: (1) Excellent amorphous forming ability: When preparing amorphous alloy powder, the amorphous forming ability of the alloy is greatly improved by the selection of alloying elements and the thermodynamic calculation of the composition; when preparing coating, a completely amorphous structure coating can be obtained without conventional rapid cooling process, and it is compatible with a wide range of processes such as LDED and supersonic flame spraying. The prepared coating shows only one broadened diffraction peak in XRD detection, without sharp crystal diffraction peaks.

[0016] (2) Outstanding comprehensive mechanical properties: hardness ≥800 HV, wear resistance is better than traditional Fe-Si-B amorphous alloys, which can meet the service requirements of wear-resistant parts.

[0017] (3) Strong corrosion resistance: Cr and Mo synergistically construct a dense passivation film, with a corrosion rate ≤0.07mm / a in 3.5% NaCl solution. Its corrosion resistance is significantly better than that of 304 stainless steel, making it suitable for corrosive environments such as marine and chemical industries.

[0018] (4) Stable preparation process: The precise proportion of Al balances the melt flowability and oxidation risk, avoiding problems such as nozzle blockage and defects caused by coating deposition process. The raw materials do not need to be high-purity powder, but conventional alloy blocks are used as much as possible to reduce production costs and facilitate industrial production.

[0019] (5) Wide range of applications: It can be made into powders of different particle sizes and is widely applicable to technologies such as LDED and supersonic flame spraying. It is not highly dependent on the cooling rate of the technology. (6) The present invention uses LDED technology to prepare iron-based amorphous coatings, which can improve the uniformity of material composition; the mechanical properties and corrosion resistance of the products prepared by this method meet the requirements of functional parts and no additional post-processing is required. Attached Figure Description

[0020] Figure 1 The XRD patterns of the iron-based amorphous alloy powder and coating prepared in Example 1 are shown.

[0021] Figure 2 The XRD patterns of the iron-based amorphous alloy powder and coating prepared for Comparative Example 1 are shown. Detailed Implementation

[0022] Example 1

[0023] A high-hardness, corrosion-resistant iron-based amorphous alloy has the following composition by mass percentage: Cr 22%, Mo 5%, B 3.8%, C 0.5%, Si 1.2%, Al 3%, Nb 2%, with the balance being Fe. The preparation method includes the following steps: (1) Raw material pretreatment: After accurately weighing high carbon ferrochrome, iron carbon ferrochrome, ferromolybdenum, boron carbide, ferrosilicon, electrolytic aluminum, ferroniobium and pure iron according to the proportion, the metal raw materials are polished with sandpaper to remove oxide scale. All raw materials are ultrasonically cleaned with alcohol for 15 minutes and then dried at 80℃ for 1 hour for later use. (2) Alloy melting: Place the raw materials into a vacuum induction melting furnace and evacuate to 3×10 -3 Pa, purged with 99.99% pure argon gas for protection, heated to 1600℃ at a rate of 10℃ / min, held at that temperature for 25min and stirred 3 times (4min each time). (3) A gas atomization process is used to atomize the molten alloy liquid into amorphous alloy powder. The atomization pressure is 5 MPa and the cooling rate is ≥10. 5 K / s, 50-150μm powder is collected by sieving.

[0024] The application of the prepared iron-based amorphous alloy in the preparation of iron-based amorphous coatings includes the following steps: (1) The substrate is cut to 100mm×50mm×5mm, polished and cleaned, preheated to 300℃ and kept warm for 30min; (2) Deposition using LDED technology: laser power 1400w, spot diameter 3mm, powder feeding rate 30g / min (argon carrier gas flow rate 2L / min), laser scanning speed 6mm / s, scanning spacing 1.5mm; (3) The laser beam and the powder feeding nozzle work together to form a molten pool on the substrate surface to achieve powder melting and deposition. Argon gas (8L / min) is continuously passed through during the deposition process to prevent oxidation, and finally a 0.5~2mm thick iron-based amorphous coating is obtained.

[0025] Example 2

[0026] A high-hardness, corrosion-resistant iron-based amorphous alloy has the following composition by mass percentage: Cr 24%, Mo 7%, B 4.0%, C 0.7%, Si 1.4%, Al 5%, Nb 3%, with the balance being Fe. The preparation method is the same as that in Example 1 and will not be repeated here.

[0027] Example 3

[0028] A high-hardness, corrosion-resistant iron-based amorphous alloy has the following composition by mass percentage: Cr 20%, Mo 3%, B 3.6%, C 0.3%, Si 1.0%, Al 1%, Nb 1%, with the balance being Fe. The preparation method is the same as that in Example 1 and will not be repeated here.

[0029] Comparative Example 1 A comparative coating was prepared with an aluminum content >5% using an iron-based amorphous alloy. The preparation method was the same as in Example 1, except that the aluminum content of the prepared iron-based amorphous alloy was 8%.

[0030] Comparative Example 2 A comparative coating was prepared with an iron-based amorphous alloy containing less than 20% chromium. The preparation method was the same as in Example 1, except that the chromium content of the prepared iron-based amorphous alloy was 18%.

