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

The influence of polymorphism on nanometric machinability of single crystal silicon carbide (SiC) has been investigated through molecular dynamics (MD) simulation. The simulation results are compared with silicon as a reference material. 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