Sudarsan Ghosh

Environment Friendly Machining of Ni–Cr–Co Based Super Alloy using Different Sustainable Techniques

In order to eradicate the use of mineral based cutting fluid, the machining of Ni–Cr–Co based Nimonic 90 alloy was conducted using environment friendly sustainable techniques. In this work, uncoated tungsten carbide inserts were employed for the machining under dry (untreated and cryogenically treated), MQL, and cryogenic cutting modes. The influence of all these techniques was examined by considering tool wear, surface finish, chip contact length, chip thickness, and chip morphology. It was found that the cryogenically treated tools outperformed the untreated tools at 40 m/min. At cutting speed of 80 m/min, MQL and direct cooling with liquid nitrogen brought down the flank wear by 50% in comparison to dry machining. Similarly at higher cutting speed, MQL and cryogenic cooling techniques provided the significant improvement in terms of nose wear, crater wear area, and chip thickness value. However, both dry and MQL modes outperformed the cryogenic cooling machining in terms of surface roughness value at all the cutting speeds. Overall cryotreated tools was able to provide satisfactory results at lower speed (40 m/min). Whereas both MQL and cryogenic cooling methods provided the significantly improved results at higher cutting speeds (60 and 80 m/min) over dry machining.

Application of Micromagnetic Technique in Surface Grinding for Assessment of Surface Integrity

Induction of tensile residual stress in grinding particularly using conventional wheel is a major problem. Assessment of residual stress on ground samples using X-ray diffraction technique is quite often time consuming. Micromagnetic technique like Barkhausen Noise analysis has been reported to be used in assessing surface integrity in different metallurgical and manufacturing process. The aim of this article is to establish a correlation between micromagnetic parameters and surface integrity of AISI 1060 steel ground using conventional alumina wheels. Results indicate significant effect of downfeed, work speed, and marginal effect of abrasive grit size on surface integrity parameters like residual stress, grain refinement, grain elongation, and microhardness. Residual stress varied in the present work over a domain of −8 MPa to 500 MPa. Despite simultaneous variation in microhardness, grain refinement, grain elongation, and residual stress during grinding, a linear correlation could be established between Barkhausen Noise parameters and residual stress (BN = 233.4 + 0.065 σ ) with a correlation coefficient of around 0.92 for BN (rms).

Comparative Study of Specific Plowing Energy for Mild Steel and Composite Ceramics Using Single Grit Scratch Tests

The present research work compares the specific plowing energy requirement of two different materials: mild steel (ductile material) and composite ceramics (brittle material) using single grit scratch tests. The comparative study of two different materials will enhance the understanding of specific plowing energy. Specific plowing energy depends both on grinding process parameters as well as material property such as hardness. The effects of the four grinding process parameters, grinding speed, table speed, grain size, and depth of cut on specific plowing energy have been investigated. Geometrical parameters of the groove produced during single grit scratch test are used to calculate and model the specific plowing energy. Specific plowing energy is mathematically modeled in terms of the process parameters. It is found to be significant component of the total specific grinding energy. Specific plowing energy is plotted with respect to depth of cut which is found to have significant effect on the plowing phenomenon. This component has become even more predominant at very low depth of cut especially in case of composite ceramics.

Influence of nanofluid application on wheel wear, coefficient of friction and redeposition phenomenon in surface grinding of Ti-6Al-4V

Difficulties in the grinding of Ti-6Al-4V originate from the three basic properties: poor thermal conductivity, high chemical reactivity and low volume specific heat of the material. Under severe grinding conditions, all these factors together lead to the accelerated wheel loading and redeposition of chips over the work surface. Redeposition and wheel loading have a significant effect on the surface finish, grinding forces, power consumption and wheel life. In this study, water-based Al2O3 nanofluid as metalworking fluid is applied during the surface grinding of Ti-6Al-4V under minimum quantity lubrication mode after dressing the wheel with different dressing overlap ratios. The severity of the redeposition over the work surface was observed by measuring various surface profiles taken perpendicular to the grinding direction at several locations on the ground surface. The nanofluid application was able to prevent redeposition over work surface that became evident from the measured surface finish parameters that results along the grinding direction. Coefficient of friction was estimated On-Machine using the measured forces for different wheel work speed ratios, depth of cut and dressing overlap ratios. The results showed the effectiveness of nanofluid in reducing friction at high material removal rate (i.e. high depth of cut and high speed ratio) conditions when compared to the dry environment. From the measured forces variation with respect to the number of passes, it became evident that, nanofluid application delayed the frequency of wheel loading and grit fracturing cycle, which leads to the increase in the wheel life.

Grindability improvement of Ti-6Al-4V using cryogenic cooling

Titanium and its alloys are well known for their difficult machinability nature. Because of Ti-6Al-4V alloy’s strong chemical affinity, high temperature and pressure during the grinding process, the formed chips easily weld onto the grinding wheel surface. This phenomenon reduces the wheel life and diminish the surface quality. To control the effect of temperature, most grinding operations today employ cutting fluids. These fluids help in improving the surface quality and increasing the wheel life. However, because of environmental and economic concerns, industries are now looking for sustainable alternative cooling techniques such as cryogenic cooling. The aim of this study is to present the application of liquid nitrogen cryogenic cooling as an alternative cooling technique for grinding Ti-6Al-4V alloys. To compare the effect of cryogenic condition, experiments were conducted under both dry and wet (soluble oil) conditions. Experimental results proved the effectiveness of cryogenic cooling in reducing the grinding force, obtaining better surface finish, and being less damaging to the surface condition. Finally, multiple regression models were developed to predict the normal force and tangential force in cryogenic condition. The developed models have been validated with experimental data, and the maximum prediction error of the model for normal and tangential forces was less than 12% and 9%, respectively.

