SiC-based composites made with SHS derived powders
Kamil Wojteczko, Agnieszka Wojteczko, Marta Strzelecka, Katarzyna Jach, Marcin Rosiński, Yongsheng Liu, Chengyu Zhang, Mirosław M. Bućko, Zbigniew Pędzich
Quarterly No. 1, 2020 pages 17-22
DOI:
keywords: silicon carbide, self-sustaining high-temperature synthesis SHS, upgraded field assisted sintering technique U-FAST, hot-pressing HP
abstract The applications of silicon carbide-based composites at extremely high temperatures and under high partial pressure of water vapor require some modifications of the silicon carbide structure and microstructure in order to increase the reliability of the composite component. One of the methods of such modification could be to introduce phases containing yttria or chromia compounds into the composite microstructure. The presented paper reports the results of investigations on the SHS of silicon carbide powders enriched with yttrium or chromium precursors. It was experimentally proven that it is possible by the means of the SHS technique to obtain powders containing only silicon carbide and dispersions of yttrium silicate or yttrium silicide. Such powders were consequently compacted by hot-pressing or the U-FAST technique. The level of densification and the phase compositions of the materials were characterized. It was found that the sintering conditions determine the phase compositions of the sintered samples. Consolidation using the hot-pressing technique leads to the decomposition of silicon carbide and reduction of the remaining starting phases. As an effect, free graphite and carbide phases (YC2 or Cr3C2) appear in the sintered samples. Applying the U-FAST technique and short sintering times lasting a few minutes allows some yttium-silicon phases from the SiC-Y system (oxide, carbide, silicide) to be preserved in the sintered material. In the SiC-Cr system after U-FAST consolidation the CrSi2 silicide phase was preserved, which is not desirable in the final material because of its relatively low melting point of 1470 °C.