Abstract
In Selective Laser Melting, the initial units produced are single tracks that overlap to create a single layer; from the sequence of layers, a 3D object is manufactured. The properties of the parts produced by SLM depend heavily on the properties of each single track and each layer formed by these tracks. This study evaluates the effect of processing parameters on the geometrical characteristics of single tracks manufactured from 17-4PH stainless steel powder. A single-mode continuous-wave ytterbium fibre laser was used to manufacture single tracks at laser powers in the range of 100-300 W with a constant spot size of ∼ 80μm. The single tracks produced were subjected to standard metallographic preparation techniques for further analysis with an optical microscope. Deep molten pool shapes were observed at low scan speeds, while shallow molten pool shapes were observed at high scan speeds. At higher laser power densities, under-cutting and humping effects were also observed. The dimensions of single tracks processed without powder generally decrease with increasing scan speed at constant laser power. However, the geometrical features of the single tracks processed with powder revealed pronounced irregularities believed to be caused by non-homogeneity in the deposited powder layer.
Highlights
Selective laser melting (SLM), known as powder bed fusion (PBF) or direct metal laser sintering (DMLS), is an additive manufacturing process that uses a laser beam to melt powder particles in order to produce 3D structures layer-by-layer directly from a 3D CAD model
A computer-controlled laser beam selectively scans the powder bed according to a 2D cross-section of each layer in order to fuse the powder particles
Part designs are optimised for low weight and high strength; SLM provides the design freedom that is missing from traditional manufacturing methods
Summary
Selective laser melting (SLM), known as powder bed fusion (PBF) or direct metal laser sintering (DMLS), is an additive manufacturing process that uses a laser beam to melt powder particles in order to produce 3D structures layer-by-layer directly from a 3D CAD model. The CAD model is generated with computer software and sliced into a finite number of layers Based on this information, a computer-controlled laser beam selectively scans the powder bed according to a 2D cross-section of each layer in order to fuse the powder particles. The initial units produced are single tracks that create a single layer; from the sequence of layers a 3D object is manufactured [1]. Forms can be created that would be impractical or unachievable in other processes This technology is optimised for low-volume, highvalue production, ensuring that the process is highly attractive for the aerospace and medical industries, among others. Part designs are optimised for low weight and high strength; SLM provides the design freedom that is missing from traditional manufacturing methods
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