Diffusion interaction in fiber-reinforced composites of the chromium alloy - Silicon carbide system

Diffusion interaction in the Cr - ZrC and Cr - HfC systems has been studied in the temperature range 1200-1400degreesC. The impurities contained in chromium or carbides were found to affect the interaction in the systems. Almost no interaction was observed when the systems were held at temperatures up to 1300degreesC for 100 h. At higher temperatures the carbides were reduced to ZrO2, HfO2, and Cr23C6 because of the presence of a slight amount of oxygen. Thermodynamic calculations indicated no interaction in these systems at temperatures up to 1600degreesC. A study of the interaction in the systems SiC - ZrC and SiC - HfC showed that a transition zone formed already in the stage of sample preparation by diffusion welding in vacuum (1300degreesC, vacuum of 10(-3) Pa, with a load applied for 20 min). During annealing (1300degreesC, 50 h) the transition zone stratified, forming a solid solution of silicon in Zr(Hf)C and SiC inclusions in the SiC - Zr(Hf)C solid solution. A transition zone formed on the zirconium carbide side when SiC interacted with Zr(Hf)C. The interaction in SiC - Zr(Hf)C casts doubt on the use of them as a barrier without antidiffusion layers.