Research On Oxidation-resistant And Lubricating Glass Based Coating For Ti Alloys

Titanium alloy which has many excellent properties, such as small density, high strength-to-weight ratio, good corrosion resistance, high and low temperature resistance performance, nonmagnetic and non-toxic, is a kind of important structural materials follow as steel and aluminum. After half a century of development, Titanium alloy have been widely used in the aerospace, aviation, navigation, chemical industry, light industry, metallurgy, machinery, medical, energy, and many other fields. However, serious oxidation of Titanium alloys at high temperatures limits their industrial applications. The study shows that the glass based coating can not only be used as a protective coating for high temperature and long time, but also can be used as a lubricant for hot working of Titanium alloy. Based on these application, in this work, two types of glass based coatings were prepared on Ti-6Al-4V alloys according to design principles of coatings: on the one hand, glass based coating contained glass-ceramic coatings for Titanium alloys working at high temperatures for a long time; on the other hand, a kind of glass protective lubricant coating for Titanium alloy forging. The work mainly includes the following aspects:?1?Three kind of Na₂O-CaO-Al₂O₃-SiO₂ glass-ceramic coatings with different Al₂O₃ content were successfully prepared on Ti-6Al-4V alloy by sintering method, which are NCAS0?NCAS5 and NCAS10.These all can be used as a long term protective coating for Ti-6Al-4V alloy. The isothermal oxidation tests?800?, 100 h? showed that three kind of the above glass-ceramic coatings have a good protection of high temperature oxidation. Compared with the XRD map of before and after oxidation, the three kinds of main metallographic for glass-ceramic coatings were found to have no change, which showed that the three kind of glass-ceramic coatings had better performance of high temperature thermal stability. From the cross section SEM morphology of the three kinds of glass-ceramic coatings, it can be found that the NCAS10 glass-ceramic coating is the most compact, the best sealing performance, and the best protection effect.?2?A kind of glass protective lubricant coating was successfully developed for Ti-6Al-4V alloy forging. It has the advantages of wide application temperature, good oxidation resistance, good lubrication effect, high temperature performance, and no lead and other toxic elements which are in line with the characteristics of environmental protection requirements. The coating has begun softening at 700?, completely melted at 800?and would not happen flowing until 1000?.It still has high temperature performance and can be applied for Ti-6Al-4V alloy forging. SEM, EDS analysis and metallographic hardness test data have showed that the coating has good oxidation resistance; as the same time, the ring upsetting tests showed that it has lower coefficient of friction. Finally, the forging tests showed that this coating has excellent oxidation resistance and lubrication performance.