Metal powder is a very important consumable in 3D printing. The metal powder used in 3D printing generally requires high purity, good sphericity, narrow particle size distribution, and low oxygen content. At present, the metal 3D printing materials used in 3D printing mainly include titanium alloy, cobalt-chromium alloy, stainless steel and aluminum alloy, etc. As the most important link in the 3D printing industry chain of metal parts, 3D printing metal powder is also the greatest value.
In the manufacturing process of 3D printed metal powder, different shapes of particles, such as a spherical, oval, porous sponge, tree, and other types, will be produced due to different requirements and different manufacturing methods. Different shapes of powder mean different fluidity and looseness, which will have different effects on the printing of products.
Generally, spherical or elliptical powder has good fluidity, so the powder supply system of the 3D printer will not be blocked due to poor circulation during printing. But also can be conveniently laid into a thin layer. Let the 3D printed objects have higher accuracy, and all parts will be more uniform. For the current technology, the spherical powder is undoubtedly a better choice. However, because of the large gap, the quality of the products printed with spherical powder is not as good as that of other shapes. If you want better quality, you need to make the diameter of the powder smaller.
Usually, it is better to make the diameter of 3D printed metal powder smaller. This is because the smaller the diameter of the powder, the better the sintering, and the higher the driving force for sintering. Not only does the smaller the diameter, the smaller the gap will be when stacking so that the quality and strength of the product will be guaranteed. However, the diameter of the powder is not as small as possible, because if the diameter of the powder is too small, it may cause the phenomenon of spheroidization during sintering, which will lead to uneven powder spreading, thus affecting the printing accuracy.
In addition, the oxygen and nitrogen contents also need to be strictly controlled. At present, the powder preparation technology for metal 3D printing is mainly based on atomization. The powder has a large specific surface area and is easy to oxidize. In special application fields such as aerospace, customers have stricter requirements on this index, such as the oxygen content of superalloy powder is 0.006%-0.018%, titanium alloy powder is 0.007%-0.013%, and stainless steel powder is 0.010%-0.025%.
The choice of particle size of metal powder for 3D printing is mainly divided according to metal printers with different energy sources. The printer with laser as an energy source is suitable for using 15-53μm powder as consumables because of its fine focusing spot and easy melting of fine powder. The powder supply method is layer by layer. The powder-spreading printer with an electron beam as an energy source has a slightly thicker focusing spot, which is more suitable for melting coarse powder, especially for coarse powder of 53-105μm; For coaxial powder feeding printer, powder with a particle size of 105-150μm can be used as consumables.