Dry sliding behaviour of the A357 aluminium alloy processed by Selective Laser Melting and anodized by Electrochemical Oxidation (ECO)

Selective Laser Melting (SLM) is increasingly employed for producing complex, customised aluminium alloys parts for engineering applications in automotive, aerospace and aircraft. However, an important limitation of these alloys is their poor tribological properties in sliding conditions, which can be improved by surface treatments such as anodizing. Processing conditions during SLM strongly affect both surface roughness and microstructure (leading to hierarchical microstructure and very fine distribution of eutectic Si network in Al-Si alloys), hence influencing the growth of the anodic oxide. In this study, Electro-Chemical Oxidation (ECO) at high voltage was applied to the A357 (AlSi7Mg) alloy produced by SLM, in order to improve its tribological behaviour. Sand cast A357, heat-treated to T6 condition was investigated as a reference for comparison. Dry sliding tests were carried out in block-on-ring configuration against a quenched and tempered SAE52100 (100Cr6) bearing steel rotating cylinder, using the anodized alloys as stationary blocks. The results of this study allowed the comparison of microstructural features and dry sliding behaviour of the oxide layers grown on both the conventional sand cast and SLM A357 alloy.