Multiple Lubrication Mechanisms and Performance Prediction in WC-cBN-MoS2 Self-Lubricating Ceramics

Lubrication performance is a critical index determining the service performance of self-lubricating ceramic cutting tools, but the coupling between mechanical properties, lubrication, and wear makes the lubrication effect challenging to predict. In this paper, WC-cBN-MoS2 self-lubricating ceramics with 15 vol% MoS2 and a range of mechanical properties (Vickers hardness: 10.33–20.22 GPa; fracture toughness: 1.8–5.95 MPa·m1/2) were fabricated by high-pressure sintering. A lubricating particle release model is established to analyze the contributions of matrix deformation and surface wear to lubricant release. It is found that matrix deformation alone cannot extrude lubricating particles to the surface; instead, wear is the primary mechanism supplying particles to the friction interface. The lubricating film, containing both ceramic matrix debris and lubricating particles, exhibits characteristics of multi-media powder lubrication, with film thickness increasing linearly with applied load and sliding speed. The friction coefficient shows a non-monotonic relationship with load and speed, attributed to the coexistence of powder lubrication within the film and quasi-boundary lubrication at the upper interface. A predictive model is established based on the superposition of these two mechanisms, and its predictions agree well with experimental measurements. This work clarifies the multiple lubrication mechanisms of self-lubricating ceramics and provides a quantitative framework for predicting their tribological performance.