EFFECT OF CONTROLLED TEMPERATURE ON SURFACE PROPERTIES OF ANODIC ALUMINUM OXIDE COMPOSITE COATING

Abstract

Bi-layered coating strategies for carbon-based materials reinforcement of composite oxide coatings show promise for producing long-lasting durable materials. The bi-layered coating comprises an oxide/graphite lubricant composite (top layer) and Diamond-like carbon (DLC)-contained oxide coating (sub-layer). Reinforcement particles contribute to the oxide coating by filling pores formed after anodizing; however, they do not alter the porous structure. However, the porous structure can be regulated by adjusting the electrolyte temperature, as anodizing temperature influences the growth and morphology of the oxide coating. A higher electrolyte temperature can increase porosity, which leads to hardness reduction. This study aims to control electrolyte temperature and examine the porous structure of the bi-layered composite oxide coating. The bi-layered composite oxide coating was fabricated on aluminum alloy (AA2017-T4) by anodizing method with various constant electrolyte temperature (30 ℃, 40 ℃, 50 ℃ & 60 ℃).  The surface roughness of the oxide coating measured by 3D optical profiler where it affected by the pore dimension of the oxide layer. Then the microhardness was measured by using the Vickers hardness test. The pore dimension of the oxide layer showed reduction. The microhardness increased approximately up to twofold (from 205.8 HV to 413.4 HV) for conventional oxide coating and up to 25.10% (from 345.8 HV to 432.7 HV) for bi-layered composite oxide coating when compared between uncontrolled electrolyte temperature with controlled electrolyte temperature due to densification of the oxide film occur when the temperature of the electrolyte during the anodization controlled, especially at 50 ℃ where the highest microhardness achieved. Therefore, this finding will contribute to automotive applications as it enhanced the properties of the aluminum alloy where it is widely used in aircraft and automotive parts.