Austenitic stainless steel powder and additive manufacturing forming method thereof based on laser powder bed melting

Abstract

The invention discloses austenitic stainless steel powder and an additive manufacturing forming method thereof based on laser powder bed melting, and the austenitic stainless steel powder comprises the following components in percentage by mass: 0.1-0.3% of Y; 17 to 18 wt% of Cr; 6 to 8 wt% of Ni; mn: 0.6 to 0.8 wt%; si: 0.1 to 0.3 wt%; c: 0.01 to 0.03 wt%; s: 0.01 to 0.06 wt%; 0.01-0.03 wt% of P, and the balance Fe and inevitable impurities. According to the method for preparing the austenitic stainless steel through powder bed melting additive manufacturing, the forming efficiency is guaranteed, and meanwhile the grain coarsening problem of the austenitic stainless steel under a high-power laser source is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of special materials for additive manufacturing, and specifically relates to an austenitic stainless steel powder and an additive manufacturing forming method thereof based on laser powder bed melting. Background Art

[0002] Austenitic stainless steel is a type of stainless steel with chromium and nickel as the main alloying elements. It is widely used in aerospace, chemical industry, energy, and shipbuilding due to its high corrosion resistance, excellent processing performance and high temperature stability, as well as non-magnetic properties. Traditional austenitic stainless steel, such as 304 and 316 series, often has carbides (such as Cr 23 The precipitation of C6 at grain boundaries leads to intergranular corrosion, requiring heat treatment to improve corrosion resistance. The commonly used heat treatment process for austenitic stainless steel is to heat it to the solution temperature range, hold it for a period of time, and then rapidly cool it to dissolve carbides and other phases, ultimately obtaining a single austenite structure to ensure good corrosion resistance. However, excessively high temperatures or long holding times will coarsen the austenite grains, thereby affecting its mechanical properties.

[0003] Additive manufacturing of metals utilizes heat sources such as lasers, electron beams, and arcs to melt and deposit metal powder or wire layer by layer along a scanning path to create three-dimensional solid parts. This technology is generally used to produce parts with complex geometries. Laser powder bed fusion uses a laser as the energy source to scan a bed of metal powder layer by layer along a pre-set path in a three-dimensional slice model. The scanned metal powder melts and solidifies, achieving a metallurgical bond, ultimately yielding the metal part designed in the model. Compared to traditional manufacturing processes, laser powder bed fusion eliminates the need for specialized molds, significantly reducing tooling and production costs.

[0004] When producing austenitic stainless steel through additive manufacturing technology, a high-power laser source is often used, but this usually leads to coarse austenite grains, which in turn reduces the mechanical properties of the parts. Since martensitic phase transformation easily occurs during the deformation process of additively manufactured austenitic stainless steel, it is difficult to improve the mechanical properties through deformation processes. Based on the existing additive manufacturing technology for preparing austenitic stainless steel parts, on the one hand, there is a lack of methods to improve forming efficiency, and on the other hand, there is a lack of processes to effectively improve the mechanical properties of austenitic stainless steel parts. This seriously restricts the development and application of additively manufactured austenitic stainless steel in aerospace, energy, shipbuilding, and chemical industries. Summary of the Invention

[0005] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of this application to avoid obscuring the purpose of this section, the abstract and the title of the invention, and such simplifications or omissions should not be used to limit the scope of the present invention.

[0006] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0007] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide an austenitic stainless steel powder and an additive manufacturing method thereof based on laser powder bed fusion.

[0008] To solve the above technical problems, the present invention provides the following technical solution: an austenitic stainless steel powder, characterized in that: calculated by mass fraction, it includes: Y: 0.1-0.3%; Cr: 17-18wt%; Ni: 6-8wt%; Mn: 0.6-0.8wt%; Si: 0.1-0.3wt%; C: 0.01-0.03wt%; S: 0.01-0.06wt%; P: 0.01-0.03wt%, and the rest is Fe and unavoidable impurities.

[0009] As a preferred embodiment of the austenitic stainless steel powder of the present invention, the powder comprises, by mass fraction, 0.3% Y, 17.5% Cr, 7.2% Ni, 0.75% Mn, 0.2% Si, 0.02% C, 0.05% S, and 0.02% P, with the remainder being Fe and unavoidable impurities.

