Evaluation of Creep Property of AS800 Silicon Nitride from As-Processed Surface Regions Page: 4 of 8
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IV. SUMMARY
Tensile creep studies on materials machined from as-processed surface layer and bulk region were
carried out at 13500C in air. Analysis of X-ray and SEM showed that materials from surface layer
region exhibited similar elongated grain microstructure and crystalline H-phase to the materials in the
bulk region. Tensile creep results showed that samples from the as-processed surface region exhibited
higher creep rates and, thus, shorter lifetimes than the samples obtained from the bulk region. The
poor creep performance of material from the as-processed surface region was due to the higher amount
of glassy phase enriched with oxygen and sintering additive elements, as identified by TEM analysis.
The presence of oxygen-enriched glassy phase, which softens at the test temperature, accelerated the
creep deformation processes of solution/precipitation, viscous flow, and grain boundary sliding,
resulting in poor high-temperature mechanical performance.
ACKNOWLEDGEMENTS
The authors thank Drs. M. Lance, T. N. Tiegs, and P. F. Becher for reviewing the manuscript.
Research sponsored by the U.S. Department of Energy, Office of Power Technologies, Microturbine
Technologies Program, under Contract DE-AC05-000R22725 with UT-Battelle, LLC.
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Lin, H. T. Evaluation of Creep Property of AS800 Silicon Nitride from As-Processed Surface Regions, article, March 9, 2001; Tennessee. (https://digital.library.unt.edu/ark:/67531/metadc715932/m1/4/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.