Direct energy deposition additive manufacturing method for corrosion-resistant maraging steel based on different laser intensities

Abstract

The invention discloses a direct energy deposition additive manufacturing method for corrosion-resistant maraging steel based on different laser intensities, which is characterized by comprising the following steps of: forming metal powder by adopting BK1900 matched with a plasma rotating electrode technology (PREP) powder manufacturing process, then adopting a direct energy deposition forming process method, respectively setting the laser power as 3000W, 3500W, 4000W, 5000W and 6000W, setting the scanning speed as 600mm / min, and carrying out direct energy deposition forming on the surface of the metal powder to obtain the corrosion-resistant maraging steel. The method comprises the following steps of: forming under the condition of controlling other process parameters to be unchanged, and carrying out full immersion corrosion and chemical corrosion experimental analysis on a formed part, so that the BK1900 steel grade adopts a PREP powder preparation process, the laser power is 3500W, and under the condition of not adjusting other process parameters, the BK1900 steel grade has the characteristics of high yield, high quality and the like, and the quality of the BK1900 steel grade is ensured to be higher than that of the BK1900 steel grade by using the PREP powder preparation process and the laser power is 3500W. And a formed part with the best corrosion resistance can be obtained in the additive manufacturing process.

Description

TECHNICAL FIELD

[0001] The application relates to the field of martensitic age steel additive manufacturing technology, and particularly relates to a direct energy deposition additive manufacturing method for corrosion-resistant martensitic age steel based on different laser intensities. BACKGROUND

[0002] In modern material science and industrial systems, high-strength and high-toughness steel is a key material supporting industrial upgrading, ensuring infrastructure safety and promoting sustainable development. Martensitic age steel is a kind of high-strength and high-toughness low-alloy steel material, which is concerned due to its high strength and excellent toughness. Corrosion resistance is one of the key indicators for measuring the long-term stability of materials in service environments, especially in extreme environments such as aerospace, marine and energy. The corrosion resistance of materials directly affects their service life and safety. For martensitic age steel, its high strength and good toughness make it have wide application prospects in high-quality production fields, but optimizing corrosion resistance is still the focus and complexity of current research. Laser power, as one of the core process parameters in the direct energy deposition forming (DED) process, not only affects the microstructure and mechanical properties of the material, but also can significantly affect the corrosion resistance of the material by changing the phase composition, grain size and residual stress distribution.

[0003] Previous studies have shown that the forming process is more sensitive to powder characteristics / properties compared to conventional processes, which mainly depends on the preparation method of the powder. At the same time, different printing power parameters in the 3D printing process can affect the quality and efficiency of the formed sample. Suitable printing power can improve the density and strength of the sample and other mechanical properties, however, there is almost no research on the comparison of corrosion resistance between different 3D printing powers. SUMMARY

[0004] Therefore, the purpose of the present application is to propose a PREP powder preparation process for corrosion-resistant martensitic age steel, and to use different laser intensities for direct energy deposition forming (DED) additive manufacturing method to study and compare the corrosion resistance variation law under different laser powers, so that the material has excellent corrosion resistance.

[0005] Based on the above purpose, the present application provides a direct energy deposition additive manufacturing method for corrosion-resistant martensitic age steel based on different laser intensities, and the specific preparation steps are as follows: (1) obtain BK1900 martensitic age steel metal powder by using plasma rotating electrode technology (PREP) powder preparation process; (2) Plasma Rotating Electrode Process (PREP), using plasma arc and melting the tip of the fast rotating electrode, under the centrifugal force effect of the high-speed rotating movement of the rod electrode, the molten metal is dispersed into a large number of small-sized droplets in the form of high-speed injection under the action of centrifugal force, in this process, centrifugal force as the main driving force, to break through the surface tension constraint, realize the morphological transformation from continuous fluid to discrete droplets, these droplets condense into spherical powder after heat exchange with the surrounding atmosphere; (3) The above-mentioned maraging steel is divided into metal powder BK1900, and the composition is shown in Table 1; Table 1 BK1900 chemical composition (%)

