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Aiming to improve the performance of self‐lubricating ceramic tools, an advanced self‐lubricating ceramic composite was developed. Core‐shell structure CaF2@Al2O3 powders were synthesized by liquid‐phase non‐uniform nucleation method. Al2O3/Ti(C,N)/CaF2@Al2O3 composite made by adding CaF2@Al2O3 powders exhibited notable improvements in microstructure and mechanical properties as compared with Al2O3/Ti(C,N)/CaF2 composite made by adding uncoated CaF2 powders. The core‐shell coated self‐lubricating ceramic tool with different content of CaF2@Al2O3 was designed and prepared by hot pressing sintering process. The results show that when the content of CaF2@Al2O3 is 10 vol%, The composite has the best mechanical properties, the flexural strength, and the fracture toughness and the hardness is 680 MPa, 6.50 MPa·m1/2, and 17.29 GPa. Compared with the tool material with only CaF2 solid lubricant added, the above performances were increased by 8.91%, 29.48%, and 14.50% respectively. The influence of different CaF2@Al2O3 content on the physical and mechanical properties and microstructure of the tool material was analyzed. [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]