Study On Pressureless Sintered SiC-based Ceramic Composites And Pipes

Silicon carbon（SiC） was used as matrix material and Al₂O₃、Al₂O₃/Y2O andMullite as sintering aids, respectively. SiC-Al₂O₃、SiC-Al₂O₃/Y₂O₃and SiC-Mullitecomposite ceramic were prepared by cold isostatic pressing（CIP） followedpressureless sintering. Effects of the additiones type, sintering technology on thephase composition, microstructure, mechanical properties, thermal properties of SiCcomposite ceramic were investigated by X-ray diffraction（XRD）, scanning electronmicroscope（SEM）, Three-point bending tests, Single edge notched beammethod（SENB） and Vickers hardness.The results show that after CIP of200MPa/100s, SiC-Al₂O₃composites exhibitthe best performance at2100℃/2h. The relative density of SiC-Al₂O₃compositesincrease of Al₂O₃addition, and get the maximum of⁹3.4%when Al₂O₃contentwas20wt.%. The bending strength, fracture toughness, Young’s modulus andVickers hardness of this component was465.9MPa,8.15MPa·m1/2,502.5GPa,28.6GPa, respectively. The thermal expansion coefficient of SiC-Al₂O₃compositeswas enhanced with increasing Al₂O₃content, and the average value range from4.22⁴.65×10-6K^-1in200¹200℃.Under the same condition of CIP, in order to improve the sintering characteristics,different content of Al₂O₃/Y₂O₃were used as the sintering additives. The resultsshow that after CIP of200MPa/100s, SiC-Al₂O₃/Y₂O₃composites exhibit the bestperformance at2000℃/2h. The relative density of SiC-Al₂O₃/Y₂O₃compositesincrease of Al₂O₃/Y₂O₃addition, and get the maximum of⁹4.3%when Al₂O₃/Y₂O₃content was15wt.%. The bending strength, fracture toughness, Young’s modulusand Vickers hardness of this component was419.1MPa、8.5MPa·m1/2、313.4GPa、20GPa, respectively. The thermal expansion coefficient of SiC-Al₂O₃/Y₂O₃composites was enhanced with increasing Al₂O₃/Y₂O₃content, and the averagevalue range from4.26⁴.58×10-6K^-1in200¹200℃. For an improved machinabilityof the green body and CIP forming process, binder was introduced to the ceramicpower slurry for spray granulating. Finally, the ceramic tube with the composition of15wt.%SiC-Al₂O₃/Y₂O₃has a relative density of85%.At the last part of this study, different content of Mullite was usded as thesintering additives. SiC-Mullite composites exhitit the best performance at2000℃/1h. The relative density of SiC-Mullite composites increase with the Mulliteaddition. and get the maximum of⁹5.5%when Mullite content was40vol.%. Thebending strength, fracture toughness, Young’s modulus and Vickers hardness of this component was363.8MPa、5.14MPa·m1/2、203GPa、12.3GPa, respectively. Thethermal expansion coefficient of SiC-Mullite composites was enhanced withincreasing Mullite content, and the average value range from3.86³.97×10-6K^-1in200¹200℃.