Some investigations in grindability improvement of Inconel 718 under ecological grinding

This work explores the improvement in grinding characteristics of Inconel 718 (IN718) using soluble oil under minimum quantity lubrication and liquid nitrogen (LN2) environments. The coolant flow rate in minimum quantity lubrication and LN2 grinding has been regulated through indigenously developed setups. Grinding performance has been studied in terms of on-machine measured grinding forces and centre line average surface roughness (Ra). The obtained grinding characteristics have been compared with the outcomes under dry and wet grinding. Surface integrity of ground surface, wheel morphology, and chip formation characteristics has been studied using scanning electron microscope, energy dispersive X-ray spectroscopy, and atomic force microscopy. Analysis of variance has been carried out to capture the variability in the experimental data for tangential forces and Ra. The main effect of the factors and their first-order interactions have been considered, and second-order regression equations have been developed using response surface methodology. LN2 grinding has been proved to be more efficient as it yielded lowest grinding forces, least oxidation, minimal ground surface damage and better surface integrity. The occurrence of almost circular chips in dry grinding indicates severe oxidation, whereas small C-type chips formed under minimum quantity lubrication and LN2 conditions indicate effective cooling under these environments. The energy dispersive X-ray spectroscopy analysis of the ground surfaces also supports these results through the occurrence of the highest oxidation in dry grinding. From this work, it has been concluded that LN2 and minimum quantity lubrication grinding offer a clean and effective means to improve grinding performance of IN718 compared to dry and wet grinding.

A modified model for estimating the contact length in surface grinding

The real contact length during the grinding process is considered as an important subject for researchers, mainly because it reflects the intensity of the responses such as grinding forces and temperature generation. In order to measure and assess the real contact length, many experimental techniques and prediction models are available in the literature. Among all these models, the model developed by Rowe and Qi is being used widely by researchers because of its ability to make close predictions with real values. Rowe and Qi coined the term called roughness factor in their model. This factor varies with grinding environments and wheel–work material combinations. To decide it for a new environment, one has to do the laborious experimental work. In this article, the roughness factor has been analysed from the grinding temperature and the heat partition ratio point of view and expressed so that without experimental work prediction of the roughness factor can be done. For this, a new factor called as the thermal factor has been proposed based on the roughness factor modifications. Its good correlation with dimensionless temperature and heat partition ratio under different grinding environments have been presented and discussed in the current communication. It seems that the thermal factor can be helped in an easy and accurate prediction of the contact length during grinding operations.

An investigation into the application of Al2O3nanofluid–based minimum quantity lubrication technique for grinding of Ti–6Al–4V

Nanofluids, suspensions of nanoparticles in base fluid, has shown attractive cooling and lubricating properties. The nano–coolants and nano–lubricants find applications in a wide variety of materials processing technologies. It is anticipated that, if properly employed, nanofluids usage could surpass the conventional cutting fluids in the future. Minimum quantity lubrication (MQL) technique also, has achieved a significant consideration in manufacturing processes to minimise the environmental loads caused by the usage of traditional cutting fluids. The aim of this work is to examine the potential of Al2O3 nanofluid under MQL mode to improve the grinding characteristics of Ti–6Al–4V alloy. 1% Volume concentration of water–based Al2O3 nanofluid was applied during the surface grinding operation using an indigenously developed MQL setup and the results have been compared with those of conventional coolant under both flood cooling and MQL mode.

Comparative grindability study of composite ceramic and conventional ceramic

Grinding is a widely used machining and finishing operation for the ceramic materials. Nowadays, a new variant of composite ceramics has also been developed. In many applications, these composite ceramics too need to be ground. The present study aims to experimentally investigate the grindability aspects of such a composite ceramic (AlSiTi) and also compare those grindability aspects of the composite ceramic with a conventional ceramic (SiC). Grinding forces, specific grinding energy and the surface integrity including the subsurface damage and surface roughness are the responses measured during the detailed experiments performed where grinding parameters like wheel speed, table speed and depth of cut are varied over a domain. Optical microscope and scanning electron microscope (SEM) have been used to analyse the ground surface, subsurface damage and the grinding swarfs. The results provide valuable insight into the grindability aspects of the composite ceramic (AlSiTi). Cracks and voids produced on the surface and subsurface of the composite ceramic are found to be significantly different from those observed while grinding the conventional ceramic under the same process parametric conditions.

Experimental investigations on grindability of bearing steel under high efficiency deep grinding (HEDG)

Bearing steel, having three different hardness (Rc32, Rc40 and Rc60), was surface ground using monolayer galvanically bonded cBN grinding wheels under high efficiency deep grinding (HEDG) domain. The grinding forces and material removal rates were determined experimentally. The specific energy requirements during HEDG were determined and compared with the specific energy requirement during the conventional grinding process. It was revealed that the HEDG process under appropriate process conditions required lower specific energy for grinding the bearing steels. The good performance of the HEDG process in this case can be attributed to the retention of sharpness and stability of the cBN grits of the monolayer wheels within the domain of the process parameters employed during this investigation and also to a certain extent due to better and effective application of the cutting fluid during the HEDG process.