Development of (W,Ti,Ta)C/CaF2 nano-self-lubricating cermet tool and its dual lubrication cutting mechanism

Abstract

A (W,Ti,Ta)C/CaF₂ nano-self-lubricating cermet tool was prepared by spark plasma coupling high-frequency induction sintering (SP–HF sintering) process. Under the optimal sintering parameters, nano CaF₂ was uniformly distributed within the matrix grain, forming an intragranular nanostructure. When the content of nano CaF₂ is 5 vol.%, the flexural strength, hardness, and fracture toughness of (W,Ti,Ta)C/CaF₂ nano-self-lubricating cermet tool were 1134 ± 28 MPa, 18.97 ± 0.22 GPa, and 8.52 ± 0.16 MPa·m^1/2, respectively. The antifriction mechanism in turning of Cr12 steel was studied with nano solid lubricating technology and minimum quantity lubrication (MQL) technology. The results showed that nano CaF₂ diffused into the internal friction zone during the cutting process to form a lubricating film, and the MQL technology provided a lubrication effect in the external friction zone. The combination of solid lubrication and minimum quantity lubrication reduced the cutting force, cutting temperature, metamorphic layer thickness, and oxidation degree. The dual lubrication mode significantly improved the wear resistance of the tool. Under the conditions of cutting speed v_c = 300 m/min, back engagement a_p = 0.15 m/min, and feed rate f = 0.102 mm/r, the tool life was about 15 000 m, and the stable wear stage was effectively extended. The surface roughness of the workpiece within the effective cutting distance was about 0.630 µm.