High Temperature Oxidation Behavior of Pure Ti TIG Welded Joint

Abstract:

The oxidation behavior, oxidation morphology, and oxidation products of pure Ti joint welded by tungsten inert gas welding technique at 550 °C for different durations (2, 4, 6, and 8 h) and those at different temperatures (650, 750, 850, and 950 °C) for 4 h were investigated. Results show that at 550 °C, the oxidation time has a slight influence on the oxidation behavior of welded joint. The oxidation temperature has a significant impact on the oxidation behavior, and the higher the temperature, the more severe the oxidation of welded joints. The oxidation kinetics is very close to the quasi-linear law at low temperatures. With increasing the temperature, the oxidation rate is increased exponentially. Additionally, the oxidation products generated on the surface of welded joint are TiO₂ with anatase and rutile structures, and the temperature barely has effect on the TiO₂ type. The oxidation process of pure Ti welded joint can be described as follows: oxygen atoms are absorbed on the surface; oxides preferentially nucleate in the defective zone; oxides grow laterally and the oxidation film becomes thicker. At relatively higher temperatures, the cracks or voids appear in the oxidation film, which become the transmission channels of O atoms, leading to the high diffusion rate of O and Ti atoms and high oxidation rate.