Research on improving the spreadability of viscous powder in additive manufacturing

The cohesive effect between particles is crucial in influencing the quality of the powder layer in additive manufacturing (AM), which will induce low reproducibility of the subsequent particle fusion process and degrade the performance of final products. In this work, the phenomenon and mechanism of interparticle cohesive effect were investigated through numerical simulations, based on which the methods that may reduce the negative effects of high cohesive interactions were proposed, assessed, and optimized. Results indicated that increasing the particle size could weaken the cohesion and effectively improve the packing fraction of the powder layer, but the surface roughness becomes worse due to the serious boundary effect of large particles under the blade. Besides, the spreading of viscous powders at low velocity and high deposition height could facilitate dense powder layers to some extent, while it contradicts the rapid fabrication and thin layer thickness required by AM. In contrast, the methods of increasing the friction resistance of substrate and optimizing the blade geometry could recover the powder layer quality under multiple indicators through limiting the scattered motion of particles and facilitating powder downward deposition, respectively. Consequently, the optimal approach was preferentially proposed to reduce the cohesive effect during spreading and obtain the powder layer with optimum packing fraction, uniformity, and surface roughness. On this basis, the operation window was further extended to high velocity and low deposition height, which can provide effective references for the practical AM process.