Laser cladding impact composite strengthened gear steel and its preparation method and application

Abstract

The present invention discloses a laser cladding impact composite strengthened gear steel and its preparation method and application, belonging to the field of laser metal material processing technology. The present invention mixes a certain amount of nano-scale TiC particles into the gear steel pre-alloyed powder, and optimizes the laser additive manufacturing process and laser surface impact strengthening parameters to prepare gear steel with TiC particle dispersion strengthening on the inside and surface compressive stress composite strengthening on the outside. The invention adopts a composite strengthening treatment process of laser additive manufacturing, oxide dispersion strengthening and laser surface impact strengthening, which not only makes up for the technical shortcomings of each process, but also gives full play to the advantages of each process, effectively improving the hardness of the gear steel.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser metal material processing, and in particular relates to a laser cladding impact composite strengthened gear steel and a preparation method and application thereof. Background Art

[0002] Attack helicopters are highly effective weapons for low-altitude missions, but they are also subject to attack from all directions, both from the ground and from the air. Consequently, their transmission systems are highly susceptible to oil leaks. Once struck and leaked, the numerous gears in the helicopter's transmission system operate without lubrication, causing a rapid increase in temperature and a significant decrease in hardness and wear resistance. This, in turn, impacts transmission efficiency and can even lead to a crash, seriously threatening mission completion and the safety of the pilot.

[0003] Traditional gear steel surface hardening processes primarily rely on high-temperature carburizing heat treatment, which involves placing the gear steel in a vacuum, high-temperature carbon environment. This process leverages the carbon potential and rapid diffusion of high-temperature carbon atoms to form a gradient of carbides on the surface, thereby improving the surface hardness and wear resistance of the gear steel. However, high-temperature carburizing heat treatment has significant shortcomings. Its carburizing depth is limited. For example, carburizing at 900°C for 4 hours only yields a depth of approximately 1mm. This results in the current dry friction performance of gear steel failing to meet practical requirements. Therefore, there is an urgent need to develop new gear steel surface hardening technologies to overcome the limitations of traditional carburizing depths.

[0004] Laser additive manufacturing, as a new material preparation method, can directly obtain near-net-shape components from metal powder. At the same time, dispersion strengthening can significantly improve the hardness of the alloy by introducing a high-density, high-temperature stable reinforcement phase into the alloy. Therefore, the advantages of additive manufacturing and dispersion strengthening technologies can be combined, and through the selection of appropriate reinforcement phases, gear steel with unlimited reinforcement depth can be prepared. However, in the process of combining the technologies, it should be considered that additive manufacturing technology will form significant tensile stress on the surface of the component due to the ultra-fast cooling rate, which is harmful to the hardness, wear resistance and fatigue performance of the alloy. It can be seen that the current methods for preparing gear steel cannot solve the problem of insufficient surface strengthening. Summary of the Invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a laser cladding impact composite strengthened gear steel and its preparation method and application, so as to solve the technical problem of insufficient surface strengthening of existing gear steel.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention discloses a laser cladding impact composite strengthened gear steel, which is composed of the following components in volume percentage:

[0008] 70%-90% pre-alloyed gear steel;

[0009] 10%-30% TiC particles;

[0010] The gear steel pre-alloy comprises, by mass percentage, 0.09%≤C≤0.20%, 0.3%≤Mn≤1.0%, 0.1%≤Si≤1.0%, 0.05%≤Mo≤0.35%, 0.5%≤Cr≤2.0%, 1.0%≤Ni≤5.0%, 0.03%≤Cu≤0.5%, 0.1%≤Ti≤0.5%, and the rest is Fe.

[0011] Preferably, the average size of the TiC particles is 40 nm.

[0012] Preferably, TiC particles are evenly and dispersedly distributed in the microstructure of the gear steel, which refines the grains, pins the grain boundaries, and improves the strength and high-temperature structural stability of the gear steel; the laser shock introduces significant surface compressive stress on the surface of the gear steel and closes tiny surface pores, further improving the mechanical properties of the gear steel and forming an internally and externally strengthened gear steel.

[0013] Preferably, the hardness of the laser cladding impact composite strengthened gear steel is 336-382 HV.