[0010] As a preferred embodiment of the austenitic stainless steel powder of the present invention, it also has the following characteristics:

[0011] (i) Yield strength of 512-535 MPa and tensile strength of 706-735 MPa at room temperature (25°C);

[0012] (ii) Elongation at room temperature (25°C) 47-57%.

[0013] Another object of the present invention is to overcome the deficiencies in the prior art and provide an additive manufacturing method based on laser powder bed melting, which is characterized in that it includes vacuum melting of the ingredients according to the mass percentage as described in any one of claims 1 to 2, laser powder bed melting after argon atomization, and air blowing for cooling.

[0014] As a preferred embodiment of the method of the present invention, the vacuum smelting conditions are as follows: a smelting temperature of 1500° C. and an air pressure in the smelting furnace of 0.4 MPa.

[0015] As a preferred embodiment of the method of the present invention, the argon atomization medium is argon gas, and the atomization pressure is 8 MPa.

[0016] As a preferred embodiment of the method described in the present invention, the laser power in the laser powder bed melting conditions is 150 to 300 W; the scanning speed is 700 to 1100 mm / s; the scanning spacing is 0.08 to 0.2 mm; the scanning layer thickness is 0.07 to 0.1 mm; the scanning strategy is layer-by-layer cross scanning, and the rotation angle between adjacent layers is 0 to 90°; the oxygen content is controlled below 0.1 wt% during printing, and the substrate preheating temperature is 100 to 200°C.

[0017] As a preferred embodiment of the method of the present invention, the air blowing cooling includes cooling the printed part after each layer is printed until the surface temperature of the part drops below 580°C before printing the subsequent part; and blowing low-temperature inert gas on the surface of the printed part at an air flow rate of 6L / min.

[0018] As a preferred embodiment of the method of the present invention, the laser powder bed melting process is to lay a first layer of powder on the substrate as a starting layer, and cross-scan 4 times according to the conditions of claim 7 to promote the bonding of the starting layer and the substrate.

[0019] As a preferred embodiment of the method of the present invention, the laser powder bed fusion is used to print the first layer, and a new layer of powder is laid on the starting layer. After the first layer is printed, the layers are printed continuously according to the method of claim 7.

[0020] Beneficial effects of the present invention:

[0021] (1) The present invention provides a method for preparing austenitic stainless steel by powder bed fusion additive manufacturing, which solves the problem of grain coarsening of austenitic stainless steel under high-power laser source while ensuring the forming efficiency.

[0022] (2) After laser 3D printing, the high-performance austenitic stainless steel powder of the present invention produces samples with low metallurgical defects, high density, and excellent formability. Furthermore, the powder exhibits excellent mechanical properties at room temperature, maintains good thermodynamic stability at high temperatures, and exhibits good corrosion resistance. This makes it an austenitic stainless steel with excellent overall performance.

[0023] (3) The present invention provides a device for additive manufacturing of austenitic stainless steel, which is used to implement the aforementioned powder bed fusion-based additive manufacturing method for austenitic stainless steel; printing is performed by selective laser melting equipment, and clear process parameters are set for the special powder proposed in the present invention, that is, the laser scanning strategy is set according to the needs of printing parts, appropriate process parameters are selected, and high-performance austenitic stainless steel powder is selected, so that the printed parts have fine structure and uniform strength, and the printing process is carried out in an inert gas environment.

[0024] (4) In the laser powder bed fusion additive manufacturing method for austenitic stainless steel described in the present invention, after each layer of powder is formed, low-temperature argon gas is continuously blown onto the surface of the formed layer to rapidly cool the formed layer. A short-wave thermal imager is simultaneously used to monitor the surface molten pool temperature in real time. When the temperature falls below the set value of 580°C, subsequent printing is performed. This cooling method further refines the austenite grains and improves the mechanical properties of the parts, thereby providing a foundation for efficient additive manufacturing of high-performance austenitic stainless steel parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort. Among them:

[0026] Figure 1 Schematic diagram of an apparatus for additive manufacturing of austenitic stainless steel based on laser powder bed fusion according to an embodiment of the present invention.

