Silicon carbide has many properties that are attractive for applications in fusion energy systems. The reliability of monolithic silicon carbide is insufficient for its use in large components, due to its brittle failure behavior and flaw sensitivity. Ceramic matrix composites, on the other hand, offer greater flaw tolerance and reliability, but their failure mechanisms are less well understood. This work has focussed on studying potential failure mechanisms in silicon carbide fiber-reinforced, silicon carbide matrix (SiCf/SiCm) composites. In the event of cracks caused by accidental overloads, excessive creep, thermal shock from plasma disruptions, handling during installation, or resulting from processing, subcritical crack growth will occur due to creep of fibers that bridge the crack faces. It is presumed that irradiation will enhance the creep rate of the fibers and, subsequently, the subcritical crack growth rate. At certain temperatures the presence of even small amounts of oxygen leads to oxidation of the interphase material to gaseous products. In this case, subcritical crack growth occurs by a separate mechanism. In addition, fiber shrinkage or weakening due to exposure to radiation can promote additional failure mechanisms, including embrittlement. These mechanisms, the conditions, under which they occur, and the current state of models of the crack growth mechanisms will be discussed.
Revised: September 7, 2011 |
Published: November 1, 2000
Citation
Lewinsohn C.A., G.E. Youngblood, C.H. Henager, E.P. Simonen, and R.H. Jones. 2000.Time-Dependent Failure Mechanisms in Silicon Carbide Composites for Fusion Energy Applications. In Proceedings of the 9th International Conference on Fusion Reactor Materials (ICFRM-9), Colorado Springs, CO, USA, October 10-15, 1999. Published in Journal of Nuclear Materials, edited by LK Mansur, et al, 283-287, 584-587. Amsterdam:Elsevier.PNNL-SA-32125.