A method of laser powder bed fusion additive manufacturing of a nickel-aluminum bronze alloy

Abstract

A method for laser powder bed fusion additive manufacturing of nickel-aluminum bronze alloys includes: creating a three-dimensional model based on the desired part shape to obtain a motion control program for the laser powder bed fusion additive manufacturing system; surface treating a substrate and mounting the substrate; drying nickel-aluminum bronze alloy powder in a vacuum drying oven; starting the laser powder bed fusion additive manufacturing system, running the motion control program, laying the dried nickel-aluminum bronze alloy powder on the substrate surface, positioning the laser head above the powder bed, and selectively melting the powder with the laser beam to form a molten pool. After the liquid molten pool solidifies, a melt channel is formed. The laser head moves one scanning interval, repeating the previous step to form the next melt channel, and a deposition layer is formed by the overlapping of the melt channels. After the deposition layer has been scanned, the deposition layer decreases by one layer thickness, and the deposition is repeated layer by layer until the shaped part is manufactured. The nickel-aluminum bronze alloy parts prepared using this invention are dense, defect-free, and have excellent mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of laser additive manufacturing technology, specifically a method for laser powder bed melting and additive manufacturing of nickel-aluminum bronze alloys. Background Technology

[0002] Nickel-aluminum bronze alloy is an aluminum bronze with nickel, iron, and manganese as its main alloying elements. Due to its excellent resistance to seawater corrosion, good fatigue resistance, and resistance to biofouling, it is widely used in ship propellers, seawater pumps, valves, and impellers. Currently, nickel-aluminum bronze components are mainly produced using sand casting followed by CNC machining to ensure dimensional accuracy. However, due to the high number of alloying elements in nickel-aluminum bronze, casting easily leads to defects such as compositional segregation (initiating selective corrosion), porosity, and shrinkage cavities. This is particularly problematic when casting impellers with complex structural surfaces, resulting in low forming accuracy and reduced strength, thus affecting corrosion resistance and service life. Some structures are even difficult to form. Therefore, existing casting + CNC machining methods for nickel-aluminum bronze components suffer from the need for molds, limited forming freedom, and the need for further improvement in corrosion resistance. Additive manufacturing, a bottom-up manufacturing method that accumulates materials, offers extremely high processing freedom, with advantages such as short processing cycles, high material utilization, and excellent part performance. It has been widely used in aerospace, nuclear power, weaponry, automotive, medical implants, and many other fields.

[0003] Laser Powder Bed Fusion (LPBF) forming technology is a rapidly developing precision additive manufacturing technology for metal parts. Currently, LPBF technology is relatively mature for common metal materials such as stainless steel, aluminum-silicon alloys, and titanium alloys. However, copper alloys, due to their high laser reflectivity, high thermal conductivity, and high melting point, often require an electric arc as the heat source for additive manufacturing. Because of the low cooling rate and large heat-affected zone in arc additive manufacturing, nickel-aluminum bronze alloy parts have lower forming accuracy, are still susceptible to selective corrosion, and their mechanical properties are only comparable to or slightly higher than those in the as-cast state.

[0004] Laser additive manufacturing technology based on powder feeding can overcome the bottlenecks of low precision and low performance in arc additive manufacturing technology. By increasing the melting and solidification rate, the microstructure is significantly refined. However, the β′ martensite phase coarsens and the content of β′ martensite phase in the deposited state is low, resulting in limited improvement in its mechanical properties and corrosion resistance. LPBF technology has a small heat-affected zone, a high temperature gradient, and a cooling rate of up to 10... 6At ℃ / s, it is hoped that the microstructure can be further refined and more β′ martensite phase can be obtained. However, there are problems such as insufficient heat input at low power, which can easily lead to metallurgical defects such as pores and cracks. Therefore, how to achieve dense, defect-free components with excellent mechanical properties at low power is a challenge for LPBF forming nickel-aluminum bronze alloys. Summary of the Invention

[0005] The purpose of this invention is to provide a method for additive manufacturing of nickel-aluminum bronze alloys by laser powder bed melting. The nickel-aluminum bronze alloy parts prepared by this method are dense, defect-free, and have excellent mechanical properties.

