High-temperature diffusion in couple of electrodeposited iridium/rhenium

Ir coated Re (Ir/Re), combining the outstanding high-temperature mechanical property of Re and excellent hightemperature oxygen permeability resistance of Ir, is a promising high-temperature material in high temperature applications, such as rocket engine combustion chambers and crucibles for crystal growth, etc. The elemental diffusion behaviors in the Ir/Re material are closely related to its failure mode and lifetime. Therefore, the diffusion behavior investigation on the Ir/Re material is essential for understanding the failure mechanism and building the lifetime prediction model of this material. In this work, a three-layered CVD Re/ED Ir/ED Re sample was fabricated and its diffusion behaviors at the temperatures ranging from 1400 to 2000 ?C were investigated. The diffusion coefficients and activation energy of ED Re diffusing into Ir using a semi-infinite diffusion model were obtained and compared with those of the CVD Re. The obviously lower diffusion activation energy of ED Re (0.98 eV) compared with the CVD Re is due to their microstructure difference. The higher defect concentration, thermodynamically unstable grain structure and preferred orientation of the ED Re layer promotes the dominant diffusion of Ir into Re, resulting in a thicker diffusion layer with a frame-shaped diffusion front.

Automated summary

The Ir coated Re (Ir/Re) material shows a lower diffusion activation energy due to the higher defect concentration and thermodynamically unstable grain structure in the ED Re layer, promoting the dominant diffusion of Ir into Re and resulting in a thicker diffusion layer.