某飞行器鼻锥热防护结构制备加工与氧化烧蚀性能研究

发布时间：2018-08-15 16:39

【摘要】：随着高超声速飞行器飞行速度的不断提升,服役环境也越来越恶劣,为保证航天飞行器安全稳定飞行,必须开展飞行器鼻锥等关键热端部件的热防护问题的研究。作为高超声速飞行器关键热端结构件,鼻锥在飞行时将面临非常严重的气动加热,为保证高超声速飞行器的整体性能,飞行器鼻锥不允许有较大变形,因此,飞行器鼻锥热防护结构材料必须满足长时间抗氧化和耐烧蚀等性能要求。超高温陶瓷复合材料因具有耐高温、抗氧化烧蚀等优异特性,是飞行器鼻锥等关键热端部件的首选材料之一,但超高温陶瓷材料难以烧结致密化以及本征脆性等特点加大了高性能鼻锥热防护结构材料的制备和加工难度。因此,开展鼻锥热防护结构超高温陶瓷材料的制备、加工以及相关性能考核具有重要的意义。本文根据飞行器鼻锥热防护结构需求,结合飞行器鼻锥的服役特点,设计了前端呈半球状后端呈圆柱状的组合式鼻锥热防护结构,并采用ANSYS软件建立了模型,对建立的鼻锥热防护结构件模型进行了温度场分析。分析结果表明鼻尖部温度最高,并依据温度场分析结果选取鼻锥热防护材料。本文选择Zr B2-Si C-G超高温陶瓷材料作为鼻锥热防护结构材料的制备体系。采用热压烧结工艺制备材料,与以前研究不同,本次制备出了综合性能优异的大尺寸鼻锥热防护结构材料,并通过组分优化和工艺优化保证材料的致密性,以及良好的力学性能。研究了不同参数对Zr B2-20vol.%Si C-G陶瓷材料的致密度、弯曲强度和断裂韧性等性能的影响,如石墨含量、烧结温度等。试验结果表明:1900℃、30MPa和1h条件下热压烧结的Zr B2-20vol.%Si C-10vol.%G材料综合性能较为优异,其中弯曲强度为487MPa,断裂韧性为6.2MPa.m1/2,致密度为99.7%。本文采用了ELID磨削技术对该超高温陶瓷烧结,然后对材料进行加工成型,并对该热结构件磨削表面粗糙度进行正交试验,同时分析了磨削工艺参数与表面粗糙度之间的关系。试验结果表明最佳磨削工艺组合为:粒度w40#、砂轮线速度26.2m/s、磨削深度0.005mm、工件转速35r/min。同时采用超声检测(UT)和X射线检测(RT)相结合的方法对鼻锥热防护结构超高温陶瓷材料进行无损检测,检测结果表明陶瓷材料内部和表面的微观孔隙含量比较少,表明该鼻锥热结构件材料具有优异的综合性能。研究了Zr B2-20vol.%Si C-10vol.%G鼻锥热防护结构超高温陶瓷材料的抗氧化烧蚀行为。地面考核实验结果表明该鼻锥热防护结构材料的宏观形貌相对完好,能保持良好的完整性;且没有出现微裂纹,表现出较强的抗氧化烧蚀能力。同时结合鼻锥热防护结构件的地面考核实验结果,对超高温陶瓷材料进行了氧化烧蚀机理分析。
[Abstract]:With the increasing flight speed of hypersonic vehicle, the service environment is becoming worse and worse. In order to ensure the safety and stability of space vehicle, it is necessary to study the thermal protection of the key hot end parts such as nose cone. As the key hot end structure of hypersonic vehicle, nose cone will face very serious aerodynamic heating in flight. In order to ensure the overall performance of hypersonic vehicle, the nose cone is not allowed to be deformed. The thermal protection materials of the nose cone of aircraft must meet the requirements of long time oxidation resistance and ablation resistance. Because of its excellent properties of high temperature resistance, oxidation resistance and ablation, ultra-high temperature ceramic composite is one of the first choice materials for the key hot end parts such as nose cone of aircraft. However, the characteristics of ultra-high temperature ceramic materials are difficult to sintering densification and intrinsic brittleness, which makes the preparation and processing of high performance nasal cone thermal protective structure materials more difficult. Therefore, it is of great significance to prepare, process and evaluate the properties of ultra-high temperature ceramic materials for the thermal protection structure of nasal cone. According to the requirements of the thermal protection structure of the nose cone of the aircraft and the service characteristics of the nose cone of the aircraft, the combined structure of the thermal protection of the nose cone with a cylindrical front end is designed, and the model is established by using ANSYS software. The temperature field of the thermal protection structure model of nasal cone is analyzed. The results show that the temperature of nasal tip is the highest, and the thermal protection material of nasal cone is selected according to the results of temperature field analysis. In this paper, Zr B2-Si C-G ultrahigh temperature ceramic material is selected as the preparation system of the thermal protection structure material of nasal cone. The hot pressing sintering process was used to prepare the materials. Different from the previous research, a large size thermal protection structure material with excellent comprehensive properties was prepared, and the densification of the material was ensured by component optimization and process optimization. And good mechanical properties. The effects of different parameters on the density, bending strength and fracture toughness of Zr B2-20vol.%Si C-G ceramics were studied, such as graphite content, sintering temperature and so on. The experimental results show that the composite properties of Zr B2-20vol.%Si C-10vol.%G sintered at 30 MPA at 1: 1900 鈩，

本文编号：2184796