Strength and microstructure of Si3N4 sintered with ZrO2 additions

Journal Article · Tue Apr 01 04:00:00 EST 1986 · Adv. Cer. Mat.; (United States)

OSTI ID:5400564

Sanders, W A; Mieskowski, D M

Densities greater than 99 percent of theoretical were obtained with stabilized ZrO2 additions to Si3N4. Material sintered at 2140 C under 2.5 MPa nitrogen overpressure with 3.8, 9.9, and 13.4 wt pct ZrO2 had a predominantaly equiaxed grain size ranging from 0.2 to 7.0 microns. At 1370 C, the latter composition exhibited a flexural strength of about 487 MPa, equal to that of a finer-grain-size, hot-pressed Si3N4 + ZrO2 material having excellent high-temperature static fatigue properties. Transmission electron microscopy of the sintered Si3N4 revealed a glassy grain-boundary phase at all three ZrO2 levels and partially crystalline triple points for the 9.9 and 13.4 wt pct ZrO2-containing materials. Slow crack growth was observed for 1370 C flexure tests and correlated with nonlinear load deflection traces for stresses greater than 503 MPa. The crystallization of the grain-boundary glass is interpreted as beneficial to the attainment of high (1370 C) flexural strength. 20 references.

• Research Organization: NASA, Lewis Research Center, Cleveland, OH
• OSTI ID: 5400564
• Journal Information: Adv. Cer. Mat.; (United States), Journal Name: Adv. Cer. Mat.; (United States) Vol. 1; ISSN ACEME
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
360203 -- Ceramics
Cermets
& Refractories-- Mechanical Properties
ADDITIVES
CHALCOGENIDES
CRACK PROPAGATION
CRYSTAL STRUCTURE
CRYSTALLIZATION
FABRICATION
FRACTOGRAPHY
GRAIN SIZE
HOT PRESSING
MATERIALS WORKING
MECHANICAL PROPERTIES
MICROSTRUCTURE
NITRIDES
NITROGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
PNICTIDES
PRESSING
SILICON COMPOUNDS
SILICON NITRIDES
SINTERING
SIZE
TRANSITION ELEMENT COMPOUNDS
ZIRCONIUM COMPOUNDS
ZIRCONIUM OXIDES