Oxidation resistance of SiO 2 bonded coating formed on Ti–Al–Zr alloy

Abstract

Methyl hydrogen silicone converted SiO₂ bonded composite coatings with high infrared emissivity additives of Cr₂O₃ and Al₂O₃ were prepared on Ti–6Al–2Zr–1Mo–1V titanium alloy by a dipping and then pyrolysing process. The phase composition and microstructure of the coating were characterised by X-ray diffraction and scanning electron microscopy. The results show that after exposing the samples to an oxidative atmosphere at 600°C for 100 h, the coated samples pyrolysed at 600 and 800°C exhibit a significantly lower weight gain (0·11 mg cm⁻²) compared with that of the titanium substrate (0·54 mg cm⁻²). The weight gain for both coated samples oxidised at 800°C increases up to 1·4 mg cm⁻², while the titanium substrate damages by oxide scale peeling. The coating pyrolysed at 800°C has a high infrared emissivity value of above 0·85, which is slightly higher than that of the coating pyrolysed at 600°C.