Wear and Tribological Behavior Of PEO Coated Al/Al2O3 Metal Matrix Composite Material Produced Via PM
Şöhret Melda Aydın Serdar Karaoğlu
AbstractAluminium and aluminium alloys have superior properties such as low density, high thermal conductivity, easy producibility and easy machinability. However, negative properties such as low hardness and low wear resistance limit the applications of aluminium. Making aluminium metal matrix composite (MMC) and various coating applications are also applied to increase wear resistance. [1]. One of the techniques used to increase the wear resistance of light metals is plasma electrolytic oxidation (PEO), in other words micro arc oxidation (MAO) [2]. PEO, an environmentally friendly coating method, allows coatings with very different mechanical and physical structures to be formed on the surfaces of materials such as Al, Mg, Ti. In this method, the sample is exposed to electrochemical oxidation similar to hard anodizing but with higher voltage. The growth of the oxide layer occurs at the potentials above the dielectric breakdown voltage of this insulating layer. Under these conditions, numerous short-time micro-arc discharges are formed on the coated surface. The coated surface usually consists of a porous oxide as a consequence of the localized electrochemical discharges at the electrode surface and the short-term melting is caused by these discharges. PEO operation provides a thick, hard oxide layer resistant to abrasion and corrosion. [3-6]. In this study, PEO coating was applied on 5% and 10% Al2O3 particle reinforced aluminium matrix composite material produced by powder metallurgy and their wear behaviours were investigated. The mixture of aluminium powder and reinforcing particles was pressed at 500MPa in a uniaxial cold press and sintered at 600°C for 8 hours. The PEO coating was applied on the samples at a constant current density of 20A/dm2 for 30 minutes in a Keronite G2 Micro Arc Oxidation unit. Scanning electron microscope (SEM) images were obtained for visual characterization of the uncoated and coated samples (Figure 1). Material stiffness was measured by micro Vickers method, applying 2kg load. It is seen that the reinforcement particles added to increase the strength increase the hardness, decrease the coating continuity and quality