Tribo-corrosion Performance of Plasma Sprayed Al2O3 on Aluminum Alloy for Thermal Barrier Coatings

Aluminium alloys have attractions to be used for a wide range of applications due to its

lower density and the formation of passive film which provide corrosion protection. At high

temperature (more than 250 0C), the passive film may be destroyed, thermally corroded and it will

easily be failed by thermal fatigue failures. This work has investigated the enhancements of plasma

sprayed Al2O3 coating on the performance of 6082-T6 aluminium alloy surface against erosion

and corrosion test environments. The study investigates the macro/microstructure and the formed

phases of the plasma sprayed Al2O3 formed layer. The erosion resistance of the coated layer, in

particular, the effect of sand concentration and temperature variations to the aqueous slurry

impingement against material properties such as adhesion, ductility, and roughness were

investigated. In addition, a series of electrochemistry tests have been conducted to verify the

corrosion performance. As a reference, the un-coated 6082-T6 aluminium substrate was instigated

in all the experiments. The resulted showed that plasma sprayed Al2O3 coating layer had lamellar

structure of approximately 86% ?-Al2O3 and 14% ?-Al2O3 phases and contained many voids and

porosity. The coated layer shows good corrosion resistance at ambient temperature. At 80 ?C,

small amount of ions penetrations was recorded. The coated layer was completely removed after

polarizing the solution up to 400 mV for 24 hours. Although there was no stability of the current

in the coating during the polarization test, the coating shows lower corrosion current density under

static anodic polarization tests compared to the aluminium substrate indicates better corrosion

resistance. It has been shown that the erosion of the coated layer shows linear erosion rate. The

erosion rates observed for the coating in elevated temperature are much lower than aluminium

substrate. As a result, the erosion resistance of aluminium alloy can be highly improved by plasma

sprayed Al2O3 coating, especially at high temperature.

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