Improvement in the oxidation resistance of Nb–Ti–Si–Cr–Al–Hf alloys containing alloyed Ge and B

• Oxidation was performed at 1200 °C and 1250 °C on Nb–Ti–Si–Cr–Al–Hf alloys.
• The presence of alloyed Ge and B improved the oxidation resistance of this alloy.
• The presence of alloyed Ge and B promoted SiO2 phase grown during oxidation.

The oxidation behaviour for Nb–Si based alloys was performed in air at 1200 °C and 1250 °C. The weight gains of Nb–24Ti–15Si–13Cr–2Al–2Hf (at.%) alloy and Nb–24Ti–15Si–13Cr–2Al–2Hf–4B–5Ge (at.%) alloy after oxidation at 1250 °C for 100 h were 156.7 mg/cm2 and 32.5 mg/cm2, respectively. The oxide scale of the Nb–24Ti–15Si–13Cr–2Al–2Hf (at.%) alloy was porous and loose, while that of the Nb–24Ti–15Si–13Cr–2Al–2Hf–4B–5Ge (at.%) alloy was dense and protective. The presence of alloyed B and Ge improved the protective SiO2 phase grown during high temperature oxidation, leading to the formation of a continuous and dense oxide scale.

A continuous and dense oxide scale is formed on the surface of Nb–24Ti–15Si–13Cr–2Al–2Hf–4B–5Ge (at.%) alloy after oxidation at 1200 °C for 100 h, the oxide scale mainly consisted of CrNbO4, TiNb2O7, Nb2O5 and SiO2 can improve the oxidation resistance of Nb–Si based alloy.Figure optionsDownload as PowerPoint slide