Investigation on the effect of the gas-to-metal ratio on powder properties and PBF-LB/M processability

Abstract

Metal powders for the laser powder bed fusion process are usually produced via gas atomization. However, due to the tight particle size distribution required for this application, the yield of the atomization process is low, resulting in a high-powder cost. In this work, atomization process parameters were varied to increase the gas-to-metal ratio to reduce the particle size distribution produced, and therefore increase the yield of the process. As a result, eight powders were produced starting from scrap AISI 136L material at different gas-to-metal ratio values, and the atomization process yield was successfully increased by 50%. First, the eight powders were characterized in terms of powder size, shape distributions, and flowability. Later, all powders were used to produce tensile specimens. The powders produced at higher yield exhibited a larger number of fine particles but slightly lower circularity, particularly in the coarse fraction. Furthermore, powders produced at a high gas-to-metal ratio demonstrated enhanced flowing properties and higher packing density. Consequently, these powders exhibited superior tensile performance, with ultimate tensile strength (UTS) ranging from 651 to 673 MPa and elongation values between 63 and 66%.

Development of plasma-arc technologies of spherical granules production for additive manufacturing and powder metallurgy

“…prep and pa methods also feature granule crystallization at super high cooling rates, creating the conditions for formation of a microcrystalline (and in some cases nanocrystalline) structure, which has a positive effect on the mechanical properties of the products made from them. also important is the fact that for ga process the gas-to-metal ratio (gmr) [17] (flow rate of atomizing gas (argon) required to produce 1 kg of powder) can be from 26 to 110, and for PA and GA processes it is not higher than 8 (for Ti-6Al-4V). PREP equipment operation runs into considerable difficulties related to producing a fine fraction of <100 μm.…”

“…where k is the kinetic energy of turbulence, m 2 /s 2 ; ε is the turbulent energy dissipation rate, m 2 /s 3 ; ρ is the medium density, kg/m 3 ; C = 0.09; μ t value has the dimension of kg/m•s. at the next stage the taylor analogue Break-up (taB) model of hydrodynamic break-up of the drops and the derived experimental data were used to model the process of dispersion of the melt forming during plasma-arc atomization at the edge of current-carrying 1.6 mm wire from AISI 316 steel (14)(15)(16)(17). TAB model draws an analogy between the mass-spring-damper system and oscillations and deformation of the liquid drops leading to their refinement.…”