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High‐Temperature Gaseous Corrosion of Si 3 N 4 in H 2 –H 2 O and Ar–O 2 Environments
Author(s) -
Kim HyounEe,
Moorhead A. J.
Publication year - 1990
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1990.tb06708.x
Subject(s) - microstructure , hot isostatic pressing , silicon nitride , flexural strength , materials science , corrosion , atmosphere (unit) , nitride , ceramic , analytical chemistry (journal) , silicon , chemistry , metallurgy , mineralogy , composite material , environmental chemistry , physics , layer (electronics) , thermodynamics
Samples of Si 3 N 4 made by chemical vapor deposition (CVD) and hot isostatic pressing (HIP) were exposed for 10 h at 1400°C to H 2 –H 2 O and Ar–O 2 environments. Variations in weight and surface morphology of the CVD‐Si 3 N 4 samples were monitored to determine the corrosion behavior of ‘pure’ Si 3 N 4 as baseline information. Additionally, the room‐temperature flexural strengths of the HIP‐Si 3 N 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 2 O or O 2 ) in the atmosphere, but the magnitudes of the weight changes observed in the HIP‐Si 3 N 4 were significantly greater. When the P H2O in the H 2 atmospheres was low ( P H2O < × 10 −5 MPa), significant weight loss and surface degradation occurred in both ceramics, accompanied by reductions in strength of the HIP‐Si 3 N 4 . However, in atmospheres with P H2O 1 × 10 −4 MPa, the weight loss was smaller and the strength of the HIP‐Si 3 N 4 was greater than that of the as‐received material. Somewhat different behavior was observed in samples exposed to Ar–O 2 environments. Weight loss of both silicon nitrides increased with increasing P o2 until a level of about 2 × 10 −5 MPa was reached. However, contrary to the results for H 2 –H 2 O exposures, even under these conditions the strength of the HIP‐Si 3 N 4 material was found to have increased above that of the as‐received material.