[0027] Figure 2 This is a scanning image of the morphology of the high-performance austenitic stainless steel powder used in Example 1 of the present invention (scale bar is 100 microns).

[0028] Figure 3 This is an electron channel contrast image of austenitic stainless steel manufactured by laser powder bed fusion additive manufacturing according to Example 1 of the present invention (scale bar is 200 μm).

[0029] Figure 4 Metallographic image of austenitic stainless steel manufactured by laser powder bed fusion additive manufacturing according to Example 1 of the present invention (scale bar is 20 μm).

[0030] Figure 5 This is a physical picture of the additively manufactured austenitic stainless steel formed in Example 1 of the present invention. DETAILED DESCRIPTION

[0031] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0032] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0033] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0034] Unless otherwise specified, all raw materials used in the examples of the present invention are commercially available. Details are shown in Table 1.

[0035] Table 1

[0036] name Commercial channels Item No. Yttrium powder Aladdin Y108777 Austenitic stainless steel plate 1688 TY000012

[0037] like Figure 1 A schematic diagram of a high-performance austenitic stainless steel powder additive manufacturing apparatus is presented. The device for temperature control during the high-performance austenitic stainless steel powder additive manufacturing process includes a substrate platform 1, a cooling airflow device 5, and a short-wave thermal imager 7. The part 9 to be formed is supported by the substrate platform 1. Specifically, a laser melts the high-performance austenitic stainless steel powder and deposits it layer by layer from bottom to top according to a predetermined forming path to form the part 9 to be formed. After each layer of powder is laid, the scraper 3 stops on the side of the powder cylinder 2. An air bearing track 4 is installed directly above and parallel to the scraper 2. A cooling airflow device 5 is installed on the air bearing track 4 and connected to a ventilation duct 6 for supplying low-temperature argon gas to the part 9 to be formed to achieve cooling. The short-wave thermal imager 7 is installed on the side of the powder cylinder 2 to monitor the surface temperature of the part 9 to be formed in real time.

[0038] The materials produced in the Examples and Comparative Examples were tested for performance as follows: The printed parts were cut into dogbone-shaped specimens using a wire EDM machine. The specimens were then ground and polished along the stacking direction using 400-, 800-, 1000-, 1500-, and 2000-grit sandpaper. The specimens were then surface-polished. After installing an external extensometer, the specimens were pulled at a rate of 0.72 mm / min on an Instron 3369 universal testing machine, and the yield strength and elongation were recorded.

[0039] Example 1

[0040] (1) The raw material composition is as follows, calculated by mass percentage: Y: 0.1%; Cr: 17wt%; Ni: 7wt%; Mn: 0.8wt%; Si: 0.3wt%; C: 0.02wt%; S: 0.03wt%; P: 0.02wt%, and the rest is Fe and unavoidable impurities.

[0041] (2) The raw materials in step (1) are vacuum melted and then powdered by argon atomization. The melting temperature is 1500°C and the pressure in the melting furnace is 0.4 MPa. The metal droplets are then atomized by argon gas at an atomization pressure of 8 MPa.

[0042] (3) The powder finally prepared in step (2) is spherical in shape. The powder of 20 to 40 μm is sieved out. The sieved powder is dried at 90° C. for 8 hours in a vacuum drying oven and can be used for SLM printing.

[0043] (4) The printing process of laser powder bed melting additive manufacturing of SLM-formed austenitic stainless steel powder is as follows: laser power: 200W; scanning speed: 700mm / s; scanning spacing: 0.08mm; scanning layer thickness: 0.07mm; scanning strategy is a 90° rotation angle between adjacent layers.

[0044] (5) After each layer is formed, low-temperature argon gas is used to blow and cool the surface of the formed layer at a flow rate of 6 L / min. A short-wave thermal imager is used to measure the temperature of the upper surface of the formed layer. When the temperature is lower than 580°C, the next layer is printed until the part is completely formed.

[0045] 3D printed high performance austenitic stainless steel powder morphology Figure 2 As shown, the metallographic image of the prepared 3D printed high performance austenitic stainless steel is as follows Figure 3 As shown, the corrosion metallography on the side and front of the sample is as follows Figure 4 As shown, the printed sample is as follows Figure 5 As shown in the figure, metallurgical defects such as pores are rare under a light microscope. The resulting printed parts have a density of 99.4%, an average hardness of 263HV0.2, a room temperature yield strength of 535MPa, and a tensile strength of 719MPa, demonstrating excellent room temperature mechanical properties.

