Effect of Duty Cycle on Properties of Al(2)O(3) Ceramic Coatings Fabricated on TiAl Alloy via Cathodic Plasma Electrolytic Deposition

In order to study the effect of duty cycle during the cathodic plasma electrolytic deposition (CPED) process, Al(2)O(3) ceramic coatings were fabricated via the CPED technique on prepared TiAl alloy in an Al(NO(3))(3) electrolyte with different duty cycles. Microstructure, morphology, and chemical compositions of coatings were analyzed by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The mechanical properties, such as thickness, hardness, and binding strength, were also characterized, and heat-resistance and wear-resistance tested. The results indicated that duty cycle mainly affected the relative crystallinity of CPED coatings. As the duty cycle increased, the crystallinity of CPED coatings increased, the content of Al(OH)(3) and γ-Al(2)O(3) decreased, and the content of α-Al(2)O(3) increased. The thickness and bonding strength both increased firstly and then decreased, while hardness increased as duty cycle increased. Heat-resistance and wear-resistance of TiAl alloy with CPED coating was highly improved compared to that of TiAl alloy substrate without CPED coating.