Publication details

Microstructural changes as postmortem temperature indicator in Ni-Co-Cr-Al-Y oxidation protection coatings

Investor logo


Year of publication 2004
Type Article in Periodical
Magazine / Source Materials Science and Engineering A
MU Faculty or unit

Faculty of Science

Field Physical chemistry and theoretical chemistry
Keywords CALPHAD; Microstructure; Ni-Co-Cr-Al-Y; Phase equilibria; Precipitates; Temperature indicator
Description Microstructural changes in a metallic oxidation protection coating (Ni-Co-Cr-Al-Y) applied on a nickel base superalloy were investigated by means of scanning and transmission electron microscopy. The changes are due either to thermal mechanical fatigue testing under high thermal gradients or to defined isothermal heat treatments. The coated specimens were quenched from temperatures between 840 and 1100 C to ambient temperature. The resultant phases, their local distribution and compositions were determined by energy dispersive X-ray (EDX) spectroscopy and electron diffraction. Phase equilibria at respective temperatures were determined by thermodynamic calculations based on the CALPHAD method. The calculated and experimentally determined phase distributions were compared. A particular microstructural feature, namely the existence and spatial distribution of spherical gamma' Ni3Al precipitates in the coating and the diffusion zone between substrate and coating, was used as a postmortem indicator for the maximum temperature experienced by the specimen during testing. This paper gives a road map for developing a microstructural-based temperature calibration for complex metallic materials using thermodynamic simulations.
Related projects:

You are running an old browser version. We recommend updating your browser to its latest version.

More info