High-performance duplex stainless steel powder and additive manufacturing method for regulating and controlling phase proportion of high-performance duplex stainless steel powder

Abstract

The invention belongs to the field of metal materials, and relates to high-performance duplex stainless steel powder and an additive manufacturing method for regulating and controlling the phase proportion of the high-performance duplex stainless steel powder, and the high-performance duplex stainless steel powder comprises the following elements in percentage by mass: 0.2-0.6% of C, 16.0-18.0% of Cr, 2.0-3.0% of Mo, 10.0-14.0% of Ni, 2.0-4.0% of V, 0.2-1.0% of Si, 0.2-0.8% of Mn, less than or equal to 0.045% of P, less than or equal to 0.03% of S, less than or equal to 0.03% of O and the balance of Fe and inevitable impurities. According to the method, the phase proportion of the duplex stainless steel is regulated and controlled through the additive manufacturing heat accumulation effect, the energy density is increased, more heat is input and ferrite-austenite transformation is promoted at the initial printing starting stage by setting reference technological parameters and initial technological parameters, the energy density is gradually reduced along with the continuous printing process, and the energy density of the duplex stainless steel is increased. According to the method, energy is provided through heat accumulation to continuously conduct ferrite-austenite transformation, by setting different initial process parameters, additive manufacturing forming of the duplex stainless steel with different phase proportions can be directly achieved, follow-up heat treatment is not needed, and the process flow is shortened.

Description

Technical Field

[0001] The invention belongs to the field of metal materials and relates to a high-performance duplex stainless steel powder and an additive manufacturing method for regulating the phase ratio thereof. Background Art

[0002] Duplex stainless steel is a stainless steel material whose microstructure is composed of two phases, ferrite and austenite. It has the advantages of both ferrite and austenite, and has excellent mechanical properties and corrosion resistance. It is widely used in important fields such as ocean, energy, chemical industry, nuclear industry, and papermaking. In the conventional forming process, duplex stainless steel is prone to produce brittle secondary precipitation phases, which leads to reduced mechanical properties and corrosion resistance. Therefore, avoiding brittle phases and improving the mechanical properties of duplex stainless steel are one of the problems that need to be solved urgently. Existing studies have shown that duplex stainless steel has the best mechanical properties when the phase ratio is 1:1. Common methods are mainly regulated by heat treatment, including solution treatment and aging treatment. However, these methods introduce additional process steps, and the heating and cooling processes are time-consuming and energy-consuming. There is also a risk of precipitation of brittle phases, which brings higher costs.

[0003] Additive manufacturing technology is a new forming technology that first divides the three-dimensional model into two-dimensional sheets, then forms each two-dimensional sheet one by one, and finally obtains a three-dimensional part by accumulating the forming layer by layer. Thanks to its highly adaptable forming mechanism, additive manufacturing can theoretically produce any complex three-dimensional configuration. At present, the research on additive manufacturing of duplex stainless steel mainly focuses on arc wire feeding and powder feeding additive manufacturing, and there are few reports on the direct forming of duplex stainless steel using powder melting method. The main reason is that the composition of existing common duplex stainless steel grades is not suitable for the rapid melting-solidification forming process and cyclic heat treatment characteristics of powder bed melting additive manufacturing technology. The ferrite-austenite transformation in duplex stainless steel does not have time to occur, and the ferrite content in the deposited material is too high, which makes the mechanical properties and corrosion resistance of duplex stainless steel materials insufficient.

[0004] In summary, the difficulty of forming duplex stainless steel by powder bed fusion technology lies mainly in the fact that the energy density of the high-energy beam is high, and the material undergoes multiple rapid melting-solidification processes, resulting in the ferrite-austenite transformation not having enough time to occur. However, the powder bed fusion technology has high precision, complex structure, and simple subsequent processing for forming parts, which is a major trend of future development. Therefore, the development of a high-performance duplex stainless steel that can be directly formed by additive manufacturing and an additive manufacturing method that controls its phase ratio has important practical application value. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a high-performance duplex stainless steel powder and an additive manufacturing method for regulating its phase ratio, so as to solve the problem that the existing additive manufacturing technology is difficult to form high-performance duplex stainless steel and the phase ratio is difficult to control, and to realize the direct forming of duplex stainless steel by additive manufacturing, so that it can obtain good mechanical properties without subsequent heat treatment.

[0006] According to stainless steel metallurgy theory and solidification forming theory, the factors affecting the microstructure phase composition of duplex stainless steel are mainly alloy composition and forming process. The present invention adjusts the composition of duplex stainless steel and designs a new alloy composition ratio to make it more compatible with the rapid melting-solidification process of additive manufacturing.

