Preparation And Characterization Of A Duplex Coating Produced On Titanium Alloy By Micro-arc Oxidation And Enameling

In this study,the MAO and enameling processes were used to improve the mechanical and anti-corrosion properties of titanium alloy.The MAO method was used to carry out a ceramic coating on titanium alloy substrate at the first step,then enamel coatings was manufactured by spraying and sintering to seal on the MAO ceramic coating to improve titanium alloy's properties at the second step.Phase structure,surface morphology,hardness and corrosion property of these coatings were analyzed by X-ray diffraction?XRD?,scanning electron microscope?SEM?,micro Vickers tester,and electrochemical workstation,respectively.Tribological property and acid corrosion property were emphatically studied with friction-wear tester and weight loss method,respectively.The results indicated that the ceramic coating consists of rutile TiO₂and anatase TiO₂ phases and the rutile phase increased while the ceramic coating was heated;the hardness of the MAO coating was improved to486HV compared to the titanium alloy's 345HV and its roughness also increased significantly;the friction coefficient of MAO coating decreased when the load was increased,but still higher than the friction coefficient of substrate;the corrosion potential of samples increased from-0.6V to-0.3V,the corrosion current density reduced two orders of magnitude,but MAO coating can not stand with the corrosion of 5wt.%H₂SO₄ at 80?.The phases of duplex coating mainly relevant to the ingredient of enamel;the hardness of the duplex coatings were improved to 730HV;both the roughness and friction coefficient of duplex coating decreased compared to ceramic coating while the wear resistance increased significantly,and the friction coefficient of duplex coatings also decreased when the load was increased.The corrosion potential of duplex coatings increased to-0.21V,the corrosion current density reduced about three orders of magnitude compared with substrate.In addition,the duplex coating has a good resistance to 5wt.%H₂SO₄ at 80?,so the corrosion property of duplex coating was better than the ceramic coating.