[0014] The present invention also discloses a method for preparing the above-mentioned laser cladding impact composite strengthened gear steel, comprising the following steps:

[0015] 1) preparing gear steel pre-alloyed powder by taking corresponding element raw materials according to the composition ratio;

[0016] 2) mixing the gear steel pre-alloyed powder and TiC particles according to a volume ratio to prepare a composite powder;

[0017] 3) The composite powder is processed by laser additive manufacturing to produce a gear steel formed component;

[0018] 4) performing surface laser shock peening treatment on the prepared gear steel formed component to prepare laser cladding shock composite strengthened gear steel;

[0019] The laser shock peening process window is as follows: laser wavelength 1064nm, laser pulse width 20ns, spot diameter 2.2mm, laser energy Gaussian distribution, constrained layer of water, impact energy 3-5J, impact times 3-5 times, overlap rate 25%-75%.

[0020] Preferably, in step 2), the gear steel pre-alloyed powder and TiC particles are mixed by ball milling, and the ball milling mixing parameters are: main disk speed of 250rpm-400rpm, revolution-rotation ratio of 1:2, ball-to-material ratio of 8:1, ball milling time of 14-35h, and 99.99% purity argon protection.

[0021] More preferably, the powder with a particle size range of 50 μm-180 μm after ball milling and mixing is screened out and dried to obtain a composite powder.

[0022] Preferably, in step 2), the gear steel pre-alloyed powder and TiC particles are mixed by acoustic resonance mixing, and the acoustic resonance mixing parameters are: vibration frequency 50Hz-80Hz, acceleration 65G-100G, vibration time not less than 20min, 99.99% purity argon protection, after mixing, drying to obtain a composite powder.

[0023] Preferably, in step 3), the additive manufacturing printing parameter window is: laser power 500-1200W, scanning speed 6mm / s-10mm / s, spot diameter 1.4mm-1.8mm, powder feeding rate 8g / min-15g / min, and 99.99% purity argon protection.

[0024] The present invention also discloses the application of the laser cladding impact composite strengthened gear steel in the preparation of aerospace equipment.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] This invention combines 10%-30% nano-TiC particles by volume with pre-alloyed gear steel powder. Through optimized laser additive manufacturing (LAM) processes and laser shock parameters, gear steel parts with fine microstructures, internally reinforced by uniformly distributed nano-TiC particles, and surface-strengthened by surface compressive stress induced by laser shock, resulting in superior mechanical properties. Research results demonstrate that within the optimized LAM process window, the addition of TiC acts as a non-uniform nucleating agent during gear steel solidification, inhibiting epitaxial grain growth and thereby refining the microstructure. Furthermore, the addition of TiC improves the printability of AM gear steel and reduces the formation of solidification defects. Furthermore, through optimized laser shock surface strengthening, the surface stress state of LAM gear steel can be significantly improved, shifting from harmful surface tensile stress to beneficial surface compressive stress, further enhancing the mechanical properties of the gear steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the microstructure of the laser cladding impact composite strengthened gear steel prepared by the present invention.

[0028] Among them: 200 is the surface compressive stress layer introduced by laser shock; 201 is TiC particles; 202 is the grain boundary of austenitic stainless steel manufactured by dispersion strengthening additive manufacturing; 203 is the intracrystalline matrix of austenitic stainless steel manufactured by dispersion strengthening additive manufacturing.

[0029] Figure 2 The laser cladding impact composite strengthened gear steel microstructure prepared by the present invention. DETAILED DESCRIPTION

[0030] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0031] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0032] The present invention is described in further detail below with reference to the accompanying drawings:

[0033] See also Figure 1 , is a schematic diagram of the microstructure of the gear steel subjected to laser cladding impact composite strengthening according to the present invention, Figure 1 As can be seen in the figure, the uniform distribution of TiC particles in the microstructure refines the grains, pins the grain boundaries, and improves the strength and high-temperature stability of the gear steel. The surface is strengthened by introducing surface stress through laser shock and closing tiny holes on the surface, further improving the mechanical properties of the gear steel and forming a gear steel that is simultaneously strengthened inside and outside. Figure 2 , is the microstructure of the laser cladding impact composite strengthened gear steel prepared by the present invention. It can be seen that high-density submicron-scale TiC is uniformly distributed in the microstructure and pins the grain boundaries.

