New Insights into Microstructure Characteristics and Tribological Property of Ti Alloy Processed by Hot-Dip Aluminizing and Heat Treatment

The poor tribological properties of Ti alloys limit their infield applications under sliding conditions. In this study, the surface of a Ti–6Al–4V alloy was coated with pure Al using a hot dipping process. The interface between coated pure Al and Ti–6Al–4V was characterized after the hot dipping and subsequent heat treatment. The effects of both processes on the interface microstructure and the formation mechanism of the Ti/Al interface were investigated. A metallurgical bond was established at the interface between Al coating and Ti–6Al–4V substrate following the hot dipping. Subjecting samples to heat treatment resulted in oxidation of Al coating and transforming into alumina (Al 2 O 3 ) while Ti–Al intermetallic compounds were formed. Microhardness and tribological properties of the Al coated Ti–6Al–4V sample were measured. When the heat treatment temperature was 750 °C, the microhardness reached the maximum of about 500 HV. The overall trend for the friction coefficient showed to decrease first, and then increased and fluctuated around a constant value. The friction coefficient of the sample subjected to heat treatment at 750 °C for 6 hours remained low. The optimized process parameters can be summarized as hot dipping at 700 °C for 15 mins, followed by a heat treatment at 750 °C for 6 hrs. This process can improve the wear resistance of Ti–6Al–4V alloy through the formation of block-like TiAl 3 phase and oxides. The results were helpful and could form a basis for further researches on enhancing the tribological property of Ti alloys. Graphical Abstract