The Effect of Powder Flowability in the Selective Laser Sintering Process

Abstract

The flowability of powder material has a significant effect on powder paving quality during selective laser sintering (SLS) and the mechanical properties of the sintered components. The flowability depends on several factors, such as particle size distribution, particle shape, and environmental temperature, etc. In general, the virgin powder possesses good flowability. The used powder which remained in forming cave after sintering cannot be reused for next SLS processing alone. In order to make full use of powder materials, and meet the mechanical properties requirements of the sintered component, it is very important to understand the flowability of the used powder. To produce a component with uniform density and small porosity, the reasonable mass ratio between virgin powder and the used powder (R_v-u) is required. The index of HR, and angle of repose were applied to character the flowability of powders in the study. The particle size distribution and particle shape of both virgin powder and used powder, and their impact on flowability were measured. The discrete element models of virgin powder and used powder were developed and the paving process was simulated. The surface roughness and mechanical properties of sintering components with different R_v-u were investigated. The surface roughness of component sintered by used powder is the worst. There exist less distinctions of the modular of elasticity and the tensile strengths among the three kinds of R_v-u. The numerical results show that the apparent density and density uniformity of the powder bed has little difference by changing the R_v-u, while the results were confirmed by experiments.