Abstract

The adhesive mechanism of thermal sprayed ceramic coating is not clear because of the complicated profile of the blasted surface and the microstructure of the coating. In particular, little research has been carried out on the adhesive mechanism on light metal substrates. The objective of this study was to investigate the effect of surface roughness on the adhesive strength of yttria-stabilized zirconia coatings applied by atmospheric plasma spraying on an aluminum alloy (JIS A5052) substrate. Tensile adhesive and interfacial indentation tests were performed to evaluate their bonding properties. The substrates were blasted at three different pressures and seven different blast angles using fused alumina abrasives of three different particle sizes. Our measurements revealed that the tensile adhesive strength decreased with increasing substrate roughness (root mean square slope, RΔq). After the tensile strength tests, the fracture surfaces were observed using an FE-EPMA analyzer and analyzed using an X-ray fluorescence analyzer. It was found from elemental analysis that the fractured part shifted to the substrate with increasing RΔq. It was concluded that the tensile adhesive strength decreased with increasing surface roughness owing to the low strength of the substrate.

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