Microstructural evolution of Fe-based amorphous alloy coatings via ultrasonic vibration-assisted laser cladding

Fe-based amorphous coatings were fabricated using laser cladding with and without ultrasonic vibration. The effect of ultrasonic vibration on microstructural evolution was studied in this paper. When compared with Fe-based amorphous coatings fabricated via laser cladding without ultrasonic vibration, the crystallisation zone at the bottom of the coating increases from 46 μm to 81 μm. It has a wavy distribution that is produced via the thermal effect and high-frequency disturbances due to ultrasonic vibration. The formed columnar dendrites break and recrystallise to form equiaxed crystals as a result of the stirring caused by ultrasonic-vibration induced streaming. However, the amorphous phase still dominates the top zone of the coating, which is less affected by ultrasonic vibration. The entire coating has a four-layer gradient microstructure from the crystalline phase to the amorphous phase, which is instrumental in reducing stress in the bonding area between the coating and substrate.