High-pressure infiltration fabrication of self-lubricating ceramic tools for dry machining: Mechanistic insights into lubrication behavior and mechanical performance

Self-lubricating ceramics are advanced tool materials used for cleaner production under extreme dry-cutting conditions. However, the mechanical properties of self-lubricating ceramic tools are degraded due to the incompatibility between the lubricating particles and the ceramic matrix. Additionally, the coupling of mechanical and lubrication properties renders the lubrication mechanisms unpredictable. To address these challenges, we propose a high-pressure infiltration scheme combined with a two-step preparation of self-lubricating ceramics. WC/cBN porous ceramics provide a pore framework with excellent mechanical properties and maintain excellent hardness when coated with high-pressure infiltrating lubricants. Moreover, the lubricant filling releases the stress field and gives rise to a phase transition toughening mechanism. Combining experiments and molecular dynamics simulations, we reveal the infiltration mechanism of lubricating phases within nanopores under extreme conditions. In addition, the coupling between the mechanical properties and lubrication performance was revealed, and the wear reduction mechanism of the self-lubricating ceramics was described and analytically modelled. Finally, the feasibility of the process demonstrated using cutting tests. The results indicated that the coefficient of friction of the ceramic tool decreased by 40 %, and the tool wear was reduced by 36 %.