[0046] Example 2

[0047] (1) The raw material composition is as follows, calculated by mass percentage: Y: 0.2%; Cr: 17.5wt%; Ni: 6.5wt%; Mn: 0.6wt%; Si: 0.2wt%; C: 0.02wt%; S: 0.04wt%; P: 0.01wt%, and the remainder is Fe and unavoidable impurities.

[0048] (2) The raw materials in step (1) are vacuum melted and then powdered by argon atomization: the melting temperature is 1500°C and the pressure in the melting furnace is 0.4 MPa; then the metal droplets are atomized by argon as the medium, and the atomization pressure is 8 MPa.

[0049] (3) The powder finally prepared in step (2) is spherical in shape. The powder of 20 to 40 μm is sieved out. The sieved powder is dried at 90° C. for 8 hours in a vacuum drying oven and can be used for SLM printing.

[0050] (4) The printing process of laser powder bed melting additive manufacturing of SLM-formed austenitic stainless steel powder is as follows: laser power: 200W; scanning speed: 700mm / s; scanning spacing: 0.08mm; scanning layer thickness: 0.07mm; scanning strategy is a 90° rotation angle between adjacent layers.

[0051] (5) After each layer is formed, low-temperature argon gas is used to blow and cool the surface of the formed layer at a flow rate of 6 L / min. A short-wave thermal imager is used to measure the temperature of the upper surface of the formed layer. When the temperature is lower than 580°C, the next layer is printed until the part is completely formed.

[0052] There are few metallurgical defects such as pores under the optical microscope. The density of the printed parts is 99.6%, the average hardness reaches 255HV0.2, the room temperature yield strength is 523MPa, the tensile strength is 710MPa, and it has good room temperature mechanical properties.

[0053] Example 3

[0054] (1) The raw material composition is as follows, calculated by mass percentage: Y: 0.3%; Cr: 17.5wt%; Ni: 7.2wt%; Mn: 0.75wt%; Si: 0.2wt%; C: 0.02wt%; S: 0.05wt%; P: 0.02wt%, and the rest is Fe and unavoidable impurities.

[0055] (2) The raw materials in step (1) are vacuum melted and then powdered by argon atomization: the melting temperature is 1500°C and the pressure in the melting furnace is 0.4 MPa; then the metal droplets are atomized by argon as the medium, and the atomization pressure is 8 MPa.

[0056] (3) The powder finally prepared in step (2) is spherical in shape. The powder of 20 to 40 μm is sieved out. The sieved powder is dried at 90° C. for 8 hours in a vacuum drying oven and can be used for SLM printing.

[0057] (4) The printing process of laser powder bed melting additive manufacturing of SLM-formed austenitic stainless steel powder is as follows: laser power: 200W; scanning speed: 700mm / s; scanning spacing: 0.08mm; scanning layer thickness: 0.07mm; scanning strategy is a 90° rotation angle between adjacent layers.

[0058] (5) After each layer is formed, low-temperature argon gas is used to blow and cool the surface of the formed layer at a flow rate of 6 L / min. A short-wave thermal imager is used to measure the temperature of the upper surface of the formed layer. When the temperature is lower than 580°C, the next layer is printed until the part is completely formed.

[0059] There are few metallurgical defects such as pores under the optical microscope. The density of the printed parts is 99.1%, the average hardness reaches 260HV0.2, the room temperature yield strength is 528MPa, and the tensile strength is 735MPa, showing good room temperature mechanical properties.

[0060] Example 4

[0061] (1) The raw material composition is as follows, calculated by mass percentage: Y: 0.1%; Cr: 18wt%; Ni: 7.5wt%; Mn: 0.7wt%; Si: 0.3wt%; C: 0.03wt%; S: 0.05wt%; P: 0.02wt%, and the remainder is Fe and unavoidable impurities.

[0062] (2) The raw materials in step (1) are vacuum melted and then powdered by argon atomization: the melting temperature is 1500°C and the pressure in the melting furnace is 0.4 MPa; then the metal droplets are atomized by argon as the medium, and the atomization pressure is 8 MPa.

