Influence of magnetic field-assisted wire material additive manufacturing on the structure and properties of Inconel 625 superalloy (HY-industry technical centre)
Guide to Shanghai HY Industry Co., Ltd’s technical centre:
Magnetic field assisted wire additive manufacturing Inconel 625 superalloy was used to study the influence of magnetic field on the microstructure and performance. The mechanism of the influence of magnetic field on the microstructure was discussed. The application of magnetic field can improve the mechanical properties of in625 alloy produced by wire additive manufacturing. performance.
Introduction
Because of its advantages of high deposition efficiency, low cost and flexible manufacturing, wire material for additive manufacturing has been widely used in the manufacturing of Inconel 625 superalloy. However, higher heat input and severe element segregation occurred during the additive manufacturing process, which reduced the quality of the formed Inconel 625 alloy and reduced its service performance. Here, a magnetic field is used to assist in the process of additive manufacturing of Inconel 625 from the cold metal transition wire to change its microstructure. The influence of the magnetic field on the microstructure and mechanical properties of CMT-WAAM (Cold Metal Transition-Wire Additive Manufacturing) was studied. The results show that the stirring effect of the magnetic field plays a role in the grain refinement during the deposition process; the convection caused by the magnetic field promotes the diffusion of elements, such as Nb and Mo, in the molten pool, thereby inhibiting the segregation of elements. The mechanical properties of Inconel 625 alloy assisted by magnetic field deposition show that the microhardness increases, the yield strength increases by about 13%, and the ultimate tensile strength and toughness increase. Based on the above work, it is very obvious that the applied magnetic field in the CMT-WAAM process refines the dendrites, suppresses element segregation, and effectively improves the performance of the deposited INCONEL 625 alloy.
background
Wire Arc Additive Manufacturing (WAAM) combines the advantages of arc welding and rapid prototyping technology. Based on the principle of layering and discrete superposition, it has the advantages of rapid manufacturing, flexible manufacturing and low-cost manufacturing. The manufacturing process overcomes the shortcomings of traditional manufacturing technology and is widely used in many important industrial occasions, such as aerospace, biomedical and automotive industries. Inconel 625 superalloy is a nickel-based super alloy with excellent mechanical properties, including Cr, Mo, Nb and other metal elements. The alloy has excellent machining properties, corrosion resistance and oxidation resistance, and is widely used in petrochemical and aviation industries.
Performance of the material is significantly affected by its microstructure. The microstructure of the material can be modified in the following ways: changing the manufacturing process; changing the process parameters, etc. For example, in high-temperature alloy materials, such as nickel-based high-temperature alloys, the use of vacuum manufacturing can significantly change its microstructure, thereby further affecting its mechanical properties.
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Shanghai HY Industry Co., Ltd has studied the vacuum induction remelting process of Ni41Al41Cr12Co6 intermetallic compound, and its high temperature creep performance and thermal stability have been improved. The reason for the improvement is that vacuum induction remelting causes the dendrite grain size to become smaller, and the inclusions and precipitate phases become smaller.
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HY-Industry technology department adopts vacuum melting process to synthesize nickel-based solid solution strengthened superalloy, its composition is conventional 15Cr-15Mo (the balance is Ni). It was found that the reduction of grain size and the dissolution of particles improved the mechanical properties and strength of the alloy. The Ni-Fe-based superalloy (43Ni-14Cr, wt%) is melted in a vacuum induction furnace and refined by vacuum arc refining. The microstructure and mechanical properties of the material were studied, and it was found that the strength of the alloy increased due to the grain refinement and the presence of precipitated phases (bct γ′ Ni3Nb and fcc γ″ Ni3Ti precipitated phases).
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HY-industry technical centre also studied the effect of holding time on the microstructure and mechanical properties of Ni-Fe-Cr alloy in vacuum induction melting. The results of the study show that the elongation of the alloy can be increased, because the number of inclusions in the alloy is reduced during the heat preservation.
