SUNConferences, RAPDASA 2014

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STRATEGY TOWARD THE MANUFACTURING OF FULLY DENSE PARTS FROM AISI 420 STAINLESS STEEL BY SELECTIVE LASER MELTING
Igor Yadroitsev, S. Marques, A. Domachenkov, I. Yadroitsava, A.F. de Souza

Last modified: 2014-10-24

Abstract


Selective laser melting (SLM) is an additive manufacturing technique that produces functional parts from metal powders. SLM is a powerful technology for automotive, medical, chemical, aerospace and other hi-tech industries. SLM is a well-suited technology for the mould industry: it can considerably reduce the time for engineering and fabrication of moulds. SLM provides extraordinary freedom to validate design of moulds and to develop new materials. The extension of applications requires different materials with specific properties. To show the potential and features of SLM for mould manufacturing applications, fully-dense samples from AISI 420 stainless steel powder were fabricated. AISI 420 stainless steel is a material widely used in the plastics-moulding industry where high hardness and wear resistance is required. The study discusses the influence of laser power, scanning speed, layer thickness and hatch distance on the formation of single tracks and layers. Algorithm for finding optimal process parameters is indicated with respect to features of single tracks, layers and 3D objects. Width of the single track determines the hatch-distance to form a single layer. Height of the tracks and scanning strategy define the morphology of the synthesized layer. Morphology of the layer has a significant impact on the variation of the thickness of the next delivered powder layer. This should be considered when choosing the optimal process parameters. An energy input should be adequate to melt powder layer and to achieve remelted depth providing good cohesion between the layers. The pore analysis (shapes and sizes) can also contribute to the identification of optimal process parameters. To produce non-porous objects from AISI 420 (–32 µm) stainless steel powder, 60 W laser power, 70 µm spot diameter, 0.12 m/s scanning speed, 120 µm hatch-distance and 40 µm thickness of powder layer and two-zone scanning strategy with following 90 turning for each next layer were applied. Microhardness of the SLM samples was 513±19.5 HV0.3 for inner regions; upper layers had 700-750 HV0.3.




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