Comparison of dynamic fatigue behavior between SiC whisker-reinforced composite and monolithic silicon nitrides

Technical Report · Fri Feb 01 04:00:00 EST 1991

OSTI ID:5663366

Choi, S R; Salem, J A

The dynamic fatigue behavior of 30 vol percent silicon nitride whisker-reinforced composite and monolithic silicon nitrides were determined as a function of temperature from 1100 to 1300{degree}C in ambient air. The fatigue susceptibility parameter, n, decreased from 88.1 to 20.1 for the composite material, and from 50.8 to 40.4 for the monolithic, with increasing temperature from 1100 to 1300{degree}C. A transition in the dynamic fatigue curve occurred for the composite material at a low stressing rate of 2 MPa/min at 1300 C, resulting in a very low value of n equals 5.8. Fractographic analysis showed that glassy phases in the slow crack growth region were more pronounced in the composite compared to the monolithic material, implying that SiC whisker addition promotes the formation of glass rich phases at the grain boundaries, thereby enhancing fatigue. These results indicate that SiC whisker addition to Si{sub 3} N{sub 4} matrix substantially deteriorates fatigue resistance inherent to the matrix base material for this selected material system.

• Research Organization: National Aeronautics and Space Administration, Cleveland, OH (USA). Lewis Research Center
• OSTI ID: 5663366
• Report Number(s): N-91-19293; NASA-TM--103707; E--5932; NAS--1.15:103707
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360203* -- Ceramics
Cermets
& Refractories-- Mechanical Properties
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CARBIDES
CARBON COMPOUNDS
COMPOSITE MATERIALS
CRACK PROPAGATION
CRYSTAL STRUCTURE
FATIGUE
FRACTURE PROPERTIES
GRAIN BOUNDARIES
MATERIALS
MATRIX MATERIALS
MECHANICAL PROPERTIES
MICROSTRUCTURE
NITRIDES
NITROGEN COMPOUNDS
PNICTIDES
SILICON CARBIDES
SILICON COMPOUNDS
SILICON NITRIDES