Application of Nd: YAG Laser in Nano WC Surface Alloying with Low Carbon Austenitic Steel in Predicting the Microstructure and Hardness

摘要

The low carbon Austenitic steel possesses excellent corrosion resistance but poor tribological properties. This work has been attempted to improve the surface hardness and wear resistance of austenitic stainless steel by alloying its surface with nano tungsten carbide (WC) using Nd: YAG laser. Austenitic 316L Stainless Steel (SS) was conceived as a substrate material. The substrate materials are prepared in the form of discs and pins. These discs and pins are coated with the prepared nano WC powder using DC Magnetron Sputtering process. Nano (WC) with an average particle size of 48 nm was prepared by thermo chemical method using a planetary ball mill. The surface alloying of the nano WC coated 316L SS substrate was performed using Nd: YAG laser processing setup. In this attempt, the optimal process parameter was also determined by varying the laser process parameters such as beam radius and defocal length. The depth of the modified layer was observed as 190 µm in one of the samples. The modified layers are characterized by Scanning Electron Microscope (SEM), Energy Dispersive X-ray Analysis (EDAX) and X-Ray Diffraction (XRD) techniques. The microhardness for all the samples were measured using Vickers’s microhardness test and the maximum value of 762HV was observed. Also, the strength of the modified layer was calculated using theory of contact mechanics. The maximum yield strength and shear strength of the samples were found to be 1.37 GPa and 0.81Gpa respectively. The tribological behavior such as wear and friction components for all the samples are studied using pin on disc setup and the results were compared with self-mating of 316L SS substrate. The coefficient of friction in nano alloyed sample was observed to be low when compared to the untreated 316L SS.Graphical abstract