Identifying low-cost, machinable, impact-resistant TiAl alloys suitable for last-stage turbine blades of jet engines

Abstract

Existing TiAl alloys used for fabricating last-stage turbine blades of jet engines are relatively cost-prohibitive and unreliable, particularly for use in next-generation engines. The present study was conducted to address these issues by uncovering new TiAl alloy compositions with a focus on improving machinability and impact resistance. Ternary alloys integrated with V or Cr were examined and compared with two commercial TiAl alloys (TiAl4822 and TNM alloy). V and Cr were selected because they are significantly cheaper than the Nb added to existing commercial TiAl alloys and can improve impact resistance (results of previous research). A comparison of the commercial alloys revealed no significant differences in impact resistance; however, TiAl4822 was notably superior to TNM alloy in terms of machinability. Moreover, the V-containing ternary alloys demonstrated significantly higher impact resistance than that of TiAl4822, yet they exhibited inferior machinability. Notably, numerous Cr-doped ternary alloys (such as 48.0Al-2.0Cr/2.5Cr) were superior to TiAl4822 in both machinability and impact resistance. Overall, the study findings indicate that a new TiAl alloy for fabricating jet engine turbine blades with significantly reduced cost and improved reliability can be obtained simply by removing Nb from the existing TiAl4822.