Metallurgical Defects and Roughness Investigation in the Laser Powder Bed Fusion Multi-Scanning Strategy of AlSi10Mg Parts

Abstract

Laser Powder Bed Fusion is the most attractive additive manufacturing technology for its capability to produce metal components with complex geometry. One of the main drawbacks is the poor surface roughness. In this work, different scan strategies and process parameters were studied and their effect on surface roughness, alloy microstructure, and metallurgical defects were discussed. The results highlighted that only tailored process conditions could combine acceptable roughness and absence of metallurgical defects. For the upskin, it has been seen that, although by increasing the Volumetric Energy Density value the Ra decreases, Volumetric Energy Density values higher than 69 J/mm3 determine meltpool instability with consequent formation of gas defects in the subsurface area. Similarly, by increasing the Linear Energy Density value, the Ra of the lateral surfaces decreases, but above 0.37 J/mm, metallurgical defects form in the subsurface area. This study also highlighted that the proposed process involves only a contained increase of the production times. In fact, the evaluation of the increased production times, related to the adoption of this multi-scanning strategy, is of fundamental importance to consider if the proposed process can be advantageously applied on an industrial scale.