On the oxidation of Ti2GeC in air

• Oxidation behavior of Ti2GeC in air in the 600 to 800 °C temperature range is studied for the first time.
• At 600 °C up to 500 h, Ti2GeC is oxidation resistance as a result of formation of a protective TiO2 layer.
• The oxidation of Ti2GeC in air occurs mostly by the inward diffusion of oxygen through rutile-based layers.

Herein we report on the oxidation of bulk Ti2GeC in air in the 600 °C to 800 °C temperature range. At 600 °C, and up to 500 h, the oxidation kinetics are sub-parabolic and the rutile TiO2 layer formed is adherent and protective. At 700 °C and 800 °C the kinetics are parabolic up to 100 h before becoming linear. X-ray diffraction confirmed the presence of two rutile structures, TiO2 and GeO2, and a hexagonal GeO2 on the oxidized surfaces. The oxidation occurs by inward diffusion of oxygen through a rutile (Ti1−xGex)O2 solid solution with x ⩽ 0.07. Additionally, and throughout the entire temperature range studied, an oxygen-induced decomposition – occurring predominantly at the oxide/carbide interface – results in the formation of an elemental Ge-rich phase. If the rutile layer is not protective, the latter oxidizes into hexagonal GeO2.