Characterization of Electroless Ni-P and Ni-P/Al₂O₃ Composite Coating on Al6061 Alloy

Abstract

Aluminum and its alloy have a light density with good properties of stiffness and corrosion resistance. Although it has a good property, aluminum alloy still vulnerable to wear and corroded. A possible solution to protect the aluminum product from wear and corrosion is by applying coating such as nickel-phosphorus (Ni-P) coating onto its surface. Co-deposition of alumina (Al2O3) particles into Ni-P coating is expected to improve the wear resistance of the Ni-P coating layer. This study investigated the Ni-P and Ni-P/Al2O3 composite coating on Al 6061 alloy via electroless coating by varying the agitation speed and amount of Al2O3. The characterization of coatings includes morphology, coating thickness, hardness and wear properties were investigated by using field emission scanning electron microscopy (FESEM), optical microscope, Vicker microhardness and pin-on-disc tribometer. The agitation improved the adherence of alumina particles to the substrate. The increment amount of alumina in Ni-P/Al2O3 composite coating showed a decrement in percentage of nickel and phosphorus present in the coating but improved the hardness of the coating. The wear rate and coefficient of friction of the Ni-P/Al2O3 composite coating were lower than Ni-P coating.