The wire tips in twin-wire arc-spraying (TWAS) are heated in three different zones. A high-speed camera
was used to observe the melting behavior, metal breakup, and particle formation under different
operating conditions. In zone (I), the wire tips are melted (liquidus metal) and directly atomized in the
form of smaller droplets. Their size is a function of the specific properties of the molten metal and the
exerting aerodynamic forces. Zone (II) is directly beneath zone (I) and the origin of the extruded metal
sheets at the wire tips. The extruded metal sheets in the case of cored wires are shorter than those
observed while using solid wires. In this study, the effects of adjustable parameters and powder filling on
melting behavior, particle formation, and process instability were revealed, and a comparison between
solid and cored wires was made. The findings can improve the accuracy of the TWAS process modeling