Preparation method of functionally graded material without adding prefabricated powder

Abstract

The invention discloses a preparation method of a functionally graded material without prefabricated powder addition, which specifically comprises the following steps: step 1, pretreatment: cutting and milling a test block workpiece, processing the test block workpiece into a fixed size and shape, and then cleaning the processed workpiece by using an ultrasonic cleaning machine; step 2, preparing a sample, and polishing the test block by using a metallographic polishing machine until the test block is polished; 3, electron beam treatment, wherein electron beams are adopted for conducting multiple times of irradiation treatment on the sample. And 4, tissue and performance testing is conducted, specifically, the microstructure is observed through a scanning electron microscope, and the mechanical performance of the functionally graded material is detected through a Vickers hardness tester. The method disclosed by the invention can be used for quickly synthesizing the functionally graded material without prefabricated addition, and has an extremely good application scene.

Description

Technical Field

[0001] This invention belongs to the field of high-energy beam surface modification technology for gear steel, specifically relating to a method for treating 30CrMo steel with a high-voltage electron beam. Background Technology

[0002] With the rapid development of modern manufacturing, the demand for high-performance steel continues to grow. Ensuring the stability and extending the service life of mechanical structures and components under harsh conditions has become a crucial issue for improving the national economy. 30CrMo steel, as a high-quality gear steel, possesses high strength, good toughness, and excellent machinability. It is widely used in key components such as heavy-duty gears, crankshafts, and drive shafts. Its superior mechanical properties and high hardness effectively meet the high strength and impact resistance requirements of industrial equipment. However, with the upgrading of industrial technology, the requirements for precision, high hardness, and corrosion resistance of parts such as plate heat exchangers and bellows are constantly increasing. Traditional heat treatment methods are no longer sufficient to meet these high-end demands, affecting the service life of components. To solve this problem, surface strengthening treatment is usually performed on the workpiece to improve its fatigue resistance, hardness, and corrosion resistance. Traditional metal surface strengthening methods, such as surface quenching, electroplating, carburizing, and nitriding, can improve hardness and mechanical properties to a certain extent, but they are often time-consuming, labor-intensive, costly, and polluting, limiting their practical application. Therefore, exploring more efficient, low-cost, and environmentally friendly processing technologies has become a trend.

[0003] Electron beam surface modification is a process that uses an electron beam to rapidly heat and melt the surface layer of a material. Because the substrate remains cold, the heat from the surface layer is quickly conducted to the substrate, resulting in a high-hardness microstructure on the surface upon cooling, significantly improving the material's mechanical properties. Compared to traditional surface modification techniques, electron beam surface modification offers the following advantages: (1) High power density, precise control, strong repeatability, and can accurately control surface temperature and hardening depth; (2) It is carried out under vacuum conditions, which effectively protects the metal, ensures high bonding strength and improves quality.

[0004] Therefore, this patent proposes a scanning electron beam surface modification process for surface strengthening of 30CrMo gear steel. Through rapid heating and cooling by the electron beam, surface grains grow along an ideal direction, significantly improving the overall mechanical properties of 30CrMo steel and giving it higher durability and reliability in applications such as heavy-duty gears. This technology can also be extended to the surface modification of other metallic materials, providing a new direction for high-energy beam surface processing. Summary of the Invention

[0005] The purpose of this invention is: This invention involves machining 30CrMo gear steel into a fixed size and shape, polishing it with a metallographic polishing machine to obtain a sample, and then performing surface modification treatment with scanning electron beam to obtain the finished sample. This invention effectively improves the gradient mechanical properties of the test block and has excellent practical application scenarios.

[0006] To address the issues raised in the appeal, the technical solution adopted in this invention is: a method for preparing functionally graded materials without the addition of pre-formulated powder, comprising the following steps: Step 1: Pre-treatment. The test block workpiece is cut and milled to a fixed size and shape. Then, the processed workpiece is cleaned with an ultrasonic cleaner to remove surface oil and impurities.

[0007] Proceed to step 2 after step 1 is completed; Step 2: Sample preparation. Use a metallographic polishing machine to grind the sample from 600 grit sandpaper to 3000 grit and then polish it.

