Chapter 23. Mechanical Reliability of Si3N4

  1. Edgar Lara-Curzio and
  2. Michael J. Readey
  1. Kedar Sharma1,
  2. P. S. Shankar1,
  3. J. P. Singh1 and
  4. M. K. Ferber2

Published Online: 26 MAR 2008

DOI: 10.1002/9780470291184.ch23

28th International Conference on Advanced Ceramics and Composites A: Ceramic Engineering and Science Proceedings, Volume 25, Issue 3

28th International Conference on Advanced Ceramics and Composites A: Ceramic Engineering and Science Proceedings, Volume 25, Issue 3

How to Cite

Sharma, K., Shankar, P. S., Singh, J. P. and Ferber, M. K. (2004) Mechanical Reliability of Si3N4, in 28th International Conference on Advanced Ceramics and Composites A: Ceramic Engineering and Science Proceedings, Volume 25, Issue 3 (eds E. Lara-Curzio and M. J. Readey), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470291184.ch23

Author Information

  1. 1

    Energy Technology Division Argonne National Laboratory Argonne, IL 60439

  2. 2

    Oak Ridge National Laboratory Oak Ridge, TN 37831

Publication History

  1. Published Online: 26 MAR 2008
  2. Published Print: 1 JAN 2004

ISBN Information

Print ISBN: 9780470051498

Online ISBN: 9780470291184

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Keywords:

  • reliable performance prediction;
  • discrepancy;
  • standard geometrical requirement;
  • making stress analysis;
  • silicon nitride

Summary

Silicon nitride ceramics are leading candidates for advanced gas turbines. Testing of miniature disk specimens in a biaxial flexure mode has the potential to provide strength data needed for reliable performance prediction of the ceramic turbine components. To this end, the biaxial flexure strength of silicon nitride disks (with and without surface machining) was measured by a ball-on-ring fixture. the biaxial strength was compared with the measured strength of conventional flexure bars in order to assess the validity of the biaxial testing. the biaxial strength was higher than the strength of the flexure bars. This discrepancy may be related to the larger stressed volume of the flexure bars. Strength of both the biaxial disks and flexure bars was dependent on the severity of surface machining. As expected, coarser machining resulted in a lower strength. Since the surface of the flexure bars needs to be machined before testing to meet the standard geometrical requirement, conventional flexure bars may not provide reliable strength data for performance prediction of turbine components with as-processed surfaces. Unlike the flexure bars, the biaxial disks do not require surface machining because of their small size. Furthermore, fractography indicated that the flexure bars are more prone to fail from the specimen corners, making stress analysis and strength prediction difficult and complex. on the other hand, the biaxial disks always fail from the center of the disk, as predicted by analysis. Therefore, biaxial testing of miniature disks is the preferred mode of strength evaluation for performance prediction.