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Effects of Sodium Silicate Exposure at High Temperature on Sintered α‐Silicon Carbide and Siliconized Silicon Carbide
Author(s) -
Butt Darryl P.,
Mecholsky J. J.,
Goldfarb Victor
Publication year - 1989
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.1151-2916.1989.tb06294.x
Subject(s) - silicon carbide , materials science , silicon , metallurgy , dissolution , grain boundary , carbide , corrosion , silicate , mineralogy , chemical engineering , microstructure , chemistry , engineering
Sintered α‐silicon carbide and siliconized silicon carbide were exposed to combustion off‐gas containing sodium silicate vapors and particulates in a combustion test facility for 24 to 373 h at 900° to 1050°C. Degradation was evaluated by measuring dimensional changes, by measuring loss in strength due to changes in flaw population, and by evaluating surface corrosion morphology. It is suggested that passive oxidation and dissolution of the silica oxidation scale play an important role in the corrosion process. These mechanisms were enhanced by the continuous removal and replenishment of corrosive material by the high‐velocity gas. These degradation phenomena caused surface pitting and an approximately 50% reduction in strength for both materials after long‐term exposure (>100 h). Morphological evaluation suggested that the grain boundaries in the α‐silicon carbide were oxidized more rapidly than the grains, while for the case of the siliconized silicon carbide the silicon phase was oxidized rapidly along with preferential oxidation of the silicon carbide grains parallel to the {0001} plains.