[0034] Example 1

[0035] A method for preparing gear steel by laser cladding impact composite strengthening comprises the following steps:

[0036] Step 1: configuring the gear steel composition by weight percentage, specifically: 0.09%≤C≤0.20%, 0.3%≤Mn≤1.0%, 0.1%≤Si≤1.0%, 0.05%≤Mo≤0.35%, 0.5%≤Cr≤2.0%, 1.0%≤Ni≤5.0%, 0.03%≤Cu≤0.5%, 0.1%≤Ti≤0.5%, and the remainder being Fe; preparing a gear steel pre-alloyed powder with a particle size of 50 μm-180 μm according to the above composition; mixing the gear steel pre-alloy with TiC particles (average size 40 nm) to obtain a composite powder, wherein the volume percentage of TiC particles in the obtained composite powder is 20%;

[0037] Step 2: The gear steel pre-alloyed powder and TiC particles from Step 1 were placed in a high-energy ball mill and thoroughly mechanically ground and mixed. The main disc speed was 300 rpm, the rotational velocity ratio was 1:2, the ball-to-material ratio was 8:1, and the milling time was 32 hours under high-purity argon (99.99%). After mixing, a powder with a particle size range of 50 μm to 180 μm was screened and dried to obtain the composite powder.

[0038] Step 3: Using the composite powder obtained in step S1, laser additive manufacturing is performed to obtain a gear steel molded component; the additive manufacturing printing parameter window is: laser power 800 W, scanning speed 8 mm / s, spot diameter 1.4 mm, powder feeding rate 8 g / min, and high-purity argon (99.99%) protection;

[0039] Step 4: The gear steel block obtained in step S2 is ground and polished by laser additive manufacturing, and then subjected to surface laser shock peening; the laser shock peening process window is: laser wavelength 1064nm, laser pulse width 20ns, spot diameter 2.2mm, laser energy Gaussian distribution, constrained layer is water, impact energy 4J, number of impacts 5 times, and overlap rate 50%.

[0040] Step 5: The laser additively manufactured gear steel block obtained in step 4 was prepared into a metallographic sample. The microhardness of the sample was measured with a maximum load of 50 g and a full load time of 10 s, which is listed in Table 1.

[0041] Example 2

[0042] A method for preparing gear steel by laser cladding impact composite strengthening comprises the following steps:

[0043] Step 1: configuring the gear steel composition by weight percentage, specifically: 0.09%≤C≤0.20%, 0.3%≤Mn≤1.0%, 0.1%≤Si≤1.0%, 0.05%≤Mo≤0.35%, 0.5%≤Cr≤2.0%, 1.0%≤Ni≤5.0%, 0.03%≤Cu≤0.5%, 0.1%≤Ti≤0.5%, and the remainder being Fe; preparing a gear steel pre-alloyed powder with a particle size of 50 μm-180 μm according to the above composition; mixing the gear steel pre-alloy with TiC particles (average size 40 nm) to obtain a composite powder, wherein the volume percentage of TiC particles in the obtained composite powder is 25%;

[0044] Step 2: The gear steel pre-alloyed powder and TiC particles from Step 1 were placed in a high-energy ball mill and thoroughly mechanically ground and mixed. The main disc speed was 250 rpm, the rotational-rotational ratio was 1:2, the ball-to-material ratio was 8:1, and the milling time was 35 hours under high-purity argon (99.99%). After mixing, the powder was screened to have a particle size range of 50 μm to 180 μm and dried to obtain the composite powder.

[0045] Step 3: Using the composite powder obtained in step 2, laser additive manufacturing is performed to obtain a gear steel formed component; the additive manufacturing printing parameter window is: laser power 800W, scanning speed 8mm / s, spot diameter 1.4mm, and powder feeding rate 8g / min;

[0046] Step 4: The gear steel block obtained in step 3 is ground and polished by laser additive manufacturing, and then subjected to surface laser shock peening; the laser shock peening process window is: laser wavelength 1064nm, laser pulse width 20ns, spot diameter 2.2mm, laser energy Gaussian distribution, constrained layer is water, impact energy 4J, number of impacts 5 times, overlap rate 25%.

[0047] Step 5: The laser additively manufactured gear steel block obtained in step 4 was prepared into a metallographic sample. The microhardness of the sample was measured with a maximum load of 50 g and a full load time of 10 s, which is listed in Table 1.

