Creep and stress rupture behavior of an advanced silicon nitride; Part 1: Experimental observations

• Published in: Journal of the American Ceramic Society 1994-05, Vol.77:5
• Main Authors: Menon, M.N., Fang, H.T., Wu, D.C., Jenkins, M.G., Ferber, M.K., More, K.L., Hubbard, C.R., Nolan, T.A.
• Format: Article
• Language: English
• Subjects: 360203 - Ceramics, Cermets, & Refractories- Mechanical Properties; CRACK PROPAGATION; CREEP; DATA; EXPERIMENTAL DATA; FAILURES; INFORMATION; MATERIALS SCIENCE; MATERIALS TESTING; MECHANICAL PROPERTIES; MECHANICAL TESTS; MICROSTRUCTURE; NITRIDES; NITROGEN COMPOUNDS; NUMERICAL DATA; PNICTIDES; RUPTURES; SILICON COMPOUNDS; SILICON NITRIDES; TEMPERATURE DEPENDENCE; TESTING
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/j.1151-2916.1994.tb05395.x

Cylindrical buttonhead specimens of an advanced silicon nitride were tested in uniaxial tension at temperatures between 1,422 and 1,673 K. In the range 1,477 to 1,673 K, creep deformation was reliably measured using high-temperature contact probe extensometry. Extensive scanning and transmission electron microscopy has revealed the formation of lenticular cavities at two-grain junctions at all temperatures (1,422--1,673 K) and extensive triple-junction cavitation occurring at the higher temperatures (1,644--1,673 K). Cavitation is believed to be part of the net creep process. The stress rupture data show stratification of the Monkman-Grant lines with respect to temperature. Failure strain increased with increase in rupture time or temperature, or decrease in stress. Fractography showed that final failure occurred by subcritical crack growth in all specimens.