The objective of this work was to determine the mechanisms of tribofilm formation during the gross slip fretting wear of Ti6Al4V and a thick nickel oxide film. This was accomplished by conducting bench level fretting wear experiments on Ti6Al4V surfaces mated with ∼75 μm thick nickel oxide scale. The nickel oxide scale was grown by oxidizing commercially pure nickel at 1000 °C. The fretting wear experiments were conducted at room temperature, 150, 300, and 450 °C, with a stroke length of 250 μm, at oscillation speeds of 2 and 30 Hz, and an approximate Hertzian contact stress of 650 MPa. It has been shown that at elevated temperatures, lubricious nanocrystalline tribofilms were formed in the fretting wear contact via a tribo-sintering mechanism. These tribofilms formed as transfer layers on the mated Ti6Al4V interface, and reduced the friction and wear on the mated surface at elevated temperatures.