Microstructural influence on high-temperature oxidation of near- α titanium alloys: Timetal 834 and 6242S

In this study, the oxidation behavior of two titanium alloys designed for high-temperature applications, Timetal 834 and Timetal 6242S, was compared. Both are classified as near- α alloys and possess alloying elements significantly enhancing their resistance to high-temperature oxidation. Applied oxidation routine included 100 and 500 hours of prolonged thermal processing in ambient dry air at 600, 650, and 700 °C. Such treated materials were investigated using complementary techniques: optical microscopy, scanning electron microscopy, electron/wave dispersive spectrometry, X-ray diffraction, and Raman spectroscopy. The results revealed that different oxide layer growth, between the two analyzed alloys, during high-temperature exposure was strongly related to their microstructures, and especially the arrangement of α and β phases. For longer exposure time (500 h), the Ti834 alloy showed better oxidation resistance, despite the formation of micrometric nodules on its surface during oxidation, which was not observed in the Ti6242S alloy. The presented data clearly indicate the important role of the microstructure as a source of solute elements that control the structure and stoichiometry of the oxide layer and, consequently, the oxidation resistance.