A Novel Surface Coating Technique for Ti Alloys

摘要

A novel packed powder diffusion coating (PPDC) technique has been developed to improve the high temperature oxidation resistance and wear resistance of Ti alloys. Optical microscopy observations show that a thick coating is formed on both pure Ti and Ti-6Al-4V substrates after PPDC treatment. The thickness varies from 100 μm to 1295 μm depending on treatment temperature and time. Applying this technique to Ti-10Cr-2Fe-3Al and Ti-6Cr-5Mo-5V-4Al alloys, uniform coatings with thickness up to 1000μm have also been successfully obtained. Cyclic oxidation tests carried out in a static air within temperature range from 800 °C to 1000 °C for 24 cycles show high oxidation resistance of Ti alloysafter PPDC treatment, which is comparable with some Ni-base superalloys. Friction and wear tests at a load of 10-50N for 30 min indicate that the average friction coefficient and volume loss of the coatings is much lower than that of the Ti-6A1-4V substrate, exhibiting a better wear resistance. Therefore, the PPDC treatment can not only effectively prevent Ti alloy substrates from oxidation in air up to 1000 °C, but can also significantly improve their room temperature wear resistance. It is predicted that, after the treatment there will be strong potential to partially replace the Ni-base or Co-base superalloys with Ti alloys for high temperature applications, leading to dramatic reduction of cost.