[0007] At the same time, a forming process that utilizes the heat accumulation characteristics of powder bed fusion additive manufacturing technology is proposed. According to the principle of powder bed fusion additive manufacturing technology, when the high-energy beam scans and forms the current layer of material, it will also remelt the formed part. In addition, as the printing continues, the heat accumulation effect gradually appears. Therefore, the heat accumulation effect can be used to use higher high-energy beam power and lower scanning speed at the beginning of printing to achieve a better remelting effect on the formed layer, accelerate the appearance of the heat accumulation effect, and make the ferrite-austenite transformation fully occur. As the number of printing layers gradually increases, the heat accumulation effect becomes more and more serious. In order to prevent excessive heat input, after each layer is formed, the high-energy beam power is reduced, the scanning speed is increased, and the heat accumulation is kept at an appropriate level to promote the ferrite-austenite transformation until the printing is completed. By setting different printing starting processes and change rates, the phase ratio in duplex stainless steel can be accurately controlled to achieve direct additive manufacturing of duplex stainless steel.

[0008] In order to achieve the above object, the present invention provides the following technical solutions:

[0009] A high-performance duplex stainless steel powder. The mass percentages of the elements in the high-performance duplex stainless steel powder are as follows: C: 0.2-0.6%, Cr: 16.0-18.0%, Mo: 2.0-3.0%, Ni: 10.0-14.0%, V: 2.0-4.0%, Si: 0.2-1.0%, Mn: 0.2-0.8%, P: ≤0.045%, S: ≤0.03%, O: ≤0.03%, and the balance is Fe and unavoidable impurities.

[0010] Furthermore, the high performance duplex stainless steel powder is a regular spherical powder with a particle size of 15-53 μm or 45-105 μm.

[0011] Furthermore, the high performance duplex stainless steel powder is prepared by gas atomization or plasma atomization.

[0012] An additive manufacturing method for regulating the phase ratio of high-performance duplex stainless steel powder comprises the following steps:

[0013] Step 1: preparing the high-performance duplex stainless steel powder as raw material, and drying the raw material in a vacuum drying oven;

[0014] Step 2: Build a three-dimensional model of the part and slice it into layers, with the number of layers being A;

[0015] Step 3: Setting reference process parameters, wherein the reference process parameters include high energy beam power, scanning speed, scanning spacing and layer thickness, and setting starting process parameters according to the reference process parameters, wherein the scanning spacing and layer thickness in the starting process parameters are the same as the scanning spacing and layer thickness in the reference process parameters, the high energy beam power in the starting process parameters is B times the high energy beam power in the reference process parameters, and the scanning speed in the starting process parameters is C times the scanning speed in the reference process parameters;

[0016] Step 4: Printing and forming using a powder bed fusion additive manufacturing device, spreading powder on the substrate once, and then printing and forming the initial layer with the initial process parameters;

[0017] Step 5: Print the first layer, spread powder on the substrate again, and complete the first layer printing after changing the process parameters;

[0018] Step 6: Repeat the above step 5 to print subsequent layers until all layers of the part are printed, thereby obtaining the printed part. As printing continues, the scanning spacing and layer thickness remain unchanged, the high-energy beam power gradually decreases, and the scanning speed gradually increases. When printing the last layer, the high-energy beam power and scanning speed in the benchmark process parameters are reached.

[0019] Furthermore, the reference process parameters include high energy beam power P=200-1000 W, scanning speed v=500-3000 mm / s, scanning spacing h=60-120 μm and layer thickness t=20-100 μm.

[0020] Furthermore, the value range of B is: 1-1.5.

[0021] Furthermore, the value range of C is: 0.5-1.

[0022] Furthermore, in the steps 5 and 6, the high energy beam power in the process parameters when printing the first layer is changed to Scan speed The scanning spacing h1 and the layer thickness t1 are the same as the scanning spacing h and the layer thickness t in the reference process parameters;

[0023] The high energy beam power in the process parameters when printing the Tth layer changes Scan speed Scanning distance h T and layer thickness t T The scanning spacing h and layer thickness t are the same as those in the benchmark process parameters.

[0024] Further, it also includes step 7;

[0025] Step 7: Use electric spark cutting to cut the printed part from the substrate to obtain a duplex stainless steel additive manufacturing part.

[0026] Furthermore, in step 4, before coating the substrate with powder, the substrate is preheated at a temperature of 30-200°C.

[0027] The beneficial effects of the present invention are:

[0028] 1. This invention proposes a new ferrite-austenite duplex stainless steel composition ratio suitable for additive manufacturing forming process. Through composition design and fine-tuning, Cr 23 The precipitation of harmful phases such as C6 and the addition of V element promote the precipitation of carbide strengthening phases such as MC, improve the mechanical properties of duplex stainless steel, and ensure good corrosion resistance.

