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The current demand for surface finishing processes that are both technically proficient and environmentally friendly is increasing, necessitating the advancement of more efficient sustainable methods. Minimum quantity lubrication (MQL) provides excellent lubrication in the tool-work interaction but insufficient cooling impact. Besides, cryogenic enhances the chilling effect but has inadequate lubrication. This research revealed the synergistic impact of hybrid CryoMQL with eco-friendly Al2O3NFs while grinding AISI D2 tool steel. CryoMQL facilitates the application of MQL-based soybean oil and deionized water (SO+DW) emulsion with 0.5 wt% and 1 wt% concentration of Al2O3NPs and liquid nitrogen (LN2) through two individual nozzles in the cutting region. The results indicated that CryoMQL reduced grinding force (tangential force, Ft, and normal force, Fn), specific grinding energy (Ug), surface roughness (Ra), and grinding temperature (Tg) by 3.64–25.66 % in Ft, 3.52–12.87 % in Fn, 3.64–25.66 % in Ug, 8.81–25.02 % in Raand 57.59–58.30 % in Tg, respectively, compared to MQL environment at 0.04 mm downfeed and 150 mm/s table feed rate. Eventually, it was observed that 1 wt% Al2O3NFs improve Ft, Fn, Ug, Raand Tgby up to 32.71 %, 20.33 %, 32.71 %, 23.55 %, and 6.81 % in comparison to 0.5 wt% Al2O3NFs in the CryoMQL mode. The effectiveness of Al2O3nanofluids with CryoMQL has resulted in good tribological conditions in the grinding zone with enhanced cooling/lubricating action of vegetable oil. Furthermore, negligible chip adhesion over finished surfaces was seen with 0.5 wt% and 1 wt% Al2O3NFs under CryoMQL grinding. This study provides numerous scientific assistance in the automotive and tooling sectors, such as a better selection of environmentally friendly coolants and sustainable parameters for excellent surface properties, to provide the solution to highly complex and close tolerances of tool steel parts using CryoMQL finishing.

Grinding generates a lot of heat in the grinding zone area during operation. Therefore, it is important to keep the temperature under control by using various cutting fluids to get a good ground surface quality. The existence of a stiff air layer surrounding the abrasive wheel is known to waste most of the cutting fluid supply in the interface area between the abrasive wheel and workpiece. Due to the high grinding speed, stiff air layers prevent cutting fluids from entering the interface area. Hence, to enhance the grinding performance, cryogenic cooling has been introduced to improve the penetration into the stiff air layer. The current work investigates the grindability of the ground surface of AISI D2 tool steel under different environments: dry, wet, and cryogenic, regarding grinding forces (i.e. tangential and normal force), specific grinding energy, and surface characterisation. This paper also proposed a method to evaluate image-based Abbott–Firestone curve (bearing area curve) parameters to characterise the ground surface topography. Significant reductions in grinding forces (64%–67% and 44%–50% in Ft, 54%–58% and 34%–39% in Fn), low specific grinding energy (64%–67% and 44%–50%), decrease in surface roughness (46%–51% and 30%–36% in Ra, 37%–41% and 31%–35% in Rz), improved 2D and 3D roughness profiles and higher bearing area ratio (89.54%) were observed at 40 µm downfeed in cryogenic cooling environments compared to dry and wet environments, respectively. Thus, observations show the importance of cryogenic cooling across the experimental domain.

