Study On Prearation Technology And Properties Of Si₃N₄-SiC Composite Sintered In Oxidating Atmosphere

Silicon carbide bonded silicon nitride(Si₃N₄-SiC) is one kind of high-tech SiCrefractories developing in recent twenty years in china. But it is restricted itsdevelopment by its high production cost fatly, and become the bottleneck of this industry.In this papers by means of "inverse reaction sintering" theory, them were studied thatpreparing Si₃N₄-SiC complex material with simple technology and low cost, moundingand firing technology, besides, and good preparing technology was generalized too.Experiments ware designed by orthogonal design about the effect of formingpressure, grain composition and agglomerate's addition in forming quality of samplesand the results were analyzed. The results showed that forming pressure's effect was thebiggest; grain composition was the second, agglomerate's addition was the least. Thesamples were achieved good forming quality under the condition that forming pressurewas 20MP, grain composition was coarse granule: middle particle: fine particle=60:20:20,agglomerate's addition was 4.5%.The rational firing system was also the key element of sintering Si₃N₄-SiCcomposite materials in oxidizing atmosphere. The performance of samples was goodunder the fire condition that heating rate was 6℃/min, the course of moderatetemperature insulation was 1400℃×8h, the course of sintering was 1450℃×2h., the bestaddition of Si₃N₄ was 10%. The cold bend strength, obvious porosity and volume densitychange rate of samples were 55.2 MP, 7.1%, 1.9% respectively.Them were studied in this paper too that covered with carbon, comparison in coldbend and high temperature strength, splat cooling treating, oxidation resistance, thermalshock resistance and erosion resistance of samples which were prepared with the goodpreparation technology. Microstructure and crystal phase of the samples were studiedwith X-ray diffraction (XRD) and Field emission scanning electron microscope(FE-SEM). The results showed that the performance of samples sintered in oxidizingatmosphere was obviously better than that sintered in burying charcoal atmosphere. Thehigh temperature(1400℃) strength of samples was rather more than their cold bendstrength. After quenching treatment, the strength of samples enhanced relatively, up 18.4%. The samples had better oxidation resistance, after oxidation treatment. 1000℃×60h, themass addition of samples only was 0.32mg/cm². The conservation rate of strength was75% after the heat shock resistance experiment under 1200℃-room temperature. Inoxidizing atmosphere, Si₃N₄-SiC composite materials sintered in oxidizing atmospherehave better properties of cryolite, Al and Mg erosion-resisting. But Cu erosion-resistingproperties were better in burying charcoal than that of them in oxidizing atmosphere.