Particle in-flight status and its influence on the properties of supersonic plasma-sprayed Fe-based amorphous metallic coatings

Abstract In order to optimize the supersonic plasma spraying process more scientifically, it is important to clearly understand the spreading behavior of molten droplet. In this study, the effects of spray parameters on the in-flight behavior and spreading behavior of Fe-based amorphous droplets were investigated. Additionally, since the morphology of the splats is a very important factor which determines the final properties of the coatings, the splats in this study were characterized in terms of their circularity, eccentricity, solidity, and spread factor. The porosity and micro-hardness of the Fe-based amorphous coatings were also evaluated. Results show that the spraying power is the most important parameters that influence the surface temperature of the Fe-based amorphous droplets, while the main factor affecting the in-flight velocity is the Ar flow rate. The melting index of in-flight particles reaches the maximum value at the spraying power of 60 kW and Ar flow rate of 110 L/min. The droplets present disk-shaped splats with the lowest solidity and eccentricity, and highest circularity and spread factor with the average velocity of 445 m/s and surface temperature of 2780 K. This is very crucial to reduce the defects of as-sprayed coatings and form fine-lamellar-structured supersonic plasma-sprayed coatings with outstanding mechanical properties.