[0006] (4) The above-mentioned BK1900 metal powder is formed into maraging steel by using direct energy deposition technology; (5) The direct energy deposition process is set, the laser power is 3000W-6000W, the scanning speed is 600 mm / min, the layer thickness is 0.5 mm, the interval is 1.8 mm, the light spot is 3.2 mm, the powder spot is 4 mm, the gas flow is 7 L / min, the scanning strategy is circular scanning, the interlayer pause is 10 s, the rotation is 90°, the cold air is blown, the argon protection is carried out during the forming process, and the working pressure is controlled at 3-5 mbar, and the oxygen content in the forming chamber is detected in real time and is less than 50ppm; (6) The raw material in the form of powder or wire is transported to the substrate of the energy source such as a focused laser beam, an electron beam or an ion / plasma / arc, so as to form a small molten pool and continuously deposit materials layer by layer, and the powder is quickly formed according to the computer graphics, until the complex part is completed; (7) Finally, the formed part is subjected to full immersion corrosion test, electrochemical corrosion test and the like.

[0007] Technical effects and advantages of the present application: The BK1900 steel produced by the PREP powder production process and the DED technology has obvious advantages in strength, toughness and plastic deformation capacity. The present application comprehensively evaluates the change rule of the corrosion resistance of the BK1900 maraging steel under different laser powers by systemically regulating the laser power, combining microstructure analysis, electrochemical test and corrosion morphology characterization and the like. DETAILED DESCRIPTION

[0008] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0009] Figure 1 This is a diagram illustrating the PREP mechanism of the present invention. Figure 2 This is a schematic diagram of the DED mechanism of the present invention; Figure 3 This is a diagram of the full immersion corrosion test apparatus of the present invention; Figure 4 These are macroscopic morphology images of different samples subjected to full immersion corrosion according to the present invention; Figure 5 The corrosion rate curves of samples with different printing powers as a function of time are shown. Figure 6 These are comparison images of the microstructure of different samples after 72 hours of corrosion according to the present invention. Figure 7 These are comparison images of the microstructure of different samples after 120 hours of corrosion according to the present invention. Figure 8 This is a diagram of the electrochemical testing device of the present invention; Figure 9 The Tafel polarization curves for different printing powers of this invention; Figure 10 Impedance spectra of samples with different printing powers according to the present invention; Figure 11 The equivalent circuit diagram for electrochemical impedance spectroscopy fitting of this invention is shown. Detailed Implementation

[0010] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings.

[0011] The technical solutions of the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The described embodiments are only some embodiments of the present invention, and not all embodiments. The scope of protection of the present invention should include the entire contents of the claims, and is not limited to this embodiment.

