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.