A study on microstructure development and oxidation phenomenon of arc consolidated Mo-Nb-Si-(Y) alloys

Two alloys of compositions Mo-26Nb-19Si and Mo-26Nb-19Si-0.5Y (at.%) were prepared by non-consumable arc melting. The alloys characterized using BSE, EDS and EBSD techniques confirmed the formation of two phase (Mo, Nb)SS-(Mo, Nb)5Si3 microstructures. Y-rich (Y2O3) particles were mainly found to be present at the inter-phase boundaries creating different phase morphologies in Mo-26Nb-19Si-0.5Y alloy. Both the phases showed a preferred orientation indicating a directional growth during solidification. Oxidation tests conducted in air at 1000 and 1300 °C showed a porous oxide scale formation on the alloy surface and loss of material due to evaporation of MoO3. The detailed SEM-EDS analysis of the oxide scale formed on these alloys in argon environment at 1000 °C, indicated the presence of Nb2O5 particles in the silica (SiO2) matrix.