[0012] Example 1 A direct energy deposition additive manufacturing method for corrosion-resistant maraging steel based on different laser intensities is disclosed, and the specific operation steps are as follows: (1) Using plasma rotating electrode technology (PREP) (e.g.) Figure 1 BK1900 martensitic aging steel metal powder was prepared by powder preparation process, and the specific chemical composition (mass%) is as follows: (2) BK1900 martensitic aging steel metal powder was formed by direct energy deposition technology and PREP powder preparation process; (3) Direct energy deposition process: laser power 3000W, scanning speed 600 mm / min, layer thickness 0.5 mm, spacing 1.8 mm, spot 3.2 mm, powder spot 4 mm, gas flow rate 7 L / min, scanning strategy is cyclic scanning, pause between layers for 10s, rotate 90°, blow cool, argon gas protection during molding process and control working pressure at 3-5 mbar, real-time detection of oxygen content in molding chamber <50ppm; (4) DED uses a high-energy-density heat source (laser, electron beam, or plasma / arc) focused on the substrate to form a small molten pool, simultaneously melting the raw material delivered to the pool in the form of powder or wire. As the heat source moves forward, the deposited metal solidifies on the substrate, forming metal tracks. The metal tracks overlap each other according to a predefined pattern filling spacing (i.e., the distance between consecutive metal tracks). After deposition is complete, the deposited layer is moved up to the next layer, such as... Figure 2 They are stacked layer by layer until the entire component is formed; (5) According to the electrochemical corrosion performance test, the performance indicators of BK1900 martensitic aging steel prepared by direct energy deposition under PREP powder preparation process in this embodiment are as follows: open circuit potential is -0.998V, breakdown potential (potential at the end of passivation zone) is -149mV, corrosion rate (current) is 0.02215mA, and solid-liquid interface charge transfer resistance (Rct) is 154.9KΩ. Example 2 A direct energy deposition additive manufacturing method for corrosion-resistant maraging steel based on different laser intensities is disclosed, and the specific operation steps are as follows: (1) BK1900 martensitic aging steel metal powder was prepared by plasma rotating electrode technology (PREP) powder preparation process, and the specific chemical composition (mass%) is as follows: (2) BK1900 martensitic aging steel metal powder was formed by direct energy deposition technology and PREP powder preparation process; (3) Direct energy deposition process: laser power 3500W, scanning speed 600 mm / min, layer thickness 0.5 mm, spacing 1.8 mm, spot 3.2 mm, powder spot 4 mm, gas flow rate 7 L / min, scanning strategy is cyclic scanning, pause between layers for 10s, rotate 90°, blow cool, argon gas protection during molding process and control working pressure at 3-5 mbar, real-time detection of oxygen content in molding chamber <50ppm; (4) DED uses a high-energy-density heat source (laser, electron beam, or plasma / arc) focused on the substrate to form a small molten pool, simultaneously melting the raw material delivered to the pool in the form of powder or wire. As the heat source moves forward, the deposited metal solidifies on the substrate, forming metal tracks. The metal tracks overlap each other according to a predefined pattern filling spacing (i.e., the distance between consecutive metal tracks). After deposition is complete, the deposited layer is moved up to the next layer, such as... Figure 2 They are stacked layer by layer until the entire component is formed; (5) According to the electrochemical corrosion performance test, the performance indicators of BK1900 martensitic aging steel prepared by direct energy deposition under PREP powder preparation process in this embodiment are as follows: open circuit potential is -0.952V, breakdown potential (potential at the end of the passivation zone) is -100mV, corrosion rate (current) is 0.02053mA, and solid-liquid interface charge transfer resistance (Rct) is 185.7 KΩ. Example 3 A direct energy deposition additive manufacturing method for corrosion-resistant maraging steel based on different laser intensities is disclosed, and the specific operation steps are as follows: (1) BK1900 martensitic aging steel metal powder was prepared by plasma rotating electrode technology (PREP) powder preparation process. The specific chemical composition is as follows (mass%): (2) BK1900 martensitic aging steel metal powder was formed by direct energy deposition technology and PREP powder preparation process; (3) Direct energy deposition process: laser power 4000W, scanning speed 600 mm / min, layer thickness 0.5 mm, spacing 1.8 mm, spot 3.2 mm, powder spot 4 mm, gas flow rate 7 L / min, scanning strategy is cyclic scanning, pause between layers for 10s, rotate 90°, blow cool, argon gas protection during molding process and control working pressure at 3-5 mbar, real-time detection of oxygen content in molding chamber <50ppm; (4) DED uses a high-energy-density heat source (laser, electron beam, or plasma / arc) focused on the substrate to form a small molten pool, simultaneously melting the raw material delivered to the pool in the form of powder or wire. As the heat source moves forward, the deposited metal solidifies on the substrate, forming metal tracks. The metal tracks overlap each other according to a predefined pattern filling spacing (i.e., the distance between consecutive metal tracks). After deposition is complete, the deposited layer is moved up to the next layer, such as... Figure 2 They are stacked layer by layer until the entire component is formed; (5) According to the electrochemical corrosion performance test, the performance indicators of BK1900 martensitic aging steel prepared by direct energy deposition under PREP powder preparation process in this embodiment are as follows: open circuit potential is -0.895V, breakdown potential (potential at the end of passivation zone) is -248mV, corrosion rate (current) is 0.02141mA, and solid-liquid interface charge transfer resistance (Rct) is 48.75KΩ. Example 4 A direct energy deposition additive manufacturing method for corrosion-resistant maraging steel based on different laser intensities is disclosed, and the specific operation steps are as follows: (1) BK1900 martensitic aging steel metal powder was prepared by plasma rotating electrode technology (PREP) powder preparation process. The specific chemical composition is as follows (mass%): (2) BK1900 martensitic aging steel metal powder was formed by direct energy deposition technology and PREP powder preparation process; (3) Direct energy deposition process: laser power 5000W, scanning speed 600 mm / min, layer thickness 0.5 mm, spacing 1.8 mm, spot 3.2 mm, powder spot 4 mm, gas flow rate 7 L / min, scanning strategy is cyclic scanning, pause between layers for 10s, rotate 90°, blow cool, argon gas protection during molding process and control working pressure at 3-5 mbar, real-time detection of oxygen content in molding chamber <50ppm; (4) DED uses a high-energy-density heat source (laser, electron beam, or plasma / arc) focused on the substrate to form a small molten pool, simultaneously melting the raw material delivered to the pool in the form of powder or wire. As the heat source moves forward, the deposited metal solidifies on the substrate, forming metal tracks. The metal tracks overlap each other according to a predefined pattern filling spacing (i.e., the distance between consecutive metal tracks). After deposition is complete, the deposited layer is moved up to the next layer, such as... Figure 2 They are stacked layer by layer until the entire component is formed; (5) According to the electrochemical corrosion performance test, the performance indicators of BK1900 martensitic aging steel prepared by direct energy deposition under PREP powder preparation process in this embodiment are as follows: open circuit potential is -0.896V, breakdown potential (potential at the end of passivation zone) is -249mV, corrosion rate (current) is 0.02284mA, and solid-liquid interface charge transfer resistance (Rct) is 25.05KΩ. Example 5 A direct energy deposition additive manufacturing method for corrosion-resistant maraging steel based on different laser intensities is disclosed, and the specific operation steps are as follows: (1) BK1900 martensitic aging steel metal powder was prepared by plasma rotating electrode technology (PREP) powder preparation process. The specific chemical composition is as follows (mass%): (2) BK1900 martensitic aging steel metal powder was formed by direct energy deposition technology and PREP powder preparation process; (3) Direct energy deposition process: laser power 6000W, scanning speed 600 mm / min, layer thickness 0.5 mm, spacing 1.8 mm, spot 3.2 mm, powder spot 4 mm, gas flow rate 7 L / min, scanning strategy is cyclic scanning, pause between layers for 10s, rotate 90°, blow cool, argon gas protection during molding process and control working pressure at 3-5 mbar, real-time detection of oxygen content in molding chamber <50ppm; (4) DED uses a high-energy-density heat source (laser, electron beam, or plasma / arc) focused on the substrate to form a small molten pool, simultaneously melting the raw material delivered to the pool in the form of powder or wire. As the heat source moves forward, the deposited metal solidifies on the substrate, forming metal tracks. The metal tracks overlap each other according to a predefined pattern filling spacing (i.e., the distance between consecutive metal tracks). After deposition is complete, the deposited layer is moved up to the next layer, such as... Figure 2 They are stacked layer by layer until the entire component is formed; (5) According to the electrochemical corrosion performance test, the performance indicators of BK1900 martensitic aging steel prepared by PREP powder preparation process in this embodiment are as follows: open circuit potential is -0.866V, breakdown potential (potential at the end of the passivation zone) is -262mV, corrosion rate (current) is 0.04458mA, and solid-liquid interface charge transfer resistance (Rct) is 20.4KΩ. Comparative Example 1: Macroscopic Morphology Experiment of Chemical Immersion Corrosion This comparative example observes and compares the macroscopic morphology of BK1900 martensitic aging steel with different laser powers to reveal the corrosion mechanism and its influence on material properties, providing a scientific basis for subsequent material optimization and protection strategies. Sample Preparation: The sample to be tested was cut according to the standard requirements of GB / T 17897-1999. Hydrochloric acid was diluted with deionized water (245-fold dilution) to obtain a 0.05 mol / L hydrochloric acid solution. 100g of analytical grade ferric chloride hexahydrate (FeCl3·6H2O) was weighed and completely dissolved in 900 mL of the 0.05 mol / L hydrochloric acid solution to obtain a 6% ferric chloride solution. The prepared solution was stirred in a magnetic stirrer for 20 minutes to ensure thorough mixing. The prepared sample was cleaned thoroughly with ethanol, acetone, and deionized water in sequence, and then immersed in the standard impregnation medium for a period of time. For the corrosion experiment, a glass beaker was used as the test container. During the full immersion corrosion process, the sample was placed horizontally parallel to the solution to minimize the contact area between the sample and the supporting test tube. Appropriate holes were also ensured at both ends of the test tube to allow for solution convection. The overall structure was as follows: Figure 3 As shown; The experimental results are as follows: Figure 4 Macroscopic morphology images of full immersion corrosion of samples with different laser intensities. From Figure 4 (a) It can be seen that all samples lost their metallic luster after corrosion. In the early stage of corrosion, the corrosion effect was not obvious. After 48 hours of corrosion, almost the entire surface layer of the sample was corroded away. After 72 hours of cumulative corrosion, significant pitting and corrosion cracks appeared on the sample surface. These pits were mostly distributed along the scratches on the material surface, indicating that during the corrosion process, the defective parts of the material surface were more susceptible to erosion by the corrosive liquid and became the initiation area of ​​pitting. As the corrosion immersion time continued to extend, the pitting continued to expand, and its radius gradually increased, spreading not only laterally on the material surface but also deep into the material interior. At this time, the corroded surface of the sample mainly showed orange-yellow and black characteristics. This phenomenon was mainly attributed to the formation of corrosion products such as α-FeOOH, γ-FeOOH, and Fe3O4, which will be explained in detail by XRD analysis later. Therefore, timely cleaning of corrosion products on the sample surface can achieve the effect of ring-forming corrosion. After 120 hours of corrosion, the corrosion degree of all five samples was relatively severe, with sample 5 being the most severe. Figure 4 (c) It can be clearly observed in the white circle that when the etching time is almost over, the morphology of sample 5 is no longer complete, and most of the sides have been etched away. When the printing power is relatively high, many holes can be clearly observed on the surface of the cut etched block of sample 5 with the naked eye. Figure 4 (c) The molded specimens have poor density; Comparative Example 2: Chemical Immersion Corrosion Rate Experiment This comparative study analyzes and compares the corrosion rates of BK1900 martensitic aging steel with different laser powers to reveal the corrosion mechanism and its influence on material properties, providing a scientific basis for subsequent material optimization and protection strategies. Sample preparation: Same as Comparative Example 1; This experiment uses the weight reduction method to measure the weight change per unit surface area per unit time, and the corrosion rate is calculated using formula (1);

