The lubrication performance of graphene used as additive in 4-n-pentyl-4′-cyanobiphyl liquid crystal (5CB) for steel/steel contacts was studied on a ball-on-plate tribotester. The friction test results show that when the graphene content in the 5CB was 0.15 wt.%, and the lubricant and friction pairs were heated to 44–46 °C before friction tests, the lubrication performance of the 5CB was most improved. Compared with pure 5CB, 5CB+0.15 wt.% graphene suspension reduced the friction coefficient and wear scar diameter by up to 70.6% and 41.3%, respectively. The lubrication mechanisms have been tentatively proposed according to the test results. We speculate that the excellent lubrication performance of graphene/5CB suspensions may be attributed to the low shear resistance adsorption layer formed by graphene and 5CB molecules on the sliding surfaces. As the protective layer, it not only prevents direct contact between the rough sliding surfaces but also is easy to slide.

This study aimed at improving the cutting performance of a ceramic tool to which were added solid lubricant particles. We prepared the self-lubricating ceramic tool by adding CaF₂@Al₂O₃ instead of CaF₂, and the self-lubricating ceramic tool with Al₂O₃ as matrix phase, Ti(C,N) as reinforcement phase. The properties of the ceramic tool with different contents of CaF₂@Al₂O₃ and CaF₂ were studied by turning 40Cr. Compared with the ceramic tool with 10 vol.% CaF₂, the main cutting force and the cutting temperature of the ceramic tool with 10 vol.% CaF₂@Al₂O₃ decreased by 67.25% and 38.14% respectively. The wear resistance and machining surface quality of the ceramic tool with CaF₂@Al₂O₃ were better than the ceramic tool to which were directly added CaF₂. The optimal content of CaF₂@Al₂O₃ particles was determined to be 10 vol.%. The addition of CaF₂@Al₂O₃ particles effectively reduces the adverse effect of direct addition of CaF₂ particles on the ceramic tool, and plays a role in improving the cutting performance of the ceramic tool.

In this paper, the Voronoimosaic model and the cohesive element method were used to simulate crack propagation in the microstructure of alumina/graphene composite ceramic tool materials. The effects of graphene characteristic size and volume content on the crack propagation behavior of microstructure model of alumina/graphene composite ceramics under different interfacial bonding strength were studied. When the phase interface is weak, the average energy release rate is the highest as the short diameter of graphene is 10–50 nm and the long diameter is 1600–2000 nm. When the phase interface is strong, the average energy release rate is the highest as the short diameter of graphene is 50–100 nm and the long diameter is 800–1200 nm. When the volume content of graphene is 0.50 vol.%, the average energy release rate reaches the maximum. When the velocity load is 0.005 m s⁻¹, the simulation result is convergent. It is proven that the simulation results are in good agreement with the experimental phenomena.

Cutting heat conduction undergoes three stages that include intensity transient-state, transient-state, and steady-states. Especially during machining with coated cutting tools, in the conduction process, cutting heat needs to pass through a few micron thick coatings and then flow into the tool body. This heat conduction presents typical non-Fourier heat conduction characteristics. This paper focuses on the cutting temperature in transient heat conduction with a coated tool. A new analytical model to characterize the thermal shock based on the non-Fourier heat conduction was proposed. The distribution of cutting temperature in mono-layer coated tools during the machining was then illustrated. The cutting temperature distribution predicted by the Fourier heat conduction model was employed to compare with that by non-Fourier heat conduction in order to reveal the non-Fourier heat conduction effect in transient heat conduction. The results show that the transient heat conduction analytical model is more suitable for the intensity transient-state and transient-state in the process of cutting heat conduction.

In this paper, an Al₂O₃ coated CaF₂ (CaF₂@Al₂O₃) nanocomposite powder is used as the additive phase of a Ti(C,N)-based self-lubricating cermet material. A novel self-lubricating ceramic material with a multilayer core–shell microstructure was prepared using a vacuum hot-pressing sintering process. The results show that the surface of the CaF₂ powder is coated with Al₂O₃, and when introduced into a Ti(C,N)–Mo–Co–Ni material system, it can utilize the high-temperature liquid phase diffusion mechanism of the metal Mo–Co–Ni phase in the sintering process. The CaF₂@Al₂O₃@Mo–Co–Ni multilayer core–shell microstructure is formed in the material. Compared with the direct addition of CaF₂ and Al₂O₃, the hardness and fracture toughness of the material are increased by 24.31% and 22.56%, reaching 23.93 GPa and 9.94 MPa·m^1/2, respectively. The formation of the multilayer core–shell microstructure is the main reason for the improvement of the mechanical properties of the material.

The Al₂O₃/Ti(C,N) ceramic material added micron ZrO₂ whisker and nano coated CaF₂@Al(OH)₃ powder was fabricated. The micron ZrO₂ whisker was for the toughening and reinforcing phase and the nano coated CaF₂@Al(OH)₃ powder was the lubricant. For obtaining a ceramic material with optimal comprehensive mechanical properties and friction properties, the influences of different compositions of the ZrO₂ whisker and nano coated CaF₂@Al(OH)₃ powder on the microstructure and mechanical properties were analyzed, respectively. The result demonstrated that as the addition of the ZrO₂ whisker was 6 vol% and the addition of the nano coated CaF₂@Al(OH)₃ powder was 10 vol%, the optimal self-lubricating ceramic material had optimal mechanical properties. The hardness of the ceramic material was 16.72 GPa, the flexural strength was 520 MPa and the fracture toughness reached 7.16 MPa·m^1/2. The formation of the intragranular structure, whisker toughening and the phase transition of ZrO₂ were the main mechanisms.