Effect of positioning impregnation on the oxidation behaviour of Ti₃SiC₂/SiC functionally graded materials at 1400 °C

Ti₃SiC₂/SiC functionally graded materials (FGMs) were prepared by hot pressing/positioning impregnation. Positioning impregnation is a novel local impregnation technique targeted at layers exhibiting poor sintering behaviour. Due to the densification effect of positioning impregnation, the density of the FGM hot pressed at 1600 °C increased from 3.47 to 3.79 g/cm³, and the open porosity decreased from 11.2% to 1.98%. The oxidation resistance of the FGM hot pressed at 1600 °C and then positioning impregnated was significantly improved, and a mass gain percentage of only 12.9% after oxidation at 1400 °C for 20 h was observed. This gain was 45% and 20% lower than those of the unimpregnated FGMs hot pressed at 1600 and 1800 °C, respectively, and 39% lower than that of the Ti₃SiC₂/30% SiC (mass fraction) composite. For the unimpregnated FGM, the central transition layers showed the best oxidation resistance, whereas the pure SiC and pure Ti₃SiC₂ layers at both ends showed poor oxidation resistance. For the impregnated FGM, the higher the SiC content in the layer, the better the oxidation resistance.