Mechanical Properties and Microstructure of Extruded SiC Ceramics

Silicon carbide tube was extruded and pressureless-sintered using hydroxypropyl methylcellulose(HPMC) as the main organic plasticizer.The effect of HPMC contents on the properties of the sintered SiC tubes and the microstructure evolution in the different sintering system were systematically studied.The results show that the radial crushing strength of SiC green bodies increases with increasing HPMC content while the average radial crushing strength obtain maximum of 462MPa with 7.5wt% HPMC.The relative density of the SiC tube sintered at 2200℃ and hold for 1h changes little with different content of HPMC obviously.The density of the sintered SiC tube in two-step sintering method increases from 3.00g/cm3 to 3.07g/cm3,and the average radial crushing strength and relative density reach 540MPa and 95.9%,respectively.The microstructure of the chemical etched surface indicate the abnormal growth of the SiC particles and the appearance of the plate-like grains.