Nickel-aluminum bronze alloy laser powder bed melting forming additive manufacturing method

Abstract

A nickel-aluminum bronze alloy laser powder bed fusion forming additive manufacturing method comprises the steps that three-dimensional modeling is conducted according to the shape of a needed part, and a motion control program of a laser powder bed fusion forming additive manufacturing system is obtained; performing surface treatment on the substrate, and mounting the substrate; the nickel-aluminum bronze alloy powder is dried in a vacuum drying oven; a laser powder bed melting forming additive manufacturing system is started, a motion control program is operated, dried nickel-aluminum bronze alloy powder is laid on the surface of a base plate, a laser head is positioned above the powder bed, the powder is selectively melted by a laser beam to form a molten pool, and a melting channel is formed after the liquid molten pool is solidified; moving the laser head by a scanning distance, repeating the previous step to form a next melting channel, and forming a deposition layer through mutual lap joint of the melting channels; and after scanning of the deposition layer is completed, the deposition layer is lowered by one layering thickness, and layer-by-layer deposition is conducted till the formed part is manufactured. The nickel-aluminum bronze alloy component prepared by the method is compact, has no defect and is excellent in mechanical property.

Description

Technical Field

[0001] The invention relates to the technical field of laser additive manufacturing, and in particular to a nickel-aluminum-bronze alloy laser powder bed fusion forming additive manufacturing method. Background Art

[0002] Nickel-aluminum bronze alloy is an aluminum bronze with nickel, iron, manganese and other elements as the main alloying elements. Because of its excellent seawater corrosion resistance, good fatigue resistance and anti-biofouling performance, it is widely used in ship propellers, seawater pumps, valves and impellers. At present, nickel-aluminum bronze parts are mainly cast by sand casting and then CNC machining to ensure their dimensional accuracy. Due to the large number of nickel-aluminum bronze alloy elements, it is very easy to cause composition segregation (causing phase selection corrosion), looseness and shrinkage defects during casting. In particular, when casting impellers with complex structural surfaces, it will lead to low forming accuracy and reduced strength, thus affecting its corrosion resistance and service life. Some structures are even difficult to form. It can be seen that the existing casting + CNC machining of nickel-aluminum bronze parts has the problems of requiring molds, limited forming freedom, and corrosion performance needs to be further improved. Additive manufacturing is a "bottom-up" manufacturing method through material accumulation, which can provide extremely high processing freedom, has the advantages of short processing cycle, high material utilization rate, and excellent performance of formed parts. It has been widely used in many fields such as aerospace, energy and nuclear power, weapons and equipment, automobile transportation, and medical implants.

[0003] Laser Powder Bed Fusion (LPBF) forming technology is a precision additive manufacturing technology for metal parts that has developed rapidly in recent years. At present, LPBF technology for common metal materials such as stainless steel, aluminum silicon alloy, titanium alloy, etc. has become mature. However, copper alloys, due to the high laser reflectivity, high thermal conductivity, and high melting point of the material itself, often use arc as a heat source for additive manufacturing. Due to the low cooling rate and large heat-affected zone of arc additive manufacturing technology, the forming accuracy of nickel-aluminum bronze alloy parts is low, phase-selective corrosion still exists, and the mechanical properties are only equivalent to or slightly higher than those of the cast state.

[0004] Laser additive technology based on powder feeding can break through the bottleneck of low precision and low performance in arc additive manufacturing technology. By increasing the melting speed, the microstructure is significantly refined, but its β′ martensite phase is coarsened and the content of β′ martensite phase in the deposited state is small, 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 6℃ / s, it is expected to further refine the microstructure and obtain more β′ martensite phase. However, there are problems such as insufficient heat input at low power, easy to produce metallurgical defects such as holes and cracks. Therefore, how to achieve dense, defect-free and excellent mechanical properties of parts at low power is a challenge faced by LPBF forming nickel-aluminum bronze alloys. Summary of the invention

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

[0006] In order to solve the above technical problems, the present invention provides a nickel-aluminum bronze alloy laser powder bed fusion forming additive manufacturing method, comprising the following steps:

[0007] Step S1, performing three-dimensional modeling according to the required component shape to obtain a motion control program of a laser powder bed fusion forming additive manufacturing system;

[0008] Step S2, performing surface treatment on the substrate, the substrate is made of stainless steel, and installing the substrate;

