Design-Oriented Comparison of Si–Me (Me = Mo, Ti, Zr, Ta, W) Infiltration Coatings on C/C Sonotrodes for Ultrasonic Atomization of CuSn8: Microstructure, Phase Constitution, Wettability, Nanoindentation, and Process Performance

This study compares five Si–Me infiltration coatings, Si:Mo (1:4), Si:Ti (1:1), Si:Zr (1:5), Si:Ta (1:1), and Si:W (1:5), deposited on C/C sonotrodes for ultrasonic atomization of CuSn8. The coatings were evaluated in terms of phase constitution, microstructure, wettability, nanoindentation response, and powder-production performance. XRD showed that the coatings formed distinct multiphase reaction layers, with Si:Ta (1:1) being the most silicide-dominated system, while the other coatings contained carbide or silicide–carbide phases. Metallization strongly improved the surface wettability of C/C, especially for Si:Zr (1:5) and Si:W (1:5). Nanoindentation indicated the most favorable H/E* and H3/E*2 descriptors for Si:W (1:5) and Si:Mo (1:4). All coatings enabled high powder yields in single-run atomization tests, while apparent differences in particle-size distribution were observed among the coating conditions. Overall, the results show that coating selection for ultrasonic atomization should combine phase constitution, surface-state descriptors, near-surface mechanical response, layer retention, and process performance. Within the investigated conditions and the limitation of single-run atomization experiments, Si:W (1:5) emerged as the most promising and best-balanced coating candidate, while Si:Ta (1:1) and Si:Mo (1:4) remained relevant alternatives.