The demand for lightweight, high-performance, and sophisticated structural components in the aerospace sector is daily growing as technology advances. While the rise of 3D printing technology has brought radical improvements to the aerospace manufacturing sector, conventional manufacturing techniques sometimes have significant restrictions in these sectors. Among them, the progress of aerospace 3D printing technology has been much facilitated by the study and development of improved metal powders.
3D printing, sometimes referred to as additive manufacturing technology, is a technique for layer by layer material accumulation to create three-dimensional items. 3D printing technology boasts better material use, quicker manufacturing cycles, and more design freedom than conventional subtractive manufacturing or equal material manufacturing alternatives. 3D printing technology is extensively applied in aerospace fields including lightweight manufacturing, engine component optimisation, drone manufacture, and aircraft component manufacture.
Particularly in the aerospace industry, where there are quite high needs for the performance of metal powder, metal powder is a crucial raw material for 3D printing technology. High grade metal powders demand properties including good sphericity, flowability, suitable particle size distribution, and high purity. These properties directly influence the quality and performance of 3D printed goods, so the development of improved metal powders has become a main driver for improving aeronautical 3D printing technology.
Two often used preparation techniques in the study and development of metal powders are vacuum induction melting argon atomisation method (VIGA) and plasma rotating electrode method (PREP). The PREP method can prepare metal powders with high sphericity, smooth surface, narrow powder particle size distribution, and good flowability, which has unique advantages in the field of 3D printing; the VIGA method has a high yield of fine powder but problems with hollow powder and satellite powder. Developing and updating a new generation of plasma rotating electrode atomisation powder technology and equipment will help to enhance the yield of fine powder and production efficiency, therefore enhancing the quality of PREP powder.
Apart from improving the preparation technique, the performance of metal powder is much influenced by its purity. For particular uses like aerospace, consumers have quite exact standards for the metal powder purity. The oxygen content of titanium alloy powder is 0.007% to 0.013%; the oxygen content of high-temperature alloy powder needs to be regulated between 0.006% and 0.018%; and the oxygen content of stainless steel powder is 0.010% to 0.025%. These rigorous purity criteria guarantee important indications such mechanical strength of 3D printed items, corrosion resistance, and high temperature performance.
Aerospace 3D printing also depends much on the particle size distribution of metal powder. varied 3D printing techniques and shaping methods demand varied powder particle size distribution criteria. For metal 3D printing, the most often utilised powder particle size range nowadays is 15–150 μ m. Because of their fine focused spot and simple melting of fine powder, printers running on lasers as energy sources are appropriate for employing powders ranging from 15 to 53 μ m; Printers employing electron beams as energy sources have somewhat coarser focused light spots, so they are better appropriate for melting coarse powders and for using powders ranging from 53 to 105 μ m. powder having a particle size of 105–150 μ m can be utilised for coaxial powder feeding printers.
An other crucial determinant of metal powder flowability is its sphericity. Generally speaking, powder particle flowability is better the higher their sphericity. To guarantee flawless powder distribution and feeding during printing, 3D printing of metal powder needs a sphericity of more than 98%. The main preparation techniques for high-quality 3D printed metal powders are aerosolization and rotating electrode techniques; thus, the powder shape produced by these two processes is essentially spherical, satisfying the high criteria of 3D printing.
Apart from advancing aircraft 3D printing technology, the research and development of new metal powders supports powder metallurgy technology innovation and development. Using techniques including pressing and sintering metal powders, powder metallurgy is a sophisticated material processing method producing different parts. Aerospace powder metallurgy is extensively applied to produce lightweight constructions and intricate shaped components. Powder metallurgy technology has been further developed and refined with the advent of 3D printing technology, therefore generating a composite manufacturing technology of "3D printing+powder metallurgy".
One novel technique combining 3D printing and powder metallurgy technologies is powder extrusion printing (PEP). First consistently mixing metal/ceramic powders with organic binders to make pellets, this technique then moulds them using a 3D printer, eliminates the binders from the produced blanks, and lastly densifies them through sintering to produce goods with consistent and outstanding performance. Apart from mould free preparation, PEP technology increases the processing capacity of high difficulty and highly complex components, so offering a more effective and flexible production solution for the aerospace sector.
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