[0048] Example 3

[0049] A method for preparing gear steel by laser cladding impact composite strengthening comprises the following steps:

[0050] Step 1: configuring the gear steel composition by weight percentage, specifically: 0.09%≤C≤0.20%, 0.3%≤Mn≤1.0%, 0.1%≤Si≤1.0%, 0.05%≤Mo≤0.35%, 0.5%≤Cr≤2.0%, 1.0%≤Ni≤5.0%, 0.03%≤Cu≤0.5%, 0.1%≤Ti≤0.5%, and the remainder being Fe; preparing a gear steel pre-alloyed powder with a particle size of 50 μm-180 μm according to the above composition; mixing the gear steel pre-alloy with TiC particles (average size 40 nm) to obtain a composite powder, wherein the volume percentage of TiC particles in the obtained composite powder is 30%;

[0051] Step 2: The gear steel pre-alloyed powder and TiC particles from Step 1 were placed in a high-energy ball mill and thoroughly mechanically ground and mixed. The main disc speed was 300 rpm, the rotational velocity ratio was 1:2, the ball-to-material ratio was 8:1, and the milling time was 30 hours. High-purity argon (99.99%) was used for protection. After mixing, a powder with a particle size range of 50 μm to 180 μm was screened and dried to obtain the composite powder.

[0052] Step 3: Using the composite powder obtained in step 2, laser additive manufacturing is performed to obtain a gear steel formed component; the additive manufacturing printing parameter window is: laser power 600W, scanning speed 8mm / s, spot diameter 1.4mm, and powder feeding rate 8g / min;

[0053] Step 4: The gear steel block obtained in step 3 is ground and polished by laser additive manufacturing, and then subjected to surface laser shock peening; the laser shock peening process window is: laser wavelength 1064nm, laser pulse width 20ns, spot diameter 2.2mm, laser energy Gaussian distribution, constrained layer is water, impact energy 3J, number of impacts 5 times, overlap rate 50%.

[0054] Step 5: The laser additively manufactured gear steel block obtained in step 4 was prepared into a metallographic sample. The microhardness of the sample was measured with a maximum load of 50 g and a full load time of 10 s, which is listed in Table 1.

[0055] Example 4

[0056] A method for preparing gear steel by laser cladding impact composite strengthening comprises the following steps:

[0057] Step 1: configuring the gear steel composition by weight percentage, specifically: 0.09%≤C≤0.20%, 0.3%≤Mn≤1.0%, 0.1%≤Si≤1.0%, 0.05%≤Mo≤0.35%, 0.5%≤Cr≤2.0%, 1.0%≤Ni≤5.0%, 0.03%≤Cu≤0.5%, 0.1%≤Ti≤0.5%, and the remainder being Fe; preparing a gear steel pre-alloyed powder with a particle size of 50 μm-180 μm according to the above composition; mixing the gear steel pre-alloy with TiC particles (average size 40 nm) to obtain a composite powder, wherein the volume percentage of TiC particles in the obtained composite powder is 15%;

[0058] Step 2: Place the gear steel pre-alloyed powder and TiC particles from Step 1 into an acoustic resonance device and thoroughly mix them. Vibrate at a frequency of 60 Hz, an acceleration of 80 G, and a vibration time of at least 40 minutes under high-purity argon (99.99%). After mixing, dry the mixture to obtain the composite powder.

[0059] Step 3: Using the composite powder obtained in step 2, laser additive manufacturing is performed to obtain a gear steel molded component; the additive manufacturing printing parameter window is: laser power 800W, scanning speed 10mm / s, spot diameter 1.6mm, and powder feeding rate 8g / min;

[0060] Step 4: The gear steel block obtained in step 3 is ground and polished by laser additive manufacturing, and then subjected to surface laser shock peening; the laser shock peening process window is: laser wavelength 1064nm, laser pulse width 20ns, spot diameter 2.2mm, laser energy Gaussian distribution, constrained layer is water, impact energy 4J, number of impacts 4 times, overlap rate 50%.

[0061] Step 5: The laser additively manufactured gear steel block obtained in step 4 was prepared into a metallographic sample. The microhardness of the sample was measured with a maximum load of 50 g and a full load time of 10 s, which is listed in Table 1.

[0062] Comparative Example 1

[0063] A method for preparing gear steel by laser cladding, which differs from the above embodiment in that no TiC particle reinforcement phase is added in this comparative example, comprises the following steps:

[0064] Step 1: Prepare the gear steel composition by weight percentage, specifically: 0.09%≤C≤0.20%, 0.3%≤Mn≤1.0%, 0.1%≤Si≤1.0%, 0.05%≤Mo≤0.35%, 0.5%≤Cr≤2.0%, 1.0%≤Ni≤5.0%, 0.03%≤Cu≤0.5%, 0.1%≤Ti≤0.5%, and the remainder is Fe; prepare gear steel pre-alloyed powder with a particle size of 50μm-180μm according to the above composition;

[0065] Step 2: Using the powder obtained in step 1, laser additive manufacturing is performed to obtain a gear steel formed component; the additive manufacturing printing parameter window is: laser power 800W, scanning speed 10mm / s, spot diameter 1.4mm, and powder feeding rate 8g / min;

[0066] Step 3: The laser additively manufactured gear steel block obtained in step 4 was prepared into a metallographic sample. The microhardness of the sample was measured with a maximum load of 50 g and a full load time of 10 s, as shown in Table 1 below:

[0067] Table 1 shows the microhardness of the samples of the embodiments of the present invention and the comparative examples.

