On the oxidation behavior of spark plasma sintered Ti–Al alloy: a comparative study on cast and aluminide coated Ti6Al4V alloys

Abstract In this study, the microstructural characteristics, surface mechanical properties, and oxidation behavior of spark plasma sintered Ti–Al alloy, cast Ti6Al4V alloy and aluminide-coated Ti6Al4V alloys are investigated. The sintered Ti–Al alloy exhibits a dense dual-phase microstructure with α-Ti and Ti–Al intermetallics, while aluminizing the cast Ti6Al4V alloy forms a continuous multilayered coating comprising TiAl 3 , TiAl, and TiAl 2 phases. Hardness measurements reveal significantly enhanced surface hardness in the aluminized Ti6Al4V due to the presence of hard intermetallic phases. Oxidation tests at 700 °C show that the aluminized Ti6Al4V alloy develops a protective and adherent alumina (Al 2 O 3 ) scale, resulting in superior oxidation resistance and minimal weight gain compared to both sintered Ti–Al and uncoated Ti6Al4V alloys. In contrast, the sintered Ti–Al alloy undergoes more pronounced oxidation with TiO 2 -rich oxide formation and internal oxidation linked to porosity. These findings demonstrate that aluminizing Ti6Al4V alloys effectively improves their high-temperature oxidation resistance and mechanical performance, making them promising candidates for aerospace and automotive applications requiring enhanced durability under oxidative environments.