Microstructure and mechanical properties of Ni₃Al-based single crystsalalloy IC21

According to the requirement of high-pressure turbine guide vane during service, the aim of this work is to design a single crystal Ni₃Al-based alloy named IC21 with low density, low cost, and high strength which can be used as high-pressure turbine guide vane material. The mass fraction of the Re has been limited less than 1.5% on purpose. The single crystal bars of IC21 were prepared by high rate solidification method. The density of IC21 is 8.0 g/cm³ and the incipient melting temperature was identified by metallography. After standard heat treatment, the distribution of the γ' precipitates is uniform with the average size of about 420 nm, and volume fraction of 80%. The tensile and yield strengths at 1100℃ are 490 and 470 MPa, respectively. Moreover, IC21 shows superior creep properties, the stress-rupture life at 1100℃, 140 MPa is 170.5 h and at 1150℃, 100 MPa still remains 110.0 h. The microstructure stability of IC21 alloy at 1080℃ for as long as 1000 h were evaluated. The results show that no precipitated phase exists during thermal exposure at 1080℃, which exhibits good stability. The oxidation kinetic curves of IC21 alloy follows a parabolic rate law in different oxidation stage during cycle oxidation for 100 h in air. IC21 alloy has a good high temperature oxidation resistance, the strengthening mechanism are attributed to high volume fraction of γ' phase, large negative misfit and well-established interface networks.