Nanoparticle additivation of powders for laser additive manufacturing of oxide-dispersion strengthened steels: a joint experimental and numerical study

点击翻译按钮获取中文摘要

Powder-based laser additive manufacturing (LAM) is a potential breakthrough technology for the production of 3D parts made of oxide dispersion-strengthened (ODS) steel. However, the ODS powders currently used as feedstock for the LAM methods of laser powder bed fusion (LPBF) and directed energy deposition (DED) are unsuitable for laser processing and prevent these technologies from further development. Therefore, the proposed joint project aims at developing a new iron-chromium-based powder for LAM by introducing a novel and versatile method of dispersing nanoparticles on metal powders. Colloidal oxide nanoparticles are produced by pulsed laser fragmentation in liquids and are adsorbed on steel powder supports via pH-controlled electrostatic interaction. After LAM processing these powders, the formed nanoinclusions should strengthen the printed material through the Orowan mechanism. However, the size and distribution of these nanoinclusions depend strongly on the melt pool physics and the nanoparticle kinematics in the melt pool and are thus sensitive to the processing method (LPBF or DED) and process parameters. For understanding and controlling the nanoparticle dispersion during LAM, non-isothermal phase-field melt pool simulations combined with a novel nanoparticle kinematic model will be developed to investigate the spatio-temporal distribution of nanoparticles and their influence on coupled physics, such as mass/heat transfer, melt pool dynamics, and resolidification. The finite element implementation of the coupled models allows numerical simulations of the melting-resolidification kinetics and microstructure on spatially and temporally resolved melt pool scales. In-depth material analytics on the nano, micro, and macro-scale will also be employed on the chain of materials synthesis and its change before and after LAM, respectively, to correlate material design with both its processability and the resulting part properties of the alloy. The simulated and characterized microstructural information, such as the distance and the size of the nanoinclusions and particularly their dependency on the powder composites and the process type and parameter, will be further used to estimate and optimize the mechanical properties of the printed materials. Due to the fundamental materials science nature of our approach, the potential impact of our project is not limited to ODS steels. It will also contribute to a mechanistic understanding of how to achieve powders that lead to material strengthening by highly dispersed nanoinclusions within a LAM-built part.