Why selective laser melting is better then a plasma coating for functionally graded materials
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Abstract:
Selective Laser Melting (SLM) is an additive manufacturing process whereby a three-
dimensional part with almost full density and good mechanical properties is built in a layer-
wise manner. During the process, a laser source selectively scans a powder bed according
to the CAD data of the part to be produced and the powder metal particles are completely
melted. In this way, SLM is capable of producing functional metallic parts with a high
geometrical freedom. However, there are some limitations to the process including
insufficient surface quality, remnant porosity (~1-2%) and stair effect which is inherent to all
layer manufacturing processes. In this study, laser re-melting is applied using a continuous
wave Nd:YAG laser during SLM of AISI 316L stainless steel parts to overcome or to weaken
these limitations. After each layer is fully molten, the same slice data is used to re-expose the
layer for laser re-melting. In this manner, laser re-melting does not only improve the surface
quality but also has the potential to improve density. The influence of laser re-melting on
density enhancement, surface quality and stair-effect is studied varying the operating
parameters such as scan speed, laser power and scan spacing. The laser re-melting method
with optimized parameter settings greatly densifies the SLM part and improves the surface
quality significantly at a cost of longer production times. The stair-effect is also greatly
eliminated when laser re-melting is applied on the inclined surfaces after the process is
completed and the surrounding powder particles are blown away.
Key Words: Selective Laser Melting, Laser Re-melting
1. INTRODUCTION
Selective Laser Melting (SLM) is an additive manufacturing technology able to fabricate 3D
physical models, parts and tools without almost any geometrical restrictions by stacking and
bonding 2D layers in a specified building direction. The process is able to produce almost
100% dense parts directly from design data using customary metal powders. The main
advantage of SLM is the ability to produce very complex parts which are almost impossible to
be made with conventional production techniques. Bone scaffolds and molds with conformal
cooling channels are good examples to explore the unlimited geometrical freedom in this
process (Figure 1). Compared to other layer manufacturing technologies, SLM has the
advantage to produce parts that have mechanical properties comparable to those of bulk
materials [1].
Figure 1: Sample parts produced by SLM.
Selective Laser Melting (SLM) is an additive manufacturing process whereby a three-
dimensional part with almost full density and good mechanical properties is built in a layer-
wise manner. During the process, a laser source selectively scans a powder bed according
to the CAD data of the part to be produced and the powder metal particles are completely
melted. In this way, SLM is capable of producing functional metallic parts with a high
geometrical freedom. However, there are some limitations to the process including
insufficient surface quality, remnant porosity (~1-2%) and stair effect which is inherent to all
layer manufacturing processes. In this study, laser re-melting is applied using a continuous
wave Nd:YAG laser during SLM of AISI 316L stainless steel parts to overcome or to weaken
these limitations. After each layer is fully molten, the same slice data is used to re-expose the
layer for laser re-melting. In this manner, laser re-melting does not only improve the surface
quality but also has the potential to improve density. The influence of laser re-melting on
density enhancement, surface quality and stair-effect is studied varying the operating
parameters such as scan speed, laser power and scan spacing. The laser re-melting method
with optimized parameter settings greatly densifies the SLM part and improves the surface
quality significantly at a cost of longer production times. The stair-effect is also greatly
eliminated when laser re-melting is applied on the inclined surfaces after the process is
completed and the surrounding powder particles are blown away.
Key Words: Selective Laser Melting, Laser Re-melting
1. INTRODUCTION
Selective Laser Melting (SLM) is an additive manufacturing technology able to fabricate 3D
physical models, parts and tools without almost any geometrical restrictions by stacking and
bonding 2D layers in a specified building direction. The process is able to produce almost
100% dense parts directly from design data using customary metal powders. The main
advantage of SLM is the ability to produce very complex parts which are almost impossible to
be made with conventional production techniques. Bone scaffolds and molds with conformal
cooling channels are good examples to explore the unlimited geometrical freedom in this
process (Figure 1). Compared to other layer manufacturing technologies, SLM has the
advantage to produce parts that have mechanical properties comparable to those of bulk
materials [1].
Figure 1: Sample parts produced by SLM.
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