Isothermal oxidation behaviour of TiAl–Cr–Nb–B alloys produced by induction melting

The oxidation behaviour of Ti-48Al-2Cr-1.5Nb-0.04B, Ti-48Al-2Cr-3Nb-0.04B, Ti-48Al-2Cr-6Nb-0.04B alloys were investigated by thermogravimetric method. Isothermal experiments were carried out at 900 °C and 1000 °C in air.The work focused on the synergistic effect of Cr and Nb on the oxidation resistance of the considered alloys when Nb content was increased from 1.5% at. to 6% at. The alloy's microstructure and composition as well as the composition distribution of the oxide scale were analysed by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and X-Ray Diffractometry (XRD). The results showed that the scale composition changes with the Nb content in the alloy and that, by increasing the Nb percentage, the mass gain decreases and the scale adherence increases, with a consequent overall improvement of the oxidation resistance.

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► Ti-48Al-2Cr-XNb-0.04B (X = 1.5÷6) alloys were produced by induction melting.
► The oxidation behaviour of those alloys at 900 and 1000 °C was investigated.
► The results show the beneficial effect of Nb.
► Nb considerably improves the oxidation resistance by enhancing the alumina formation.