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SiC and Si3N4 Recession Due to SiO2 Scale Volatility Under Combustor ConditionsSiC and Si3N4 materials were tested under various turbine engine combustion environments, chosen to represent either conventional fuel-lean or fuel-rich mixtures proposed for high speed aircraft. Representative CVD, sintered, and composite materials were evaluated in both furnace and high pressure burner rig exposure. While protective SiO2 scales form in all cases, evidence is presented to support paralinear growth kinetics, i.e. parabolic growth moderated simultaneously by linear volatilization. The volatility rate is dependent on temperature, moisture content, system pressure, and gas velocity. The burner tests were used to map SiO2 volatility (and SiC recession) over a range of temperature, pressure, and velocity. The functional dependency of material recession (volatility) that emerged followed the form: exp(-QIRT) * P(exp x) * v(exp y). These empirical relations were compared to rates predicted from the thermodynamics of volatile SiO and SiO(sub x)H(sub Y) reaction products and a kinetic model of diffusion through a moving, boundary layer. For typical combustion conditions, recession of 0.2 to 2 micron/h is predicted at 1200- 1400C, far in excess of acceptable long term limits.
Document ID
19990062338
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Smialek, James L.
(NASA Lewis Research Center Cleveland, OH United States)
Robinson, R. Craig
(NASA Lewis Research Center Cleveland, OH United States)
Opila, Elizabeth J.
(NASA Lewis Research Center Cleveland, OH United States)
Fox, Dennis S.
(NASA Lewis Research Center Cleveland, OH United States)
Jacobson, Nathan S.
(NASA Lewis Research Center Cleveland, OH United States)
Date Acquired
August 19, 2013
Publication Date
January 1, 1999
Publication Information
Publication: Advanced Composite Materials
Publisher: VSP
Volume: 8
Issue: 1
Subject Category
Inorganic And Physical Chemistry
Meeting Information
Meeting: Processing and Testing on CMC Parts, Components and Pieces
Location: Tajimi
Country: Japan
Start Date: September 11, 1998
End Date: September 12, 1998
Distribution Limits
Public
Copyright
Other

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