Characterization of Oxidation Protection Coatings for High Temperature Applications by Means of Nanoindentation and Scanning Electron Microscopy Methods

Abstract

Oxidation protection coatings are required for thermally highly stressed components such as turbine blades in aircraft engines. Cyclic oxidation experiments were performed on a NiCoCrAlY protective coating of a nickel-based superalloy and hardness and modulus of elasticity (mechanical properties) were determined by nanoindentation before and after the experiments. Microstructure and chemical composition were characterized by means of scanning electron microscopy. Here, the focus is on the phase identification by combining electron backscatter diffraction and energy dispersive X-ray spectroscopy. Findings indicate that the chemical composition strongly influences the mechanical properties.

Microcantilever Fracture Tests of α‐Cr Containing NiAl Bond Coats

“…The notch is placed in the α-Cr phase. some oxides (black inclusions) are formed above the interface, as described by Webler et al [13] Figure 3 shows the microstructural changes of sample B after the cyclic oxidation by EDX mappings. One of the major changes is that the coating thickness increases to 78.4 AE 3.5 μm after oxidation.…”

“…The size distributions of the α‐Cr phases for all states are shown in Supporting Information. In addition, some oxides (black inclusions) are formed above the interface, as described by Webler et al [ 13 ]…”

“…This long holding time for eight cycles allowed diffusion between the substrate and the coating, as well as the formation of an oxide layer. Nanoindentation measurements by Webler et al [ 13 ] on these coatings revealed that cyclic oxidation reduces the hardness of the coating. Their microstructure and composition were analyzed with scanning electron microscopy (SEM, 1540Esb, Carl Zeiss, Germany) and energy‐dispersive X‐ray spectroscopy (EDX, Inca, Oxford, GB).…”