[0068] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Hardness (HV) 356 373 382 336 272

[0069] In summary, in order to further improve the hardness of gear steel, the present invention adopts a composite treatment process of laser additive manufacturing, dispersion strengthening, and laser shock strengthening to effectively regulate its internal microstructure and surface stress state, thereby refining the alloy grains, effectively pinning grain boundaries and dislocations, and regulating the surface stress from harmful tensile stress to beneficial compressive stress, while closing the surface micropores, thereby improving the mechanical properties of the gear steel.

[0070] The above content is only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A laser cladding impact composite strengthened gear steel, characterized in that: Calculated by volume percentage, it is composed of the following components: 70%-90% pre-alloyed gear steel; 10%-30% TiC particles; The gear steel pre-alloy comprises, by mass percentage, 0.09%≤C≤0.20%, 0.3%≤Mn≤1.0%, 0.1%≤Si≤1.0%, 0.05%≤Mo≤0.35%, 0.5%≤Cr≤2.0%, 1.0%≤Ni≤5.0%, 0.03%≤Cu≤0.5%, 0.1%≤Ti≤0.5%, and the remainder is Fe; The interior of the gear steel is composed of TiC particles uniformly and dispersedly distributed in the microstructure; the surface of the gear steel is subjected to significant surface compressive stress introduced by laser shock, and tiny surface pores are closed, forming a gear that is synchronously strengthened inside and outside.

2. The laser cladding impact composite strengthened gear steel according to claim 1, characterized in that: The average size of the TiC particles is 40 nm.

3. The laser cladding impact composite strengthened gear steel according to claim 1, characterized in that: The hardness of the laser cladding impact composite strengthened gear steel is 336~382 HV.

4. The method for preparing laser cladding impact composite strengthened gear steel according to any one of claims 1 to 3, characterized in that: The following steps are involved: 1) Prepare gear steel pre-alloyed powder by taking corresponding element raw materials according to the component ratio; 2) Mixing gear steel pre-alloyed powder and TiC particles according to volume ratio to prepare composite powder; 3) The composite powder is processed by laser additive manufacturing to produce gear steel formed components; 4) The surface of the prepared gear steel formed component is subjected to laser shock peening treatment to prepare laser cladding shock composite strengthened gear steel; The laser shock peening process window is as follows: laser wavelength 1064nm, laser pulse width 20ns, spot diameter 2.2mm, laser energy Gaussian distribution, constrained layer of water, impact energy 3-5J, impact times 3-5 times, overlap rate 25%-75%.

5. The method for preparing laser cladding impact composite strengthened gear steel according to claim 4, characterized in that: In step 2), the gear steel pre-alloyed powder and TiC particles are mixed by ball milling. The ball milling mixing parameters are: main disk speed of 250 rpm-400 rpm, revolution-to-rotation ratio of 1:2, ball-to-material ratio of 8:1, ball milling time of 14-35 h, and 99.99% pure argon protection.

6. The method for preparing laser cladding impact composite strengthened gear steel according to claim 5, characterized in that: The powder with a particle size range of 50 μm to 180 μm after ball milling and mixing is screened out and dried to obtain a composite powder.

7. The method for preparing laser cladding impact composite strengthened gear steel according to claim 4, characterized in that: In step 2), the gear steel pre-alloyed powder and TiC particles are mixed by acoustic resonance mixing. The acoustic resonance mixing parameters are: vibration frequency 50Hz-80Hz, acceleration 65G-100G, vibration time not less than 20min, 99.99% purity argon protection, and after mixing, drying to obtain a composite powder.

8. The method for preparing laser cladding impact composite strengthened gear steel according to claim 4, characterized in that: In step 3), the additive manufacturing printing parameter window is: laser power 500-1200W, scanning speed 6mm / s-10mm / s, spot diameter 1.4mm-1.8mm, powder feeding rate 8g / min-15g / min, and 99.99% purity argon protection.

9. Use of the laser cladding impact composite strengthened gear steel according to any one of claims 1 to 3 in the manufacture of aerospace equipment.

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