Ordered metal substitution in Ti₃AlC₂ and the effect on tribological behaviors in a wide temperature range

In this work, tribological properties of Ti₃AlC₂, Cr₂TiAlC₂, and Mo₂TiAlC₂ MAX are evaluated in a wide temperature range of 25–800 ℃. By replacing the 4 f Wyckoff site Ti atoms of Ti₃AlC₂ with Cr or Mo, the MAXs deliver lower coefficient of friction (COF) than Ti₃AlC₂. Interestingly, as confirmed by the morphological, structural, and chemical analyses, the two MAXs are applicable in different temperatures. For Cr₂TiAlC₂, the lowest wear rate is 2.30 × 10⁻⁷ mm³ N⁻¹ m⁻¹ at 800 ℃, while the lowest wear rate of Mo₂TiAlC₂ is achieved at room temperature of 3.83 × 10⁻⁷ mm³ N⁻¹ m⁻¹. These distinct tribological behaviors are ascribed to the altered M-A and M-C bindings, as well as the properties of the produced oxides.