Research On The Preparation Technology And Application Of Ceramic With The Properties Of Thermal Shock-Wear Resistance

Aiming at the problem that ceramics used in the liner of slurry pump need boththermal shock and wear resistance, three ceramic series namly SiAlON, SiAlON/SiC,ZrO₂/Al₂O₃have been designed to fabricate the materials of thermal shock resistance.Orthogonal experimental design is used in this experiment; specimens are fabricated bycold isostatic pressing and pressureless sintering; effects of the sintering powder bed,sintering temperature, SiC content and heat treatment’s temperature on microstructure andproperties of the composites have been systematically investigated by XRD, SEM, EDS,etc. At last, thermal shock resistance is tested by molten steel casting.The results shows that SiAlON ceramic series specimens which sintered in Si3N4powder bed have higher density, weight loss rate and shrinkage than others. Due to it isclose to the decomposing limit in pressureless sintering circumstance, Si3N4decompositioneasily and possibly. The decomposition of Si3N4powder bed improves the specimenssintering atmosphere, which can inhibit further decomposition of the nitrogenouscompounds in the ceramic green. XRD results showed that Si-Al-O-N has existed in thespecimens sintered in1800℃, however, it has not appeared below1800℃. SEM resultsshowed that specimens sintered in1750℃are density higher and pore less. Specimenssintered in1800℃which appeared SiAlON columnar grain obviouslyare grain combinedbetter.The results of SiAlON/SiC ceramic series shows that SiC particle’s content, sinteringtemperature and heat treatment’s temperature have important effects on shrinkage, density,weight loss rate and columnar grain formation. The result of orthogonal experimentaldesign showed that rdial shrinkage and axial shrinkage are all decreased with the theincreasing of SiC. Their density increase first then decrease, and weight loss rate just do the opposite. Microstructure is dense and homogeneous at the content of5wt%SiC;columnar SiAlON diameter decreased with the increasing of SiC. With the increasing ofsintering temperature, rdial shrinkage increase first then decrease, and axial shrinkage justdo the opposite. The highest density happens at1800℃, weight loss rate decreased withthe increasing of sintering temperature; microstructure is dense and homogeneous,columnar grain is longer and thicker. Columnar grain can be kept when heat treatment at1000℃and1250℃, and it is oxidated at1500℃.The ZrO₂/Al₂O₃ceramic series results shows that some of ZrO₂combined with Al₂O₃forms ZrO₂/Al₂O₃solid solutions, and the others form particles which are distributed ongrain boundaries and matrixes with different shapes. Those ZrO₂particles locating in theboundaries enhance the ceramic’s toughness by two modes: fracturing and tearing, andwhich one to be occur depends on the location relationship between load and boundaryinterface. The composition transition, i.e. the solid solution consisting of ZrO₂/Al₂O₃hasformed encircling ZrO₂particles, and it has a positive contribution to ceramics toughnessthrough the combination of chemical bond.Thermal shock resistance results shows that all of the ZrO₂/Al₂O₃specimens arecracked. It can validate that the material are unsuitability to the casting process; M31, M33,M34of SiAlON and N122, N133, N223, N321of SiAlON/SiC series are not cracked,which can fit the casting process. It is found that columnar grain SiAlON is benefit fordeveloping thermal shock resistance after analyse the test results of thermal shockresistance. Due to SiC particles added in, SiAlON/SiC have better thermal shockresistance.