Accession Number : ADA325790

Title :   Hot Corrosion of Nicalon Fiber Reinforced Glass-Ceramic Matrix Composites: Microstructural Effects.

Descriptive Note : Final rept.,

Corporate Author : NAVAL AIR WARFARE CENTER AIRCRAFT DIV WARMINSTER PA AIR VEHICLE AND CREW SYST EMS TECHNOLOGY DEPT

Personal Author(s) : Kowallk, R. W. ; Wang, S. W. ; Sands, R. R.

PDF Url : ADA325790

Report Date : NOV 1992

Pagination or Media Count : 24

Abstract : Continuous Nicalon fiber-reinforced calcium aluminosilicate (SiC/CAS) and lithium aluminosilicate (SiC/LAS) are two glass-ceramic composites that show promise for turbine engine applications. A study was undertaken to determine the hot corrosion resistance of these two composites. The composites were coated with 3.Omg/sq.cm. of sodium sulfate and atmospherically exposed at 900 C from 1 to 100 hours. Reactions appeared to initially occur at the exposed fibers in both systems. In the CAS system, the dissolution of the matrix occurred with the formation of CaSiO3 and NaAlSiO4. The LAS system studied (URC2OO) was doped with B2O3. Apparently the boron oxide glass reacted at 900 C and formed a protective layer around the Nicalon fiber. After exposure, two additional phases (SiO2 and an amorphous phase) in the LAS system were detected a thin surface layer of molten so appeared to have little effect on the LAS system since exposure at the same temperature without sodium sulfate produced similar microstructures and diffraction patterns. However, when the same specimen was subjected to a hot corrosion crucible test, where the specimen is completely immersed in molten salt, it was severely attacked within one hour of exposure.

Descriptors :   *CERAMIC MATRIX COMPOSITES, *CORROSION RESISTANCE, MICROSTRUCTURE, EXPOSURE(GENERAL), DIFFRACTION, SILICON CARBIDES, BORON OXIDES, SILICATES, LITHIUM COMPOUNDS, TURBINE COMPONENTS, SODIUM SULFATES.

Subject Categories : Laminates and Composite Materials

Distribution Statement : APPROVED FOR PUBLIC RELEASE