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In this work, a Cu/h-BN self-lubricating coating was prepared on cemented carbide by electrospark deposition (ESD). The microstructure and properties of the coating were examined. The results showed that no decomposition of or reactions with h-BN occurred. As the h-BN content and capacitance increased, the number of pores and microcracks in the coatings increased. Additionally, as the capacitance increased, the electrode mass loss increased. However, the specimen mass increased first and then decreased. The coating thickness was affected by the capacitance, deposition time, and volume ratio of h-BN to Cu. The results exhibited were consistent over the tests. The self-lubricating coating exhibited excellent tribological behavior under the test conditions, and the worn surface showed features consistent with shear slippage and abrasive wear.

Al 2 O 3 /TiC ceramic composites with the additions of CaF 2 solid lubricants were produced by hot pressing. Sliding wear tests against cemented carbide were performed on these ceramic composites using the ring-block method. The friction coefficient and wear rates were measured. Results showed that the friction coefficient and the specific wear rate decreased with the increase of CaF 2 content up to 10 vol.%, with further increases in CaF 2 content, both the friction coefficient and the wear rate increased rapidly. SEM observations showed that self tribofilms were consistently formed on the wear surfaces. Two types of tribofilms are present on the worn surface depending on the CaF 2 content. A dense self tribofilm with a smooth surface associated with small friction coefficient and low wear rate was formed by the releasing and smearing of CaF 2 solid lubricants on the wear surface when with low CaF 2 content (less than 10 vol.%). This dense self tribofilm acted as solid lubricant film between the sliding couple, protected the ceramics from severe wear by brittle microfracture, and thus significantly reduced the friction coefficient and the wear rate. A broken tribofilm associated with high friction coefficient and large wear rate was formed when with high CaF 2 content (more than 10 vol.%). The reason is that large degradation of mechanical properties occurred in samples with high CaF 2 contents.

An Al 2 O 3 /TiC ceramic cutting tool with the additions of CaF 2 solid lubricant was produced by hot pressing. The fundamental properties of this ceramic cutting tool were examined. Dry machining tests were carried out on hardened steel and cast iron. The tool wear, the cutting forces, and the friction coefficient between the tool–chip interface were measured. It was shown that the friction coefficient at the tool–chip interface in dry cutting of hardened steel and cast iron with Al 2 O 3 /TiC/CaF 2 ceramic tool was reduced compared with that of Al 2 O 3 /TiC tool without CaF 2 solid lubricant. The mechanisms responsible were determined to be the formation of a self-lubricating film on the tool–chip interface, and the composition of this self-lubricating film was found to be mainly CaF 2 solid lubricant, which was released and smeared on the wear track of the tool rake face, and acted as lubricating additive between the tool–chip sliding couple during machining processes. The appearance of this self-lubricating film contributed to the decrease of the friction coefficient. Cutting speed was found to have a profound effect on this self-lubricating behavior.

Al 2 O 3 /TiC, Al 2 O 3 /Ti(C,N), Al 2 O 3 /(W,Ti)C, and Al 2 O 3 /SiC w alumina-based composites, which provided a reasonably wide range of mechanical properties and microstructure, were produced by hot pressing. The unlubricated friction and wear behaviors of these composites against cemented carbide were studied in air atmosphere using the ring-block method. The friction coefficient and wear rates were measured, and the wear mechanisms were discussed in relation to mechanical properties and microstructure. Results showed that additions of TiC, Ti(C,N), (W,Ti)C, or SiC w to the Al 2 O 3 matrix increased the flexural strength, fracture toughness, and hardness compared to the monolithic Al 2 O 3 matrix. The friction coefficient showed a downward trend with the increasing of the sliding speed, and decreased dramatically with increasing applied load for all the alumina-based composites. The Al 2 O 3 /TiC composite showed the highest wear rate, and the Al 2 O 3 /SiC w the lowest one under identical test conditions. The higher wear resistance of Al 2 O 3 /SiC w composite corresponded to its higher fracture toughness and hardness.

In this paper, Al 2 O 3 /TiB 2 ceramic cutting tools with different TiB 2 content were produced by hot pressing. The fundamental properties of these ceramic cutting tools were examined. Dry high-speed machining tests were carried out on hardened steel. The tool wear, the cutting temperature, the cutting forces, and the friction coefficient between the tool and the chip were measured. It was shown that both the wear rates and the friction coefficient at the tool–chip interface of Al 2 O 3 /TiB 2 ceramic cutting tools in dry high-speed machining of hardened steel were reduced compared with that of in low-speed machining. The mechanisms responsible were determined to be the formation of a self-lubricating oxide film on the tool–chip interface owing to the tribological–chemical reaction by the elevated cutting temperature. The composition of the self-lubricating film was found to be the oxidation product of TiB 2 grains, which serves as lubricating additive on the wear track of the tool rake face. The appearance of this self-lubricating oxide film contributed to the improvement in wear resistance and the decrease of the friction coefficient. This action was even more effective with higher TiB 2 content. Cutting speed was found to have a profound effect on the self-lubricating behavior. In dry low-speed machining of hardened steel, the Al 2 O 3 /TiB 2 tools showed mainly adhesive and abrasive wear. While in dry high-speed machining, oxidation wear of the ceramic tools was the dominant mechanism due to the very high cutting temperature. No oxide film was formed on the tool–chip interface while machining in nitrogen atmosphere, and the tool wear resistance was correspondingly decreased.