[0006] To solve the above-mentioned technical problems, the present invention provides a method for additive manufacturing of nickel-aluminum bronze alloys by laser powder bed melting, comprising the following steps:

[0007] Step S1: Perform a 3D model based on the required part shape to obtain the motion control program for the laser powder bed fusion additive manufacturing system;

[0008] Step S2: Perform surface treatment on the substrate. The substrate material is stainless steel. Then, mount the substrate.

[0009] Step S3: Dry the nickel-aluminum bronze alloy powder in a vacuum drying oven;

[0010] Step S4: Start the laser powder bed melting additive manufacturing system, run the motion control program, lay dried nickel-aluminum bronze alloy powder on the substrate surface, position the laser head above the powder bed, and selectively melt the powder to form a molten pool. After the liquid molten pool solidifies, a melt channel is formed.

[0011] Step S5: The laser head moves one scanning interval and repeats step S4 to form the next melting channel. The deposition layer is formed by the overlapping of the melting channels.

[0012] Step S6: After the deposition layer is scanned, the deposition layer is reduced by one layer thickness. Steps S4 to S5 are repeated to deposit layer by layer until the shaped part is manufactured and a nickel-aluminum bronze component is obtained.

[0013] Furthermore, in step S3, the nickel-aluminum bronze alloy powder is dried in a vacuum drying oven at a temperature of 80–120°C for 1.5–2.5 hours.

[0014] Furthermore, in step S3, the drying temperature is 100°C and the holding time is 2 hours.

[0015] Furthermore, in step S4, the oxygen content in the forming cavity of the laser powder bed fusion additive manufacturing system is ≤50ppm, and the protective gas is argon.

[0016] Furthermore, in step S4, the process parameters of the laser powder bed melting additive manufacturing system are of two types: (1) when substrate preheating is used, the preheating temperature is 100℃~200℃, the laser power is 300W~500W, the scanning rate is 500mm / s~1000mm / s, the layer thickness is 0.02mm~0.03mm, and the scanning spacing is 0.09mm~0.15mm; (2) when substrate preheating is not used, the laser power is 500W~1000W, the scanning rate is 1000mm / s~2000mm / s, the layer thickness is 0.04mm~0.05mm, and the scanning spacing is 0.12mm~0.18mm.

[0017] Furthermore, the particle size of the nickel-aluminum bronze alloy powder is 25μm to 60μm.

[0018] Furthermore, the nickel-aluminum bronze nominally conforms to ASTM grade C95800 and GB / T1176-1974 grade ZQAl9-4-4-2 nickel-aluminum bronze alloy.

[0019] Furthermore, the tensile strength of the prepared nickel-aluminum bronze components in the deposited state was 1037.3 MPa to 1069.4 MPa, and the elongation after fracture was 0.45% to 9.0%.

[0020] The present invention has the following beneficial effects:

[0021] (1) The present invention controls the water and oxygen content during the forming process by drying powder and introducing protective gas, which suppresses the generation of pores and improves the mechanical properties of nickel-aluminum bronze alloy parts.

[0022] (2) This invention simultaneously employs low power, substrate preheating, low scanning speed, and small powder layer thickness, or high power, no substrate preheating, high scanning speed, and large powder layer thickness to increase energy input and residence time of liquid metal, promote complete spreading of liquid metal, expel gas, suppress the formation of pores and cracks, and achieve interlayer metallurgical bonding; at the same time, laser powder bed melting has extremely high temperature gradient and cooling rate, which promotes the formation of fine β′ martensite phase, achieving the purpose of dense, defect-free, and high-performance forming, providing a new manufacturing method for nickel-aluminum bronze alloys in the manufacture of marine seawater pump valves, pipes, impellers and other parts. Attached Figure Description

[0023] Figure 1 This is a diagram of the impeller of the vortex pump formed by laser powder bed melting of nickel-aluminum bronze alloy according to the present invention.

[0024] Figure 2 This is a scanning electron microscope image of the nickel-aluminum bronze alloy powder used in this invention.

[0025] Figure 3 This is a metallographic image of the alloy sample in Example 1 of the present invention.

