Oxidation of Experimental Ti-Si-Al Based Alloys

Abstract

Despite the fact that conventional high temperature titanium alloys possess a good combination of low weight, high strength and good corrosion resistance, their operational temperatures do not exceed 540-600 °C, since at higher temperatures they suffer from extensive oxidation, scaling and formation of a brittle oxygen-reach diffusion layer on their surface, so-called ‘apha-case’. The alloying with silicon was regarded as a promising way to raise the working temperatures of titanium alloys, since silicon is known to improve oxidation resistance, oxide scale adherence and high temperature creep behavior of titanium without noticeable deterioration of its ductility. The present paper was focused on studying of the oxidation kinetics and the formation of oxide scale and alpha-case layers on a series of experimental Ti−Al−Si based alloys, additionally alloyed with zirconium and tin. The oxidation kinetics of the experimental alloys upon exposure in air at 700 °С for up to 240 hours was examined and compared with that of commercially available Ті−6242 alloy. The oxide scale thickness, its phase composition and crystal morphology were characterized using X-ray diffraction and scanning electron microscopy (SEM), while the alpha-case layer was analyzed using SEM and microhardness measurements. According to the experimental findings, the experimental Ti−Al−Si based alloys demonstrated a good potential for their use at high temperatures.