Study of the Mechanical Properties and Thermal Control Performance of Plasma-Sprayed Alumina Coating on Aluminum Alloy Surface

Abstract

Thermal control coating is an important means of ensuring that a spacecraft remains operational at high temperatures. Due to limitations regarding preparation technology and material properties, the mechanical properties of the conventional thermal control coatings still need to be improved. To solve this problem, nanostructured alumina coatings (NCs) and conventional alumina coatings (CCs) were prepared using plasma-spraying technology. The microscopic morphology, phase structure, hardness, and thermal control properties (solar absorptance (αs) and emissivity (ε)) of the nanostructured alumina coatings were investigated and compared with those of conventional alumina coatings. The results show that the NC has a higher hardness value (1168.8 HV) and that its reflectivity exceeds 75% in the wavelength range of 446–1586 nm, while a high degree of emissivity of 0.863–0.87 is still maintained at 300–393 K. Furthermore, the results show that these highly reflective properties are related to the phase composition and internal micromorphology of the NC, whereby the solar absorption of the coating is reduced due to the increase in the alpha phase content (21.4%), the high porosity (5.21%) and the nanoparticles favoring the internal scattering. All these properties can improve the performance of this CC coating with low solar absorptance (αs) and high emissivity (ε).

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“…These limitations of thermal and mechanical properties can be counteracted by adding micro-or nanomaterials to aluminum alloys or optimizing the coating process. He et al [88] explored the mechanical and thermal properties' differences between conventional (CC) and nanostructured (NC) alumina coatings prepared using plasma-spray technology. The NC revealed a higher hardness value (1168.8 HV) and a reduced solar absorbance (0.26) compared to the CC (1079.7 HV and 0.324, respectively) within the 200-2500 nm wavelength range (Figure 11) [88].…”

“…He et al [88] explored the mechanical and thermal properties' differences between conventional (CC) and nanostructured (NC) alumina coatings prepared using plasma-spray technology. The NC revealed a higher hardness value (1168.8 HV) and a reduced solar absorbance (0.26) compared to the CC (1079.7 HV and 0.324, respectively) within the 200-2500 nm wavelength range (Figure 13) [88]. As expected, the distinct microscopic morphology between the two types of coating is responsible for differences in spectral reflectance.…”