Study on micro-crack induced cutting of 4H-SiC, sapphire and Si along tetrahedral micro-crater tips

Abstract

The precision cutting of brittle materials requires the accumulation of nanoscale cut depth for ductile-mode removal without any micro-cracks, leading to inefficiency. Hence, a rapid cutting of brittle material is proposed through the micro-crack propagation along micro-crater tips on workpiece surface. The objective is to understand the feasibility of micro-crack induced cutting for various difficult-cut materials such as 4H-SiC, sapphire and Si. First, a diamond cone micro-tip was used to fabricate the tetrahedral micro-crater array; then the cutting force was modelled in micro-crack induced cutting; finally, the cutting performance was evaluated. It is shown that the indentation force ranging from 0.1–10 N produces the integrated micro-cracks along micro-crater tips. An increase in the micro-crack length leads to a decrease in cutting force and cutting time and an increase in cut form error. Moreover, the micro-crack propagation is little related to the crystal orientation. Unexpectedly, the cutting force, the cutting time and the cut form error for the hardest 4H-SiC was less than the ones for sapphire and Si, respectively. Its precision and mirror cutting efficiency reaches 10 mm2 s−1 with the micro-indentation time of 12 s. The indentation force related to micro-crack propagation may be used to predict and control the micro-crack induced cutting performance.