Powder-based laser metal deposition of VDM Alloy 780: strategy development for efficient buildup of thin-walled components

Abstract

Powder-based laser metal deposition (LMD) represents a future-oriented additive manufacturing process given the large number of available materials as well as the high degree of geometric freedom. These potentials are further enhanced by high build rates and a better material utilization compared to turning or milling. However, the LMD process is very complex as a result of the large number of machine and process parameters. Different thermal conditions occur during layer-by-layer buildup. Newly supplied energy due to the laser-material interaction with the newest layer is supplemented by the heat energy still stored in the solidified component, which is distributed inhomogeneously depending on material and part geometry. In order to avoid dimensional deviations and microstructural defects, the machining parameters have to be adjusted during the LMD process. The following paper presents a strategy for the efficient and process-safe buildup of thin-walled VDM Alloy 780 geometries on 316L substrates using powder-based LMD. Adaptive adjustment of parameters and monitoring of cooling times improve the dimensional accuracy of the geometry while avoiding defects. The fabricated specimens are then analyzed using optical microscopy, SEM and EDX. Porosity analysis is performed by various methods. In addition, mechanical properties are determined by tensile tests in perpendicular and parallel directions as well as by macrohardness tests.