Study On Preparation And High Temperature Oxidation, Hot Corrosion Property Of Enamel Coating And Micro-arc Oxidation Coating

Titanium alloys play an important role in materials used for gas turbine engines due to their low density and high strength-to-density ratio.The problem of poor ductility of these materials at room temperature has been mostly solved by alloying and microstructure controlling. Thus the problem of farther improving high temperature oxidation and corrosion resistance has become one of the most important research subjects. Based on studying and analysing the effect of micro-arc oxidation (MAO)coating and enamel coating on high temperature oxidation and corrosion protective performance , a effective functional coating to improving the high temperature oxidation and corrosion protective performance of titanium alloys is put forward.Silicate solution was adopted as the most suitable solution for preparing the micro-arc oxidation coatings on Ti6Al4V alloy. By using optimized processing parameters, dense micro-arc oxidation coatings with good adhesion to Ti6Al4V alloy substrate were successfully prepared. In order to low the sinter temperature of the enamel coating, the enamel frit was milled in to submicron particles by ball milling,and it can be sintered at 950℃.Effect of enamel coating on oxidation property of Ti6Al4V alloy was studied and was compared with MAO coating. After oxidation, the surface of Ti6Al4V formed TiO2, and the oxidation film was completely fell of, but no oxidation and inter-diffusion was detected at the interface of enamel/Ti6Al4V.Enamel coating improved the oxidation resistance of Ti6Al4V alloy significantly. The MAO coating was metallurgical bonded between the coating and steel substrate. The dense micro-arc oxidation coatings can effectively prevent Ti6Al4V alloy from high temperature oxidation..Effect of enamel coating and MAO coating on hot corrosion property in molten salt of Ti6Al4V alloy was studied.Ti6Al4V alloy suffered heavy corrosion from molten salt. During corrosion, three layers with little protectiveness formed on Ti6Al4V alloy. However, MAO coating failed in this environment, the coating was completely fell off, and a thick corrosion layers appeared. Enamel coating showed rather chemically inert to corrosive environment , thus it could act as a barrier to corrosion by molten NaCl+Na2SO4 salt .