Synthesis of quinary M₃AlC₂ (M = Ti, Cr, and Mo) o-MAX and its energy dissipation-enhanced anti-wear performance

MAX phase ceramics are a promising candidate for high-temperature self-lubricity, while improving their tribological performance under insufficient oxidation-coupling conditions is still challenging. Herein, a new quinary out-of-plane ordered M₃AlC₂ (M = Ti, Cr, and Mo) MAX is constructed, and its tribological properties are comparatively studied with its M₄AlC₃ analogue at 25–800 ºC in the air. The capacity of energy dissipation (E_r²/H) is proven to be an indicator of the tribological properties. For M₃AlC₂ with a higher E_r²/H, a lower COF in the tested temperature window is achieved. Meanwhile, under insufficient oxidation-coupling conditions, the improved anti-wear performance of M₃AlC₂ is in agreement with its higher E_r²/H. The current study paves the new route for the design of MAX solid lubricant.