STUDY OF ENVIRONMENTAL FRIENDLY DIAMOND LIKE COATING ON TOOL INSERTS FOR PRECISION MACHINING

Abstract

In this research work, attempts have been made to improve the machining parameters. For this, diamond-like carbon (DLC) coated tool inserts were used. The DLC coating on the tungsten carbide (WC) tool inserts were coated using the thermal chemical vapor deposition (CVD) method. For the growth of DLC coating, sugarcane bagasse was used as a carbon precursor. For characterization of the DLC coated tool inserts, Raman spectroscopy, a field emission scanning electron microscope (FESEM), and X-ray diffraction (XRD) were used, to confirm the presence of DLC coating on the tungsten carbide tool inserts. For inspecting the hardness of the self-developed DLC coated and uncoated tool inserts, the tests of micro-hardness were also executed. The average values of the Vickers hardness for the uncoated and the DLC coated substrates were found to be 953.95 HV to 1478.78 HV respectively. It was observed that the hardness of the WC was increased by a factor of 1.5 after the coating process. As per ASTM G-99 standards, the tribological behaviour of the self-developed DLC coated substrate was considered in the scope of this research work using a pin-on-disc tribometer. The tribological tests showed improvement in the wear resistance of the DLC coated WC tool inserts as there was a decrease in the value of wear by 58.02 %. The value of the coefficient of friction (COF) was also found to be decreased by 51.48%. The coated tool inserts were evaluated for the crater wear, cutting force, surface roughness, and temperature in the cutting zone using conventional lathe machine tools and computer numeric control (CNC) lathe machine tools at different levels of the type of tools, feed, speed, and depth vii of cut. It was found that for precision machining, computer numeric control (CNC) machine tools exhibit better results as compared to conventional ones. Further, the process parameters were optimized using TOPSIS and the Genetic Algorithm method. While optimizing the process parameters of the turning process on the conventional lathe machine tool using TOPSIS, the optimum values of cutting speed, feed, and depth of cut for achieving the minimum value of the selected response variables were found to be 60.52 m/min, 0.15 mm/rev and 0.192 mm respectively and from the Genetic Algorithm, the obtained optimized value of crater wear was found to be 461.07(µm), at a feed of 0.375mm/rev, a speed of 360m/min and a depth of cut of 0.2 mm. Further, the performance of the coated tool inserts was enhanced by utilizing the surface texturing technique. Four shapes of the surface textures were fabricated on the coated tool inserts. These were line and wave texturing placed parallel and perpendicular to the tool nose radius. The textured tools were evaluated for the crater wear, cutting force, surface roughness, and temperature in the cutting zone. After optimizing the parameters, it was found that the tool inserts with wave texture parallel to the tool nose radius exhibit the best results when compared to the other texturing pattern and placement.