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Na 2 SO 4 deposit‐induced hot corrosion of SiC fibers relevant for SiC CMCs
Author(s) -
Herweyer Lucas A.,
Opila Elizabeth J.
Publication year - 2021
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/jace.17982
Subject(s) - tridymite , corrosion , materials science , cristobalite , fiber , porosity , layer (electronics) , oxide , metallurgy , chemical engineering , composite material , quartz , engineering
Hi Nicalon, Hi Nicalon S, Sylramic, and Sylramic iBN SiC fibers were exposed to ~60 μg/cm 2 of Na 2 SO 4 in a 0.1% SO 2 /O 2 gaseous environment for times between 0.75 and 24 h at 1000°C. After exposure, the corrosion products were characterized using SEM, EDS, ICP‐OES, TEM, and EFTEM to determine their high‐temperature resistance to Na 2 SO 4 and key reaction mechanisms. All SiC fiber types tested in this work exhibited little resistance to Na 2 SO 4 deposit‐induced attack relative to their behavior in dry O 2 environments. It was found that Hi‐Nicalon displayed the least resistance to Na 2 SO 4 deposit‐induced attack due to excess carbon content resulting in the formation of a highly porous crystalline oxide and promotion of basic corrosion conditions. All fiber types formed a crystalline SiO 2 reaction product, either cristobalite or tridymite. Sylramic and Sylramic iBN formed a crystalline SiO 2 reaction layer containing TiO 2 needles due oxidation of TiB 2 particles. Additionally, Na 2 SO 4 deposits resulted in pitting of all fiber surfaces.