Self-lubrication of Al2O3/TiC/CaF2 ceramic composites in sliding wear tests and in machining processes

Al2O3/TiC ceramic composites with the additions of CaF2 solid lubricants were produced by hot pressing. Sliding wear tests against cemented carbide and dry machining tests on hardened steel were performed on these ceramic composites. Results showed that the ceramic composites exhibited self-lubricating property both in sliding wear tests and in machining processes. Scanning electron microscopy observations showed that a self-tribofilm was consistently formed on the wear surfaces, and the composition of the self-tribofilm was found to be mainly CaF2 solid lubricants. This self-tribofilm was formed by the releasing and smearing of CaF2 solid lubricants on the wear surface, acted as a lubricating additive between the sliding couple or on the tool–chip interface, protected the ceramics from severe wear by brittle microfracture, and significantly reduced the friction coefficient.