Particle size characteristic requirements of titanium alloy powder
Titanium alloy (Ti6Al4V) is one of the most widely used materials in SLM metal printing, and its powder characteristics have a decisive impact on printing quality. The ideal titanium alloy powder particle size distribution is in the range of 15-45 μm, showing a normal distribution shape. Powder with a particle size that is too small (less than 15 μm) has poor fluidity and is easy to agglomerate. It also produces flying dust during the powder spreading process, affecting printing quality and operational safety. Powders with excessively large particle sizes (greater than 45 μm) are not fully melted and are prone to non-fusion defects. The D10, D50, and D90 values of the powder need to be controlled within the specified range, and the D50 value is preferably 25-35 μm. The particle size distribution width (span) of the powder should be less than 1.5. A distribution that is too wide will lead to inconsistent melting behavior.
The relationship between powder sphericity and fluidity
Powder sphericity is a key indicator for evaluating the quality of SLM materials. The sphericity of high-quality titanium alloy powder should be greater than 90%, which is close to a perfect sphere. Spherical powder has better fluidity and powder spreading uniformity, ensuring consistent thickness of each layer of powder. Satellite particles (small particles attached to the surface of larger particles) reduce powder flowability and should be controlled to a minimum. Powder surface roughness also affects fluidity, and the powder surface prepared by the inductively coupled plasma (IGA) atomization method is smoother. Powder flowability test includes Hall flow rate test and angle of repose test. The flow rate value should be less than 25s/50g.
The influence of particle size distribution on melting behavior
There are differences in the absorbance and melting speed of powder particles with different particle sizes under laser irradiation. Fine particles have a large specific surface area, high light absorption efficiency, and fast melting speed, but they are prone to overheating and ablation. The melting of coarse particles requires higher energy input and the melting depth is larger. Uneven particle size distribution will lead to unstable melt channels and affect the density and surface quality of parts. Laser parameters need to be optimized based on powder characteristics. Too high an energy density will cause a keyhole effect, and too low an energy density will result in lack of fusion. The scanning strategy also affects the melting effect, and the reasonable scanning spacing needs to match the powder particle size.
The relationship between surface quality and dimensional accuracy
Powder particle size directly affects the surface roughness of printed parts. Fine powder can obtain a more delicate surface, and the Ra value can be controlled in the range of 5-10μm. The surface printed by coarse powder is rougher, and the Ra value is usually 15-25μm. For parts with high surface quality requirements, finer powders need to be used, or machined and polished after printing. Powder characteristics will also affect the dimensional accuracy of parts. Powder with good fluidity can ensure consistent powder coating thickness and improve Z-direction accuracy. The bulk density of the powder affects the densification shrinkage after melting, which in turn affects the part size.
Powder quality control and recycling management
Quality control of titanium alloy powder needs to run through the entire process of procurement, use and recycling. When purchasing new powder, you need to obtain a material certificate and a particle size analysis report to confirm that it meets the technical specifications. Screening is required before use to remove agglomerates and large impurities. During the printing process, it is necessary to monitor the powder status, replenish new powder regularly, and keep the powder particle size in the powder pool stable. When recycling powder, it is necessary to regularly detect changes in particle size distribution and screen out fine powder and impurities. Powder must be stored in a dry, inert atmosphere to avoid moisture absorption and oxidation. It is recommended that the number of times the powder is used should be controlled within 5-8 times. The performance of the powder will be significantly reduced after multiple cycles.
Submit a model, drawing, image or written notes. Engineers will review material, process, finishing and delivery based on actual use.