大尺寸碳化硅结构陶瓷件制备研究

发布时间：2018-04-14 16:31

本文选题：碳化硅 + 大尺寸　；参考：《北京科技大学》2015年博士论文

【摘要】：大尺寸碳化硅结构陶瓷件在许多特殊工况及部位具有迫切的应用需求。本文结合行业需求,选取耐腐蚀、耐磨损特种离心泵用大尺寸、复杂形状碳化硅陶瓷叶轮作为对象展开研究工作。论文的主要内容包括以下几个方面：将造粒技术引入到凝胶注模成型技术中,通过喷雾造粒和压块造粒使初始亚微米级碳化硅粉末平均粒径由0.51μ m粗化至40μ m和8.2μ m,显著降低了陶瓷浆料的粘度。由喷雾造粒和压块造粒配制的陶瓷浆料(50vo1%,剪切速率为100s-1)粘度分别为未造粒粉末浆料的1/2.5和1/3.5。压块造粒粉末配制的浆料粘度比喷雾造粒粉末浆料低58mPa·s。喷雾造粒和压块造粒粉末制备的凝胶注模生坯弯曲强度分别达到未造粒粉末生坯的3倍和3.5倍。存在于生坯和浆料中的造粒粉末团粒在烧结过程中彻底消失,两种造粒粉末制备的烧结样品弯曲强度达到了相同的水平,均为未造粒级粉末烧结样品的2.2倍。采用凝胶注模工艺制备了短切碳纤维增强增韧的固相烧结碳化硅复合陶瓷材料(Csf/SiC)。随着Csf添加量的增加,凝胶注模浆料的粘度单调增高；弯曲强度和断裂韧性均为先增高后降低,当5wt%Csf时弯曲强度达到最大值420MPa,比纯碳化硅材料弯曲强度提高80MPa,比模压成型复合材料弯曲强度最大值高30MPa；而断裂韧性在7.5wt.%Csf时达到最大值4.61MPa·m1/2,比纯碳化硅材料断裂韧性提高0.88MPa·m1/2,比模压成型复合材料断裂韧性局0.4MPa·m1/2,主要增韧增强机制为纤维拔出和纤维断裂,其中凝胶注模中的有机物裂解产生的裂解碳包裹在碳纤维表面,对纤维增强增韧效果具有促进作用。采用凝胶注模成型大尺寸、复杂形状碳化硅陶瓷叶轮,利用造粒技术粗化初始粉末,显著降低了浆料的粘度,经叶轮结构特征优化和模具设计,控温控湿干燥及湿坯受力状态平衡控制,抑制了干燥裂纹的产生；经烧结支撑设计和温度场控制,克服烧结变形问题,最终制备出复杂形状陶瓷叶轮样品(160mm),材料相对密度达96%,密度偏差0.5%,弯曲强度为420MPa。用户耐磨损性能台架对比试验表明,本文研制的陶瓷叶轮磨损率仅为厂家主导产品超高分子量聚乙烯叶轮的1/l0。目前尚未见到该类大尺寸固相烧结体系碳化硅陶瓷叶轮产品及制备技术的相关报道。
[Abstract]:Large-size silicon carbide structure ceramic parts have urgent application needs in many special working conditions and parts.In this paper, the large size and complex shape of silicon carbide ceramic impeller for special centrifugal pump with corrosion resistance and wear resistance is selected as the research object.The main contents of the thesis include the following aspects:The granulation technology was introduced into the gel injection molding technology. The average particle size of the initial submicron silicon carbide powder was coarsened from 0.51 渭 m to 40 渭 m and 8.2 渭 m by spray granulation and pressing granulation, which significantly reduced the viscosity of the ceramic slurry.The viscosity of ceramic slurry prepared by spray granulation and press granulation is 1 / 2.5 and 1 / 3.5of that of ungranulated powder size, respectively, with shear rate of 100s-1.The viscosity of the slurry prepared by pressing granulated powder is lower than that of spray granulated powder size, 58mPa s.The bending strength of the gel injection mould blank prepared by spray granulation and pressing granulation powder is 3 and 3.5 times of that of the ungranulated powder blank, respectively.The sintering strength of the sintered samples prepared by the two kinds of granulated powders has reached the same level, and the bending strength of the sintered samples is 2.2 times of that of the ungranulated powder sintered samples.The short cut carbon fiber reinforced and toughened solid phase sintered silicon carbide composite ceramic material was prepared by gel casting process.With the increase of Csf content, the viscosity of gel casting paste increases monotonously, and the bending strength and fracture toughness increase first and then decrease.The maximum bending strength of 5wt%Csf is 420 MPA, which is 80 MPA higher than that of pure silicon carbide, and 30 MPa higher than the maximum bending strength of molded composites, while the fracture toughness of 7.5wt.%Csf reaches the maximum value of 4.61MPa M1 / 2, which is higher than that of pure silicon carbide.To improve the fracture toughness of 0.88MPa M1 / 2, compared with 0.4MPa M1 / 2, the main toughening and reinforcing mechanisms are fiber pull-out and fiber fracture.The pyrolytic carbon produced by the organic cracking in the gel casting mold is wrapped on the surface of carbon fiber, which can promote the reinforcing and toughening effect of the fiber.The large size and complex shape silicon carbide ceramic impeller was molded by gel injection, and the initial powder was coarsened by granulating technology. The viscosity of the slurry was significantly reduced, and the impeller structure was optimized and die design was carried out.Temperature-controlled wet drying and force balance control of wet billet can restrain the production of drying crack and overcome the problem of sintering deformation through sintering support design and temperature field control.Finally, the ceramic impeller sample with complex shape was prepared. The relative density of the material was 96, the density deviation was 0.5 and the bending strength was 420 MPA.The wear resistance of the ceramic impeller developed in this paper is only 1 / 10 of that of the UHMWPE impeller produced by the manufacturer.At present, there are no reports on the product and preparation technology of silicon carbide ceramic impeller for this kind of large scale solid-phase sintering system.
【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TQ174.7

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