Corrosion behavior and high temperature oxidation kinetics of nano-TiO2/Y2O3 dispersed zirconium alloys

Corrosion behavior and high temperature (Isothermal/Non-isothermal) kinetics of Zirconium alloys (Zr45Fe30Ni20Mo5, Zr44Fe30Ni20Mo5(TiO2)(1), Zr44Fe30Ni20Mo4(TiO2)(2), Zr44Fe30Ni20Mo5 (Y2O3)(1) and Zr44Fe30Ni20Mo4(Y2O3)(2) (in wt%)) synthesized by mechanical alloying followed by spark plasma sintering (at 950 degrees C) have been investigated. Alloy specimens were subjected to potentiodynamic polarization test in a 3 mol NaCl solution to study the mechanism and rate of corrosion. The study indicates that increase in TiO2/Y2O3 dispersoid content upto 1-2 wt% increases the corrosion resistance of the zirconium alloys. It was observed that isothermal oxidation kinetics follow the parabolic rate law. Oxidized specimens were analyzed by X-ray diffraction and SEM. X-ray diffraction of the alloys depicted the oxide scale formed during oxidation to be composed mainly of ZrO2 along with other stable oxides. Dispersoid added samples exhibit higher extent of oxidation due to presence of more number of grain boundaries and greater diffusion path. Non-isothermal oxidation study was done by thermo gravimetry (TG) technique with different heating rates from room temperature to 1273 K (1000 degrees C). Alloys without dispersoids show marginally better oxidation resistance in terms of activation energy than those of samples sintered with TiO2/Y2O3 dispersoids. (C) 2016 Elsevier B.V. All rights reserved.