Hot corrosion behaviour of Ni3Al in sulphate–chloride mixtures in the atmosphere

Abstract Hot corrosion of Ni3Al intermetallic compound in the presence of sulphate–chloride mixtures was studied. A comminuted Ni3Al mixed with NaCl–Na2SO4, NaCl–Li2SO4, LiCl–Na2SO4, LiCl–Li2SO4 additions was oxidized in the air up to 1000 °C with linearly increasing temperature and isothermally within the temperature range of 500–700 °C. The corrosion process was observed by thermogravimetric method using Mettler thermoanalyzer. The experiments indicated that LiCl (∼10 wt.%)–Li2SO4 mixture was the most corrosive agent. It was also found that by addition of MgO the corrosion of Ni3Al was reduced. Phase composition of the corrosion products was established by X-ray diffraction analysis; there were detected Al2O3, Al2S3, NaAlO2 (or LiAlO2) as intermediate products, nickel sulphides, NiO and NiAl2O4. NiAl2O4 spinel was formed only at the highest temperatures, while at lower temperatures alumina was present instead of spinel. Hot corrosion behaviour of Ni3Al in sulphate–chloride mixtures in air atmosphere.