Combined effect of particle size and surface cohesiveness on powder spreadability for additive manufacturing

The dependence of powder flowability on particle cohesion can often be captured by a dimensionless Bond number, however, whether the same is true for powder spreadability remains unclear. This paper thus presents a particle-scale study on the spreading of cohesive fine powders for additive manufacturing, focusing on the combined effect of particle size and surface cohesiveness. With an experimental validated model, detailed analysis revealed two competing mechanisms due to geometrical constraint and interparticle cohesion. For small particles that allows multiple particles across blade clearance, layer homogeneity is largely maintained before deteriorating sharply, while for large particles that forming a mono-layered packing structure, an optimum homogeneity can be obtained at a moderate level of particle cohesion. The efficacy of increasing blade clearance to improve layer quality was also evaluated. This study can help to identify a critical set of powder descriptors that defines spreading performance.