This paper describes the potential of non-destructive techniques such as micro-magnetic Barkhausen noise (MBN) to assess the grinding burn flaws in terms of microstructural and mechanical indices of hardened AISI H13 die steel. To overcome this grinding burn issue, minimum quantity lubrication grinding with eco-friendly machining fluids like paraffin oil (PO) and castor oil (CO) was adopted and compared its performance with well-established conventional grinding like wet and dry. Ground surface integrity with castor oil (CO) was found to be significantly improvement in surface quality including lower surface roughness (Rα: 0.23 μm and Rz: 1.83 μm) with uniform surface topography, absence of oxidization and carbonization film, and negligible change in microhardness and microstructure. The reason is strong and uniform anti-friction and anti-wear tribo-film was produced by castor oil, which minimizes heat penetration through limited ploughing and rubbing action. The MBN outcome i.e., root mean square (RMS) has followed a linear relation with microhardness and temperature of the ground sample with a correlation coefficient of 0.993 and 0.981. Besides, lower amplitude and wide peak envelope get shifted towards a higher magnetic field in the MQL-CO grinding caused by poor thermal softening effect on the ground sample, which restricts magnetic domain wall movement and rotation. These outcomes could guide tooling industries for efficient sustainable grinding with faster thermal damage assessment, which helps to minimize production cycle time and back to clean environment.

Economical welding of dissimilar titanium alloys has always been a challenge for the aerospace and nuclear industries, where these alloys are extensively used because of their high strength-to-weight ratio. The present investigation deals with the development of a novel shielding setup for the successful welding of commercially pure titanium (α-phase) to Ti–6Al–4V ((α + β)-phase) without any atmospheric contamination using gas tungsten arc welding. Commercially pure titanium (CP-Ti) and Ti–6Al–4V sheets of 3 mm thickness were butt-welded autogenously and using CP-Ti filler metal. Metallographic studies, energy-dispersive X-ray spectroscopy, X-ray diffraction analysis, microhardness measurements, tensile testing, and fractography were carried out to understand the evolution of the microstructure and characterize the welds. Grain coarsening in heat-affected zone and weld, and variation in the distribution of phases were observed from the optical micrographs and energy-dispersive X-ray spectroscopy spectrum of different zones. An unsymmetrical variation of hardness was observed in the weld region, and a 15% reduction in hardness value (280 HV0.2) was obtained at the weld center of using filler metal weld than autogenous weld. Comparable strengths with little drop from as-received CP-Ti (307 MPa) were observed for welded specimens. Welds produced using CP-Ti filler metal (272 MPa) had higher strength than autogenous welds (214 MPa). As-received tensile specimens fractured nearly from the center of gauge length, but welded tensile specimens fractured near the base/heat-affected zone boundary of the CP-Ti side.

Deposition of copper on top of a steel substrate combines the advantages of the corrosion resistance of copper with the high tensile strength of steel. Due to their diverse properties, it is challenging to deposit copper on steel. In this work, the deposition of a 3 mm-thick copper layer has been carried out on top of a 6 mm thick steel substrate, utilizing the friction stir welding (FSW) process. During the process, several repetitive passes are required with a suitable tool offset to cover the entire plate effectively. A smaller tool pin offset results in the requirement of more passes, while too large a pin offset leaves the area between two passes unbonded. To optimize the tool offset distance, a series of trial experiments with offset values of 6, 8, 10, and 12 mm were carried out. Metallography examination along with X-ray radiography was carried out on the prepared clad samples. The average grain size of the steel substrate below the clad layer showed refined grains with a size of 5 μm, indicating an improvement of more than 60 % over the base steel. SEM and EDS map analysis revealed proper bonding of the cladding material with the substrate. Uniaxial tensile tests on flat specimens were carried out for base copper, base steel, and copper clad steel samples. The copper clad steel has a YS of 261 MPa and tensile strength of 359 MPa in comparison to the base copper, which has a YS of 131 MPa and a UTS of 227 MPa. Fractography analysis revealed stretching marks between copper and steel due to the difference in elongation rates of both materials. A guided bend test for face bend, root bend, and side bend revealed no delamination or crack initiation along the convex surface. Microhardness analysis was carried out across the interface from copper to steel, where a maximum hardness value of 226 HV was recorded near the interface close to the steel region.