[0029] 2. The present invention proposes an additive manufacturing method for regulating the phase ratio of high-performance duplex stainless steel powder, which utilizes the heat accumulation effect of additive manufacturing to regulate the phase ratio of duplex stainless steel. By setting the baseline process parameters and the starting process parameters, the energy density is increased and more heat is input at the beginning of printing to promote the ferrite-austenite transformation. As the printing process continues, the heat accumulation effect begins to be significant, and the energy density is gradually reduced. The ferrite-austenite transformation is continuously carried out by relying on heat accumulation to provide energy, thereby avoiding the risk of overmelting caused by heat accumulation. By setting different starting process parameters, the additive manufacturing of duplex stainless steel with different phase ratios can be directly achieved without the need for subsequent heat treatment, shortening the process flow.

[0030] The method for controlling the phase ratio of duplex stainless steel provided by the present invention is simple, highly feasible, low cost, shortened process, and the ratio is precisely controllable, thus having high practical application value.

[0031] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0033] Figure 1 This is a morphology picture of the high performance duplex stainless steel powder in Example 1;

[0034] Figure 2 This is a microstructure diagram of high performance duplex stainless steel powder bed fusion forming in Example 1;

[0035] Figure 3 This is a phase ratio diagram of the high performance duplex stainless steel powder bed melt forming in Example 1;

[0036] Figure 4 is a phase ratio diagram of the duplex stainless steel formed in Comparative Example 1;

[0037] Figure 5 Mechanical properties test results of high performance duplex stainless steel powder bed fusion forming. DETAILED DESCRIPTION

[0038] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0039] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0040] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0041] Example 1

[0042] like Figure 1 As shown, a high-performance duplex stainless steel powder is specifically a ferrite-austenite duplex stainless steel powder, wherein the mass percentage of each element is: C: 0.31%, Cr: 16.9%, Mo: 2.86%, Ni: 10.8%, V: 2.51%, Si: 0.45%, Mn: 0.46%, P: 0.031%, S: 0.028%, O: 0.026%, and the balance is Fe and unavoidable impurities.

[0043] The high-performance duplex stainless steel powder is a regular spherical powder with a particle size of 15-53 μm or 45-105 μm.

[0044] An additive manufacturing method for regulating the phase ratio of high-performance duplex stainless steel powder comprises the following steps:

[0045] Step 1: Dry high-performance duplex stainless steel powder to remove moisture and improve fluidity;

[0046] Step 2: Use 3D modeling software to build a 3D model of the part, and import it into a dedicated slicing software for layered slicing, with the number of layers being 3500 (A);

[0047] Step 3: Set the benchmark process parameters: high energy beam power: P = 300 W, scanning speed: v = 1000 mm / s, scanning spacing: h = 90 μm, layer thickness: t = 40 μm;

[0048] Set the initial process parameters: the scanning spacing h and layer thickness t remain unchanged, the high-energy beam power P is 1.2 (B) times the benchmark process parameters, and the scanning speed v is 0.8 (C) times the benchmark process parameters.

[0049] Step 4: Print using a powder bed fusion additive manufacturing device, set the substrate preheating temperature to 160°C, spread powder on the substrate once, print the initial layer with the initial process parameters, then print the first layer, and spread powder on the substrate again. At this time, the high-energy beam power becomes: At this time, the scanning speed becomes: The scanning distance h and the slice thickness t remain unchanged.

[0050] Step 5: Repeat step 4 above until all layers of the part are printed, and the completed part is obtained;

[0051] Step 6: Use electric spark cutting to cut the printed parts from the substrate to directly obtain high-performance duplex stainless steel additive manufacturing parts.

[0052] Specifically, the powder bed fusion additive manufacturing equipment used in this embodiment is a conventional additive manufacturing equipment, and the high-energy beam can be one of a laser, an ion beam, and an electron beam.

[0053] Samples were taken for metallographic characterization, and the microstructure was as follows: Figure 2 As shown in Figure 2, the structure is fine equiaxed crystals, and EBSD is used for phase ratio analysis, such as Figure 3 As shown in the figure, the ferrite content is 54.8%, the austenite content is 45.2%, and the ferrite-austenite ratio is close to 1:1. The mechanical properties test results are shown in Figure 5 As shown, the performance exceeds 1000MPa.

[0054] Furthermore, the present embodiment also provides a high-performance duplex stainless steel and an additive manufacturing system for regulating the phase ratio thereof, the system comprising: a processor and a memory for storing executable instructions;

[0055] The processor is configured to execute the executable instructions to perform the additive manufacturing method for regulating the phase ratio of high-performance duplex stainless steel as described in any one of the above aspects.

