High-temperature gaseous corrosion of Si[sub 3]N[sub 4] in H[sub 2]-H[sub 2]O and Ar-O[sub 2] environments

Journal Article · Mon Oct 01 00:00:00 EDT 1990 · Journal of the American Ceramic Society; (United States)

OSTI ID:7165592

Kim, Hyounee; Moorhead, A J ^[1]

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1. Oak Ridge National Lab., TN (United States)

Samples of Si[sub 3]N[sub 4] made by chemical vapor deposition (CVD) and hot isostatic pressing (HIP) were exposed for 10 h at 1,400C to H[sub 2]-H[sub 2]O and Ar-O[sub 2] environments. Variations in weight and surface morphology of the CVD-Si[sub 3]N[sub 4] samples were monitored to determine the corrosion behavior of pure' Si[sub 3]N[sub 4] as baseline information. Additionally, the room-temperature flexural strengths of the HIP-Si[sub 3]N[sub 4] were determined and correlated with observed changes in weight and microstructure. The corrosion behavior of both materials depended on the level of oxidant (H[sub 2]O or O[sub 2]) in the atmosphere, but the magnitudes of the weight changes observed in the HIP-Si[sub 3]N[sub 4] were significantly greater. When the P[sub H[sub 2]O] in the H[sub 2] atmospheres was low (P[sub H[sub 2]O] < 2 [times] 10[sup [minus]5] MPa), significant weight loss and surface degradation occurred in both ceramics, accompanied by reductions in strength of the HIP-Si[sub 3]N[sub 4]. However, in atmospheres with P[sub H[sub 2]O] [ge] 1 [times] 10[sup [minus]4] MPa, the weight was greater than that of the as-received material. Somewhat different behavior was observed in samples exposed to Ar-O[sub 2] environments. Weight loss of both silicon nitrides increased with increasing P[sub O[sub 2]] until a level of about 2 [times] 10[sup [minus]5] MPa was reached. However, contrary to the results for H[sub 2]-H[sub 2]O exposures, even under these conditions the strength of the HIP-Si[sub 3]N[sub 4] material was found to have increased above that of the as-received material.

• DOE Contract Number: AC05-84OR21400
• OSTI ID: 7165592
• Journal Information: Journal of the American Ceramic Society; (United States), Vol. 73:10; ISSN 0002-7820
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
SILICON NITRIDES
CORROSION
AMBIENT TEMPERATURE
CHEMICAL VAPOR DEPOSITION
CORRELATIONS
CORROSIVE EFFECTS
EXPERIMENTAL DATA
FLEXURAL STRENGTH
HOT PRESSING
HYDROGEN
LOSSES
MICROSTRUCTURE
MORPHOLOGY
OXYGEN
SURFACES
VARIATIONS
WEIGHT
CHEMICAL COATING
CHEMICAL REACTIONS
CRYSTAL STRUCTURE
DATA
DEPOSITION
ELEMENTS
FABRICATION
INFORMATION
MATERIALS WORKING
MECHANICAL PROPERTIES
NITRIDES
NITROGEN COMPOUNDS
NONMETALS
NUMERICAL DATA
PNICTIDES
PRESSING
SILICON COMPOUNDS
SURFACE COATING
360205* - Ceramics
Cermets
&amp; Refractories- Corrosion &amp; Erosion