Ultrasonic vibration-assisted dry grinding is a sustainable hybrid manufacturing technology that decreases the negative environmental impact of coolant, reduces manufacturing costs, and improves surface integrity. The present investigation analyses the mechanisms associated with ultrasonic vibration-assisted dry grinding of AISI D2 tool steel with an alumina grinding wheel. It also compares the influence of traditional dry grinding and traditional wet grinding modes with the ultrasonic vibration-assisted dry grinding mode at different ultrasonic vibration amplitudes. Ultrasonic vibration was applied to the sample in the longitudinal feed direction. Further, kinematics of the abrasive grit path during the traditional grinding and ultrasonic vibration-assisted dry grinding is presented schematically. In this research, the impacts of ultrasonic vibration amplitude as well as the depth of cut on the process yields such as ground surface topography, grinding force, specific grinding energy, force ratio, surface finish, microstructure, and hardness were investigated experimentally. Experimental results revealed that the highest decline in tangential and normal grinding forces in ultrasonic vibration-assisted dry grinding at ultrasonic vibration amplitude 10 µm and the reduction in surface roughness parameter (Ra, Rq, and Rz) in ultrasonic vibration-assisted dry grinding was 43.23%, 42.59%, and 33.69%, respectively, in comparison to those in traditional dry grinding and 26.35%, 26.94%, and 27.48%, respectively, in comparison to those in traditional wet grinding. It was observed that ultrasonic vibration-assisted dry grinding is beneficial as the profile produced by ultrasonic vibration-assisted dry grinding has a comparatively flat tip, and profile points are shifted to the bottom of the mean line. This study is expected to assist ultrasonic vibration-assisted dry grinding of hard materials.

According to tooling industries, grinding is the most effective and economical machining for AISI D2 tool steel owing to its low thermal conductivity. The first objective is to investigate the effect of grinding environments on surface integrity of AISI D2 tool steel. Grinding performance like force ratio and grinding temperature was investigated under wet and dry environments. The second objective is to qualitatively assess the thermal damage of ground surface using non-destructive hysteresis loop (HL) technique. The result shows that higher force ratio and surface roughness were obtained under flood grinding. Maximum thermal damage in terms of drastic variation in microstructure and microhardness were observed under dry grinding owing to serious plastic deformation at higher grinding temperature. HL outcomes like lower average permeability, higher coercivity and remanence were obtained with higher thermal damage on ground surface. Finally, linear correction was obtained between HL outcomes and microhardness of ground samples.

The aim of present study is to experimentally investigate and compare the effect of grinding parameters, i.e. downfeed, work velocity and lubricating environments, on the surface integrity of hardened AISI D2 tool steel. The surface integrity of ground surface was evaluated in terms of surface roughness, surface topography, microstructure and microhardness variation. Grinding performance was investigated concerning grinding force, specific grinding energy and grinding temperature. Quasi-steady-state moving heat source model was used to estimate grinding temperature under different environments, viz. dry and flood. The second objective of the present work is the non-destructive evaluation of thermally damaged ground surface by the novel Barkhausen noise technique. The results showed that flood environment reduces grinding force, specific grinding energy and grinding temperature owing to effective cooling and lubrication medium. A thick redeposition layer over ground surface along with minimum surface roughness was observed under dry grinding. Further, drastic change in microstructure and microhardness was observed under dry environment due to a number of passes of grinding wheel over ground surface without coolant, which induced excess heat and developed martensite layer near the nascent surface. Finally, poor BN response such as lower root mean square (rms) and peak value was found in thermally damaged sample owing to large obstacles for magnetic domain wall displacement.

