| Titanium alloy is widely used in aviation,aerospace,automobile and ship areas with the advantages of high strength,high fatigue strength,good toughness and low forging temperature.Micro arc oxidation(MAO)is a surface treatment technology on metal such as titanium,aluminum and magnesium.With the MAO process,the compact oxidation coating are obtained on the surface of alloys,and the properties of the alloy are improved.Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe alloy is one of β high strength titanium alloy,and its commonly used heat treatment methods for strength increasing is solution/aging heat treatment and for plasticity improving is solution heat treatment.At present,there are many studies of micro arc oxidation on titanium alloy,but the deep research on the effects of heat treatment on properties of MAO coating is still needed.Hence,this study is focus on the connection of heat treatment and micro arc oxidation on titanium alloy.In order to study the effect of heat treatment on the characteristics of MAO coating on β titanium alloy.The Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe alloy was treat by MAO process after different heat treatment processes.The characteristics of MAO coatings were investigated by SEM,XRD and EDS.The growth process of MAO coating was also discussed in this work.The results show that the phase structure,distribution of element and electric potential of the Ti-3.5Al-5Mo-6V-3Cr-2Sn-0.5Fe alloy were changed,and the characteristics of the coating were affected.The thickness of the coating on alloy with750℃ was 76.3 μm and the roughness was 7.49 μm,and the thickness and roughness of the film treated by solid solution at 850℃ were the lowest 48.3 μm and 7.45 μm.The results of SEM show that the densification of the coating increased.It indicates that the phase composition,element distribution and electric potential of the substrate alloy affect the properties of MAO coating which changed by heat treatment.At the preliminary stage(120 s)of MAO,the thickness and roughness of the coating increased,and the surface morphology show that the size of the discharge hole and the amount of the molten material increased with the increasing of the oxidation time.The most smooth and smallest roughness coating was obtained on the surface of alloy with 750℃ solution heat treatment.The corrosion resistance of the coating on the alloy with 750 ℃ was better than that of the casting alloy and alloywith 850℃ solution heat treatment. |
