Mechanical property and cutting performance of (W,Ti)C based ceramic composites with the addition of nano-sized CaF2

In order to improve the mechanical property of self-lubricating ceramic cutting tool, (W,Ti)C based ceramic composites with the additions of nano-sized CaF2 solid lubricants were produced by vacuum hot pressing. Results showed that nano-sized CaF2 was mainly located in matrix grains and formed the intragranular self-lubricating nanostructure. The optimal mechanical properties were achieved at 1650 degrees C and 15 min. The flexural strength, hardness and fracture toughness reaches the maximum of 497 MPa, 16.3GPa and 6.48 MPa.m(1/2), respectively. Compared with the ceramic composite without CaF2, the fracture toughness was increased by 13.0%. Dry machining tests of hardened 40Cr steel were performed with these ceramic cutting tools. It indicated that with the additions of nano-sized CaF2 as solid lubricant, the main cutting force and cutting temperature were reduced by 13.2% and 26.9%, the average friction coefficient of rake face was reduced from 0.59 to 0.32. SEM micrograph showed that a self-tribofilm was consistently formed on the rake wear area which has a good selflubricating effect.