[0063] (3) The powder finally prepared in step (2) is spherical in shape. The powder of 20 to 40 μm is sieved out. The sieved powder is dried at 90° C. for 8 hours in a vacuum drying oven and can be used for SLM printing.

[0064] (4) The printing process of laser powder bed melting additive manufacturing of SLM-formed austenitic stainless steel powder is as follows: laser power: 200W; scanning speed: 700mm / s; scanning spacing: 0.08mm; scanning layer thickness: 0.07mm; scanning strategy is a 90° rotation angle between adjacent layers.

[0065] (5) After each layer is formed, low-temperature argon gas is used to blow and cool the surface of the formed layer at a flow rate of 6 L / min. A short-wave thermal imager is used to measure the temperature of the upper surface of the formed layer. When the temperature is lower than 580°C, the next layer is printed until the part is completely formed.

[0066] There are few metallurgical defects such as pores under the optical microscope. The density of the printed parts is 99.7%, the average hardness reaches 275HV0.2, the room temperature yield strength is 512MPa, the tensile strength is 706MPa, and it has good room temperature mechanical properties.

[0067] Example 5

[0068] (1) The raw material composition is as follows, calculated by mass percentage: Y: 0.2%; Cr: 18wt%; Ni: 7.2wt%; Mn: 0.75wt%; Si: 0.2wt%; C: 0.02wt%; S: 0.05wt%; P: 0.02wt%, and the rest is Fe and unavoidable impurities.

[0069] (2) The raw materials in step (1) are vacuum melted and then powdered by argon atomization: the melting temperature is 1500°C and the pressure in the melting furnace is 0.4 MPa; then the metal droplets are atomized by argon as the medium, and the atomization pressure is 8 MPa.

[0070] (3) The powder finally prepared in step (2) is spherical in shape. The powder of 20 to 40 μm is sieved out. The sieved powder is dried at 90° C. for 8 hours in a vacuum drying oven and can be used for SLM printing.

[0071] (4) The printing process of laser powder bed melting additive manufacturing of SLM-formed austenitic stainless steel powder is as follows: laser power: 200W; scanning speed: 700mm / s; scanning spacing: 0.08mm; scanning layer thickness: 0.07mm; scanning strategy is a 90° rotation angle between adjacent layers.

[0072] (5) After each layer is formed, low-temperature argon gas is used to blow and cool the surface of the formed layer at a flow rate of 6 L / min. A short-wave thermal imager is used to measure the temperature of the upper surface of the formed layer. When the temperature is lower than 580°C, the next layer is printed until the part is completely formed.

[0073] There are few metallurgical defects such as pores under the optical microscope. The density of the printed parts is 99.3%, the average hardness reaches 263HV0.2, the room temperature yield strength is 519MPa, the tensile strength is 717MPa, and it has good room temperature mechanical properties.

[0074] Table 2 Mechanical properties of the alloys prepared in Examples 1 to 5 at room temperature (25°C)

[0075] Room temperature tensile properties Yield strength MPa Tensile strength MPa Elongation % Example 1 535 719 47 Example 2 523 710 50 Example 3 528 735 57 Example 4 512 706 54 Example 5 519 717 57

[0076] As shown in Table 2, the alloy system of the present invention exhibits significant advantages in the comprehensive mechanical properties (yield strength, tensile strength, and elongation) of printed samples using the aforementioned laser powder bed fusion additive manufacturing process. Examples 3 and 5 exhibit the best overall performance. The alloy system of the present invention also offers the technical advantage of high performance and low cost.

[0077] Comparative Example 1

[0078] The raw material composition, calculated by weight percentage, is as follows: Y: 0.3%; Cr: 17.5wt%; Ni: 7.2wt%; Mn: 0.75wt%; Si: 0.2wt%; C: 0.02wt%; S: 0.05wt%; P: 0.02wt%, with the remainder being Fe and unavoidable impurities. The raw materials are vacuum-melted and then powdered using argon atomization at a melting temperature of 1500°C and a furnace pressure of 0.4MPa. The molten metal droplets are then atomized using argon at an atomization pressure of 8MPa. The resulting powder is spherical and sieved to obtain a 20-40μm powder. The sieved powder is then dried in a vacuum oven at 90°C for 8 hours, ready for SLM printing. Afterwards, the SLM-formed austenitic stainless steel powder was subjected to laser powder bed fusion additive manufacturing (LABM) printing process with the following parameters: laser power: 200W; scanning speed: 700mm / s; scanning pitch: 0.08mm; scanning layer thickness: 0.07mm; and the scanning strategy was a 90° rotation angle between adjacent layers until the part was fully formed.

