Abstract: The high purity Nb powder and Si powder with the average particle size of 80 μm are used as raw powder and four kinds of Nb-16Si binary alloys are fabricated by laser melting deposition of double coaxial powder feeder method with 500 W, 750 W, 1000 W and 1 500 W laser beam as the energy resource. The macro- and micro-structure evolution and Vickers hardness of these alloys are investigated with scanning electron microscope (SEM), X-ray energy dispersive spectroscopy (EDS) and X-ray diffraction spectrometer (XRD), etc. The results show that with the laser power increasing from 500 W to 1 500 W, the surface morphology of the as-deposited alloys gradually becomes smooth, and the relative density increases from 91.1% to 98.5%. The laser power of LMD has no obvious effect on the phase constitution of Nb-16Si alloys, and the metastable Nb₃Si and Nb_SS(Niobium solid solution, Nb_SS) phases are synthesized directly by the in-situ reaction between pure Nb powder and pure Si powder under the laser beam heating condition. With the increase of laser power, the morphology of pro-eutectic Nb_SS phase changes from dendrite to fine equiaxed gradually, and its average size is also refined from about 50 μm to 1 μm approximately. The microstructure of Nb_SS+Nb₃Si eutectic in the as-deposited alloys changes from fine lamellar eutectic to irregular eutectic of nanometer Nb_SS distributing on Nb₃Si matrix. The Vicker's hardness of as-deposited Nb-16Si alloys increases from 605 HV to 898 HV with the increase of laser power.

Key words: Nb-16Si binary alloys, laser melting deposition, laser power, in-situ reaction, microstructure