Layered Microstructure Distribution and Forming Mechanism of Laser-Processed Ni-Fe-B-Si-Nb-C Amorphous Composite Coatings

抄録

A Ni-based amorphous composite coating was fabricated via laser processing. Its microstructure was observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Cooling behavior during the laser remelting process was simulated using a finite element method. The results indicated that four layers with different microstructures were formed. The layers consist of coarse dendrites, fine dendrites, equiaxed dendrites, and a layer of NbC particles/amorphous phase. Heterogeneous nucleation from NbC particles was observed at the clad/remelt interface. An amorphous phase was the primary phase in the laser remelted layer. Numerical simulation results showed that the cooling rates decreased along the depth direction from the top coating surface. The cooling rate was on the order of 10⁴ K/s. When the cooling rate was higher than the critical cooling rate threshold, an amorphous phase was formed in the remelted layer after the laser remelting process.