2017A, 6061 ve 7039 alüminyum alaşımlarının mikroark oksidasyon yüzey kaplama yöntemi ile sert seramik kaplanması

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Thesis Type: Doctorate

Institution Of The Thesis: Kocaeli University, Fen Bilimleri Enstitüsü, Makina Mühendisliği Bölümü, Turkey

Approval Date: 2009

Thesis Language: Turkish

Student: AYTEKİN POLAT

Principal Supervisor (For Co-Supervisor Theses): Murat Makaraci

Open Archive Collection: AVESIS Open Access Collection

Abstract:

In this study, thick and hard alumina coatings resistant to wear and corrosion were fabricated on 2017A, 6061 and 7039 Al alloy substrates for different coating parameters by using of microarc oxidation (MAO) technique in an alkali-silicate electrolytic solution. The influence of the coating parameters such as the oxidation time, the current density and electrolyte concentration on the kinetic, phase composition, microstructure, hardness, surface roughness, adhesion to substrates, wear, corrosion of the coating and impact and tensile properties of al alloys were investigated. The results show that the kinetic of coating mainly depends on applied current density and, the coating thickness is increased linearly with increasing oxidation time. The surface roughness of coating is a function of coating thickness and increases with increasing coating thickness. The XRD results revealed that the coatings are composed of ?-Al2O3, ?-Al2O3 and mullite phase. The relative ratio of harder and denser ?-Al2O3 phase was increased with increasing current density and coating thickness. MAO coatings typically exhibit micro hardness gradient across the coating thickness with maximum hardness close to the interface and the lowest hardness at the surface of the coating. The surface roughness of the coatings was increased with increasing the coating time, current density and electrolyte concentration. MAO treatment will not greatly decrease the mechanical properties of the Al-based materials; especially it will enhance elastic modulus to some extend when appropriate coating parameters are selected. The wear and corrosion resistance of the Al alloy substrates are significantly increased after the modification of the microarc oxidation.Key Words: Aluminum Alloys, Surface Modification, Ceramic Coating, Microarc Oxidation, Wear, Hardness, Wear, Tribology, Corrosion, Hardness, Adhesion, Surface Roughness