[0056] In another embodiment, a computer-readable storage medium is provided, on which a computer program is stored, and when the computer program is executed by a processor, the additive manufacturing method for regulating the phase ratio of high-performance duplex stainless steel as described above is implemented.

[0057] Example 2

[0058] The difference from Example 1 is that the initial high-energy beam power P is 1.1 times the benchmark process parameter, and the scanning speed v is 0.9 times the benchmark process parameter. At this time, the ferrite content of the duplex stainless steel is 38.5%, and the austenite content is 61.5%.

[0059] Comparative Example 1

[0060] The difference from Example 1 is that the initial process parameters are not used, and the benchmark process parameters are used throughout the forming process. The phase ratio analysis of the formed parts is performed using EBSD, as shown in FIG. Figure 4 As shown, the ferrite content is 90.2% and the austenite content is only 9.8%.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A high performance duplex stainless steel powder, characterized in that: The mass percentage of each element component in the high-performance duplex stainless steel powder is: C: 0.2-0.6%, Cr: 16.0-18.0%, Mo: 2.0-3.0%, Ni: 10.0-14.0%, V: 2.0-4.0%, Si: 0.2-1.0%, Mn: 0.2-0.8%, P: ≤0.045%, S: ≤0.03%, O: ≤0.03%, and the balance is Fe and unavoidable impurities.

2. The high performance duplex stainless steel powder according to claim 1, characterized in that: The high-performance duplex stainless steel powder is a regular spherical powder with a particle size of 15-53 μm or 45-105 μm.

3. The high performance duplex stainless steel powder according to claim 1, characterized in that: The high-performance duplex stainless steel powder is prepared by gas atomization or plasma atomization.

4. An additive manufacturing method for regulating the phase ratio of high-performance duplex stainless steel powder, characterized in that: The following steps are involved: Step 1: preparing the high-performance duplex stainless steel powder according to any one of claims 1 to 3 as a raw material, and drying the raw material in a vacuum drying oven; Step 2: Build a three-dimensional model of the part and slice it into layers, with the number of layers being A; Step 3: Setting reference process parameters, wherein the reference process parameters include high energy beam power, scanning speed, scanning spacing and layer thickness, and setting starting process parameters according to the reference process parameters, wherein the scanning spacing and layer thickness in the starting process parameters are the same as the scanning spacing and layer thickness in the reference process parameters, the high energy beam power in the starting process parameters is B times the high energy beam power in the reference process parameters, and the scanning speed in the starting process parameters is C times the scanning speed in the reference process parameters; Step 4: Printing and forming using a powder bed fusion additive manufacturing device, spreading powder on the substrate once, and then printing and forming the initial layer with the initial process parameters; Step 5: Print the first layer, spread powder on the substrate again, and complete the first layer printing after changing the process parameters; Step 6: Repeat the above step 5 to print subsequent layers until all layers of the part are printed, thereby obtaining the printed part. As printing continues, the scanning spacing and layer thickness remain unchanged, the high-energy beam power gradually decreases, and the scanning speed gradually increases. When printing the last layer, the high-energy beam power and scanning speed in the benchmark process parameters are reached.

5. The additive manufacturing method for adjusting the phase ratio of high-performance duplex stainless steel powder according to claim 4, characterized in that: The reference process parameters include high energy beam power P=200-1000 W, scanning speed v=500-3000 mm / s, scanning spacing h=60-120 μm and layer thickness t=20-100 μm.

6. The additive manufacturing method for adjusting the phase ratio of high-performance duplex stainless steel powder according to claim 5, characterized in that: The value range of B is: 1-1.

5.

7. The additive manufacturing method for adjusting the phase ratio of high-performance duplex stainless steel powder according to claim 5, characterized in that: The value range of C is: 0.5-1.

8. The additive manufacturing method for adjusting the phase ratio of high-performance duplex stainless steel powder according to claim 5, characterized in that: In step 5 and step 6, the high energy beam power in the process parameters when printing the first layer is changed to Scan speed The scanning spacing h1 and the layer thickness t1 are the same as the scanning spacing h and the layer thickness t in the reference process parameters; The high energy beam power in the process parameters when printing the Tth layer changes Scan speed Scanning distance h T and layer thickness t T The scanning spacing h and layer thickness t are the same as those in the benchmark process parameters.

9. The additive manufacturing method for adjusting the phase ratio of high-performance duplex stainless steel powder according to claim 4, characterized in that: Also includes step 7; Step 7: Use electric spark cutting to cut the printed part from the substrate to obtain a duplex stainless steel additive manufacturing part.

10. The additive manufacturing method for adjusting the phase ratio of high-performance duplex stainless steel powder according to claim 4, characterized in that: In step 4, before coating the substrate with powder, the substrate is preheated at a temperature of 30-200°C.

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