Faculty Publications
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Item Micro-mechanical characterization and wear performance of TiAlN/NbN PVD coated carbide inserts during End milling of AISI 304 Austenitic Stainless Steel(Elsevier Ltd, 2018) Varghese, V.; Dupadu, D.; Ramesh, M.R.A multi-layer TiAlN/NbN coated on tungsten carbide insert by physical vapor deposition method (PVD) was selected for studying tool wear performance during end milling of AISI 304 Austenitic stainless steel. Stainless steel AISI 304 belongs to the class of difficult to machine materials, which tends to work harden during machining. The coating has been studied for its micro-mechanical characteristics using SEM/EDS, XRD, 3D confocal microscope & Nano indentation. Characterization results revealed that TiAlN/NbN coatings was well deposited. Dry milling experiments were carried out to evaluate tool life & failure mechanisms of coated tool. It was shown that micro chipping and peeling of coatings were major wear mechanisms observed during dry end milling of AISI 304 using coated inserts. © 2017 Elsevier Ltd. All rights reserved.Item Optimisation of machining parameters for end milling of maraging steel MDN 250 using TiAlSiN and TiSiN coated WC-Co inserts(American Institute of Physics Inc. subs@aip.org, 2020) Varghese, V.; Jagmalpuria, A.; V Badiger, P.V.; Ramesh, M.R.Thin film coatings TiSiN, TiAlSiN were deposited on WC-Co milling inserts using RF magnetron sputtering. The machinability studies of maraging steel is carried out using thin film coatings of TiSiN TiAlSiN. The maching parameters of cutting speed, feed rate and depth of cut will be varied to analyse machining responses such as surface roughness and cutting force. The performance of each coating will be evaluated and compared along with tool wear and tool life. A Taguchi based grey relational analysis will be used to optimize the machining parameters and analysis of variance (ANOVA) is used to find the most significant factor. © 2020 Author(s).Item Experimental investigation and optimization of machining parameters for sustainable machining(Taylor and Francis Inc. 325 Chestnut St, Suite 800 Philadelphia PA 19106, 2018) Varghese, V.; Ramesh, M.R.; Dupadu, D.A detailed investigation on the effects of cutting parameters and different cooling environments on machinability of austenitic stainless steel AISI 304 is presented in this study. The need for sustainable manufacturing and better surface quality urged to explore the merits of cryogenic cooling over the other conventional cooling techniques. The end milling experiments were designed based on three parameter and three-level design considering dry, wet, and cryogenic machining environments to have a comparative study. The machinability studies such as surface roughness, tool wear, cutting forces, chip morphology, and chip reduction coefficient were investigated and compared with different machining environments. The machining parameters were optimized using Taguchi-based grey relational analysis. The cryogenic machining had the most influence on milling of AISI 304 steel and resulted in the reduction of cutting forces, surface roughness, and chip reduction coefficient in comparison with the conventional wet and dry machining. © 2018, © 2018 Taylor & Francis.Item Influence of deep cryogenic treatment on performance of cemented carbide (WC-Co) inserts during dry end milling of maraging steel(Elsevier Ltd, 2019) Varghese, V.; Ramesh, M.R.; Dupadu, D.Cryogenic treatment has developed as a technique to improve the life of the cutting tool, especially tungsten carbide inserts. The present study investigates the effect of cryogenic treatment of cemented carbide (WC-Co) inserts at the different soaking period of 18 h (CT-18), 24 h (CT-24) and 32 h (CT-32) at a sub-zero temperature of ?196 °C. The soaking period plays a crucial role in improving the wear resistance of the cryogenically treated tools. It is vital to determine the critical soaking period for the cryogenic treatment of cemented carbides. The mechanical and metallurgical characterization of cryogenically treated cemented carbide insert is carried out to understand the changes in the microstructure, grain size, chemical composition, microhardness and electrical conductivity after cryogenic treatment. The end milling experiments on maraging steel under dry environment are carried out using cryogenically treated inserts at different holding time and untreated inserts (UT). The machining performance of treated and untreated inserts are compared with respect to tool wear, surface roughness and cutting forces. The results revealed that cryogenic treatment is effective in resisting tool wear even at high spindle speeds. The cryogenically treated inserts exhibited higher tool life, better surface finish and lower cutting forces during machining at different spindle speeds. The optimum soaking time for cryogenic treatment of WC-Co inserts is found to be 24 h (CT-24) beyond which there is no improvement in microhardness and wear resistance. © 2018Item Characterisation and performance evaluation of TiSiN &tiAlSiN coatings by RF magnetron sputtering deposition during end milling of maraging steel(Institute of Physics Publishing helen.craven@iop.org, 2019) Varghese, V.; Ramesh, M.R.; Dupadu, D.; Shaik, H.Monolayer nanostructured thin films of TiSiN & TiAlSiN were deposited on WC-Co milling inserts using RF magnetron sputtering for metal cutting. The alloy targets of TiSi (80/20 at%) & TiAlSi (34/56/10 