Reactivity of materials towards carbon of graphite foil during Spark Plasma Sintering: A case study using Ni–W powders

• Published in: Materials letters Vol. 168; pp. 62 - 67
• Main Authors: Dudina, Dina V., Bokhonov, Boris B., Ukhina, Arina V., Anisimov, Alexander G., Mali, Vyacheslav I., Esikov, Maxim A., Batraev, Igor S., Kuznechik, Oleg O., Pilinevich, Leonid P.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.04.2016
• Subjects: Carbides; Carbon; Compacts; Diffusion; Foils; Graphite; Mechanical alloying; Ni-W alloys; Nickel; Nickel base alloys; Spark Plasma Sintering; Diffusion; Spark Plasma Sintering; Carbon; Mechanical alloying; Ni-W alloys; Carbides
• ISSN: 0167-577X; 1873-4979
• DOI: 10.1016/j.matlet.2016.01.018

In this study, the issue of reactivity of materials towards carbon of graphite foil during Spark Plasma Sintering has been addressed through a case study using Ni-15at% W powders prepared by mechanical alloying or simple mixing. Tungsten carbide WC was found at the flat ends of the compacts obtained from both mixtures. In case of the mechanically alloyed powder, carbon diffusion into the sintered compact resulted in the formation of Ni2W4C particles in a Ni-based matrix throughout the compact volume. In contrast to the compact obtained from the mechanically alloyed powder, no carbon-containing phases were detected in the interior of the compacts produced from mixed Ni+W powders sintered in the same conditions. The uptake of carbon caused by its inward diffusion was facilitated by a much higher concentration of defects and a greater volume of grain boundaries in the mechanically alloyed powder. The compacts Spark Plasma Sintered from the mechanically alloyed powders were much harder (620HV) than the compacts produced from the mixed powders (315–370HV) due to the presence of submicron Ni2W4C reinforcing particles distributed in a Ni-based solid solution-strengthened matrix. [Display omitted] •Reactivity of Ni–W powders towards carbon during Spark Plasma Sintering was studied.•The Ni-15at% W powders were prepared by mechanical alloying or simple mixing.•Tungsten carbide WC formed at flat ends of compacts obtained from both mixtures.•In case of the mechanically alloyed powder, Ni2W4C were found in compact's interior.•Hardness of compacts from mechanically alloyed and mixed powders was 620 and 370HV.