[0013] In the formula: M_a is the mass before corrosion; M_b is the mass after corrosion; S is the exposed area of ​​the corroded sample; H is the corrosion time; The experimental results are as follows: Figure 5 The corrosion rate curves of samples with different printing powers over time are shown. Analysis of the corrosion rate-time curves reveals that the test materials exhibit significant rapid corrosion characteristics in the initial 24 hours of the corrosion test. The corrosion rate changes of samples 2 and 4 are particularly significant, showing large fluctuations. In the later stages of the corrosion test, the corrosion rates of all five samples show a clear slowing trend, especially towards the end when the corrosion rates become essentially uniform. The higher initial corrosion rates of samples 2 and 4 are mainly due to their higher self-corrosion potentials. The corrosion rate-time curves indicate that the initial period is crucial for protecting materials in corrosive environments. Comparative Example 3: Microscopic Morphology Experiment of Chemical Immersion Corrosion This comparative example systematically investigated the corrosion morphology, defect distribution, and elemental composition changes of BK1900 martensitic aging steel surface with different laser powers using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) to reveal the corrosion mechanism and its influence on material properties, providing a scientific basis for subsequent material optimization and protection strategies. Sample preparation: Same as Comparative Example 1; The experimental results are as follows: Figure 6 The images show a comparison of the microstructures of five different samples after 72 hours of corrosion. At 72 hours, the material matrix suffered significant damage, and the sample surfaces exhibited prominent pitting characteristics (marked by arrows in the images). In some localized areas, the formation of pits was extremely pronounced, and the pits were essentially fully developed, extending significantly from the surface into the matrix. Numerous fine micropore structures emerged both around and within the pits. These microstructure characteristics reflect the complexity and dynamic evolution of the corrosion process. Figure 7Comparative microstructure images of five different samples after 120 hours of corrosion. After 120 hours of corrosion, the samples underwent significant corrosion damage, with numerous new crack-like micropores appearing on the sample surfaces. The outer layer of material on the sample surfaces was almost completely corroded away, exposing surface defects of varying degrees. Samples 1, 3, 4, and 5, in particular, showed significant cracks, pores, and corrosion pits, indicating that these samples suffered severe damage in the corrosive environment. The presence of cracks may be due to brittle fracture caused by stress concentration during corrosion, while the formation of pores and corrosion pits may be the result of localized intensified corrosion, especially when the corrosive medium reacts electrochemically with the material surface, resulting in a significantly higher corrosion rate in localized areas compared to other areas. In contrast, sample 2 showed relatively mild corrosion, with no obvious deep pits or corrosion pits on the surface, and the size of the corroded area was smaller. This indicates that sample 2 has better corrosion resistance, which may be related to the passivation film formed on the sample surface, thus slowing down the corrosion process to some extent. Comparative Example 4: Electrochemical Corrosion Polarization Curve Experiment In this comparative example, potentiodynamic polarization tests were conducted using a CHI660E electrochemical workstation. The scan rate was controlled at 1 mV / s, and the corrosion current density (icorr) and breakdown potential were quantitatively analyzed using the Tafel extrapolation method. Sample preparation: First, the metal to be tested was cut into small blocks of 10×10×3mm. One exposed surface was successively ground with 600#, 800#, 1000#, 1500#, and 2000# sandpaper, followed by mechanical polishing with diamond polishing wheel W1.5 until the surface was smooth. Then, it was cleaned with acetone, ethanol, and ultrasonically for 10 minutes and dried. Electrochemical experiments were conducted using a three-electrode system. The metal was used as the working electrode, and the Pt wire and Ag / AgCl electrode were used as the counter and reference electrodes, respectively. A 0.1M NaCl solution was used as the corrosive medium, forming a three-electrode testing system. Figure 8 ; The experimental results are as follows: Figure 9Tafel polarization curves of samples printed at different powers in 3.5% NaCl solution are shown. All five samples exhibit varying degrees of passivation. The main reason for the corrosion resistance of metallic materials is the active formation of a thin passive film on the material surface. Conversely, corrosion resistance largely depends on the composition, structure, and surface thickness of the passive film. Samples 1 and 2 show the longest passivation intervals, indicating the formation of a good passivation protective film and thus better corrosion resistance. After the passivation band, the curves show a clear inflection point. A steeper slope of the polarization curve indicates a gradual decrease in polarization resistance and a gradual increase in corrosion rate. When the potential exceeds the breakdown potential, the corrosion current increases sharply. Furthermore, with increasing printing power, the passivation range of the samples initially increases and then decreases, and the slope of the polarization curve initially flattens and then steepens.

