Accession Number : ADA302143

Title :   The Development of an IrAl Coated SiC-C Functionally Gradient Composite for Oxidation Protection of Graphite and Carbon-Carbon Composites.

Descriptive Note : Final rept. 15 Jul 92-14 Jul 95,

Corporate Author : WASHINGTON UNIV SEATTLE DEPT OF MECHANICAL ENGINEERING

Personal Author(s) : Richards, M. R. ; Richards, A. C. ; Ohuchi, F. S. ; Taya, M.

PDF Url : ADA302143

Report Date : 27 OCT 1995

Pagination or Media Count : 48

Abstract : This report is the final summary for AFOSR project number F49620-92-J-0367. The purpose of this research was to evaluate the oxidation protection afforded to graphite or C/C composites by combining IrAl with SiC-C functionally gradient coatings FGCs. This project involved the design and construction of a novel cold wall levitation chemical vapor deposition (LCVD) reactor capable of producing continuous FGCs, and the modification of an existing physical vapor deposition (PVD) system to allow for codeposition of Ir and Al. The SiC-C FGCs were produced using the SiCl4-C3H8-H2 gas system. By continuously varying the Si to C ratio in the gas stream the composition of the coatings could be precisely controlled and tailored to fit a predetermined compositional profile. IrAl was deposited onto the SiC-C FGC by alternately depositing layers of Ir and Al and reacting them at 700 deg C, in vacuum, to form IrAl. Analysis of the as reacted film indicated that IrAl had indeed formed, however, a secondary reaction had occurred between the Ir and SiC producing IrSi3 and graphite. Cracking of the IrAl coating was also observed and was attributed to the CTE mismatch between SiC and the IrAl coating. Upon exposure to a high temperature oxidizing flame (<2100 deg C for 5 min.), the IrAl formed a protective layer of alumina, however, the extensive cracking of the IrAl layer allowed the SiC-C FGC layer to oxidize. jg p3

Descriptors :   *GRAPHITE, *CARBON, *COATINGS, *CARBON CARBON COMPOSITES, *OXIDATION, *PROTECTION, *SILICON CARBIDES, *ALUMINIDES, *IRIDIUM, LOW TEMPERATURE, LAYERS, PHYSICAL PROPERTIES, HIGH TEMPERATURE, SECONDARY, CRACKS, VACUUM, CHEMICAL VAPOR DEPOSITION, DEPOSITION, PROFILES, ALUMINUM OXIDES, FLAMES, CONTINUITY, COMPOSITION(PROPERTY), GRADIENTS, GAS FLOW.

Subject Categories : Inorganic Chemistry
      Physical Chemistry
      Coatings, Colorants and Finishes
      Laminates and Composite Materials

Distribution Statement : APPROVED FOR PUBLIC RELEASE