A study of the cycle oxidation behavior of the Cr/Mn/Mo alloyed Ti–48Al–based intermetallics prepared by ECAS
Özet
Today the electric current activated sintering (ECAS) technique is commonly preferred as it has many advantages such as microstructure control, reduction of process time, rapidly heating rate and sintered parts with full density. Two-phased (?2-Ti3Al+?-TiAl) TiAl alloys have drawn considerable interest for automotive, aerospace and gas turbine industry applications because of their low density and superior high-temperature properties. The study aims to investigate the effect of the alloying elements (Cr, Mn, Mo) on the oxidation resistance of TiAl based intermetallics produced by ECAS under the cyclic condition. The cycle oxidation behavior of two-phased intermetallics in air at 700, 800 and 900 °C for 180 h was studied. The phase composition, microstructure, surface morphology and cross-sectional microstructure of the specimens were examined using SEM, EDS and XRD. According to the XRD and EDS results, the formed scale was composed mainly of TiO2 and Al2O3 phases. The cross-section SEM images show that the oxide scales of the alloys featured strong adhesion of scale with a multi-layered structure. The scales on the Mo-added alloys are thinner, compact and adherent and thus the scale-exfoliation resistance is enhanced. The activation energy values calculated for the oxidation of specimens varied between 50 and 116 kJ mol?1. Considering the thermodynamic and kinetic factors, possible oxidation mechanism of studied specimens was discussed. © 2019 Elsevier B.V.