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Nano CaF 2 particles of different sizes were prepared by direct precipitation. The diameters of nano CaF 2 particles prepared in mixed solvent can reach 5–7 nm, and can be effectively dispersed. The surface of nano CaF 2 was modified and coated by heterogeneous nucleation method. A shell layer of Al(OH) 3 was coated on the surface of nano CaF 2 , and the structure and coating mechanism of the coated powder were analyzed. Under varying preparation conditions, the surface morphology of CaF 2 @Al(OH) 3 was analyzed using TEM and SEM. The results showed that the coating powder showed good dispersion in mixed solvents, and the particle size of the composite powder was about 20 nm. Self-lubricating ceramic tool materials were prepared by adding coating particles to the Al 2 O 3 /Ti(C,N) matrix. The coating powder shell and the matrix material melt during sintering, so that CaF 2 forms nanostructures in the particles. thereby improving the mechanical properties of the material. Cutting experiments show that the addition of coating particles can effectively reduce the temperature, cutting force and friction coefficient in the cutting process of the tool, thus improving the cutting performance of the tool material. [ABSTRACT FROM AUTHOR]

Abstract Due to the poor mechanical properties of solid lubricants, direct addition to the ceramic matrix will reduce the mechanical properties of the material. In this study, Al(OH) 3 was coated on the surface of nano CaF 2 by non-uniform nucleation method and added to Al 2 O 3 /Ti(C,N) ceramic matrix. Al 2 O 3 /Ti(C,N)/CaF 2 @Al 2 O 3 was prepared by vacuum hot pressing sintering. Compared with the material directly added with nano-solid lubricant, the mechanical properties of ceramic tools added with coated nano-solid lubricant have been significantly improved. Among them, when the content of coated nano-solid lubricant is 10 vol%, the ceramic material has better comprehensive mechanical properties. SEM observation shows that the cross-sectional particle distribution of nano-coated powder ceramic material is relatively uniform and has good compactness. The fracture mode of ceramic materials is a mixed fracture mode of intergranular fracture and transgranular fracture. Highlights • Al 2 O 3 was coated on the surface of nano CaF 2 by non-uniform nucleation method. • The mechanical properties of ceramic tools coated with nano-solid lubricants were significantly improved. • The microstructure of ceramic materials with coated nano-powders was studied. [ABSTRACT FROM AUTHOR]

The CaF 2 @Al 2 O 3 coated powder with shell-core structure was prepared by liquid-phase non-uniform nucleation method. Based on the successful preparation of Al(OH) 3 coated CaF 2 powder, Al 2 O 3 /TiC self-lubricating tool was prepared by wet dispersion mixing and vacuum hot pressing sintering process. The microstructure and performance of the self-lubricating ceramic tool with different volume content of CaF 2 @Al(OH) 3 coated powders were investigated. The results show that when the CaF 2 @Al 2 O 3 content is 10 vol%, the comprehensive mechanical properties of Al 2 O 3 /TiC/CaF 2 @Al 2 O 3 tool materials is the best, the hardness is 16.86 GPa, the flexural strength is 662 MPa, and the fracture toughness is 6.34 MPa·m 1/2 . Compared with the traditional Al 2 O 3 /TiC/10 vol%CaF 2 self-lubricating ceramic cutting tools, Al 2 O 3 /TiC/10 vol% CaF 2 @Al 2 O 3 ceramics in flexural strength, fracture toughness and hardness were increased 19.06%, 36.9%, 12.25%, of which the most obvious increase in fracture toughness. [ABSTRACT FROM AUTHOR]