Splat formation mechanism of droplet-filled cold-textured groove during plasma spraying

Abstract

In this study, a numerical simulation and experiments were performed to analyze the formation process of splat in the laser texture groove of filling molybdenum droplets during atmospheric plasma spraying. Texture grooves were extracted using a 3D surface topography instrument, and the heat transfer and phase transition processes of droplet hydrodynamics were analyzed. A 3D numerical model of the droplet-filling texture groove was developed using a commercial software. The droplet diameter, impact velocity, and temperature were set to 50 μm, 110 m/s, and 2917 °C, respectively, to fill the cold-textured grooves. The cross-sectional morphology and element distribution of the filled coating were characterized using scanning electron microscopy and energy dispersive spectroscopy, respectively. Numerical results are consistent with those of the experiment. This study reveals the splat formation mechanism of droplet impact, spreading, and solidification in textured grooves and the grooves’ wall temperature. Results show that the fastest spreading velocity of the droplet contact groove is 4.63 times that of the initial impact velocity. The groove wall has a maximum melting depth of 2.6 μm. In the process of droplet spreading, the fluid layer gradually solidifies, and the transient spreading is accompanied by solidification.