The aim of this work was to develop a new coating material based on Ni20Cr alloy modified with up to 50%wt. rhenium. The modification was carried out by the mechanical mixing of the base powder and ammonium perrhenate with the subsequent thermoreduction in an H₂ atmosphere. The obtained powder consists of a nickel–chromium core surrounded by a rhenium shell. The characterization of the powders—including their microstructure, phase and chemical composition, density, flowability, particle size distribution, and specific surface area—was performed. The influence of plasma current intensity and hydrogen gas flow on in-flight particle temperature and velocity were investigated. The results indicate that there is interdiffusion between the base Ni20Cr and the rhenium shell, resulting in intermediary solid solution(s). The modified powders have a higher specific surface area and a lower flowability, but this does not prevent them from being used as feedstock in plasma spraying. In-flight measurements reveal that increasing the content of rhenium allows for the higher temperature of particles, though it also reduces their speed.

The primary goal of this study was to comprehensively characterize the microstructure of refractory powder materials, particularly molybdenum (Mo) and molybdenum-rhenium (Mo-Re), in both non-spherical and spherical forms. The characterization was carried out with the use of advanced techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and nanohardness testing. This combination of analysis techniques provided a multi-scale understanding of the microstructural evolution and elemental distribution within the powders. Mo-Re powders were synthesized through powder metallurgy processes, while the spherical powders were produced with the use of the plasma spheroidization technique. Detailed analyses were conducted on the surface of powders, its cross-sections and thin foils. Spherical powders exhibited significant morphological changes, with evidence of rhenium diffusion within the molybdenum grain structure. This study provides detailed microstructural analysis of Mo-Re powders synthesized via plasma spheroidization, highlighting the role of rhenium in enhancing grain stability. The observed morphological changes in the spherical powders are indicative of enhanced material properties, which may influence their performance in critical applications. These findings provide valuable insights into the material properties, which may be crucial for demanding applications in high-temperature and high-stress environments, such as aerospace.

The research conducted in this paper is a practical example of the Design of Experiments methodology. In accordance with the assumptions of the experimental design, the authors drew attention to the problem: how should the spark plasma sintering process be planned to obtain the maximum amount of information needed to optimise the consolidation of the WC-6Co composite at the lowest possible cost? The DOE methodology—a powerful technique for investigating new processes and gaining knowledge about existing ones in order to optimise them for high performance—was employed in the study. The aim of the research was to optimise the consolidation of the spark-plasma sintering process of the WC-6Co composite using the DoE (Design of Experiments) methodology. Four sintering factors were selected for the study: sintering temperature (factor A, 1300–1400 °C); heating rate (factor B, 100–300 °C/min); sintering time (factor C, 150–600 s); and pressure (factor D, 40–50 MPa). Each consolidation factor was designed to cover three levels. The L9 orthogonal array was used. It was found that sintering temperature and heating rate had the greatest impact on apparent density. To validate the statistical model, sintering tests were performed at a temperature of 1380 °C, a heating rate of 100 °C/min, a sintering time of 150 s and a pressing pressure of 45 MPa. Validation analysis of the statistical model demonstrated consistency with the experimental results. The WC-6Co composite achieved an apparent density of 14.85 g/cm³, corresponding to 97.42% of the theoretical density, with a hardness of 1809 HV30 and total porosity of 2.583%. X-ray diffraction studies revealed the presence of tungsten carbide and cobalt in the structure.