For certain additive manufacturing technologies the choice of available materials is currently limited. The development of process parameters is especially elaborate for powder bed technologies. Currently, there is no common approach concerning the procedure and documentation. This work proposes a methodology for the initial development of process parameters for new L-PBF (laser powder bed fusion) alloys. Key elements are the examination of the laser–powder-bed interaction by single laser track experiments and an iterative design of experiment (DoE) approach for the development of volumetric parameters. Two types of single laser track experiments are presented and provide information regarding the laser track width and depth as well as the resulting surface roughness and melt pool classification. Based on the information gained, suitable process windows for a DoE study can be defined by avoiding parameter settings unsuitable for production or measurement. Gradually, input variables are identified and iterative steps reduce the process window in order to optimize the desired target values. Near-surface exposure parameters are developed by a one-dimensional parameter variation and metallographic investigations. The approach is primarily designed for the initial development of process parameters for new L-PBF alloys. However, the information gained can also be used to optimize established parameter sets regarding new target values (productivity, mechanical properties), optimize process parameters for specific components or for a microstructural design.

The Laser Beam Melting (LBM) Additive Manufacturing technology for metal processing is based on the local application of an intense laser beam, causing a characteristic microstructure, which can achieve higher mechanical properties than conventionally manufactured equivalents. The material is created incrementally in sections that are processed with different manufacturing parameters. This paper proposes the creation of Designed Materials by varying the manufacturing parameters and exposure strategy in order to induce a gradient or a local change of properties by designing the microstructure. Such materials could also be created by changing the material topology on a micro-, meso-, or macro-scale, or on multiple scales at once. This enables systematic creation of material types like Functionally Graded Materials (FGMs), Metamaterials, or other Designed Materials, in which characteristics can be varied locally in order to create a customized material. To produce such materials by LBM, it is necessary to gain a detailed understanding about the influence of the manufacturing parameters. Experimental studies have been carried out to investigate the melt pool geometry and microstructure resulting from the exposure parameters. Based on the results, parameter sheets have been derived, which support the process of finding optimized parameter sets for a specific purpose. General methods and their ability to influence the material structure and properties were tested and evaluated. Furthermore, the resulting change of the microstructure was analyzed and a first Graded Material was generated and analyzed to show the potential and possibilities for Designed Materials on multiple scales by Laser Beam Melting.

This study aims to measure the cooling rates or, more precisely, the cooling durations of single laser tracks by pyrometry within the laser powder bed fusion (L-PBF) process. Two-color, as well as one-color pyrometers are tested within this work. Regarding the second, the emissivity of the investigated 30CrMoNb5-2 alloy is determined in-situ within the L-PBF system in order to measure temperature instead of arbitrary units. This is done by heating up printed samples and verifying the measured pyrometer signal by comparing it to values obtained by thermocouples attached to the samples. In addition, the precision of two-color pyrometry is verified for the given setup. Following the verification experiments, single laser track experiments are conducted. The obtained signals prove to be partially distorted mainly due to by-products such as smoke and weld beads arising from the melt pool. To encounter this problem, a new fitting method is presented and experimentally validated. Melt pools resulting from different cooling durations are analyzed by EBSD. These measurements show areas of extreme deformation or potential amorphization correlating with the cooling durations. The obtained cooling duration can be used for the validation of simulations as well as for the correlation of corresponding microstructure and process parameters.

The additive manufacturing technique laser powder bed fusion (L-PBF) opens up potential to process metal matrix composites (MMCs) with new material pairings free from limitations of conventional production techniques. In this work, we present a study on MMC material development using L-PBF. The generated composite material is composed of an X3NiCoMoTi 18-9-5 steel as matrix and spherical tungsten particles as filler material. A Design of Experiment (DoE)-based process parameter adaption leads to an Archimedean density close to the theoretical density in the case of 60 vol% tungsten content. A maximum ultimate tensile strength of 836 MPa is obtained. A failure analysis reveals a stable bonding of the tungsten particles to the steel matrix. This encourages the investigation of further material combinations. An additional heat treatment of the MMC indicates the potential to design specific material properties; it also highlights the complexity of such treatments.