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Super-clean and super-spherical FGH4095 superalloy powder is produced by the ceramic-free electrode induction-melt inert gas atomization (EIGA) technique. A continuous and steady-state liquid metal flow is achieved at high-frequency (350 kHz) alternating current and high electric power (100 kW). The superalloy is immersed in a high-frequency induction coil, and the liquid metal falling into a supersonic nozzle is atomized by an Ar gas of high kinetic gas energy. Numerical calculations are performed to optimize the structure parameters for the nozzle tip. The undesired oxidation reaction of alloying elements starts at 1000 °C with the reaction originating from the active sites on the powder surfaces, leading to the formation of oxides, MexOy. The role of active sites and kinetic factors associated with the diffusion of oxygen present in the atomization gas streams are also examined. The observed results reveal that the oxidation process occurring at the surface of the produced powders gradually moves toward the core, and that there exists a clear interface between the product layer and the reactant. The present study lays a theoretical foundation for controlling the oxidation of nickel-based superalloy powders from the powder process step. [ABSTRACT FROM AUTHOR]

The crucible-free electrode induction melting gas atomization (EIGA) technology is an advanced technology for preparing ultra-clean nickel-based superalloy powders. One of the key issues for fabricating powders with high quality and yield is the consecutive induction melting of a superalloy electrode. The coupling of a superalloy electrode and coil, frequency, output power, and heat conduction are investigated to improve the controllable electrode induction melting process. Numerical simulation results show that when the coil frequency is 400 kHz, the output power is 100 kW, superalloy liquid flow with a diameter of about 5 mm is not consecutive. When the coil frequency is reduced to 40 kHz, the output power is 120 kW, superalloy liquid flow is consecutive, and its diameter is about 7 mm. [ABSTRACT FROM AUTHOR]

Powder metallurgy (PM) superalloys are an important class of high temperature structural materials, key to the rotating components of aero engines. In the purview of the present challenges associated with PM superalloys, two novel approaches namely, powder preparation and the innovative spray-forming technique (for making turbine disk) are proposed and studied. Subsequently, advanced technologies like electrode-induction-melting gas atomization (EIGA), and spark-plasma discharge spheroidization (SPDS) are introduced, for ceramic-free superalloy powders. Presently, new processing routes are sought after for preparing finer and cleaner raw powders for disk superalloys. The progress of research in spray-formed PM superalloys is first summarized in detail. The spray-formed superalloy disks specifically exhibit excellent mechanical properties. This paper reviews the recent progress in innovative technologies for PM superalloys, with an emphasis on new ideas and approaches, central to the innovation driving techniques like powder processing and spray forming. [ABSTRACT FROM AUTHOR]