Surface aluminizing on Ti-6Al-4V alloy via a novel multi-pass friction-stir lap welding method: Preparation process, oxidation behavior and interlayer evolution

► A novel multi-pass FSLW method was used for surface aluminizing on Ti-6Al-4V alloy. ► Significantly thick coating was obtained with solid-state joint-typed adhesion. ► Abundant Al content benefited anti-oxidation and Ti/Al aluminide interlayer formation. ► Thick aluminide interlayer exerted a main protection role of oxygen corrosion.