[0079] The resulting austenitic stainless steel showed increased metallurgical defects under a light microscope, including visible pores and microcracks. The sample had a density of 97.3%, an average hardness of 231 HV0.2, a yield strength of 487 MPa at room temperature, and a tensile strength of 682 MPa, but an elongation of only 39%. The sample also had poor formability and could not be formed into large-scale samples.

[0080] Comparative Example 2

[0081] The raw material composition, calculated by weight percentage, is as follows: Y: 0.2%; Cr: 18wt%; Ni: 7.2wt%; Mn: 0.75wt%; Si: 0.2wt%; C: 0.02wt%; S: 0.05wt%; P: 0.02wt%, with the remainder being Fe and unavoidable impurities. The raw materials are vacuum-melted and then powdered using argon atomization at a melting temperature of 1500°C and a furnace pressure of 0.4MPa. The molten metal droplets are then atomized using argon at an atomization pressure of 8MPa. The resulting powder is spherical and sieved to obtain a 20-40μm powder. The sieved powder is then dried in a vacuum oven at 90°C for 8 hours, ready for SLM printing. The printing process for laser powder bed fusion additive manufacturing of SLM-formed austenitic stainless steel powder is as follows: laser power: 200W; scanning speed: 700mm / s; scanning spacing: 0.08mm; scanning layer thickness: 0.07mm; the scanning strategy is a 90° rotation angle between adjacent layers until the part is fully formed.

[0082] The resulting austenitic stainless steel showed increased metallurgical defects under a light microscope, including visible pores and microcracks. The sample had a density of 96.7%, an average hardness of 227 HV0.2, a yield strength of 471 MPa at room temperature, and a tensile strength of 669 MPa, but an elongation of only 38%. The sample also had poor formability and could not be formed into large-scale samples.

[0083] Table 3 Mechanical properties of the alloys obtained in Comparative Examples 1 and 2 at room temperature (25°C)

[0084]

[0085] As shown in Table 3, the additive manufacturing method of the present invention significantly improves the yield strength and elongation of parts produced compared to conventional additive manufacturing methods. Compared with Comparative Example 1, Example 3 shows increases of 8.4% and 46.2%, respectively. Compared with Comparative Example 2, Example 5 shows increases of 10.2% and 47.3%, respectively.

[0086] Comparative Example 3

[0087] The difference from Example 3 is that in step (1), the raw material composition, calculated by mass percentage, is as follows: Cr: 17.5 wt%; Ni: 7.2 wt%; Mn: 0.75 wt%; Si: 0.2 wt%; C: 0.02 wt%; S: 0.05 wt%; P: 0.02 wt%, with the remainder being Fe and unavoidable impurities. Otherwise, the austenitic stainless steel sample obtained has a density of 98.9%, an average hardness of 219 HV0.2, a yield strength of 475 MPa at room temperature, and a tensile strength of 696 MPa, but an elongation of only 41%.

[0088] Comparative Example 4

[0089] The difference from Example 5 is that in step (1), the raw material composition, calculated by mass percentage, is as follows: Cr: 18 wt%; Ni: 7.2 wt%; Mn: 0.75 wt%; Si: 0.2 wt%; C: 0.02 wt%; S: 0.05 wt%; P: 0.02 wt%, with the remainder being Fe and unavoidable impurities. Otherwise, the austenitic stainless steel sample obtained has a density of 98.7%, an average hardness of 215 HV0.2, a yield strength of 488 MPa at room temperature, and a tensile strength of 684 MPa, but an elongation of only 44%.

