High-temperature compatibility between vapor-deposited SiC filaments and titanium

Abstract

High-temperature compatibility between vapor-deposited, silicon carbide filaments and commercially-pure titanium was studied for the temperature range 650 to 1050°C. Diffusion of carbon and silicon into the matrix and the diffusion of titanium into the filament produced distinct reaction zones for the temperature range studied. Reaction-zone widths for the temperature range 700 to 1050°C increased with time and temperature according to the expression: log 10 (x/t 1 2 ) = −2·347 − 3980/T where x = zone width in centimeters, t = time in seconds, and T = absolute temperature in °K. Apparent activation energy for the diffusion reaction is 36·5 kcal/mole. Microprobe analysis suggested the predominant compounds formed in the reaction zone are TiC and Ti 5Si 3. Electron diffraction studies verified, however, only the presence of TiC. Formation of TiC particles outside the reaction zone at 1050°C indicated that the reaction process may be altered at temperatures of 1050°C and above by the diffusion of appreciable amounts of carbon into the matrix. Since it appeared that the tungsten core of the filament begins to react with the silicon carbide at some temperature between 950 and 1050°C, the use of silicon carbide reinforced titanium may not be practical for applications where temperatures exceed about 950°C.