[0026] Figure 4 This is the stress-strain curve of the alloy sample in Example 1 of the present invention.

[0027] Figure 5 This is a scanning electron microscope image of the fracture surface of the alloy sample in Example 1 of the present invention.

[0028] Figure 6 This is a metallographic image of the alloy sample in Example 2 of the present invention.

[0029] Figure 7 This is a metallographic image of the alloy sample in Example 3 of the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] To enable those skilled in the art to better understand the technical solution of this application, the technical solution of this application will be described in detail below with reference to specific embodiments. Unless otherwise specified, experimental conditions are generally as per conventional conditions or the conditions recommended by the reagent company. The reagents, consumables, etc., used in the following embodiments can be obtained commercially unless otherwise specified.

[0032] Example 1

[0033] A method for additive manufacturing of nickel-aluminum bronze alloys using laser powder bed fusion forming, which produces nickel-aluminum bronze alloy parts using laser powder bed fusion forming additive manufacturing process.

[0034] This embodiment includes the following steps:

[0035] Step S1: Perform a 3D model based on the required part shape to obtain the motion control program for the laser powder bed fusion additive manufacturing system;

[0036] Step S2: Process a stainless steel substrate of the required size with a thickness of 30mm, wipe it with anhydrous ethanol to remove other impurities, and then clamp the substrate.

[0037] In step S3, the nickel-aluminum bronze alloy powder produced by gas atomization is kept at 100°C for 2 hours in a vacuum drying oven. The composition of the nickel-aluminum bronze alloy powder includes: Al 9.96%, Ni 4.3%, Fe 4.5%, Mn 1.4%, and the average particle size is 39μm. By performing vacuum drying pretreatment on the nickel-aluminum bronze alloy powder, the moisture in the alloy powder can be effectively removed, and the moisture on the surface of the powder particles can be evaporated, thereby improving the fluidity of the powder and reducing the formation of pores during solidification.

[0038] S4. Start the laser powder bed fusion additive manufacturing system, run the motion control program, and set the substrate preheating temperature to 125℃, laser power to 300W, scanning speed to 1000mm / s, scanning spacing to 0.11mm, phase angle to 67°, and layer thickness to 0.03mm. Dry nickel-aluminum bronze alloy powder is laid on the substrate surface, the laser head is positioned above the powder bed, and the laser beam selectively melts the powder to form a molten pool. After the liquid molten pool solidifies, a melt channel is formed.

[0039] After the current layer of S5 is scanned, the forming cylinder descends by one layer thickness, and steps four and five are repeated to deposit layer by layer until the entire forming part is manufactured.

[0040] Metallographic analysis of the prepared nickel-aluminum bronze parts samples prepared in the furnace revealed no defects. Tensile testing was performed on the horizontal tensile specimens prepared in the furnace, showing a tensile strength of 1069.4 MPa and an elongation after fracture of 9.0%. Tensile testing was also performed on the vertical tensile specimens prepared in the furnace, showing a tensile strength of 1037.3 MPa and an elongation after fracture of 0.45%. The performance was excellent, and the tensile strength was far superior to that of forgings.

[0041] Example 2

[0042] This embodiment provides a method for additive manufacturing of nickel-aluminum bronze alloys by laser powder bed melting, which can achieve dense, defect-free, and high-performance materials. The specific preparation method is the same as in Embodiment 1, except that the laser power is set to 350W and the scanning speed is 1000mm / s in step S4.

[0043] Example 3

[0044] This embodiment provides a method for additive manufacturing of nickel-aluminum bronze alloys by laser powder bed melting, which can achieve dense, defect-free, and high-performance materials. The specific preparation method is the same as in Embodiment 1, except that the laser power is set to 400W and the scanning speed is 1000mm / s in step S4.

[0045] Example 4

[0046] This embodiment provides a method for additive manufacturing of nickel-aluminum bronze alloys using laser powder bed melting, which can achieve dense, defect-free, and high-performance materials. The specific preparation method is the same as in Embodiment 1, except that: in step S3, the powder composition is Al 8.88%, Ni 4.28%, Fe 4.29%, and Mn 1.83%; in step S4, the laser power is set to 580W, the layer thickness is 0.04mm, the scanning spacing is 0.12mm, the scanning speed is 1300mm / s, and the substrate does not require preheating.

