Microstructural and strength stability of a developmental CVD SiC fiber

Conference · Fri Sep 01 04:00:00 EDT 1995

OSTI ID:147158

Bhatt, R T; Garg, A; Hull, D R

The effects of thermal exposure on the room temperature tensile strength and microstructure of a developmental 50 micron CVD SiC fiber have been studied. The fibers were heat treated between 600 and 2000 C in 0.1 MPa argon and air environments for up to 100 hr. In the as-fabricated condition, the fibers showed approximately 6 GPa tensile strength. After argon treatment, the fibers showed strength degradation after 1 hr exposure beyond 1000 C, but those exposed between 1600 and 2000 C retained approximately 2 GPa strength. TEM results showed microstructural changes both in the surface coating and SiC sheath. Flaws created by the rearrangement of carbon in the surface coating and growth of equiaxed SiC grain zone in the SiC sheath are the suggested mechanisms of strength degradation. After air treatment, fibers showed strength degradation after only 2 min exposure at 600 C. Strength retention after 2 min at 1500 C was approximately 2 GPa. Oxidation of the surface coating is the primary reason for strength degradation.

• Research Organization: National Aeronautics and Space Administration, Cleveland, OH (United States). Lewis Research Center
• OSTI ID: 147158
• Report Number(s): N--96-13390; NASA-TM--107008; E--9792; NAS--1.15:107008; ARL-TR--877; CONF-940416--; CNN: RTOP 505-63-12
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
FIBERS
MICROSTRUCTURE
SILICON CARBIDES
TENSILE PROPERTIES
THERMAL DEGRADATION