Particle size-dependent flowability, impact behaviour, and post-deposition heat treatment microstructure evolution in cold-sprayed Ti-5553

The particle size distribution (PSD) significantly influences powder flowability, feeding stability, in-flight particle acceleration, deposition thickness, porosity, and particle deformation during cold spray (CS) of the Ti-5Al-5Mo-5V-3Cr (Ti-5553) alloy. In this study, Ti-5553 feedstock powder was investigated in four PSD groups, which are fine, medium, large, and broad. Powder flowability and mass flow rates were measured by Hall flowmeter tests and a powder feeder. Deposit deformation was examined using scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). In-flight impact velocities ( V imp ) and the bow shock effects on fine particles were modelled with a computational fluid dynamics (CFD) model. Additionally, critical velocities ( V cr ) for the different particle sizes were estimated by finite element analysis (FEA). The fine powder exhibited the poorest flowability and the lowest feeder mass flow rate, and produced the thinnest deposit at 190 ± 11.7 µm; however, the medium, large, and broad PSDs produced deposits of 1785 ± 66.1 µm, 1876 ± 44.6 µm, and 1884 ± 68.8 µm, respectively. The medium PSD exhibited a significant improvement in flowability between as-received (AR) and dried conditions in the Hall flowmeter tests. Porosity measurements showed that the medium PSD had 12.5 ± 1.9% porosity, while the large PSD had 19.1 ± 2.1%. Finally, the AR deposits were heat-treated at 800 °C for 5 h to examine the effect on the porosity, and characterised by electron channelling contrast imaging (ECCI) and EBSD to resolve α/β evolution. The study provides guidance on PSD selection by considering feeding behaviour, V imp and V cr , deposition porosity and thickness, and post-deposition heat treatment microstructural evaluation.