A quantitative assessment of nanometric machinability of major polytypes of single crystal silicon carbide

Cutting hardness was adopted as a quantifier of the machinability of the polytypes of single crystal SiC. 3C-SiC offered highest cutting resistance (∼2.9 times that of silicon) followed by the 4H-SiC (∼2.8 times that of silicon) whereas 6H-SiC (∼2.1 times that of silicon) showed the least. Despite its high cutting resistance, 4H-SiC showed the minimum sub-surface crystal lattice deformed layer depth, in contrast to 6H-SiC. Further analysis of temperatures in the cutting zone and the percentage tool wear indicated that single point diamond turning (SPDT) of single crystal SiC could be limited to either 6H-SiC or 4H-SiC depending upon quality and cost considerations as these were found to be more responsive and amenable to SPDT compared to single crystal 3C-SiC.