Properties of Ti-Al intermetallic coatings obtained by electrospark processing in a mixture of Ti and Al granules

Abstract

Titanium alloys attract a wide attention of researchers due to the unique combination of low density and high strength, hardness, corrosion resistance, biocompatibility, etc. Therefore, the study of new methods for processing titanium and the development of coatings from titanium intermetallic compounds seems relevant. In this paper, we consider the properties of Ti-Al coatings deposited by electrospark processing of a Ti6Al4V titanium alloy in a mixture of granules of titanium and aluminum in five different ratios with an aluminum content of 24 to 87 at.%. X-ray phase analysis showed the evolution of the intermetallic composition of the coatings with an increase in the aluminum content in the mixture of granules from the AlTi 3 to Al 3 Ti phase. Potentiodynamic polarization tests in a 3.5 % NaCl solution showed that coatings could improve the corrosion resistance of the Ti6Al4V alloy. A high-temperature gas corrosion test for 100 hours at a temperature of 900°C showed that coated samples were oxidized 1.1-3.4 times less than the Ti6Al4V alloy. The best properties was exhibited by the coating with the highest aluminum content. The coatings had an increased microhardness of 6.4-9.4 GPa. Coatings with a closer ratio of titanium to aluminum had the highest hardness. The wear resistance of the coatings in the dry slip mode at loads of 10 and 25 N was 4-27 and 6-36 times, respectively, higher than that of the Ti6Al4V alloy. The wear rate of the coatings decreased with increasing titanium concentration. The dependence of the wear resistance of coatings on their hardness for the obtained Ti-Al coatings is exponential, which is consistent with the Archard law.