ELECTROCHEMICAL PROPERTIES OF SPARK PLASMA SINTERED TUNGSTEN

摘要

The increased application of spark plasma sintering (SPS) for powder metallurgy (PM) is due to the benefits of fast heating rate, uniform heating condition, lower sintering temperature and shorter dwell time. This method involves the Joule heating of specimens by a pulsed dc coupled with axial pressure. The limitation of PM is the reduced mechanical strength and corrosion properties as compared to solid-state sintering. Tungsten cermets are prospective next generation nuclear materials and the corrosion resistance of these cermets will be influenced by the native oxide associated with tungsten. The behavior of tungsten in acidic environments has been shown to be associated with the dissolution of the outer layer of WO_3(H_2O)X that rests on the compact inner layer of WO_3. The application of sintering temperatures at 1300 °C and 1700 °C with dwell times of 5 minutes yielded SPS tungsten specimens from two tungsten powders of different sizes with varying levels of porosity. Potentiodynamic polarization and electrochemical impedance spectroscopic experiments were performed on these specimens under pH 1 and pH 11 conditions. The data was analyzed using equivalent electrical circuits to determine the influence of the morphology on the electrochemical behavior of the sintered tungsten.