FeCoNiCu Alloys Obtained by Detonation Spraying and Spark Plasma Sintering of High-Energy Ball-Milled Powders

In the present work, a medium-entropy alloy, FeCoNiCu, was selected as a model system to demonstrate the possibility of fabricating solid solution-type alloy coatings by detonation spraying. A mixture of Fe+Co+Ni+Cu powders was first treated in a high-energy planetary ball mill. The evolution of the microstructure of the FeCoNiCu alloy particles with the milling time was investigated. After 20 min of milling, the powder was nearly a single-phase solid solution of face-centered cubic structure. A bulk alloy was obtained by consolidating the ball-milled powders by spark plasma sintering. The coatings and sintered material were studied by x-ray diffraction and scanning electron microscopy/energy-dispersive spectroscopy/elemental mapping. No oxidation of the material occurred during detonation spraying. The coatings and sintered alloy obtained from the powder mixture milled for 20 min were nearly single-phase with a major phase of face-centered cubic structure. The residual porosity of the coatings and sintered alloy was as low as ~1%. The hardness values of the coatings and sintered alloy were found to be close to each other (~400 HV300). This work showed that a combination of high-energy milling and detonation spraying is a viable route for the formation of nearly single-phase medium-entropy FeCoNiCu alloy coatings.