Design of Plasma Electrolytic Oxidation Coatings on Ti-30Zr-5Mo Alloy and Assessment of Corrosion Resistance in Simulated Physiological Environment

نوع: Type: Thesis

مقطع: Segment: masters

عنوان: Title: Design of Plasma Electrolytic Oxidation Coatings on Ti-30Zr-5Mo Alloy and Assessment of Corrosion Resistance in Simulated Physiological Environment

ارائه دهنده: Provider: aida soltani seif

اساتید راهنما: Supervisors: Dr. Arash Fattah-Alhosseini

اساتید مشاور: Advisory Professors: Dr. Razieh Charmahali

اساتید ممتحن یا داور: Examining professors or referees: Dr. Omid ImanTalab and Dr. Mazdak Izadi

زمان و تاریخ ارائه: Time and date of presentation: 2026

مکان ارائه: Place of presentation: سالن کنفرانس

چکیده: Abstract: In this study, plasma electrolytic oxidation (PEO) coatings were formed on a Ti–30Zr–5Mo titanium alloy in an alkaline electrolyte. The effects of current density (40, 80, and 120 mA/cm²), process time (5, 7, and 9 min), duty cycle (20, 50, and 80%), and frequency (10, 100, and 1000 Hz) on the microstructure, phase composition, and corrosion behavior of the coatings were investigated. The microstructure and chemical composition of the coated samples were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). To study the corrosion behavior of the coatings formed under different conditions, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests were used in simulated body fluid (Ringer's solution). In the current density study, the sample treated at 80 mA/cm² with a surface porosity of 5.33% exhibited the lowest porosity and the densest microstructure. This sample also had the highest resistances of the inner and outer layers and the lowest corrosion current density. X-ray diffraction patterns showed the formation of anatase and rutile TiO₂ phases, monoclinic zirconium oxide, and ZrTiO₄ in all samples; at the same time, the peaks related to the α and β phases of the substrate were retained. In the process time study, the coating formed for 7 min showed the lowest surface porosity and the most uniform microstructure, and it had the highest resistances of the inner and outer layers, the lowest corrosion current density, and the most positive corrosion potential. Under a 50% duty cycle, a uniform and dense microstructure was also obtained, and the highest resistances of the inner and outer layers and the lowest corrosion current density were achieved. Moreover, at a frequency of 1000 Hz, the formed coating had a dense and uniform microstructure and showed the lowest corrosion current density and the most positive corrosion potential. XPS analysis confirmed the formation of a multi-component oxide layer containing TiO₂, ZrO₂, MoO₃, and MoO₂. The predominant oxidation states included Ti⁴⁺, Zr⁴⁺, and mixed Mo⁶⁺/Mo⁴⁺ states. The presence of the stable oxides titanium dioxide and zirconium dioxide indicates the suitable chemical stability of the oxide layer and its role in improving the corrosion resistance of the coating. These findings show that plasma electrolytic oxidation coatings are an effective approach for significantly increasing the corrosion resistance of the Ti–30Zr–5Mo alloy, thereby expanding its biomedical application.