Comparative Analysis of the Properties of ASTM F75 Alloy Powders Atomized with Argon and Nitrogen: Numerical and Experimental Insights

Abstract

ASTM F75 alloy powders are widely used in biomedical implants, aerospace, and turbine components and are often produced via additive manufacturing. However, the effects of process parameters on particle size distribution, microstructure, and cooling behavior, as well as the impact of gas heating, remain unexplored. This study investigates the differences in the production of ASTM F75 powders using the gas atomization method with argon and nitrogen gases through experimental and numerical analyses. The experimental study compared the powder particle distributions, surface micrographs, and microstructures of powders produced with argon and nitrogen gases at a temperature of 300 K and a pressure of 3.5 MPa. For the ASTM F75 powder in the 0–53 μm range, the Dv(10), Dv(50), and Dv(90) values are 7.94, 18.2, and 39.4 μm for nitrogen gas, while for argon gas these values are 11.3, 23, and 41.8 μm, respectively. Thus, it was observed that smaller particle size distributions were achieved in the production carried out with nitrogen. When comparing the surface micrographs, dendrite formation was observed during production with both gases. Therefore, it was determined that the cooling rates at 300 K and 3.5 MPa were not sufficient, as indicated by the dendritic structures observed on the surface. In the scanning electron microscope (SEM) images of the produced powders, more satellite was observed in the production carried out with nitrogen. Since experimentally studying the gas atomization parameters would be costly, the effect of gas heating on gas flow dynamics was investigated numerically. The experimentally validated numerical analyses were conducted in ANSYS Fluent using the standard k–ε turbulence model. The numerical simulations were performed at an inlet gas pressure of 3.5 MPa, ensuring consistency with the experimental conditions. As the gas temperatures increased to 300, 400, 500, and 600 K, the maximum velocities for argon gas are 399.45, 458.58, 509.59, and 555.32 m/s, while these values are 516.21, 592.31, 658.88, and 719.27 m/s for nitrogen gas, respectively. As the temperature of both gases increased, a decrease in mass flow rate was recorded. As the gas was heated, an increase in velocity and a decrease in mass flow rate were observed. Therefore, it was concluded that higher kinetic energy could be achieved with lower gas consumption. It leads to stronger aerodynamic forces acting on the molten metal, which enhances its fragmentation and promotes the formation of finer powder particles. As a result, compared to argon, powders atomized with nitrogen achieved a reduction of approximately 29.73% in Dv(10), 20.87% in Dv(50), and 5.74% in Dv(90) values. Additionally, based on numerical calculations, gas heating resulted in an average reduction of approximately 10.96% in gas consumption for argon and 11.79% for nitrogen per 100 K increase in temperature, highlighting its potential for improving process efficiency. These findings provide a comprehensive guide for the production of ASTM F75 powders using the gas atomization method with argon and nitrogen gases.