Comparative study of AA6061 and AA6063 aluminum alloy coating on mild steel using friction surfacing

Friction surfacing is one of the recent technologies applied in surface engineering for the development of surface materials. It is a solid-state technique employed to coat one material over the another in order to reconstruct the worn-out parts. Friction surfacing is done to enhance the wear and corrosion resistance, as well as mechanical properties in materials. It is an environmentally safe process in which a consumable rod is deformed plastically and forms a deposit of viscoelastic material over the substrate. In this study, aluminum alloys (AA), such as, AA6061 and AA6063 were deposited over mild steel by friction surfacing process. The consumable aluminium alloys were provided a constant rotational speed of 2000 rpm and axial force of 10 kN, at three different travel speeds of 250 mm/min, 400 mm/min and 630 mm/min for the deposition of aluminium over mild steel substrate plate. The AA-samples were prepared by "wire electric discharge machining (WEDM)" process and were finished by rotating wheel polishing machine. The thickness and width of the coatings were measured after the deposition. The 'optical microscope' and 'field emission scanning electron microscope (FESEM)' were utilized to do the microstructural assessment of the deposited surface. The surface roughness was analyzed by non-contact type profilometer. The X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) analysis were performed for the study of different phases present in the coating samples. The hardness variation over the coating surface due to varying travel speed was measured by Vickers micro hardness tester. The coating done by AA6063 alloy was found harder than the coating of AA6061. The surface roughness of aluminum alloy AA6063 coating is higher at 250 mm/min and slightly less at 630 mm/min, compared to aluminum alloy AA6061 coating. In addition, examination of the interface area of aluminium deposit over mild steel was done using FESEM. Through EDS elemental analysis it is established that aluminium is present in more than 90% with other elements like Mg and Si. By XRD analysis high intensity peaks of aluminium were recorded on different planes. Results show poor bonding between layers at 250 mm/min and 630 mm/min, while good bonding at 400 mm/min which improves properties.