RESEARCH PAPER 3D laser metal deposition: process steps for additive manufacturing B. Graf 1 & A. Marko 1 & T. Petrat 1 & A. Gumenyuk 1,2 & M. Rethmeier 1,2,3 Received: 21 July 2017 /Accepted: 26 March 2018 # International Institute of Welding 2018 Abstract Laser metal deposition (LMD) is an established technology for two-dimensional surface coatings. It offers high deposition rates, high material flexibility, and the possibility to deposit material on existing components. Due to these features, LMD has been increasingly applied for additive manufacturing of 3D structures in recent years. Compared to previous coating applications, additive manufacturing of 3D structures leads to new challenges regarding LMD process knowledge. In this paper, the process steps for LMD as additive manufacturing technology are described. The experiments are conducted using titanium alloy Ti-6Al-4V and Inconel 718. Only the LMD nozzle is used to create a shielding gas atmosphere. This ensures the high geometric flexibility needed for additive manufacturing, although issues with the restricted size and quality of the shielding gas atmosphere arise. In the first step, the influence of process parameters on the geometric dimensions of single weld beads is analyzed based on design of experiments. In the second step, a 3D build-up strategy for cylindrical specimen with high dimensional accuracy is described. Process parameters, travel paths, and cooling periods between layers are adjusted. Tensile tests show that mechanical properties in the as-deposited condition are close to wrought material. As practical example, the fir-tree root profile of a turbine blade is manufactured. The feasibility of LMD as additive technology is evaluated based on this component. Keywords Laser metal deposition . Build-up strategy . Deposition rate . Additive manufacturing 1 Introduction Today, the trend to individualized products and decreasing time to market leads to an industrial demand for flexible manufacturing technologies [1]. These technologies must al- low the resource-efficient production of long-life capital goods. Additive manufacturing technologies offer high flexi- bility regarding complex design features and allow direct manufacturing from CAD data without tooling, therefore sav- ing time and costs [2]. Additive processes gain an importance especially in the aviation industry, where components with high Bbuy-to-fly^ ratio are common. For example, the machin- ing of a blade integrated disk from forgings leads to a material loss of around 80–90%. In these cases, additive technologies have a high potential for material savings. A prominent laser- based method is laser metal deposition (LMD), which has been applied as coating technology for over 20 years. Additive manufacturing of 3D parts with LMD emerged as a new field of application. In order to apply LMD as additive technology, new process knowledge is necessary to adjust the weld bead size, to create a build-up strategy for high net shape, and to understand the achievable mechanical properties. 2 State of the art LMD is shown in Fig. 1. The process utilizes a powder nozzle for material delivery. Powder particles are transported with a carrier gas, while the laser beam creates a molten pool on the substrate. After solidification, single weld beads are formed. In additive manufacturing, these weld beads are placed next to each other to form layers, and multiple layers on top of each other form volumes. This article is part of the collection Welding, Additive Manufacturing and Associated NDT * B. Graf benjamin.graf@ipk.fraunhofer.de 1 Fraunhofer IPK, Pascalstraße 8-9, 10587 Berlin, Germany 2 Bundesanstalt für Materialforschung und –prüfung BAM, Unter den Eichen 87, 12205 Berlin, Germany 3 Technische Universität Berlin, Straße des 17. Juni, 10623 Berlin, Germany Welding in the World https://doi.org/10.1007/s40194-018-0590-x