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In situ formation and high-temperature reinforcing effect of MoSi2and WSi2on reaction-bonded Si3N4

Authors
Journal
Materials Science and Engineering A
0921-5093
Publisher
Elsevier
Publication Date
Identifiers
DOI: 10.1016/s0921-5093(97)00623-0
Keywords
  • Molybdenum Disilicide
  • Tungsten Disilicide
  • Silicon Nitride
  • High-Temperature Strength

Abstract

Abstract A three-step procedure consisting of presintering, reaction-bonding and post-hot-pressing was employed to prepare Si 3N 4/MoSi 2 and Si 3N 4/WSi 2 composites, using as starting materials powder mixtures of Si–Mo and Si–W, respectively. A presintering step in an Ar-base atmosphere was performed for the in situ formation of intermetallic compounds—MoSi 2 and WSi 2; the nitridation in an N 2-base atmosphere with a total cycle of 1350°C×20 h+1400°C×20 h+1450°C×2 h in order to realize the complete conversion of Si into Si 3N 4; post-hot-pressing was employed for the further densification of the reaction-bonded specimens. The 3- and 4-point bend tests were performed at 25, 1000, 1200 and 1400°C. Si 3N 4/MoSi 2 composite shows a maximum value of bend strength at about 1200°C, whereas the bend strength of Si 3N 4/WSi 2 composite slightly increases from room temperature up to 1000°C.

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