Synthesis of nanosized composite powders via a wet chemical process for sintering high performance W-Y2O3 alloy

Abstract

With the aim of preparing high performance oxide dispersion strengthened tungsten-based alloys by powder metallurgy, the W-Y2O3 composite nanopowders were prepared by an improved bottom-up wet chemical method. Ultrasonic treatment and anionic surfactant sodium dodecyl sulfate (SDS) addition were innovatively introduced into this wet chemical method in order to fabricate homogeneous, ultrafine W-Y2O3 composite nanopowders. As a result, the average tungsten grain size of 40–50nm was obtained for this composite nanopowders. For comparison, W-Y2O3 composite powders were also prepared by traditional mechanical milling. After that, spark plasma sintering (SPS) was employed to consolidate the powders prepared by either mechanical milling or wet chemical method to yield high density as well as suppress grain growth. It is found that the W-Y2O3 alloy prepared by wet chemical method and subsequent SPS possesses smaller grain size (0.76±0.17μm) and higher relative density (99.0%) than that prepared by mechanical milling and subsequent SPS. Moreover, the oxide nanoparticles (about 2–10nm) are dispersed within tungsten grains and at grain boundaries more uniformly in W-Y2O3 alloy prepared by wet chemical method and subsequent SPS. Due to the ultrafine grains, high sintering density and homogeneously distributed oxide nanoparticles, the Vickers microhardness of yttria dispersion strengthened tungsten-based alloy prepared in our work reaches up to 598.7±7.3HV0.2, higher than that reported in the previous studies. These results indicate that the improved bottom-up wet chemical method combined with ultrasonic treatment and anionic surfactant addition developed in our work is a promising way to fabricate high performance oxide dispersion strengthened tungsten-based alloys with ultrafine grain and high density.