钛合金表面微弧氧化与溶胶凝胶法制备高发射率涂层

发布时间：2018-03-22 01:06

  本文选题：复合膜层　切入点：发射率　出处：《哈尔滨工业大学》2011年硕士论文　论文类型：学位论文

【摘要】：当飞行器在大气中作超音速飞行时,由于气体粘性作用,其外表面高速气流会受到压缩和摩擦而形成气动加热,在飞行器表面产生高温和温度梯度,高温不断由飞行器外表面向结构内部传递,从而导致飞行器外形及结构强度和刚度的改变,并产生热应变还会产生材料烧蚀等现象,对飞行器的正常飞行造成严重影响。同时所产生的热量向飞行器内部传送,引起飞行器内部温度升高,造成内部工作环境恶化。本论文通过在钛合金表面用微弧氧化法与溶胶凝胶法制成高发射率涂层提高钛合金的高温抗氧化性能并使飞行器表面蒙皮的热量通过辐射传热的方式及时发散,使飞行器表面温度降低。 以Na_3P_O4为电解液体系的主盐,选择钛合金TC4为基体,电源输出电压为460V,脉冲频率60HZ,占空比45%,氧化时间15min,通过在7g/L-16g/L范围内改变电解液Na_3PO_4的浓度来制备了微弧氧化陶瓷膜层厚度在5-20μm范围内可控的陶瓷膜层样片。通过XRD测试分析发现经过700℃煅烧之后,陶瓷膜层中除了锐钛矿TiO2相,又产生了少量的金红石TiO_2相。对陶瓷膜层进行剪切强度测试以及发射率测试,发现随着膜层厚度的增加,剪切强度降低。在5-20μm范围内剪切强度都大于15MPa,满足膜层使用条件要求。陶瓷膜层发射率随膜层厚度变化的规律呈现为:先增大,增大到一定值之后,又开始减小。 采用旋涂法在陶瓷层表面涂覆溶胶凝胶膜层,再经过700℃高温煅烧,形成复合膜层。对不同复合膜层进行XRD分析,相比陶瓷膜层分别多了CuO、Cr_2O_3、CoTiO_3、CaCu_3Ti_4O_(12)的物相。对复合膜层的剪切强度及其发射率进行了探讨,发现复合膜层与基体之间的结合强度都比较高,而且与陶瓷膜层剪切强度相近。复合膜层的发射率相比陶瓷膜层的发射率有了明显的提高,其中含过渡金属Cr的复合膜层3-8μm波段的发射率达到0.7以上,8-20μm波段的发射率达到0.9以上。
[Abstract]:When the aircraft is flying at supersonic speed in the atmosphere, the high velocity airflow on the outer surface will be compressed and rubbed to form aerodynamic heating due to the viscous effect of the gas, which will produce high temperature and temperature gradient on the surface of the aircraft. The high temperature is continuously transferred from the exterior of the aircraft to the interior of the structure, which leads to the change of the shape, strength and stiffness of the aircraft, and the thermal strain will also produce the phenomenon of material ablation, etc. It has a serious impact on the normal flight of the aircraft. At the same time, the heat generated is transmitted to the interior of the aircraft, causing the internal temperature of the aircraft to rise. In this paper, the high emissivity coating was prepared on the surface of titanium alloy by micro-arc oxidation and sol-gel method to improve the oxidation resistance of titanium alloy at high temperature and make the heat of the skin of aircraft surface pass through the radiations. The mode of heat transfer in a timely manner, Reduce the surface temperature of the aircraft. Taking Na_3P_O4 as the main salt of electrolyte system, choosing titanium alloy TC4 as matrix, The output voltage of the power supply is 460V, the pulse frequency is 60HZ, the duty cycle is 45Hz, and the oxidation time is 15min. By changing the concentration of electrolyte Na_3PO_4 in the range of 7g/L-16g/L, the ceramic film samples with the thickness of micro-arc oxidation ceramic film controlled in the range of 5-20 渭 m have been prepared by XRD. The test results show that after calcination at 700 鈩，

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