[0008] Proceed to step 3 after step 2 is completed; Step 3: Electron beam treatment. The sample is placed in the heat treatment chamber of the electron beam welder, and a vacuum is drawn to achieve a vacuum level of 1.33 × 10^(-3) Pa in the electron gun chamber and 5 × 10^(-2) Pa in the processing chamber. The electron beam welder process parameters are set as follows: electron beam accelerating voltage of 60 kV, focusing current of 340 mA, electron beam current of 15 mA, electron beam down-beam frequency of 300 Hz, down-beam time of 20 ms, and electron beam spot radius of 6 mm. The treated sample is then cut into small pieces, cleaned using an ultrasonic cleaner, and subjected to metallographic preparation to obtain the finished product.

[0009] Step 4: Organization and performance testing. The microstructure of the sample was observed using a Quanta FEG450 field emission scanning electron microscope (SEM). The Vickers hardness of the sample cross-section after sanding was tested using an HVS-1000 digital display micro Vickers hardness tester.

[0010] 2. The method for preparing a functionally graded material without pre-formed powder addition according to claim 1, characterized in that: the pretreatment in step 1 requires cutting and milling, cutting the 30CrMo steel workpiece into 10mm×10mm×10mm test blocks, and performing metallographic polishing.

[0011] 3. The method for preparing a functionally graded material without pre-formed powder addition according to claim 1, characterized in that: step 3 uses a high-voltage electron beam for surface treatment.

[0012] 4. The method for preparing a functionally graded material without pre-formulated powder as described in claim 1, characterized in that: after step 3, the material will have grain refinement and dendrite growth effects.

[0013] Compared with the prior art, the present invention has the following beneficial effects: This invention employs a high-voltage, low-frequency electron beam to modify the surface of 30CrMo gear steel, effectively improving the gradient mechanical properties of the sample cross-section. The high-voltage, low-frequency electron beam treatment provides high energy density, rapidly heating the 30CrMo gear steel to its melting point, followed by rapid cooling. This rapid heating and cooling process transforms the microstructure of the modified layer and the matrix, refining the grains and causing dendrites to grow along ideal directions, providing anisotropy in mechanical properties and significantly improving the wear resistance of the sample surface.

[0014] The scanning electron beam process of 30CrMo gear steel described in this invention is carried out in a vacuum processing chamber, which ensures that the processing environment is pollution-free and avoids contact between 30CrMo gear steel and the outside world; at the same time, the energy transfer medium is electrons, which has the characteristics of high energy conversion and good effect.

[0015] The matrix hardness of the 30CrMo gear steel prepared by this invention is 233.52 HV. 0.1 The hardness of the molten zone can reach up to 607.58 HV. 0.1 It is the matrix (233.52 HV) 0.1 2.6 times that of ). Attached Figure Description Figure 1 This is a schematic diagram of the working principle of the electron beam in this invention; Figure 2 This is the cross-sectional microstructure of the 30CrMo gear steel obtained after implementing the present invention; Figure 3 This is an enlarged view of the microstructure of 30CrMo gear steel before the implementation of this invention; Figure 4 This is a cross-sectional microhardness contour plot of the 30CrMo gear steel obtained after implementing this invention. The following are specific embodiments of the present invention. The solutions of the present invention will be further described with reference to the accompanying drawings, but the present invention is not limited to these embodiments. Detailed Implementation A method for electron beam treatment of 30CrMo gear steel includes the following steps: 1. A method for electron beam treatment of 30CrMo gear steel, comprising the following steps: Step 1: Pre-treatment. The test block workpiece is cut and milled to a fixed size and shape. Then, the processed workpiece is cleaned with an ultrasonic cleaner to remove surface oil and impurities.

[0016] Proceed to step 2 after step 1 is completed; Step 2: Sample preparation. Use a metallographic polishing machine to grind the sample from 600 grit sandpaper to 3000 grit and then polish it.

