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With a view to illustrating that more complex shape geometries could be built, to take advantage of the freeform technology, some prototypes were prepared as shown in Fig. 13. In this study, the composition with a 6% addition of carbides was selected. On the right of the figure, a gear is presented as an example of a component subjected to stresses and wear, which could be typically found, for example, in the automotive industry. In this sector, a good strength and wear resistance response combined with the lighter structures obtained by this processing technology should be of interest. Additionally, honeycomb structures (left in Fig. 13) for possible application as catalysts, have also been processed. Being tailor-made, three-dimensional structures of high added value, SLM technology looks to be of great potential value, because of the ability to reduce material wastage significantly. In the SEM images in Fig. 14, the differences in cell size can be appreciated for two of the structures designed. Major concerns in SLM parts are generally residual stresses and distortion. Due to localised heating, complex thermal and phase transformation stresses are generated during the process. In addition, frequent thermal expansion and contraction of the previously solidified layers during fabrication generates considerable thermal stresses and stress gradients that can lead to part distortion or fracture initiation. The cell sizes are reported in Fig. 14 and no significant distinction between the interior and surface locations was found, indicating low levels of distortion. Metallographic examination of the processed honeycombs revealed a fine cellular-dendritic microstructure and epitaxial growth determined by the heat flow. Based on the built component demonstrators, it was concluded that SLM was a viable route for the manufacture of complex-shaped parts from these stainless steel matrix composites.
Vol. 3 No. 1 © 2017 Inovar Communications Ltd
World PM2016: New materials
Fig. 12 Wear rates and friction coefficients for the SLM-processed materials [2]
Fig. 13 Prototypes of 316L-6%Cr3C2 processed by SLM [2]
Interior: 974 ±38 μm | Surface: 974 ±51 μm
Interior: 1536 ±78 μm | Surface: 1531 ±107 μm
Fig. 14 Details of the cell sizes of two different honeycombs [2]
Metal Additive Manufacturing | Spring 2017
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