Production of nanomaterials through machining

Nanocrystalline materials exhibit superior mechanical properties such as higher
strength, hardness and ductility etc. Severe plastic deformation is the process to produce
nanocrystalline materials. This research work focuses on the production of nano crystalline
materials through machining and high energy ball milling route. Nanocrystalline materials
were generated through oblique machining by the large strain plastic deformation imposed
by the cutting tool during machining. Stainless Steel 316L (SS) bar of 50mm diameter
and length 300mm was chosen for this study. Machining parameters such as speed, feed,
depth of cut and rake angle were chosen for the investigation. Coated tungsten carbide
cutting tool was used for the study. Machined chips were collected and cleaned using
ultrasonic machine for microstructure analysis. These chips were then mounted, polished
and etched for microstructure evaluation. Scanning electron microscope (SEM) and
X-ray Diffraction (XRD) analysis of the chips revealed crystalline sizes in the range of
50- 60 nm. These chips were further processed using the high energy ball mill for preparing
the components through powder metallurgy route. The machine nanocrystalline SS chips
were milled with milling speed of 350 rpm, milling time of 20hrs and ball to powder
ratio of 10:1 in inert atmosphere using stainless steel hardened bowl and balls. The
milled powders were then characterized using TEM (Transmission Electron Microscope),
SEM and X-ray Diffraction (XRD). The crystalline sizes of the milled powders were
determined by using Scherer formula. Results showed that the milled powders were in
the range of 20 - 50 nm.