Effect of the remelting scanning speed on the amorphous forming ability of Ni-based alloy using laser cladding plus a laser remelting process

Amorphous coatings exhibit prominent properties, including high hardness and good wear resistance properties. In this study, Ni-based amorphous composite coatings with a composition of (Ni0.6Fe0.4)68B18Si10Nb4 were prepared on a mild steel substrate via high power diode laser cladding plus laser remelting processes. The microstructure of the coating was studied using X-ray diffraction (XRD) and a scanning electron microscope (SEM). The effect of the remelting scanning speed on the amorphous forming ability of the Ni-based alloy was studied systematically by experimental and numerical simulation methods. The results indicated that there was no amorphous phase formed when the scanning speed was 4 m/min and 5 m/min. The amorphous phase was observed when the remelting scanning speed was 6 m/min. The amorphous phase volume fraction increased with an increase in the remelting scanning speed. The fraction was found to be approximately 64% when the remelting speed was 8 m/min. The simulation results indicate that the increase in the remelting scanning speed may lead to lower residence time and higher cooling rate of the melted pool. As a result, high remelting scanning speed can be concluded to be a necessary condition for the formation of the amorphous phase when using the laser cladding plus laser remelting process.