Friction stir welding (FSW) is a promising joining process for age-hardened aluminum alloys. However, when the process is used for welding age-hardened aluminum alloys, the hardness and joint efficiency are poor mainly because the strengthening precipitates become incoherent and/or get dissolved during the welding process. In this novel work, efforts have been made to enable the reprecipitation of the strengthening precipitates using multi-pass FSW. After producing FSW welds on AA2024 alloy, the welds have been processed by the same tool and at the same parameters several times to facilitate the reprecipitation of strengthening precipitates. As the precipitation kinetics of age-hardened aluminum alloys are temperature-dependent, a thermal imaging camera was utilized to record the temperature history during welding and subsequent cooling of the welded plates. The metallurgical examination of welded samples was carried out using optical microscopy, Scanning Electron Microscope (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and microhardness test. It was observed that grain refinement occurs continuously due to dynamic recrystallization and severe plastic deformation up to the third FSW pass, after which there is no significant change in grain size. Generally, the microhardness value was higher in the stir zone than the heat-affected zone (HAZ), and the hardness in the stir zone increased after 4 passes of FSW. SEM images show clusters of incoherent precipitates, fragmentation, precipitate dispersion, dissolution, and reprecipitation of precipitates during each subsequent pass. The identification of the precipitates was carried out using EDS and XRD analysis.

The prediction of the accurate thermal and clad geometry characteristics plays a significant role in obtaining a better metallurgical bond between the cladding material and the substrate. The estimation of temperature distribution is difficult experimentally within the melt pool. A suitable and accurate heat flux is needed to apply during the numerical modeling to get clear and accurate process parameters before conducting the actual experiments. Therefore, different heat flux is used to get the best-suited heat flux which gives an accurate response during the laser cladding. The same processing parameters were considered during the simulation for the different heat sources. In all the cases, the maximum temperature was obtained at the center of the melt pool and decreased when moving away from the center of the melt pool in-depth and across the scanning speed direction. A similar shape of the melt pool is formed when three-dimensional volumetric Gaussian heat flux and conical heat flux are used, which gave best suited and efficient heat flux for the numerical simulation before actually conducting experiments. When egg-shaped heat flux is applied, an insufficient temperature was reached at the interface of the powder and substrate, whereas more dilution appeared for parabolic heat flux.

The research goal of present experimental work was to analyse the variation in magnetic response (at different magnetising frequency and magnetic field intensity) of IS-2062 steel of grade B upon friction stir welding (FSW). Tungsten carbide tool having 15 mm shoulder diameter was used to weld the steel plates having 3 mm thickness with welding speed of 150 mm per minute and revolving speed of 800 revolutions per minute. Welded steel plates were characterised using Barkhausen Noise analyser. Magnetic response of material, before welding and after welding was recorded in terms of Barkhausen Noise signal parameters that are root mean square (rms) value of signal and number of pulses. Both the signal parameters was observed to correlate well with grain refinement and changes in micro-hardness upon FSW of steel at different analysis parameters such as magnetic field intensity and excitation frequency.

The goal of present research work is to study the variation in the shape of hysteresis loop owing to change in the analysis parameter i.e., magnetising frequency and applied magnetic field strength upon pack carburised low carbon steel samples. Pack carburised heat treatment performed at three different temperatures to induce varying hardness into steel samples. Hysteresis loop characteristics such as coercivity, permeability, power loss and remanence were measured in a wide range of magnetising frequency and magnetic field intensity. Coercivity is observed to increase with increase in magnetising frequency and applied field strength. In low-frequency range (<1 Hz), remanence and power loss were found to decrease, with an increase in frequency, in a contrary, increase in frequency in high-frequency range (>1 Hz) results into increase in remanence and power loss. However, with an increase in magnetic field strength both remanence and power loss were found to increase.

There is a rapid increase in global warming over the years. This follows with continues campaign on reducing the energy consumption and protecting the earth against climate change. The Feed-In Tariff (FiT) program was introduced to encourage people to use renewable energy. One of the alternative energies that has shown significant potential is solar energy, which could be harvested using the solar photovoltaic (PV) technology. This project is intended in developing an online application system to help the user in making a decision about installing a solar PV system. This system will help the user to calculate the size of solar panel that a user should install, the amount of electricity generated from the system and the profit that the user will gain after a few years in implement solar PV system in his premise (s) or house (s).