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Performance requirements for materials in SLM metal 3D printing

2024-03-05 16:11

1. Purity
Ceramic inclusions can significantly reduce the performance of the final product, and these inclusions generally have a high melting point, making them difficult to sinter into shape. Therefore, there must be no ceramic inclusions in the powder. In addition, the oxygen and nitrogen content also need to be strictly controlled. At present, the powder preparation technology used for metal 3D printing is mainly based on atomization method. The powder has a large specific surface area and is easy to oxidize. In special application fields such as aerospace, the requirements for this index are more strict, such as the oxygen content of high-temperature alloy powder is 0.006% -0.018%, titanium alloy powder is 0.007% -0.013%, and stainless steel powder is 0.010% -0.025%.

 

2. Powder flowability and loose density
The flowability of powder directly affects the uniformity of powder spreading and the stability of powder feeding during the printing process. The fluidity is related to the powder morphology, particle size distribution, and loose packing density. The larger the powder particles, the more regular the particle shape, and the smaller the proportion of extremely fine powder in the particle size composition, the better their fluidity; The particle density remains unchanged, but as the relative density increases, the powder flowability increases. In addition, the adsorption of water, gas, etc. on the surface of particles can reduce the flowability of the powder.

 

3. Powder particle size distribution
Different 3D printing equipment and forming processes have different requirements for powder particle size distribution. The current commonly used powder particle size range for metal 3D printing is 15-53 μ M (fine powder), 53-105 μ M (coarse powder). The selection of metal powder particle size for 3D printing is mainly based on the classification of metal printers with different energy sources. Printers with laser as the energy source are suitable for using 15-53 due to their fine focusing spot and easy melting of fine powder μ The powder of m is used as a consumable, and the powder supply method is layer by layer powder spreading; A powder spreading printer using an electron beam as the energy source, with a slightly thicker focusing spot, is more suitable for melting coarse powder, and is suitable for use with 53-105 μ Mainly coarse powder of m; For coaxial powder feeding printers, a particle size of 105-150 can be used μ M's powder is used as a consumable.

 

4. Powder morphology
The morphology of the powder is closely related to the preparation method of the powder. Generally, when the metal gas or molten liquid is transformed into powder, the shape of the powder particles tends to be spherical. When the solid state changes to powder, the powder particles are mostly irregular in shape, while the powder prepared by aqueous solution electrolysis method is mostly dendritic. Generally speaking, the higher the sphericity, the better the flowability of the powder particles. 3D printing of metal powder requires a sphericity of over 98%, making it easier to lay and feed the powder during printing.