CC BY
8LM-I-17
LASER-MATTER INTERACTION
Porosity reduction and structural features of 316L stainless steel fabricated using combined laser metal deposition with laser remelting
A. V. Dubrov, Y. N. Zavalov, P. S. Rodin, E. S. Makarova and V. D. Dubrov
ILIT RAS - Branch of the FSRC «Crystallography and Photonics» RAS, Svyatoozerskaya 1, 140700, Shatura, Moscow Region, Russia dubrov. av@mail.ru
Laser metal deposition (LMD) is one of the additive manufacturing technologies. In order to achieve the required quality and defect-free LMD part, it is necessary to ensure the maintenance of optimal solidification conditions of the material at each point of the build trajectory. However, when creating objects of complex geometries, for example, including full-bodied, thin-walled and overhanging elements, thermodynamic conditions along the construction path can vary greatly, which becomes a significant challenge in terms of determining optimal technological parameters and/or their dynamic adjustment. If the thermodynamic regime does not correspond to the target one, defects are likely to form in the material, for example, areas of incomplete fusion, cracks, etc. [1]. A possible way to solve this problem is to modify the original LMD technology by adding an auxiliary laser remelting (LR) stage after depositing each LMD layer [2].
In this paper, a parametric experimental study of the combined LMD+LR technology was carried out using 316L stainless steel powder. The possibility of correcting defects that occur at the LMD stage when the thermodynamic regime deviates from the optimal one by adding the LR stage was considered. Attention was paid to the evolution of various types of defects in the material, the influence of the LR process on the properties of the material, as well as processes occurring at the micro-level. The mechanisms that play a role in reducing the defect of the material were analyzed. The influence of LR on the microhardness and structural features of the material was considered. It was found that the use of the LR stage leads to a marked decrease in the interlayer porosity. In this case, there may be a slight increase in the intralayer porosity. It is also demonstrated that the structure of the material of samples obtained by the LMD+LR technology, under certain technological parameters, is layered, in which layers with different properties formed at the LMD and LR stages alternate.
The work was supported by the Russian Foundation for Basic Research (grant No 20-21-00158).
[1] Sun, Guifang, Rui Zhou, Jinzhong Lu, and Jyotirmoy Mazumder. "Evaluation of defect density, microstructure, residual stress, elastic modulus, hardness and strength of laser-deposited AISI 4340 steel." Acta Materialia, 84, pp. 172-189, (2015).
[2] dos Santos Paes, Luiz Eduardo, et al. "Understanding the behavior of laser surface remelting after directed energy deposition additive manufacturing through comparing the use of iron and Inconel powders." Journal of Manufacturing Processes, 70, pp. 494507, (2021).
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