Al-1050 위에 플라즈마 전해 산화법으로 형성된 Al2O3피막 특성에 미치는 듀티사이클의 영향

Abstract

Oxide coatings were prepared on Al-1050 substrates by an environment-friendly plasma electrolytic oxidation (PEO) process using an electrolytic solution of Na₂SiO₃ (8 g/L) and NaOH (3 g/L). The effects of three different duty cycles (20%, 40%, and 60%) and frequencies (50 ㎐, 200 ㎐, and 800 ㎐) on the structure and micro-hardness of the oxide coatings were investigated. XRD analysis revealed that the oxides were mainly composed of α-Al₂O₃, γ-Al2O3, and mullite. The proportion of each crystalline phase depended on various electrical parameters, such as duty cycle and frequency. SEM images indicated that the oxide coatings formed at a 60% duty cycle exhibited relatively coarser surfaces with larger pore sizes and sintering particles. However, the oxides prepared at a 20% duty cycle showed relatively smooth surfaces. The PEO treatment also resulted in a strong adhesion between the oxide coating and the substrate. The oxide coatings were found to improve the micro-hardness with the increase of duty cycle. The structural and physical properties of the oxide coatings were affected by the duty cycles.