原位SiC结合刚玉基材料抗氧化与抗侵蚀性研究

【作者】 谷晓雷；

【导师】 钟香崇；

【作者基本信息】 郑州大学 ， 材料学， 2009， 硕士

【摘要】 以矾土基高铝刚玉颗粒为骨料,电熔白刚玉细粉和α-Al₂O₃微粉为基质,将Si引入到刚玉基材料中去,于1450℃埋碳条件下合成了原位SiC结合刚玉基复合材料,研究复合材料的常温物理性能、高温机械性能和抗氧化性,并重点研究其抗侵蚀性。探讨了SiC、SiAlON和Al粉对原位SiC结合刚玉材料组成、结构和性能的影响。结果表明:（1）在刚玉材料中加入Si粉,材料在1450℃保温3h埋碳条件下烧结良好。Si与气氛中的CO和N₂原位反应生成纤维状、粒状SiC和SiAlON等,形成了非氧化物结合,为反应烧结。复合材料具有较高的高温强度和良好的抗热震性,1400℃的高温抗折强度为9～12MPa;△T=1100℃（水冷一次）的残余强度和强度保持率为11～19MPa和35～64%。随Si加入量增加,非氧化物生成量增加,高温抗折强度和抗热震性略有提高。（2）在加入2～8%Si粉的基础上,再加5%SiC粉和5%β-SiAlON粉可提高材料的高温抗折强度和抗热震性,且加入SiC可明显提高抗热震性,加入β-SiAlON可显著提高高温抗折强度。在加5%Si粉的基础上,加入1～3%的Al粉,试样于1400℃高温抗折强度显著提高（提高至21MPa）,且保持了优良的抗热震性。（3）原位SiC结合刚玉基材料具有良好的抗氧化性,其在1000℃和1500℃下的抗氧化性均随Si加入量的增加而提高,且1500℃的抗氧化性略好于1000℃的。这是由于:在1000℃下,少量非氧化物发生氧化,氧化产物为SiO₂和Al₂O₃;1500℃下,非氧化物先氧化生成SiO₂和Al₂O₃,SiO₂和Al₂O₃进一步反应生成莫来石,并形成莫来石致密层,阻止氧气进入试样内部。在加5%Si粉的基础上加入Al粉,试样1000℃和1500℃的抗氧化性略有提高。（4）原位SiC结合刚玉基材料对碱度为1.1的高炉渣具有良好的抗侵蚀性（1500℃）,侵蚀层厚度≤2.6mm。在加2～8%Si粉的基础上,再加入5%SiC和5%β-SiAlON,材料中非氧化物的量增加,抗侵蚀性明显提高,渣侵蚀厚度最低降至1.0mm左右。在加5%Si粉的基础上,再加入1～3%Al粉,材料的抗侵蚀性略有提高,侵蚀层厚度从2.5mm降至1.9mm。（5）原位SiC结合刚玉基材料的抗侵蚀机理为:高温下材料基质中的SiC和SiAlON等非氧化物氧化生成SiO₂和Al₂O₃,SiO₂和Al₂O₃与熔渣中CaO与SiO₂以及基质中的Al₂O₃反应生成低熔相钙长石（CAS₂）,使材料逐渐被熔蚀;熔渣侵蚀刚玉颗粒时CaO与Al₂O₃反应生成高熔点的CA₆晶体在颗粒表面固定下来,阻挡了进一步侵蚀。侵蚀过程中CaO大量消耗,致使渣粘度增大,削弱了其侵蚀渗透能力。渗透层中仍存在一定量的非氧化物,由于非氧化物难被熔渣润湿,且原位生成的非氧化物填充在气孔里,堵塞了熔渣渗透的主要通道。因此,随Si或Al加入量增加以及外加SiC和SiAlON,材料中非氧化物的量增加,抗侵蚀性明显提高。更多还原

【Abstract】 In-situ SiC bonded Al₂O₃ based materials are prepared by using bauxite based corundum （as aggregates）, fused corundum （as fines）, ultra fineα-Al₂O₃ and silicon powder as starting materials and fired at 1450℃in carbon embedded condition. The physical properties, high temperature mechanical properties, oxidation resistance and corrosion resistance have been studied. The effects of SiC, SiAlON and Al addition on the phase composition, microstructure and properties of in-situ SiC bonded corundum based materials have been discussed in this thesis. The results indicated that:（1） When the silicon powder is added into Al₂O₃ based materials, after forming and firing at 1450℃for 3 hours in carbon embedded condition, the specimens are well sintered. Si reacted with CO and N₂ to in-situ formed fibrous or granular SiC and SiAlON. The sintering mechanism of the composites is nonoxides bonded reaction sintering. These composite materials possess high hot temperature strength and good thermal shock resistance, the hot modulus of ruputure （HMOR） at 1400℃is 9～12MPa; the residual strength ratio after one thermal shock atΔT=1100℃（water cooling） is 35～65% and residual strength is 10.8～18.8MPa.（2） On the basis of 2～8% Si addition, 5% SiC and 5% SiAlON addition can increase HMOR and TSR. SiC addition would contribute to increase in TSR noticeably and SiAlON addition would contribute to increase in HMOR. When 5% Si and 1～3% Al are simultaneously addition, HMOR increases noticeably （maximum 21.0MPa） and TSR is relatively good.（3） The in-situ SiC bonded Al₂O₃ baesd materials exhibit good oxidation resistance, and the oxidation resistance performance was improved at 1000℃and 1500℃along with the addition of Si. The oxidation resistance at 1500℃is better than that of at 1000℃, it is because oxidation productions, SiO₂ and Al₂O₃, of non-oxide materials formed dense mullite protective layer at 1500℃, which inhibite the penetration of O₂. On the basis of adding 5% Si, the oxidation resistance would be improved slightly with further addition of Al.（4） The composite materials exhibit good corrosion resistance at 1500℃, the thickness of corrosion layer is less than 2.6mm. On the basis of adding 2～8% Si, the corrosion resistance would be improved obviously with further addition of 5% SiC andβ-SiAlON, because of the increased amount of nonoxide. The thickness of corrosion layer is less than 1.0mm. On the basis of adding 5% Si, the corrosion resistance would be improved slightly with further addition of 1～3% Al. The thickness of corrosion layer is decreases from 2.5mm to 1.9mm.（5） The corrosion mechanism is: SiC and SiAlON reacted with O₂ and the production were SiO₂ and Al₂O₃. CaO reacted with SiO₂ and Al₂O₃ to form CAS2, then the matrix was corroded because the melting point of CAS2 is very low, CaO reacted with Al₂O₃ grains to form CA₆, and the corrosion retarded because of the high melting point of CA₆. Viscosity of slag increased because of CaO consumed quickly, then the corrosion and penetration ability of slag were rapidly decreased. There were certain amount nonoxide materials in the penetration layer, they existed in the hole and blocked the entrance of slag penetrating. With further addition of Si, Al, SiC or SiAlON, nonxides content increases in the matrix, so the corrosion resistance is improved obviously.更多还原