at%) were used for the deposition in an Ar + N atmosphere. The deposition time and parameters are optimized to develop a uniform and homogenous coating. The mechanical and metallurgical properties are characterized to analyze the wear resistance of the coating. The machinability studies on MDN 250 maraging steel is carried out using TiSiN and TiAlSiN coated WC-Co inserts under dry and wet environment. The machining responses such as surface roughness, cutting force, tool wear and tool life are analyzed by varying spindle speed. The results showed that TiAlSiN coating had a higher wear resistance and machining performance compared to the TiSiN coating owing to the high hardness and plasticity index of the coating. © 2020 IOP Publishing Ltd.Item Investigation on the performance of AlCrN and AlTiN coated cemented carbide inserts during end milling of maraging steel under dry, wet and cryogenic environments(Elsevier Ltd, 2019) Varghese, V.; K, A.; Ramesh, M.R.; Dupadu, D.The present study investigates the machining performance of AlCrN and AlTiN coated cemented carbide inserts during end milling of MDN 250 maraging steel. The mechanical and metallurgical characterization is carried out to determine the properties of the PVD coatings developed. The end milling experiments under dry, wet and cryogenic environment is carried out using coated uncoated inserts (UC) at different spindle speeds to evaluate the machining performance in terms of tool life, surface roughness and cutting forces. The coated inserts showed higher tool life, better surface finish, and low cutting forces during machining at different spindle speeds. It is found that the AlCrN coating had a better wear resistance and machining performance in comparison with AlTiN coating. The cryogenic environment reduced the surface roughness & cutting force and improved the tool life of the cutting tool compared to conventional dry and wet environment. It is revealed that coated tools along with cryogenic cooling can be employed for high-speed machining applications. © 2019 The Society of Manufacturing EngineersItem Experimental investigation of cryogenic end milling on maraging steel using cryogenically treated tungsten carbide-cobalt inserts(Springer, 2019) Varghese, V.; Ramesh, M.R.; Dupadu, D.The cryogenic machining and cryogenic treatment have already emerged as the sustainable manufacturing process of the future generation. The cryogenic treatment improves the cutting tool life, but the high cutting temperature developed during high-speed machining reduces the effect of cryogenic treatment of cutting tool. This study investigates the possible improvements in cutting tool life by combining cryogenic cooling and cryogenic treatment. The authors believe that these two techniques can replace conventional machining approaches using dry and wet machining conditions using coated carbide tools. The tungsten carbide-cobalt inserts are cryogenically treated (CT) at a soaking temperature of ? 195.8 °C for a period of 24 h and are used to evaluate milling performance under dry, wet, and cryogenic cutting environments. The machining experiments are conducted on maraging steel MDN 250 using one factor at a time approach by varying spindle speed and keeping feed rate and depth of cut as constant. The cutting force, surface roughness, tool wear, and subsurface microhardness are some of the machining responses evaluated and compared with an untreated cutting tool (UT). The tool life improved up to 24% during cryogenic machining using CT tools at a spindle speed of 270 rpm. © 2019, Springer-Verlag London Ltd., part of Springer Nature.Item Experimental Investigation on Surface Integrity in Cryogenic Machining of Maraging Steel(Springer, 2025) Varghese, V.; Sharma, P.; Ramesh, M.R.; Dupadu, D.; Sunilkumar, S.The study investigated the effect of machining environments such as cryogenic, wet, and dry conditions on the surface integrity of machined surfaces during end milling of MDN 250 maraging steel. During the machining of maraging steel, cutting temperatures and strain rates increased, resulting in a loss of mechanical properties and surface integrity of the machined surface. Surface integrity was an important factor influencing the components’ functional performance and quality, just like dimensional accuracy. In this study, the machining parameters such as spindle speed, feed rate, and depth of cut were kept constant, and the cutting environment was varied between cryogenic, dry, and wet conditions respectively. Surface integrity metrics such as surface roughness, microstructure evolution, residual stress, and microhardness were analyzed using Talysurf, electron back-scattered diffraction, x-ray diffraction, and Vickers microhardness test respectively. The correlated results conceded that cryogenic machining improved surface integrity compared to dry and wet machining. It also demonstrated that cryogenic machining was a viable manufacturing substitute to traditional machining using cutting fluids. The average grain size of the machined surface of the maraging steel under cryogenic, wet, and dry conditions was found to be 20.56, 24.92, and 11.54 µm respectively. The surface roughness was also reduced by up to 50% under the cryogenic environment compared to the dry environment. The residual stress results showed that stresses were compressive under dry, wet, and cryogenic environments, and the highest compressive stress was reported under a cryogenic environment (? 355 MPa). © ASM International 2025.