Hot corrosion effect of the vacuum arc melted (a₂/γ)Ti-48Al-2Nb-0.7Cr-0.3Si alloy under an environment of NaCl-Na₂SO₄ salt

¹ Council of Scientific Industrial Research, Materials Science and Manufacturing, Light metals, Meiring Naude Road, P O Box 395 Pretoria, South Africa
² Department of Material Science and Metallurgical Engineering, Faculty of Engineering, Built Environment and Information Technology, University of Pretoria, South Africa
³ Department of Physics, University of the Western Cape, Private Bag X 17, Bellville 7535, South Africa
⁴ Department of Physics, University of the Free State, P.O. Box 339, Bloemfontein, ZA9300, South Africa

^* Corresponding author: magogodistevens@gmail.com

Abstract

The Ti-48Al-2Nb-0.7Cr-0.3Si alloy comprising of α₂-Ti₃Al and γ-TiAl phases was successfully fabricated using vacuum arc melting. To study its hot corrosion behaviour, the alloy was subjected to cyclic thermal loading under a Na₂SO₄ + 25wt.%NaCl molten salt mixture at 900 °C for up to 60 h. Mass change per unit surface was measured to determine the corrosion kinetics of the alloy. The alloy experienced severe hot corrosion attacks up to -50.94 mg/cm². SEM indicated the formation of a mixture of TiO₂/Al₂O₃ scales on the alloy's surface. XRD confirmed the presence of hot corrosion products such as Na₂Ti₃O₇, TiO₂, Al₂O₃, and Cr₂O₃. The presence of chlorine gas in the hot corrosion environment resulted in the delamination of the protective scale on the surface, indicating its detrimental effect.