Abstract
Niobium is an important material for high temperature applications, in space, in superconductors or in chemical process constructions. Laser-based powder bed fusion of niobium (PBF-LB/M/Nb) offers new opportunities in design, though it is still an expensive technique. The build-up rate is an important factor for economical manufacturing using PBF-LB/M/Nb. It is largely influenced by variation of process parameters, affecting the heat flow during the manufacturing process. In this work, an empirical model for PBF-LB/M/Nb is developed. Based on this model, manufacturing parameter sets using different volume build-up rates are predicted and confirmed. They enable the manufacture of parts with homogeneous and crack-free microstructure with more than 99.9% relative density. Tensile and hardness tests of specimens, which were manufactured using different parameter sets, are performed to determine the effects of the build-up rate—and thus the heat flow during manufacturing—on different mechanical properties. The ultimate tensile strength and yield strength of as-manufactured specimens reach values up to 525 MPa and 324 MPa, respectively, while the elongation at break ranges between approximately 8 and 16%. The Vickers hardness of all specimens was in the range of 149 ± 8 HV0.1. In addition, the microstructure of the manufactured samples is investigated by means of light as well as scanning electron microscopy.
Highlights
Niobium belongs to the group of refractory metals, which are characterized by a high resistance to electrochemical corrosion, high temperature strength and good electrical and heat conducting properties [1]
The relative densities of all 72 (2 × 36) specimens of the central composite design were used for the mathematical approximation to determine the relative density as a function of the laser power, scanning speed and hatch spacing
The present study describes an approach for the development of process parameter combinations for the additive manufacturing of spherical niobium powders by means of PBF-LB/M
Summary
Niobium belongs to the group of refractory metals, which are characterized by a high resistance to electrochemical corrosion, high temperature strength and good electrical and heat conducting properties [1]. The major consumer of niobium is the steel industry, where it is used as an alloying element to improve the welding behaviour, the heat resistance and the yield and tensile strength [2]. Applications for pure niobium are in the electronic industry, i.e. capacitors [3,4,5], in superconductors due to the high superconducting transition temperature [6,7,8], in the chemical process industry due to the high corrosion resistance [9] and the low thermal neutron capture cross-section [10] makes it suitable to control nuclear reactions.
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