Metal additive manufacturing (AM) by Laser-Directed Energy Deposition (L-DED) usually results in the formation of textured columnar grains along the build direction, leading to anisotropic mechanical properties. This can negatively affect the intended application of the product. Anisotropy can be eliminated by modifying the material through an additional exposure to ultrasound (US-assisted) during the L-DED process. In this paper, a multi-track sample was manufactured from AISI H13 (TLS Technik, Bitterfeld-Wolfen, Germany) tool steel by a US-assisted (28 kHz) L-DED process using a specially designed cooling system. The study also included post-process annealing and quenching with the tempering heat treatment of the modified steel, resulting in the retention of the properties, as confirmed by hardness measurements. XRD analysis was used to measure the structural parameters of the unit cell, and the hardness properties were measured in two directions: longitudinally and parallel to the deposition direction. It was found that US-assisted L-DED allows us to obtain a more isotropic structure with an equal size of the coherent scattering region in two printing directions, and to reduce the residual stresses in the material. The anisotropy of the hardness was significantly reduced, with 636 and 640 HV found between the XY and XZ planes. Based on the obtained hardness data, it should be noted that some of the heat treatments studied herein can also result in a decrease in the anisotropy of the properties, similarly to the US-assisted effect.@en

Direct laser deposition (DLD), implemented on the basis of a 5-axis robot manipulator, is a very flexible technique with many adjustable process parameters affecting the quality of the final product. Objects manufactured by the DLD method may contain defects significantly reducing mechanical and functional properties. This article provides an overview of possible DLD process-induced defects that were identified by increasing the density of the produced material. The following defects were identified and discussed in the current work: Lack of fusion, porosity, cracking, oxide inclusions, and metal influx. It is shown that by changing such process parameters as laser power, powder feed rate, head lift and hatch distance, it is possible to improve the quality of the cladding and substantially reduce the process-induced defects.

@en