Ductile regime single point diamond turning of CVD - SiC resulting in an improved and damage - free surface

Silicon carbide (SiC) is one of the advanced engineered ceramic materials designed to operate in extreme environments. One of the main reasons for the choice of this material is due to its excellent electrical, mechanical or optical properties that benefit the semiconductor, MEMS and optoelectronic industry respectively. Manufacturing this material is extremely challenging due to its high hardness, brittle characteristics and poor machinability. Severe fracture can result when trying to machine hard brittle materials like SiC due to its low fracture toughness. However, from past and current research efforts, it has been proven that ductile regime machining of nominally brittle materials is possible. The main goal of the subject research is to improve the surface quality of a chemically vapor deposited (CVD) polycrystalline SiC, to be used as optics devices (mirrors), via single point diamond turning (SPDT). Sub-surface damage analysis was carried out on the machined sample using non-destructive methods such as Raman spectroscopy and Scanning Acoustic Microscopy. Surface roughness (Ra) values of less than 88 nm (for CVD coated SiC), without sub surface damage were obtained. In addition to improving the surface roughness of the material, the research also emphasized increasing the material removal rate (MRR) and minimizing the diamond tool wear. Machining parameters that make this manufacturing process more time and cost efficient were also identified.