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

[0010] Step S4, starting the laser powder bed fusion forming additive manufacturing system, running the motion control program, laying the dried nickel-aluminum-bronze alloy powder on the surface of the substrate, positioning the laser head above the powder bed, and selectively melting the powder with a laser beam to form a molten pool, and forming a melt path after the liquid molten pool solidifies;

[0011] Step S5, the laser head moves a scanning distance, and step S4 is repeated to form the next melt path, and a deposition layer is formed by overlapping the melt paths;

[0012] Step S6, after the deposition layer is scanned, the deposition layer is reduced by a layer thickness, and steps S4 to S5 are repeated, depositing layer by layer until the formed part is manufactured, thereby obtaining a nickel-aluminum-bronze component.

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

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

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

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

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

[0018] Furthermore, the nickel aluminum bronze nominally complies with 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 parts in the tensile state is 1037.3MP to 1069.4MPa, and the elongation after fracture is 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 the powder and introducing a protective gas, thereby suppressing the generation of pores and improving the mechanical properties of nickel-aluminum bronze alloy parts.

[0022] (2) The present invention simultaneously adopts low power, substrate preheating, low scanning speed, small powder layer thickness or high power, no substrate preheating, high scanning speed, and large powder layer thickness to increase energy input and the residence time of liquid metal, promote the complete spreading of liquid metal, exhaust gas, inhibit the formation of holes and cracks, and achieve interlayer metallurgical bonding; at the same time, laser powder bed fusion forming has an 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, and provides a new manufacturing method for the manufacture of nickel-aluminum bronze alloys in marine seawater pumps, valves, pipelines, impellers and other components. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

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

[0029] Figure 7 This is the metallographic image of the alloy sample in Example 3 of the present invention. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] In order to enable those skilled in the art to more clearly understand the technical solution of the present application, the technical solution of the present application will be described in detail below in conjunction with specific embodiments. If the specific experimental conditions are not indicated in the embodiments, they are usually in accordance with conventional conditions or the conditions recommended by the reagent company: the reagents, consumables, etc. used in the following embodiments, unless otherwise specified, can be obtained through commercial channels.

[0032] Example 1

[0033] A nickel-aluminum-bronze alloy laser powder bed fusion forming additive manufacturing method adopts a laser powder bed fusion forming additive manufacturing process to prepare nickel-aluminum-bronze alloy parts.

[0034] This embodiment includes the following steps:

[0035] Step S1, performing three-dimensional modeling according to the required component shape to obtain a motion control program of a laser powder bed fusion forming additive manufacturing system;

[0036] Step S2, processing a stainless steel substrate of a required size with a thickness of 30 mm, wiping it with anhydrous ethanol to remove other impurities, and clamping the substrate;

[0037] Step S3, the atomized nickel-aluminum bronze alloy powder is kept at 100° C. in a vacuum drying oven for 2 hours, wherein the nickel-aluminum bronze alloy powder comprises: Al 9.96%, Ni 4.3%, Fe4.5%, Mn 1.4%, and the average particle size of the powder is 39 μm; 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 generation of pores during the solidification process.

[0038] S4, start the laser powder bed fusion forming additive manufacturing system, run the motion control program, set the substrate preheating temperature to 125°C, the laser power to 300W, the scanning speed to 1000mm / s, the scanning spacing to 0.11mm, the phase angle to 67°, and the layer thickness to 0.03mm; lay the dried nickel-aluminum bronze alloy powder on the substrate surface, position the laser head 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 path is formed;

[0039] S5: After the current layer is scanned, the forming cylinder descends by one layer thickness, and steps 4 to 5 are repeated, depositing layer by layer until the entire formed part is manufactured.

[0040] Metallographic analysis was carried out on the furnace samples of the prepared nickel-aluminum bronze parts, and no defects were found. The tensile test was carried out on the horizontal tensile test samples of the prepared nickel-aluminum bronze parts, and the tensile strength was 1069.4MPa, and the elongation after fracture was 9.0%. The tensile test was carried out on the vertical tensile test samples of the prepared nickel-aluminum bronze parts, and the tensile strength was 1037.3MPa, and the elongation after fracture was 0.45%. The performance is good, and the tensile strength is much better than the forging standard.

[0041] Example 2

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

[0043] Example 3

[0044] This embodiment provides a nickel-aluminum-bronze alloy laser powder bed fusion forming additive manufacturing method, which can achieve compactness, defect-freeness, and excellent performance. The specific preparation method is the same as that of Example 1, except that: in step S4, the laser power is set to 400 W and the scanning speed is set to 1000 mm / s.