[0014] The corrosion potential and corrosion current were obtained using the Tafel linear extrapolation method, as shown in Table 2. The self-corrosion potential, as a key parameter, effectively reflects the potential trend of material corrosion, while the corrosion current density is an important indicator of the material's corrosion resistance. By comparing and analyzing the self-corrosion potential and current density data in the Tafel polarization curves, the influence of different printing powers on the corrosion behavior of martensitic aging steel can be systematically explored. From the perspective of corrosion mechanism, the corrosion current originates from the material's dissolution process; therefore, the lower the value, the less the material dissolves in the corrosive medium, and the better its corrosion resistance. On the other hand, the level of the self-corrosion potential is directly related to the material's corrosion tendency; the higher the potential value, the more difficult it is for the material to undergo corrosion under specific conditions. Sample 2 had the lowest corrosion current of 0.02053 mA, indicating the best corrosion resistance, but its low self-corrosion potential suggests a higher probability of corrosion, corresponding to the previous time-corrosion rate curve (…). Figure 5 It can be seen that sample 2 is more prone to corrosion at the beginning, resulting in a very high corrosion rate initially, which then decreases rapidly over time. Sample 5 has the most negative breakdown potential; at -262mV, it is at the corrosion potential and begins to corrode, while the other four samples remain cathodic and do not corrode. When the potential shifts positively to -250mV, sample 5 is at the anodic potential and undergoes severe corrosion. In contrast, the other four remain cathodic and do not corrode. Similarly, a more positive shift in the breakdown potential indicates better pitting corrosion resistance. The polarization curves show that the corrosion rate of these five samples initially decreases and then increases with increasing printing power, indicating that the material's corrosion resistance initially increases and then decreases with increasing printing power. Sample 2 exhibits the best corrosion resistance. Table 2 Polarization curve fitting data

