Characterization of nanoparticle mixed 316 L powder for additive manufacturing

Nanoparticles reinforced steels have many advantaged mechanical properties. Additive manufacturing offers a new method for fabricating nanoparticles reinforced high performance metal components. In this work, we report the application of low energy ball milling in mixing nanoparticles and micron 316 L powder. With this method, 0.3 and 1.0 wt% Y₂O₃ nanoparticles can be uniformly distributed on the surface of 316 L powder with the parameters of ball-to-powder ratio at 1:1, speed at 90 rpm and 7 h of mixing. The matrix 316 L powders remain spherical in shape after the mixing process. In the meantime, the effect of low energy ball milling and the addition of Y₂O₃ nanoparticles on the powder characteristics (flowability, apparent density and tap density) are also studied. Results show that the process of low energy ball milling itself can slightly decrease the flowability and apparent density of the 316 L powder. The addition of 0.3 and 1.0 wt% Y₂O₃ nanoparticles can also decrease the flowability, the tap density and the apparent density compared with the original 316 L powder. All of these changes result from the rough surface of the mixed powder produced by ball milling and the addition of Y₂O₃ nanoparticles. The powder's rough surface can increase the coefficient of friction of powders. The mixture of 316 L powder and Y₂O₃ nanoparticles can be successfully used for selective laser melting (SLM). The relative density of SLM 316 L-Y₂O₃ is measured at 99.5 %. However, Y₂O₃ agglomerations were observed which is due to the poor wettability between 316 L and Y₂O₃.