Parametric optimization for the low cost production of nanostructure stainless steel powder

Abstract

In recent years, nanocrystalline materials have drawn the attention of researchers in the field of materials science engineering due to its enhanced mechanical properties such as high strength and high hardness. However, the cost of nanocrystalline materials is prohibitively high, primarily due to the expensive equipments used and the low output. Recently, researchers have attempted to produce nanocrystalline materials through machining. This research work focuses on the production of nanocrystalline 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 under different cutting conditions. Taguchi L16 orthogonal array was adopted and optimized the machining parameters. 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 characterized using Scanning electron microscope (SEM) and X-ray Diffraction (XRD) analysis. From the optimized machining conditions chips were generated and further processed using the high energy ball mill for preparing nanocrystalline powders. High energy ball mill parameters such as milling speed, milling time and ball to powder ratio were optimized using taguchi method. The milled powders were then characterized using Transmission electron microscope (TEM), SEM and XRD. Results show that the milled powders were in the range of 20 – 50 nm.

Keywords: Nanocrystalline materials, Machining, High energy ball milling, Optimization