Effect of particles size distribution and packing density on the formation of balling defects during SLM of In718
Balling is a defect that can occur when the molten pool created during selective laser melting (SLM=L-PBF) becomes discontinuous and breaks into separated islands. In this post, we report and discuss how the powder particle arrangement impact the bead geometry and formation of balling defects during SLM.
Powder production routes, actual AM process and recycling methods all influence particles characteristics. In powder bed fusion, these properties affect the homogeneity and density of the powder layers spread across the build platform and, in turn, the process repeatability and the parts quality. Quantifying a combination of factors defining a ‘good’, process-able powder is still required for AM. Yet little has been studied to link traditional powder measurements to its flowability and to its AM process-specific spreading abilities. In this post, let’s discuss suitable parameters and values to qualify flowability of metal powders for selective laser melting (SLM).
Obtaining high density components is a trade-off between build rate and powder irradiation time (ie scanning speed). Achieving high density is usually the 1st step in parameters development for SLM and EBM. But do we have to assume (close to) 100% density to obtain satisfactory mechanical properties? This blog post addresses the impact of defects obtained in SLM on mechanical properties of Ti64.
Aluminium alloys are notoriously difficult materials to cast or weld. Their naturally high reactivity with the environment favours oxidation and moisture pick up that promotes pores formation during solidification. Among other mechanisms, gas porosity need to be addressed. In casting, this can be done by adjusting the cooling rate . In welding, it can be done by scanning the surface . This post addresses a few ways to decrease hydrogen porosity formed during Selective Laser Melting.
SLM technology can produce AlSi10Mg components nearing 100% density . Their mechanical properties are comparable and even better than that of parts produced by casting  due to their SLM-specific fine microstructure . Here we review the physical mechanisms involved in formation of hydrogen pores during SLM.
Where the coarse acidular silicon acts as crack initiation sites in conventional cast alloys, refined eutectic microstructure of Al–Si alloys machined by SLM tends to dramatically improve their mechanical properties - specifically strength and ductility . Here we report the latest findings on AlSi12 where SLM combined with solution heat treatment generates 25% tensile ductility. 
Aeromat 15, the conference dealing with materials and processing methods focused on aerospace applications, was held last week in Long Beach, California. As additive manufacturing technologies mature, numerous presenters discussed aspects such as materials properties of SLMed components, successful industrial applications by world-leading institutes such as TWI, MCAM or remaining challenges being addressed.