Effect of Processing Parameters on Ti3Al-based Alloy High-Temperature Cyclic Oxidation Kinetics

Abstract

Efficient exploitation of the industrial components at elevated temperatures and in aggressive environments is demanded in modern industrial production. The Ti3Al-based alloys are proposed as materials that can meet these demands since it is determined that improved high- temperature corrosion resistance of industrial construction materials is often more significant for industrial exploitation than the improvement of their mechanical properties. Therefore, the aim of the present research was to determine the effect of various parameters, i.e. initial microstructure and high-temperature processing conditions, on the cyclic oxidation kinetics of the Ti3Al-based alloy with the Ti-24Al-11Nb (at.%) composition. Cyclic oxidation tests were conducted in air at 600 and 900 oC. The oxidation process was monitored up to 120 h by recording mass gain data as a function of time to define the kinetic models. Examination of alloy microstructure and alloy degradation during the cyclic oxidation was undertaken using light microscopy (LM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Alloy hot-rolled at 1050 oC and hot-rolled alloy subsequently thermally treated at 1200 oC were examined before and after cyclic high-temperature oxidation. Obtained results indicated that the initial alloy microstructure has a significant influence on its high-temperature oxidation behavior. Namely, hot-rolled alloy thermally treated at 1200 oC with a higher volume fraction of the β phase in the microstructure shows improved oxidation resistance compared to the alloy only hot-rolled at 1050 oC. An increase in oxidation temperature caused the progress in alloy degradation. In contrast to the compact external layer formed at the alloy surface after cyclic oxidation at 600 oC, during cyclic oxidation at 900 oC formation of a multi-layer scale was observed. The main products of oxidation are Al2O3 and TiO2. Kinetic models of the Ti-24Al-11Nb (at.%) alloy cyclic oxidation at 600 oC and 900 oC in the air are defined with linear and parabolic oxidation curves for most of the examined conditions.