[0015] Comparative Example 5: Electrochemical Corrosion Impedance Spectroscopy Experiment In this comparative example, a sinusoidal perturbation signal with an amplitude of 10mV was applied in the frequency range of 10KHz to 100KHz, and the electrochemical impedance spectroscopy (EIS) was fitted using ZView software. Based on the characteristics of the obtained impedance spectrum and the fitted data, the kinetic process and related mechanism in the electrode system were inferred. Sample preparation: Same as Comparative Example 4; The experimental results are as follows: Figure 10 Impedance spectra of samples with different printing powers are shown. EIS reflects charge transfer at the interface of the prepared sample. The solid-liquid interface charge transfer resistance (Rct) represents the interface charge transfer rate. The smaller the Rct value, the smaller the charge transport resistance, the higher the electron transfer rate, and the easier it is for the metal to corrode. In the figure, the dashed lines represent actual data, and the dots represent fitted data. The high-frequency part of the sample spectrum represents capacitive arc characteristics. The EIS results were fitted using ZView software. The equivalent circuit diagram consists of the solution resistance Rs, the charge transfer resistance Rct, and the electric double layer CPE1 between the solution and the passivation film, as shown. Figure 11 As shown. After fitting, the charge transfer resistance Rct of the five samples from largest to smallest is as follows: Sample 2 (185.7KΩ) > Sample 1 (154.9KΩ) > Sample 3 (48.75KΩ) > Sample 4 (25.05KΩ) > Sample 5 (20.4KΩ). As the printing power of the samples gradually increased, the polarization resistance (Rp) showed a pattern of first increasing and then decreasing. This indicates that the ability of the rust layer to resist corrosive media and its protective efficacy against the substrate underwent a process of first increasing and then decreasing. Therefore, as the printing power continued to increase, the radius of the substrate capacitive arc also first increased and then decreased. Among the five samples, sample 2 had the highest charge transfer resistance value. This result indicates that the corrosion rate of the alloy sample by corrosive ions such as chloride ions in the solution was the slowest, indicating that this sample had the best corrosion resistance. Therefore, it can be inferred that the passivation film of sample 2 has high stability. Sample 5 had the smallest capacitive arc, indicating that when the printing power is appropriate, a relatively stable passivation film will form on the material surface. When the printing power is higher, the material is less likely to form a passivation film naturally. The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use this disclosure. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects without departing from the scope of this disclosure. Therefore, this disclosure is not intended to be limited to the aspects shown herein, but rather to be carried out within the widest scope consistent with the principles and novel features disclosed herein.

