A comparative study on Aluminum-Silicon coatings fabricated by Electrospark Deposition

In today's industrial sector, there is a growing interest in eco-friendly practices, along with the essential goal of improving the durability and resistance to wear and corrosion of mechanical components exposed to harsh environments by applying coatings. A key technology meeting these objectives is Electrospark Deposition (ESD), a micro-welding process that allows electrically conductive substrates to be coated with different materials. ESD also facilitates precise, small-scale repairs of high-value components damaged, worn, or affected by manufacturing defects. This study examines and compares the quality of A357 and C355 aluminium alloy coatings deposited on homologous substrates using ESD technology. It focuses on microstructural characteristics, mechanical properties, and stereological features. Three different discharge power levels were used to deposit coatings on both aluminium alloys. The cross-sectional coatings were examined using scanning electron and optical microscopy to analyse their microstructure and evaluate the coating quality in detail. Additionally, the mechanical properties of the coatings were assessed through Vickers microhardness testing. The microstructural analysis indicates that irrespective of the discharge power employed, all coatings exhibit a very fine microstructural morphology attributed to rapid solidification. Furthermore, experimental findings reveal that all coatings exhibit defects, manifested in the form of various morphologies of voids. Additionally, unlike the A357 samples, the C355 samples display cracks at the interface between the substrate/coating, extending into the base material. The defects percentage within the A357 and C355 coatings, primarily attributed to mass transport and stress thermal, is less than 4 and 8%, respectively. Finally, microhardness values in all coatings, irrespective of discharge power settings, are lower than the substrate material. This is primarily attributed to the presence of internal defects.