| Ceramic toolmaterials have the advantages of high hardness and good wear resistance,However,there are many disadvantages such as large brittleness and easy to break edge.Cubic boron nitride（c-BN）is thermal stability andinert to iron group elements.It is suitable for processing materials with high hardness and toughness.It is an ideal ceramic material reinforcement.In this paper,c-BN was used as the reinforcing phase and Co as the metal bonded phase.The new ceramic tool material with excellent comprehensive mechanicalperformance was prepared fabricatedby vacuum hot-pressing process.The effect of the differentcontent of c-BN and sintering process on（Ti,W）C-based cermet material properties were sdudied.The effects of cubic boron nitride on the toughening mechanism of（Ti,W）C-based cermet tool were analyzed.The cutting performance and wear mechanism of the new type（Ti,W）C-based cermet were studied.In this paper,the physical and chemical compatibility of c-BN composite（Ti,W）C-based cermet tool materials are analyzed.c-BN is dispersed by sodium dodecyl sulfate to decrease its agglomeration.The effects of composition contents and sintering process on the mechanical properties of c-BN composite（Ti,W）C-based cermet tool were studied.It shows that the mechanical properties of（Ti,W）C-based composite cermet tools are the best when c-BN content is 1.5wt%.When the sintering temperature is 1450℃,holding time is 30min and the sintering pressure is 30MPa,the properties of（Ti,W）C-based composite cermet tools are the best.The flexural strength,the fracture toughness and the hardness is 996MPa,8.57MPa·m1/2 and 20.78GPa,respectively.The corrosion of c-BN composite（Ti,W）C-based cermet tool was studied.The results show that c-BN can reduce the brittle phase in the matrix,and c-BN particles can act as particle pinning in the matrix,which is beneficial to the mechanicalimprovement of the properties of（Ti,W）C-based cermet tool materials.（Ti,W）C-WC-Co tool materials with different c-BN were prepared by vacuum hot pressing under the sintering process of sintering temperature 1450℃,holding time60min and sintering pressure 30MPa.The mechanical properties of（Ti,W）C-WC-Co tool are the best when the amount of c-BN is 1wt%,the flexural strength,fracture toughness and hardness of composites is 769MPa,6.64MPa·m1/2 and 22.83GPa,respectively.It is found that c-BN has the similar effects on the microstructure of two（Ti,W）C-based cermet tool materials.The addition of c-BN could effectively refine the grains and reduce the defects such as pores and holes.The addition of c-BN makes the（Ti,W）C-based cermet tool material fracture mainly shifted from intergranular fracture to transgranular fracture.The change of fracture mode can significantly improve the comprehensive mechanical properties of（Ti,W）C-based cermet tool materials.However,because of the difficulty of c-BN dispersion,the mechanical properties of（Ti,W）C-based cermet tool materials are obviously decreased for the presence of agglomeration and phase transformation for the high content of c-BN.The cutting performance of（Ti,W）C-based cermet cutting tools for continuous cutting of 45 steel was studied.The cutting force and the cutting temperature of（Ti,W）C composite cermet tool increases with the increase of cutting speed.At the same time,the surface roughness of the workpiece decreases with the increase of cutting speed.Considering the cutting force,cutting temperature and material surface roughness of workpiece,CTW1 should be used when cutting speed is lower.When the cutting speed is high,CTW1 or CT1.5 can be used.When the cutting speed,feed rate and cutting depth is 120m/min,0.2mm/r and 0.5mm,respectively,CT1.5 and CTW1have longer life than CT0 and CTW0.CTW1 cutting life is highest,up to 1200m.The addition of c-BN can effectively increase the tool life.Under the same cutting conditions,the addition of c-BN can effectively improve the tool wear resistance.The CT0 is obviously chipping phenomenon,and the wear type is mainly adhesive wear.The addition of c-BN tool has better comprehensive mechanical properties,the wear of tool flank face is more even,and the life of tool is higher. |
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