[0016] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this disclosure to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations therein.

Claims

1. A method for direct energy deposition additive manufacturing of corrosion-resistant maraging steel based on different laser intensities, characterized by comprising: The material is self-made maraging steel micro-spherical powder; the direct energy deposition forming process is used, other process parameters are controlled to be unchanged, argon protection is adopted during the forming process, the working pressure is controlled to be 5 mbar, the oxygen content in the forming chamber is detected in real time and is less than 50 ppm, the BK1900 maraging steel metal powder is obtained by using the PREP powder making process, then the direct energy deposition forming is carried out by using different laser intensities, the full immersion corrosion and electrochemical corrosion experiment analysis of the formed parts are carried out, and it is shown that the self-made maraging steel has the corrosion resistance of the formed parts improved under the condition that the laser power is 3500 W and other process parameters are not adjusted.

2. A direct energy deposition additive manufacturing method of a maraging steel based on different powder metallurgy processes according to claim 1, characterized in that : The self-made maraging steel (BK1900).

3. A direct energy deposition additive manufacturing method of a maraging steel based on different powder metallurgy processes according to claim 1, characterized in that : The powder making process of the formed parts: plasma rotating electrode technology (PREP).

4. A direct energy deposition additive manufacturing method of a maraging steel based on different powder metallurgy processes according to claim 1, characterized in that : During the process of the formed parts, other process parameters are controlled to be a scanning speed of 600 mm / min, a layer thickness of 0.5 mm, a spacing of 1.8 mm, a light spot of 3.2 mm, a powder spot of 4 mm, and a gas flow of 7 L / min, and the formed parts with the best performance are obtained in the additive manufacturing process under the best laser power.

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