[0045] Example 4

[0046] The present embodiment provides a nickel-aluminum bronze alloy laser powder bed fusion forming additive manufacturing method, which can achieve compactness, defect-freeness and excellent performance. The specific preparation method is the same as that of Example 1, except that: in step S3, the powder composition is Al8.88%, Ni 4.28%, Fe 4.29%, and Mn1.83%; 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 need to be preheated.

[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 an optical microscope (OM, DMM-400C) and the fracture morphology was analyzed by a field emission scanning electron microscope (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 The nickel-aluminum bronze impeller part manufactured by laser powder bed fusion forming is shown. Figure 2 The scanning electron microscope image shows the morphology of nickel aluminum bronze powder used in laser powder bed fusion forming. Figure 3 The metallographic image of the sample of Example 1 is shown. Figure 4 The stress-strain curve of the horizontal tensile sample of Example 1 is shown. Figure 5 The scanning electron microscope image of the fracture morphology of the horizontal tensile sample of Example 1 is shown. Figure 6 The metallographic image of the sample of Example 2 is shown. Figure 7 The metallographic image of the sample of Example 3 is shown. From the density statistical data in Table 1, it can be seen that the density of the samples prepared in Examples 1 to 4 can reach more than 99.9%.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A method for additive manufacturing of nickel-aluminum-bronze alloy by laser powder bed fusion forming, characterized in that: The following steps are involved: Step S1, performing three-dimensional modeling according to the required component shape to obtain a motion control program of a laser powder bed fusion forming additive manufacturing system; Step S2, performing surface treatment on the substrate, the substrate is made of stainless steel, and installing the substrate; Step S3, drying the nickel-aluminum bronze alloy powder in a vacuum drying oven; Step S4, starting the laser powder bed fusion forming additive manufacturing system, running the motion control program, laying the dried nickel-aluminum-bronze alloy powder on the surface of the substrate, positioning the laser head above the powder bed, and selectively melting the powder with a laser beam to form a molten pool, and forming a melt path after the liquid molten pool solidifies; Step S5, the laser head moves a scanning distance, and step S4 is repeated to form the next melt path, and a deposition layer is formed by overlapping the melt paths; Step S6, after the deposition layer is scanned, the deposition layer is reduced by a layer thickness, and steps S4 to S5 are repeated, depositing layer by layer until the formed part is manufactured, thereby obtaining a nickel-aluminum-bronze component.

2. The nickel-aluminum-bronze alloy laser powder bed fusion forming additive manufacturing method according to claim 1, characterized in that: In step S3, the nickel-aluminum-bronze alloy powder is kept in a vacuum drying oven at a drying temperature of 80 to 120°C for 1.5 to 2.5 hours.

3. The nickel-aluminum-bronze alloy laser powder bed fusion forming additive manufacturing method according to claim 2, characterized in that: In step S3, the drying temperature is 100°C and the holding time is 2 hours.

4. The nickel-aluminum-bronze alloy laser powder bed fusion forming additive manufacturing method according to claim 1, characterized in that: In step S4, the oxygen content in the forming chamber of the laser powder bed fusion forming additive manufacturing system is ≤50ppm, and the protective gas is argon.

5. The nickel-aluminum-bronze alloy laser powder bed fusion forming additive manufacturing method according to claim 1, characterized in that: In step S4, there are two types of process parameters of the laser powder bed fusion forming additive manufacturing system: (1) when substrate preheating is adopted, 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 adopted, 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.

6. The nickel-aluminum-bronze alloy laser powder bed fusion forming additive manufacturing method according to claim 1, characterized in that: The particle size of the nickel-aluminum-bronze alloy powder is 25 μm to 60 μm.

7. The nickel-aluminum-bronze alloy laser powder bed fusion forming additive manufacturing method according to claim 1, characterized in that: The nickel aluminum bronze nominally conforms to ASTM grade C95800 and GB / T 1176-1974 grade ZQAl9-4-4-2 nickel aluminum bronze alloy.

8. The nickel-aluminum-bronze alloy laser powder bed fusion forming additive manufacturing method according to claim 1, characterized in that: The tensile strength of the prepared nickel-aluminum bronze parts in the tensile state is 1037.3MP-1069.4MPa, and the elongation after fracture is 0.45%-9.0%.

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