Young’s modulus and fatigue behavior of plasma-sprayed alumina coatings |
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Authors: | O Ková?ík J Siegl J Nohava P Chráska |
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Affiliation: | (1) Department of Materials, Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University, Prague, Czech Republic;(2) Institute of Plasma Physics, Academy of Sciences of the Czech Republic, Prague, Czech Republic |
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Abstract: | The fatigue behavior and Young’s modulus of plasma-sprayed gray alumina on low-carbon steel substrates were investigated.
The investigation of the properties of composites that were defined as “coating-substrate” composites included measurements
of the microhardness profile, the residual stress on the top of the coating, and the residual stress profile in the substrate.
Fatigue samples were periodically loaded as a cantilever beam on a special testing machine. Failed samples were observed with
a scanning electron microscope to determine the failure processes in the coating. The Young’s modulus of the coating was measured
by the four-point bending method. Samples were tested both in tension and compression under low (300 N) and high (800 N) loads.
The authors’ experiments revealed that the average fatigue lives of coated specimens were nearly two times longer than those
of the uncoated specimens. The measurements of Young’s modulus of the coating yielded values that varied between 27 and 53
GPa, with an average value of 43 GPa. Loading in tension caused a decrease in the Young’s modulus of the coating, while loading
in compression led to an increase in Young’s modulus. The increase in the lifetime of coated samples was likely due to compressive
residual stresses in the substrate, originating during the spray process. The failure of the coating was due to several processes,
among which the most important were splat cracking, splat debonding, and the coalescence of cracks through the voids in the
coating. |
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Keywords: | alumina fatigue plasma spray Young’ s modulus |
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