Mechanical Properties and Microstructure of VPS and HVOF CoNiCrAlY Coatings |
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Authors: | S Saeidi K T Voisey D G McCartney |
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Affiliation: | (1) Materials, Mechanics and Structures Research Division, Faculty of Engineering, The University of Nottingham, Nottingham, NG7 2RD, UK; |
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Abstract: | In this study, high velocity oxy-fuel (HVOF) and vacuum plasma spraying (VPS) coatings were sprayed using a Praxair (CO-210-24)
CoNiCrAlY powder. Free-standing coatings underwent vacuum annealing at different temperatures for times of up to 840 h. Feedstock
powder, and as-sprayed and annealed coatings, were characterized by scanning electron microscopy (SEM), energy dispersive
spectroscopy (EDS), and x-ray diffraction (XRD). The hardness and Young’s modulus of the as-sprayed and the annealed HVOF
and VPS coatings were measured, including the determination of Young’s moduli of the individual phases via nanoindentation
and measurements of Young’s moduli of coatings at temperatures up to 500 °C. The Eshelby inclusion model was employed to investigate
the effect of microstructure on the coatings’ mechanical properties. The sensitivity of the mechanical properties to microstructural
details was confirmed. Young’s modulus was constant up to ~200 °C, and then decreased with increasing measurement temperature.
The annealing process increased Young’s modulus because of a combination of decreased porosity and β volume fraction. Oxide
stringers in the HVOF coating maintained its higher hardness than the VPS coating, even after annealing. |
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