碳基陶瓷隔热瓦表面高发射耐烧蚀抗氧化涂层的制备及性能研究

Study on preparation and performance of high emission ablative and anti-oxidation coatings for the surface of carbon-based ceramic tile

摘要:

碳基陶瓷隔热瓦耐高温、质轻、热导率低，是高超声速飞行器热防护系统中急需的隔热材料。但该材料不耐气流冲刷，易氧化烧蚀。本文采用大气等离子喷涂技术在碳基陶瓷隔热瓦ZrB2-SiC-玻璃内涂层表面制备镍铬尖晶石高发射涂层以提高其抗氧化耐烧蚀性能。利用XRD和SEM对粉体和涂层的相结构和微观形貌进行分析，采用氧-乙炔火焰对涂层进行烧蚀试验。结果表明，Cr2O3、NiO摩尔比为1：1.2，1200 ℃固相反应2 h，可以得到物相较纯的NiCr2O4尖晶石粉体；Cr2O3、NiO摩尔比不变，掺入15 wt.%TiO2、25 wt.%MnO2，1200 ℃固相反应2 h可以得到复杂的混合尖晶石粉体。NiCr2O4涂层及掺杂NiCr2O4涂层的发射率在1-22 μm波段分别达到0.955和0.954。喷涂后NiCr2O4发生了轻微的分解，发射率有所降低，而掺杂NiCr2O4相结构稳定，没有分解，发射率稳定。氧-乙炔火焰烧蚀考核结果表明，当火焰温度大于2000 ℃时，掺杂NiCr2O4涂层表面温度比NiCr2O4涂层降低了240 ℃，其红外辐射性能优于NiCr2O4涂层。掺杂NiCr2O4涂层能耐受大于2000 ℃，300 s烧蚀考核，具有良好的高发射耐烧蚀性能。

Abstract:

Carbon-based ceramic tile is urgently needed high-temperature anti-insulation materials in the thermal protection system of hypersonic vehicles due to the high temperature resistance, low density, and low thermal conductivity. But the material is easy to destroyed by oxidation erosion and ablation. In this experiment,, the Ni-Cr spinel high-emission ablation-resistant anti-oxidation coating was prepared by atmospheric plasma spraying technology on the surface of a carbon-based ceramic thermal insulation tile substrate on which a ZrB2-SiC-glass inner coating has been prepared. The phase structure and microstructure of the powder and coating were examined by XRD and SEM, and the coating was ablated by oxygen-acetylene flame. The results show that when the mole ratio of Cr2O3 and NiO is 1: 1.2, the pure NiCr2O4 spinel powder can be obtained by the solid phase reaction at 1200 ℃ for 2 h. To get complex spinel powder, 15 wt.% TiO2 and 25 wt.% MnO2 were added to the former consititute system and the same manufacture method was applied. The emissivity of NiCr2O4 high-emission coatings and NiCr2O4-doped high-emission coatings reached 0.955 and 0.954 respectively in the 1-22 μm band. The NiCr2O4 was slightly decomposed after spraying, and the emissivity was reduced. The Mn-Ti doped NiCr2O4 phase structure was stable, no decomposition, and the emissivity was stable. The result of the ablation shows that the surface temperature of Mn-Ti doped NiCr2O4 coating lower than NiCr2O4 coating by 240 ℃ and the infrared radiation performance is far higher than NiCr2O4 coating, when the flame temperature is 2000 ℃. Mn-Ti-doped NiCr2O4 coating is more stable than NiCr2O4 coating at high temperature, which keeps high emission performance. The Mn-Ti doped NiCr2O4 coating keeps stable after the 2000 ℃, 300 s ablation assessment, which perform a better radiation and ablation resistance.