Thermal softening effect on the deposition efficiency and microstructure of warm sprayed metallic powder

Micron-size titanium powder was deposited on a steel substrate by a warm spraying process, in which particles were accelerated and simultaneously heated by a supersonic gas flow. The gas temperature was controlled to soften the metal below its melting point before impacting onto the substrate. The particles were deposited with very high efficiency and bonded well to the substrate due to the thermal softening. Remarkably, fully nanocrystalline particles were formed by dynamic recrystallization without any pretreatment of the powder.