Fabrication of Ni-based amorphous composite coating using laser processing and its nano-indentation test

Ni-Fe-B-Si-Nb amorphous composite coating was fabricated using laser cladding plus laser remelting process using high powder diode laser on mild steel surface. The phase and microstructure of the coating were studied using X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). The mechanical properties of the coating were studied by nano-indentation tests. The results showed that Ni40.8Fe27.2B18Si10Nb4 amorphous composite coating was obtained when the laser cladding power was 0.8 kW, the scanning speed was 0.36 m/min, the powder feed rate was 12g/min, the laser remelting power was 3.5 kW and the scanning speed was 8 m/min. It was found that the laser remelting coatings exhibited dense amorphous structure matrix embedded by some crystal phases((Fe,Ni) and NbC). Nano-indentation test results indicated that the microhardness and elastic modulus of the remelting coating were far higher than that of the laser cladded coating, and they were also higher than that of BMGs with the same nominal compositions. The average microhardness and elastic modulus of the laser remelting coating were 1 227.9 HV and 277.4 GPa, respectively.