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.