The aim of this work is to analyze the morphology and composition of iron-aluminide (FeAl) powders produced by liquid metal atomization using a de Laval nozzle. The variables studied are atomization gas pressure and melt nozzle diameter. Different sized powders were characterized via SEM, XRD, and EDS analysis and were found to be similar in composition and shape (spherical) regardless of their size. The paper provides a detailed description of how the powders were produced, classified, and tested, and presents and interprets the results.

Liquid metal atomization using a De Laval nozzle has proven its efficiency in producing fine and narrow sized powder. The modeling work of gas dynamics related to nozzle geometry has led to a better understanding of the effects of the processing parameters. During the emptying of the crucible, the decrease in the static height of the melt acts on the metal mass flow rate. An experimental study on the particle size distribution in the cross-section of the spray and its evolution during the process has confirmed the unsteadiness of the process. By establishing a model to fit the gas pressure to the mass flow rate evolution, an almost steady state can be reached for the process. This has brought us to reduce the mean particle size and to improve the narrowness of the as-atomized particle size distribution.

In this study, the impact melting phenomenon at the interfaces of particles deposited by cold spraying and its effect on coating microstructure were examined. Different powders with various thermal and mechanical properties were selected as feedstock. They are respectively Al2319, Ti, Ti-6Al-4V, Ni and MCrAlY powders. The results showed that most of the sprayed materials possibly experienced local melting at the contact interfaces of particles under certain gas conditions. Low melting point and reaction with the atmosphere are the two main factors contributing to the impact fusion during cold spraying. The results indicated that the local melting would benefit the formation of the metallurgical bonding between the deposited particles and enhance the coating adhesion.

This study was undertaken to investigate the influence of the initial powder particle size on the microstructure development in a Cu-3wt% Ag alloy obtained by vacuum plasma spraying of a mixture of copper and silver powders. Various mixtures of powder particles were used where the copper powder particle size was kept as –80/+40 μm, while the silver powder particle size fraction was varied. Vacuum plasma spraying (VPS) in inert gas atmosphere was used to elaborate thick coatings (2 mm) with limited oxygen contamination. Significant variations in microstructure were obtained depending on the Ag powder size fraction that was used. These differences in behavior are discussed taking into account differences in the solid state precipitation mechanisms in the alloy.