[0047] Performance testing

[0048] The samples prepared in Examples 1 to 4 were separated from the substrate by wire cutting. The density of the samples was analyzed by optical microscopy (OM, DMM-400C) and the fracture morphology was analyzed by field emission scanning electron microscopy (ZEISS GeminiSEM 300). The density results are shown in Table 1.

[0049] Table 1

[0050] Density Example 1 99.95％ Example 2 99.92％ Example 3 99.94％ Example 4 99.91％

[0051] Figure 1 This image shows a nickel-aluminum bronze impeller part manufactured using laser powder bed fusion additive manufacturing. Figure 2 This shows a scanning electron microscope image of the morphology of nickel-aluminum bronze powder used in laser powder bed fusion forming. Figure 3 Metallographic images of the sample from Example 1 are shown. Figure 4 The stress-strain curve of the horizontally tensile sample of Example 1 is shown. Figure 5 The image shows a scanning electron microscope image of the fracture morphology of the horizontally stretched sample from Example 1. Figure 6 Metallographic images of the sample from Example 2 are shown. Figure 7 Metallographic images of the sample from Example 3 are shown. As can be seen from the density statistics in Table 1, the density of the samples prepared in Examples 1-4 all reached over 99.9%.

[0052] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any person skilled in the art may make changes or modifications to the disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for additive manufacturing of nickel-aluminum bronze alloys using laser powder bed fusion molding, characterized in that, Includes the following steps: Step S1: Perform a 3D model based on the required part shape to obtain the motion control program for the laser powder bed fusion additive manufacturing system; Step S2: Perform surface treatment on the substrate. The substrate material is stainless steel. Then, mount the substrate. Step S3: Dry the nickel-aluminum bronze alloy powder in a vacuum drying oven; Step S4: Start the laser powder bed melting additive manufacturing system, run the motion control program, lay dried nickel-aluminum bronze alloy powder on the substrate surface, position the laser head above the powder bed, and selectively melt the powder to form a molten pool. After the liquid molten pool solidifies, a melt channel is formed. Step S5: The laser head moves one scanning interval and repeats step S4 to form the next melting channel. The deposition layer is formed by the overlapping of the melting channels. Step S6: After the deposition layer is scanned, the deposition layer is reduced by one layer thickness. Steps S4 to S5 are repeated to deposit layer by layer until the shaped part is manufactured and a nickel-aluminum bronze component is obtained. In step S3, the nickel-aluminum bronze alloy powder is dried in a vacuum drying oven at 100°C for 2 hours. In step S4, the process parameters of the laser powder bed melting additive manufacturing system are of two types: (1) When the substrate is preheated, the preheating temperature is 100℃~200℃, the laser power is 300 W~500 W, the scanning rate is 500 mm / s~1000 mm / s, the layer thickness is 0.02 mm~0.03 mm, and the scanning spacing is 0.09 mm~0.15 mm; (2) When the substrate is not preheated, the laser power is 500 W~1000 W, the scanning rate is 1000 mm / s~2000 mm / s, the layer thickness is 0.04 mm~0.05 mm, and the scanning spacing is 0.12 mm~0.18 mm. The tensile strength of the sedimentary samples in the tensile state ranged from 1037.3 MPa to 1069.4 MPa, and the elongation after fracture ranged from 0.45% to 9.0%. The nickel-aluminum bronze nominally conforms to ASTM grade C95800 and GB / T 1176-1974 grade ZQAl9-4-4-2 nickel-aluminum bronze alloy.

2. The method for additive manufacturing of nickel-aluminum bronze alloys using laser powder bed melting as described in claim 1, characterized in that: In step S4, the oxygen content in the forming cavity of the laser powder bed fusion additive manufacturing system is ≤50 ppm, and the protective gas is argon.

3. The method for additive manufacturing of nickel-aluminum bronze alloys using laser powder bed fusion molding as described in claim 1, characterized in that: The particle size of the nickel-aluminum bronze alloy powder is 25 μm to 60 μm.

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