Faculty Publications
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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 Tribological characteristics of HVOF sprayed Fe-based composite coatings at elevated temperatures(SAGE Publications Ltd, 2025) T V, C.; Joladarashi, S.; Ramesh, M.R.This study evaluates the tribological performance of Fe-based composite coatings for aerospace and automotive applications, focusing on wear resistance at elevated temperatures. The coatings, comprising 15% WC-Co and Cr3C2 in an SS316L matrix, were deposited onto maraging steel via HVOF spraying. Microstructural analysis and adhesive strength testing confirmed strong particle bonding, with the coatings achieving a hardness of 711 ± 14?HV. Dry sliding wear behaviour was assessed using a ball-on-disc tribometer with alumina as the counterface under 10?N and 30?N loads at 25?°C, 300?°C, and 600?°C. Results indicated a decrease in the coefficient of friction and specific wear rate with increasing load and temperature. At 600?°C, wear rates were reduced by ?97.56% (10?N) and ?97.12% (30?N) than uncoated steel. Abrasive wear dominated at room temperature, while adhesive and oxidative wear mechanisms emerged at 600?°C, attributed to protective glaze layer formation. © The Author(s) 2025.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.