[0017] Proceed to step 3 after step 2 is completed; Step 3: Electron beam treatment. The sample is placed in the heat treatment chamber of the electron beam welder, and a vacuum is drawn to achieve a vacuum level of 1.33 × 10^(-3) Pa in the electron gun chamber and 5 × 10^(-2) Pa in the processing chamber. The electron beam welder process parameters are set as follows: electron beam accelerating voltage of 60 kV, focusing current of 340 mA, electron beam current of 15 mA, electron beam down-beam frequency of 300 Hz, down-beam time of 20 ms, and electron beam spot radius of 6 mm. The treated sample is then cut into small pieces, cleaned using an ultrasonic cleaner, and subjected to metallographic preparation to obtain the finished product.

[0018] After step 3 is completed, proceed to step 4; Step 4: Organization and performance testing. The microstructure of the sample was observed using a Quanta FEG450 field emission scanning electron microscope (SEM). The Vickers hardness of the sample after sanding was tested using an HVS-1000 digital Vickers hardness tester.

[0019] The Vickers hardness of the sample after sanding was tested using an HVS-1000 digital display micro Vickers hardness tester. A 10N load was applied and held for 10 seconds. Measurements were taken at 50μm intervals. After processing... The hardness of the molten zone can reach up to 607.58 HV. 0.1 It is the matrix (233.52 HV) 0.1 It is 2.6 times that of the surface layer. The mechanical properties change nonlinearly from the surface to the matrix.

[0020] The microstructure of the samples was examined using a Quanta FEG450 field emission scanning electron microscope (SEM). For example... Figure 2 As shown, the cross-section is divided into a modified layer and a matrix. The fusion lines in each region are obvious, and the grains of the modified layer are significantly refined, indicating that the matrix has a good modification effect. Figure 3 To amplify the local modification effect, it can be observed that grain refinement is achieved, and the wear resistance of the material is greatly improved. Figure 4 The microhardness contour plot of the cross section reveals that the properties of lixue decrease nonlinearly in a gradient manner.

[0021] The above description is a detailed explanation of feasible examples of the present invention. However, the embodiments are not intended to limit the scope of the patent application of the present invention. All equivalent changes or modifications made under the technical spirit of the present invention should fall within the patent scope covered by the present invention.

Claims

1. A method for preparing functionally graded materials without the addition of pre-formed powder, comprising the following steps: Step 1: Pre-treatment. The test block workpiece is cut and milled to a fixed size and shape. Then, the processed workpiece is cleaned with an ultrasonic cleaner to remove surface oil and impurities.

2. Proceed to step 2 after step 1 is completed; Step 2: Sample preparation. Use a metallographic polishing machine to grind the sample from 600 grit sandpaper to 3000 grit and then polish it.

3. Proceed to step 3 after step 2 is completed; Step 3: Electron beam treatment. The sample is placed in the heat treatment chamber of the electron beam welding machine, and a vacuum is drawn to achieve a vacuum level of 1.33 × 10⁻⁶ Ω·cm in the electron gun chamber. Pa, the vacuum degree of the processing chamber is 5× Pa. The electron beam welding machine process parameters were set as follows: electron beam accelerating voltage 60kV, focusing current 340mA, electron beam current 15mA, electron beam down-beam frequency 300Hz, down-beam time 20ms, and electron beam spot radius 6mm. The processed sample was then cut into small pieces, cleaned using an ultrasonic cleaner, and subjected to metallographic preparation to obtain the finished product.

4. Step 4: Organization and performance testing. The microstructure of the sample was observed using a Quanta FEG450 field emission scanning electron microscope (SEM). The Vickers hardness of the sample after sanding was tested using an HVS-1000 digital display micro Vickers hardness tester.

5. The method for preparing a functionally graded material without pre-formed powder addition according to claim 1, characterized in that: the pretreatment in step 1 requires cutting and milling, cutting the 30CrMo steel workpiece into 10mm×10mm×10mm test blocks, and performing metallographic polishing.

6. The method for preparing a functionally graded material without pre-formed powder addition according to claim 1, characterized in that: step 3 uses a high-voltage electron beam for surface treatment.

7. The method for preparing a functionally graded material without pre-formulated powder according to claim 1, characterized in that: after step 3, the material will have grain refinement and dendrite growth effects.

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