IMPROVEMENT OF OXIDATION RESISTANCE OF CA RBON CARBON COMPOSITES BY THE MULTILAYER CVD COATING TECHNIQUE/

Carbon/carbon composites are promising material for use at ultra high temperature in gas turbines, space plane airframes and engines because of their low density and high thermal resistance. However, one of the problems with carbon/carbon composites is their low oxidation resista nce. In this study, multi-layer coated carbon/carbon composites by the CVD technique were developed to improve the oxidation resistance. Fou r kinds of multi-layer coating with TiC and SiC were applied to carbon /carbon composites by the CVD technique and the oxidation resistance w ere evaluated in air at high temperatures. In multi-layer-coated carbo n/carbon composites with thin TIC layer, cracks in the coating layer w ere far narrower than those in the single-layer-coated carbon/carbon c omposites. As results of oxidation tests at 1773 K and 1273 K, the mul ti-layer-coated carbon/carbon composites showed much better oxidation resistance than the single-layer coated carbon/carbon composites. This improvement is thought to be caused by two reasons; (1) in multi-laye r coated carbon/carbon composites, the cracks of the coating-layer clo se at much lower temperature than in singlelayer coated carbon/carbon composites. (2) TiO2 produced by oxidation of TiC in multi-layer coati ng seals the cracks of the coating-layer.