[0090] Table 4 Mechanical properties of the alloys prepared in Comparative Examples 3 to 4 at room temperature (25°C)

[0091]

[0092] As shown in Table 4 above, the yield strength and elongation of parts prepared using the austenitic stainless steel powder of the present invention are significantly improved compared to austenitic stainless steel powder without the addition of rare earth element Y. Compared with Comparative Example 1, Example 3 shows increases of 11.2% and 39.0%, respectively. Compared with Comparative Example 2, Example 5 shows increases of 6.4% and 29.5%, respectively.

[0093] In summary, by adding a suitable percentage of Y rare earth element to austenitic stainless steel alloy and preparing austenitic stainless steel parts by the laser melting additive manufacturing method, not only can the crack sensitivity be reduced, but the prepared alloy also has excellent room temperature mechanical properties, low metallurgical defects, and high density.

[0094] This invention addresses the problems of grain coarsening, poor room temperature mechanical properties, and poor formability in the printing process of existing additively manufactured austenitic stainless steel. It innovatively proposes a high-performance austenitic stainless steel powder and its additive manufacturing forming method based on laser powder bed melting. After each layer is formed, low-temperature argon gas is used to blow and cool the surface of the forming layer to interrupt the grain coarsening process, and laser powder bed melting technology is used to achieve multi-scale synergistic strengthening, thereby significantly improving the room temperature mechanical properties of austenitic stainless steel parts.

[0095] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. 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 solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, and all of these should be included in the scope of the present invention.

Claims

1. An austenitic stainless steel powder, characterized in that: Calculated by mass fraction, it includes: Y: 0.1~0.3%; Cr: 17~18wt%; Ni: 6~8wt%; Mn: 0.6~0.8wt%; Si: 0.1~0.3wt%; C: 0.01~0.03wt%; S: 0.01~0.06wt%; P: 0.01~0.03wt%, and the rest is Fe and unavoidable impurities.

2. The austenitic stainless steel powder according to claim 1, wherein: Calculated by mass fraction, it includes: Y: 0.3%; Cr: 17.5wt%; Ni: 7.2wt%; Mn: 0.75wt%; Si: 0.2wt%; C: 0.02wt%; S: 0.05wt%; P: 0.02wt%, and the rest is Fe and unavoidable impurities.

3. The austenitic stainless steel powder according to claim 1 or 2, characterized in that: It also has the following features: (i) Yield strength of 512-535 MPa and tensile strength of 706-735 MPa at room temperature (25°C); (ii) Elongation at room temperature (25°C) 47-57%.

4. An additive manufacturing method based on laser powder bed fusion, characterized by: include, The materials are vacuum melted and argon atomized according to the mass percentages in any one of claims 1 to 2, and then laser powder bed melted and cooled by air blowing.

5. The additive manufacturing method according to claim 4, wherein: The vacuum melting conditions are as follows: a melting temperature of 1500° C. and an air pressure in the melting furnace of 0.4 MPa.

6. The additive manufacturing method according to claim 4, wherein: The argon atomization medium is argon gas, and the atomization pressure is 8 MPa.

7. The additive manufacturing method according to claim 4, wherein: The laser powder bed melting conditions include a laser power of 150 to 300 W, a scanning speed of 700 to 1100 mm / s, a scanning pitch of 0.08 to 0.2 mm, a scanning layer thickness of 0.07 to 0.1 mm, a layer-by-layer cross-scanning strategy, and a rotation angle of 0 to 90° between adjacent layers. The oxygen content during printing is controlled below 0.1 wt%, and the substrate preheating temperature is 100 to 200°C.

8. The additive manufacturing method according to claim 4, wherein: The air blowing cooling includes cooling the printed part after each layer is printed until the surface temperature of the part drops below 580°C before printing the subsequent part; Blow low-temperature inert gas on the printed surface at a flow rate of 6L / min.

9. The additive manufacturing method according to claim 7, wherein: The laser powder bed fusion process is to lay a first layer of powder on the substrate as a starting layer, and cross-scan four times according to the conditions of claim 7 to promote the bonding of the starting layer and the substrate.

10. The additive manufacturing method according to claim 9, wherein: The laser powder bed fusion is used to print the first layer, and a new layer of powder is laid on the starting layer. According to the method of claim 7, after the first layer printing is completed, the layers are repeatedly printed continuously.

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