Yttria dispersion strengthened nickel-based superalloy by mechanical alloying

Present work involves preparation of nano sized yttria dispersed nickel-based superalloy by mechanical alloying (MA) in a planetary ball mill and optimization of process parameters. Nanocrystalline (NC) yttria was synthesized using a simple and economical sol-gel route. Elemental powders of composition Ni-20Cr-3Fe-0.5Ti-0.3Al-0.6Y2O3 wt% were mechanically alloyed at various milling times (5-40 h) in dry milling. Purity of the alloy and phase evolution was characterized by XRD. The alloying behaviour, particle size, particle shape and compositional analysis were done by SEM/EDAX. TEM of MA powders showed grain size in the micrometer range. The powders were consolidated by spark plasma sintering at temperatures from 1173-1373 K and microhardness measurements were also done. The sample sintered at 1173 K had the highest hardness; higher than that reported in the literature. (author)