Most nickel-based superalloy parts have complex structures and very high manufacturing costs. WAAM manufacturing technology can manufacture parts with complex structures at a lower cost, so Inconel 625 superalloy can be manufactured by WAAM technology. However, due to the high heat input and complex heat transfer and mass transfer, the use of WAAM technology to manufacture INCONEL 625 often results in a decrease in product quality, such as cracks or poor roughness. At the same time, a large number of alloying elements in Inconel 625 alloy, such as Nb, Cr, Mo can improve its performance through solid solution strengthening during solidification. These elements also increase the solid-liquid two-phase temperature range during solidification. The increase in temperature deteriorates the degree of enriched elements, such as Nb and Mo elements, resulting in the formation of unfavorable phases such as (Ni, Fe) 2 (Nb, Mo, Cr, Ti), which will seriously affect the properties of the alloy. Therefore, the key to improving the WAAM process is to overcome the problems mentioned above, so that Inconel 625 alloy with better performance can be manufactured.
In recent years, magnetic field stirring technology has been used as an auxiliary method to improve the properties of alloys. This technology can not only affect the shape of the molten pool and refine the grains, but also change the mass transfer during the solidification of the alloy, change the distribution of elements and the microstructure, thereby improving the performance of the alloy.
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HY-Industry studied the changes in the microstructure and mechanical properties of aluminum alloys A356.0 and A413.1 under the condition of changing the intensity of the pulsed magnetic field. It was found that the magnetic field led to the formation of fine grains in the alloy, thereby increasing the hardness of the alloy to 8-10%. The magnetic field also affects the ultimate tensile strength of the alloy, but hardly changes its toughness.
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HY researchers used the GMAW process to prepare the aluminum alloy with the assistance of a magnetic field. It was found that the spatter was reduced by 1.8%, the microstructure was significantly refined, and the yield strength was increased by at least 31.5MPa. This is because the arc is compressed, and the temperature gradient and degree of subcooling of the arc are optimal. The condition is that the frequency of the magnetic field exceeds 60 Hz.
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HY technical department applies an external magnetic field during welding. It was found that the welding and the droplet were rotated due to the Loren magnetic force, thereby evening the heat distribution and changing the flow of the molten metal during the welding process. In addition, the external magnetic field force inhibits the diffusion of Fe and the formation of brittle phases, resulting in a higher yield strength. These studies have focused on the influence of magnetic fields on single-layer welding and connection joints. Few studies are about WAAM.
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HY’s R&D department proposed a new arc welding-based additive manufacturing technology, assisted by a longitudinal magnetic field. It is found that the external longitudinal magnetic field induces the stirring of the molten pool in the tangential direction and drives the molten metal to move to the edge of the molten pool, thereby reducing the temperature gradient in the forming area. In addition, it is found that the tangential stirring force can reduce the height of a single deposition layer and increase the width of a single deposition layer, and improve the surface accuracy of arc welding-based additive manufacturing.
In the current study, Inconel 625 alloy was manufactured using WAAM under the condition of an external constant magnetic field. The unique feature of this work is that the magnetic field is applied during the directional solidification of the alloy (that is, during the WAAM manufacturing process). The feasibility of magnetic field stirring to improve the microstructure and mechanical properties of Inconel 625 alloy manufactured by WAAM was also demonstrated.
main conclusion
Magnetic field is used to assist WAAM to manufacture Inconel 625 alloy. The effect of magnetic field on the microstructure and mechanical properties of WAAM to manufacture Inconel 625 alloy is studied, and the results are compared with the results when no magnetic field is used. The main conclusions are as follows:
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Applying an external magnetic field can significantly reduce the size of dendrites, which is reduced by about 1/3 compared with no magnetic field;
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Convection caused by the magnetic field reduces the segregation of strengthening elements such as Nb and Mo among the dendrites, thereby increasing the mechanical properties of the Inconel 625 alloy when deposited.
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Microhardness and room temperature yield strength of the Inconel 625 alloy deposited under the assisted magnetic field are higher than that of the deposited alloy without the assisted magnetic field. The improvement of the mechanical properties of the Inconel 625 alloy deposited by the magnetic field is attributed to the change of the microstructure: mainly: the refinement of the dendrite; the uniformity of the direction of the dendrite and the suppression of the segregation of alloying elements.
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Microstructure and mechanical properties of Inconel 625 alloy deposited by WAAM are significantly different from traditional Metal Active Gas (MAG) welding. This is due to the specific metal transition characteristics.
