【作者】 刘春阳；

【导师】 张力；

【作者基本信息】 东北大学 ， 冶金工程（专业学位）， 2021， 硕士

【摘要】 目前,航空发动机普遍使用具有高效气冷结构的空心叶片来提高推重比,而形成空心叶片的复杂内腔必须借助陶瓷型芯来实现。镁基陶瓷型芯高温化学稳定性好,与合金及型壳的热胀匹配性优良,使用有机弱酸脱除不会腐蚀铸件材料,未来的发展前景十分广阔。本论文着重研究了镁基陶瓷型芯和镁铝尖晶石-氧化镁复合陶瓷型芯的收缩率、显气孔率、抗热震性,并且兼顾抗弯强度和脱芯性能。实验以氧化镁和镁铝尖晶石为基体材料,添加二氧化钛作为烧结助剂,采用热压注成型法压制陶瓷生坯,常压分步烧成陶瓷型芯试样,探究了终烧温度和镁铝尖晶石对陶瓷型芯组织性能的影响。研究结论如下:(1)研究了不同脱蜡制度对陶瓷型芯成品质量的影响,确定了较佳脱蜡工艺:以1℃/min的速率升温,分别在100、300和600℃保温1h,脱蜡的陶瓷型芯样品合格率高。(2)研究了不同终烧温度对镁基陶瓷型芯组织性能的影响,确定了较佳的终烧温度为1420℃。温度升高促进了型芯致密化,在终烧温度为1420℃时型芯中产生了低熔点液相,也促进了烧结。终烧温度为1420℃时,镁基陶瓷型芯的烧结收缩率为17.70%,显气孔率为18.04%,抗热震循环次数为4次,室温抗弯强度为92.06 MPa,脱芯率为42.81%。(3)研究了不同镁铝尖晶石添加量对复合陶瓷型芯组织性能的影响,确定了较佳的镁铝尖晶石添加量为60%。添加镁铝尖晶石显著降低了复合陶瓷型芯的烧结收缩率,提高了气孔率和抗热震性,很好的解决了镁基陶瓷型芯的缺陷。镁铝尖晶石添加量为60%时,复合陶瓷型芯的烧结收缩率为1.99%,显气孔率为38.24%,抗热震循环次数为13.67次,室温抗弯强度为25.93 MPa,脱芯率为20.58%,能够满足精密铸造过程对陶瓷型芯的要求。更多还原

【Abstract】 At present,aviation engines generally use hollow blades with high-efficiency air-cooling structure to increase the thrust-to-weight rati’o,and the complex inner cavity of the hollow blades must be realized with the help of ceramic cores.Magnesium oxide ceramic cores have good high temperature chemical stability,excellent thermal expansion matching with alloy and mold shell,and the use of organic weak acid removal will not corrode the casting material,which have very broad development prospects in the future.In this paper,the shrinkage rate,apparent porosity,thermal shock resistance of magnesium-based ceramic core and MgAlO3-MgO composite ceramic core were studied,and the flexural strength and core removal performance were taken into account.In the experiment,magnesium oxide and magnesia-alumina spinel were used as matrix materials,titanium dioxide was added as sintering aid,and the ceramic green blank was pressed by hot press injection molding.After that,the ceramic core specimen was sintered step by step at atmospheric pressure,and the effect of final sintering temperature and magnesia-alumina spinel on the structure property of ceramic cores was investigated.The research conclusions are as follows:(1)The effect of different dewaxing systems on the quality of the finished ceramic cores was studied,and the better dewaxing process was determined:heating at a rate of 1℃/min,and holding at 100℃,300℃ and 600℃ for one hour respectively,and the qualified rate of ceramic core samples dewaxed under this process was high.(2)The effect of different final sintering temperatures on the structure property of magnesium-based ceramic cores was studied,and the better final sintering temperature was determined to be 1420℃.The increase of temperature promoted the densification of the core,and when the final sintering temperature was 1420 ℃,a low-melting liquid phase was generated in the core,which also promoted sintering.When the final firing temperature was 1420℃ the sintering shrinkage rate of the magnesium-based ceramic core was 17.70%,the apparent porosity was 18.04%,the number of thermal shock cycles was 4 times,the room temperature flexural strength was 92.06 MPa,and the core removal rate was 42.81.%.(3)The effect of different magnesia-alumina spinel additions on the structure property of composite ceramic cores was studied,and the better addition of magnesia-alumina spinel was determined to be 60%.The addition of magnesium-aluminum spinel significantly reduced the sintering shrinkage of the composite ceramic core,improved the porosity and thermal shock resistance,and well solved the defects of the magnesium-based ceramic core.When the addition amount of magnesia-alumina spinel was 60%,the sintering shrinkage rate of the composite ceramic core was 1.99%,the apparent porosity was 38.24%,the number of thermal shock cycles was 13.67 times,the room temperature flexural strength was 25.93 MPa,and the core removal rate was 20.58%,which could meet the requirements of the investment casting process for ceramic cores.更多还原