Wetting and Interface Microstructure in the System of Al2O3-SiO2 Based Ceramics/Nb-Containing Melts

Wettability and interface microstructure were studied for Nb-containing melts in the contact with ceramic oxide materials of Al2O3-SiO2 system. Ni-40.5 at.%Nb and Au-(0-20) at.%Nb alloys were investigated as prospective alloys for high temperature brazes. Ceramic samples ranged in composition from pure Al2O3 to pure SiO2. The wettability was measured by the sessile drop method. Microstructure of the oxide/metal interface was investigated by scanning electron microscopy and X-ray diffraction methods. The results showed that contact angles decreased with the increase of SiO2 content in the solid substrate for all the melts. Al2O3 was dissolved insignificantly in the melts under study. SiO2 formed intermediate chemical compounds at the interface with the melts: NbO, Nb6Ni6O and Nb5Si3 with the Ni-based melt and NbO2, Nb2O5 with the Au-based melt. Obtained results allow consideration of Nb alloys under study as high-temperature brazes for the Al2O3-SiO2 materials.