Oxidation Behaviour And Thermal Analysis Of Spark Plasma Sintered Co-Based Ternary Superalloy
Keywords:
SPS, Superalloys, Co-W-Ta, Laser Flash Analyzer, Diffusivity, CarbidesAbstract
Cobalt-based superalloys are currently used for gas-turbine vanes because of a combination of superior structural and thermal properties compared with nickel-base superalloys. Presently, superalloy fabrication is mostly done by casting, forming and arc melting. However, powder metallurgy brings unique advantages i.e. reduced machining, grain refinement and high-melting elements alloying. In this work, Co-based superalloy was prepared by spark plasma sintering (SPS) from high purity metallic powders of Co, W and Ta. The powders were vigorously mixed for 12 h, stacked in a graphite and compacted in vacuum furnace at 1000 and 1200 °C. The dwelling time of 10 and 15 min and heating rate of 150 °C/min were used. Structural characterizations of the superalloys were carried out using SEM-EDX and X-ray diffractometer, while thermal and oxidation tests were performed using Laser Flash Analyzer (LFA) and a high temperature furnace. Results indicated formation Corich main phase with dispersions of carbides and oxides phases of the metallic species within the material. Co-based superalloys sintered at 1000 °C have higher thermal conductivity (TC) at lower temperature range, while alloys sintered at 1200 °C exhibited proportional increase in TC values in the 700 – 1000 °C range. Cyclic oxidation resistance of the alloys increases with sintering temperature
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