Abstract Nanotwinned cubic boron nitride (nt-cBN) is a promising tool material for ultra-precision cutting of ferrous metals. However, high hardness and excellent thermal stability make it difficult to obtain sharp cutting edge by using conventional methods. In this study, the factors influencing the material removal modes and edge sharpness in mechanical lapping process have been investigated, and a novel method combining mechanical lapping and ion beam polishing is proposed for achieving the sharp nt-cBN cutting edge. The results show that the material removal in mechanical lapping is mainly contributed by the transgranular ductile failure at the nanometer scale. Besides, high material hardness with a low Poisson's ratio and small impact force on the cutting edge are beneficial for obtaining sharp cutting edge. Therefore, the ion beam polishing process is adopted to sharpen the mechanically lapped cutting edge. By using a steel baffle plate with straight profile and eliminating the clearance between the baffle plate and rake/flank face with resin filler, the edge radius is observed to decrease from micrometre scale to about 60 nm. The proposed method represents a promising strategy for the preparation of ultra-sharp cutting edge with low cost and high accuracy.

中文翻译：

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机械研磨和离子束抛光相结合制备纳米孪晶cBN切削刃

摘要 纳米孪晶立方氮化硼（nt-cBN）是一种很有前途的黑色金属超精密切削刀具材料。然而，高硬度和优异的热稳定性使得使用常规方法难以获得锋利的切削刃。在这项研究中，研究了影响机械研磨过程中材料去除模式和刃口锋利度的因素，并提出了一种机械研磨和离子束抛光相结合的新方法，以实现锋利的nt-cBN切削刃。结果表明，机械研磨中的材料去除主要是由纳米尺度的穿晶延性破坏造成的。此外，材料硬度高，泊松比低，切削刃上的冲击力小，有利于获得锋利的切削刃。所以，采用离子束抛光工艺，使机械研磨的切削刃锋利。通过使用具有直线轮廓的钢挡板，并用树脂填料消除挡板和前刀/后刀面之间的间隙，观察到边缘半径从微米级减小到约 60 nm。所提出的方法代表了一种以低成本和高精度制备超锋利切削刃的有前途的策略。