Atomic-Scale Structural and Chemical Study of Columnar and Multilayer Re–Ni Electrodeposited Thermal Barrier Coating

Rhenium alloys exhibit a unique combination of chemical, physical, and mechanical properties that makes them attractive for a variety of applications. Herein, we present atomic-scale structural and atomic part-per-million level three-dimensional (3D) chemical characterization of a Re–Ni coating, combining aberration-corrected scanning transmission electron microscopy (STEM) and atom-probe tomography (APT). A unique combination of a columnar and multilayer structure is formed by single-bath dc-electroplating and is reported here for the first time. Alternating thicker Re-rich and thinner Ni-rich layers support a mechanism in which Ni acts as a reducing agent. The multilayers exhibit hetero-epitaxial growth resulting in high residual shear stresses that lead to formation of corrugated interfaces and an outer layer with mud-cracks.