Investigation on the wear performance of CoCrNi matrix self-lubricating composites at cryogenic temperature

The mechanical and tribological properties of CoCrNi-based composites at low temperature make them have the potential for cryogenic applications. However, traditional oil/grease lubrications are infeasible under ultra-low temperature, which limits further cryogenic applications of CoCrNi-based composites. Solid lubrication presents an effective approach to solving friction reduction and wear resistance issues at low temperature. In this work, the CoCrNi-Al₂O₃-Ni/MoS₂ self-lubricating composite were firstly proposed and its cryogenic tribological properties were investigated by ball-on-disk rotary wear tests. Compared to the CoCrNi-Al₂O₃ composite at 0 °C, the friction coefficient (COF) decreased to 0.38, meanwhile, the wear resistance increased by 14.8 times. Even under ultra-low temperatures of −120 °C, the wear rate remained at 6.78 × 10⁻⁵ mm³/Nm, maintaining a quite high wear resistance without significant deterioration. As the temperature decreases, the wear resistance of the CoCrNi-Al₂O₃ composite improved due to grain refinement and abundant deformation twins. The COF of the self-lubricating composite was reduced by the introduction of Ni/MoS₂. In addition, the interlayer shear of MoS₂ at −120 °C was indicated by molecular dynamics (MD) simulation to be less prone to occur. This work elucidates the cryogenic lubrication and wear-resistant properties of the CoCrNi-Al₂O₃-Ni/MoS₂ composite, highlighting its strong potential for cryogenic applications.