[0031] The amorphous content, microhardness, wear resistance, and corrosion rate in 3.5 wt.% NaCl solution of the iron-based amorphous alloy powders prepared in Examples 1-3 and Comparative Examples 1-2 were obtained experimentally. XRD patterns of the coatings were measured using an X-ray diffractometer, and the corresponding amorphous content was calculated using the pseudo-Voigt semi-quantitative method. The microhardness of each coating was tested using a microhardness tester, with the average value of 20 test points for each sample. The room temperature wear of the coatings was tested using a tribological testing machine at a rotation speed of 15.9 rpm and a load of 600 g. The maximum wear depth was used to characterize the wear resistance of the coating. Electrochemical corrosion was performed using a CS2350 electrochemical workstation to test the potentiodynamic polarization curves, and the corresponding corrosion rate was obtained by converting the corrosion current density. The test results are shown in Table 1.

[0032] Implementation Amorphous content (%) Microhardness (HV) Maximum wear depth (μm) Corrosion rate (mm / a) Example 1 97 881 2.9 0.05 Example 2 92 836 3.1 0.06 Example 3 90 825 3.2 0.07 Comparative Example 1 37 639 4.9 0.09 Comparative Example 2 43 704 4.6 0.09 As shown in Table 1, coatings with high amorphous content were prepared using the alloy composition described in this invention (Examples 1-3). These amorphous coatings exhibit both excellent corrosion resistance and wear resistance, demonstrating the effectiveness and advancement of the composition design and corresponding coating preparation process proposed in this invention. This solves the problem of limited performance and difficulty in simultaneously achieving high performance and high amorphous formation capability in existing iron-based amorphous coating technologies, showing broad application prospects under harsh conditions of coupled corrosion and wear. In Example 1, the coating has complete peaks (…). Figure 1 This indicates that the coating has an almost entirely amorphous structure; when the Al content in the iron-based amorphous powder is high (Comparative Example 1), the amorphous content of the resulting coating decreases significantly (only 37%), such as... Figure 2 As shown. This low amorphous content results in the coating's hardness, corrosion resistance, and wear resistance all falling short of expectations.

Claims

1. A high-hardness, corrosion-resistant iron-based amorphous alloy, characterized in that, The components, by mass percentage, are: Cr 20%-24%, Mo 3%-7%, B 3.6%-4.0%, C 0.3%-0.7%, Si 1.0%-1.4%, Al 1%-5%, Nb 1%-3%, with the balance being Fe.

2. The high-hardness, corrosion-resistant iron-based amorphous alloy as described in claim 1, characterized in that, The components, by mass percentage, are: Cr 22%, Mo 5%, B 3.8%, C 0.5%, Si 1.2%, Al 3%, Nb 2%, with the balance being Fe.

3. The method for preparing the high-hardness, corrosion-resistant iron-based amorphous alloy as described in claim 1, characterized in that, Includes the following steps: (1) Raw material pretreatment: Select high carbon ferrochrome, iron-carbon ferrochrome, ferromolybdenum, boron carbide, ferrosilicon, electrolytic aluminum, ferroniobium and pure iron as raw materials, weigh them accurately according to the composition ratio, remove the oxide scale and oil stains on the surface of the raw materials, and dry them for later use; (2) Alloy melting: The pretreated raw materials are placed in a vacuum induction melting furnace and vacuumed to a vacuum degree ≤5×10 - 3 Pa, introduce inert gas for protection, heat to 1550-1650℃, hold for 20-30 minutes to completely melt and uniformly mix the raw materials, and use electromagnetic stirring during the process to ensure uniform alloy composition; (3) The molten alloy liquid is atomized into amorphous alloy powder by gas atomization process, cooled, and sieved to collect the powder.

4. The method for preparing the high-hardness, corrosion-resistant iron-based amorphous alloy as described in claim 3, characterized in that, In step (2), the inert gas is nitrogen or argon, and the gas purity is ≥99.99%.

5. The method for preparing the high-hardness, corrosion-resistant iron-based amorphous alloy as described in claim 3, characterized in that, In step (2), the electromagnetic stirring is performed 2-3 times, and each stirring time is 3-5 minutes.

6. The method for preparing the high-hardness, corrosion-resistant iron-based amorphous alloy as described in claim 3, characterized in that, In step (3), the atomization pressure is 3-5 MPa.

7. The method for preparing the high-hardness, corrosion-resistant iron-based amorphous alloy as described in claim 3, characterized in that, In step (3), the cooling rate is ≥10 5 K / s.

8. The method for preparing the high-hardness, corrosion-resistant iron-based amorphous alloy as described in claim 3, characterized in that, In step (3), the particle size of the powder collected by sieving is 50-150 μm.

9. The application of the high-hardness, corrosion-resistant iron-based amorphous alloy as described in claim 1 in the preparation of wear-resistant and corrosion-resistant iron-based amorphous coatings.

10. The application as described in claim 9, characterized in that, The powder deposition and coating preparation method using laser-directed energy deposition (LDED) includes the following steps: (1) Substrate pretreatment: Grind the surface of the metal substrate to remove oxide scale and surface impurities; (2) Set LDED parameters: laser power is 1300-1500w, powder feeding rate is 20-25 g / min, laser scanning speed is 6-8mm / s, and the metal substrate is preheated to 300℃; (3) Coating preparation: A molten pool is generated on the surface of the metal substrate by a laser beam. The laser beam and the powder nozzle work together to send the metal powder into the melting area and solidify and deposit it. Argon gas is continuously introduced during the deposition process to prevent oxidation.

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