L.M. Ferreira, C. Oskay, M.C. Galetz, R.P. Cardoso, E.P. Cardozo, A.S.C. Monteiro D'Oliveira
Surface and Coatings Technology 530 (2026), 133540, DOI: 10.1016/j.surfcoat.2026.133540
The rapid transformation in society through technology and the necessity to achieve decarbonization in the near future, imposes demands for new developments in materials that lead to an increase in efficiency, namely refractory metals. The use of Niobium alloys in a wide range of temperatures relies on alloying elements and/or surface protection to mitigate the restricted oxidation resistance. This study investigates the protection of metallic Nb and a Nb cast alloy Nb26Ti1Zr (wt%) for operations at intermediate temperatures (600 °C) by Ti-rich coatings. Pack titanizing at 950 °C and 1000 °C was carried out with varying pack mixtures for pure Nb and the Nb26Ti1Zr alloy. Thermogravimetric analysis (TGA) and quasi-isothermal tests at 600 °C, were carried out to assess the oxidation behavior of coatings. Further microstructural investigation of coatings, including SEM, EPMA and XRD, revealed the formation of a Ti-rich oxide scale on coated samples suppressing the non-protective Nb-rich oxides up to Ti-coating consumption. Ti-rich coatings offered a significant increase in oxidation resistance (by a factor of six for metallic Nb and a factor of two for the Nb-based alloy), holding a promising solution for the use of Nb-based alloys at intermediate temperatures. This study successfully provides a proof of concept for improving the oxidation resistance of Nb and NbTiZr alloys through Ti addition.
