Integrative Production Technology for High-Wage Countries: Individualized Production: Selective Laser Melting

 

Selective Laser Melting (SLM) is a metal additive manufacturing (metal AM) technique, commonly referred to as a three-dimensional (3D) printing method. In contrast to conventional production, metal AM is capable of manufacturing complex metallic structures directly from 3D data based on computer-aided design (CAD) models. Parts are build in a 2D layer-wise fashion by repetitively melting a material feedstock (powder) by use of a laser as the energy source. The project is part of the Cluster of Excellence "Integrative Production Technology for High-Wage Countries". In the Cluster of Excellence (CoE) the SLM process, originally used for rapid prototyping, is supposed to be developed to an industrial manufacturing process for the production of individual parts and small series. Within the CoE, the Steel Institute (IEHK) is working in close cooperation with the Fraunhofer Institute for Laser Technology ILT on the production of near-net-shape parts with higher functionality: for example density reduced lattice structures, which are additively manufactured by SLM.

To make optimal use of the full potential of metal AM, we investigate both metallurgical and technological aspects that influence the microstructure evolution during AM as well as during post-processing. The synergy between optimized chemical composition, processing parameters, and geometry allows us to tailor the properties of the final additively manufactured parts. In order to understand the influence of the particular AM process used, initial powder, process parameters, etcetera on the microstructure evolution, we use state of the art techniques for material characterization at various length scales (Fig. 1).

  Microstructural analysis of SLM-produced parts of X30Mn22 at various length scales by LOM, SEM, EDS and APT. IEHK Figure 1: Microstructural analysis of SLM-produced parts of X30Mn22 at various length scales by LOM, SEM, EDS and APT.
 
 

The microstructure of additively manufactured parts differs strongly from conventionally produced ones. Directionally solidified grains, pronounced textures, homogeneous elemental distribution, high residual stresses, etc. are usually inherent to AM materials. These characteristics can be used to tailor the mechanical properties of these materials (Fig.2).

  (A) Substrate plate with tensile specimens after the SLM-process; (B) Engineering stress-strain curves of SLM-produced tensile specimens, which are produced under 0°, 45°, and 90° angle between scan direction and tensile axis in comparison with conventio IEHK (A) Substrate plate with tensile specimens after the SLM-process; (B) Engineering stress-strain curves of SLM-produced tensile specimens, which are produced under 0°, 45°, and 90° angle between scan direction and tensile axis in comparison with conventio