Effect of particle morphology on flow characteristics of a composite plasma spray powder

The effects of BaF2-CaF2 particle morphology on National Aeronautics and Space Administration (NASA) PS304 feedstock powder flowability were investigated, BaF2-CaF2 eutectic powders were fabricated by comminution (producing an angular morphology) and by gas atomization (producing a spherical morphology). The fluoride powders were added incrementally to the other powder constituents of the NASA PS304 feedstock, (Ni-Cr, Cr2O3, and Ag powders). A linear relationship between flow time and concentration of the BaF2-CaF2 powder was found. The flow of the powder blend with spherical BaF2-CaF2 was better than that with angular BaF2-CaF2. The flowability of the powder blend with angular fluorides decreased linearly with increasing fluoride concentration. However, the flow of the powder blend with spherical fluorides was independent of fluoride concentration. The results suggest that for this material blend, particle morphology plays a significant role in flow behavior, offering potential methods to improve powder flowability and enhance the commercial potential. These findings may be applicable to other difficult-to-flow powders such as cohesive ceramics.