Microstructure of Nb/SiC system gradient material fabricated by laser 3D printing method and reaction mechanism

Nb/SiC system gradient material was fabricated by laser 3D printing method. The Nb/SiC sample with composition changing from pure Nb to 60% SiC (volume fraction) was prepared. The microstructure of gradient material was analyzed with scanning electron microscope (SEM) and electro-probe microanalyzer (EPMA), and X-ray diffraction (XRD) spectrometer was used for determination of the formed phases in graded layers. It was found that chemical reaction took place between Nb and SiC in the gradient layers during laser melting process, and the reaction products included Nb5Si3, Nb₂C, NbC and NbSi₂. With increasing of SiC content, the products of gradient material changed as follows: Nb+Nb₅Si₃+Nb₂C+NbC→Nb₅Si₃+NbSi₂+SiC+NbC→NbSi₂+SiC+NbC. Residual SiC particles began to appear when the SiC content reached 30%, and residual SiC content and its size in the material gradually increased with the increase of SiC ratio.