Enhanced infrared emissivity of MAO coatings formed on Ti₂AlNb alloy

Abstract

In order to improve infrared emissivity property, microarc oxidation (MAO) ceramic coatings have been fabricated on Ti₂AlNb alloy by adding NH₄VO₃ and Cr₂O₃ into a Na₂SiO₃ electrolyte. Microstructure and chemical compositions of MAO ceramic coatings are investigated by X-ray diffraction and scanning electron microscopy equipped with energy dispersive X-ray spectroscopy. Normal spectral emissivity values of both coated and bared Ti₂AlNb samples are measured at 600°C in the infrared wavelength range of 3–20 μm. The infrared emissivity of MAO ceramic coatings has been improved by different additives of NH₄VO₃ and Cr₂O₃. Microarc oxidation coating with NH₄VO₃ has a high emissivity of 0·7 in short wavebands, while Cr₂O₃ additive increases the emissivity value up to 0·9 in the waveband of 10–20 μm. Furthermore, the S–10Cr–6V ceramic coating exhibits the best infrared emission property due to the synergistic effects of NH₄VO₃ and Cr₂O₃.

Keywords:

• High emissivity coating
• Microarc oxidation
• Ti₂AlNb alloy
• NH₄VO₃ addition
• Cr₂O₃ addition

Acknowledgements

This work was financially supported by the National Natural Science Foundation of China (NSFC, Grant No. 51021002 and No. 60776803), and the Fundamental Research Funds for the Central Universities (Grant No. HIT.BRET1·2010006).