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 CaF 2 solid lubricants were produced by vacuum hot pressing. Results showed that nano-sized CaF 2 was mainly located in matrix grains and formed the intragranular self-lubricating nanostructure. The optimal mechanical properties were achieved at 1650 °C and 15 min. The flexural strength, hardness and fracture toughness reaches the maximum of 497 MPa, 16.3GPa and 6.48 MPa·m1/2, respectively. Compared with the ceramic composite without CaF 2 , 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 CaF 2 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 self-lubricating effect. • Nano-sized CaF 2 solid lubricant is introduced into ceramic cutting tools. • (W,Ti)C-based ceramic composites with nano-sized CaF 2 solid lubricants were prepared by vacuum hot pressing method. • The flexural strength, hardness and fracture toughness reaches the maximum of 497 MPa, 16.3GPa and 6.48 MPa·m1/2. • CaF 2 effectively reduces the coefficient of friction on the front face of the tool. [ABSTRACT FROM AUTHOR]