Formation of Ti-Al intermetallics on a surface of titanium by non-vacuum electron beam treatment

Abstract

Titanium and titanium alloys are highly important structural materials for many industries where low density in combination with high mechanical strength and corrosion resistance are required. However, titanium is not applicable for tribological or high temperatures purposes due to its interaction with atmospheric gases and friction seizure during the contact with most metallic materials. To protect the surface of titanium and improve its wear resistance intermetallic coatings can be applied. In this study, the Ti-Al intermetallic layers were fabricated on Ti surface by electron beam melting of Al and Ti powders. By variation of Al/Ti ratio in the initial powders it was possible to control elemental and phase composition of the layers. The formation of TiAl, Al2Ti and Ti3Al phases was observed in the layers. Independently on Al content the layers had lamellar type of structure. Microhardness, wear resistance and oxidation resistance were measured to evaluate the quality of the layers. The microhardness and wear resistance were in good agreement with each other. The coating, consisted of pure Ti3Al phase, demonstrated the highest level of these properties. Oxidation resistance of the coatings increased proportionally to the aluminium content due to formation of alumina in oxide scale.