High-speed milling of titanium alloys is widely used in aerospace industries due to its high efficiency and good quality product. The paper empirically studies surface roughness, topography and microhardness variations in high speed milling of Ti6Al4V alloy. The experiments were conducted under minimum quantity lubrication environment. Carbide end mill tool with TiAlN coating and 6 millimeter diameter was used. Full factorial method was used to design experiments and analyze the effect of machining parameters including cutting speed and feed rate on surface roughness, topography and microhardness. The other cutting parameters, i.e. axial depth of cut and radial depth of cut were constant. The results showed that a high quality surface with roughness of 0.2 mm can be obtained by using high speed machining method. Also, microhardness variations versus cutting speed has two-fold nature. It indicates that firstly, by increasing cutting speed up to 375 m/min, microhardness increases and after that declines remarkably. In addition, by increasing feed rate, surface microhardness rises and the maximum microhardness was obtained at cutting speed of 375 m/min and feed rate of 0.08 mm/tooth, which showed 57% increase with regard to hardness of the base material. The images of surface topography showed that increasing of the cutting speed has a significant effect on reduction of surface tears and smears.

In grinding operation, cutting fluid is utilized for lubrication, cooling, chip removal from contact zone and also cleaning of grinding wheel. Despite these advantages, grinding fluids make many economic and environmental issues. On the other hand, dry grinding generally leading to thermal damages and reduction of surface quality level. minimum quantity lubrication (MQL) technique is a new approach to elimination or reduction of cutting fluids that improves grinding performance by efficient penetration to the cutting zone. In this paper, in order to investigate the effect of MQL on grinding of steels, raw and hardened High Speed Steel has been selected. Grinding performance such as tangential grinding force, friction coefficient, roughness and morphology of the ground surface and chip form in three states of dry, conventional fluid and MQL have been studied and compared. The results show that MQL technique in comparison with the others lead to improvement of surface quality and also reduction of tangential grinding force and friction coefficient in hardened steel, but in the case of raw steel despite of reduction of tangential grinding force and friction coefficient, the surface quality is worst.

Reducing energy consumption in production is an urgent need. In manufacturing processes, especially machining, more than 90% of the environmental impacts are due to energy consumption in machine tools. The purpose of the present study is to estimate and compare the energy consumption of AISI 316 steel milling process in conventional (wet) and minimum quantity lubrication (MQL) modes as well as the experimental measurement of energy consumption in each of these two modes. Studies have suggested different types of energy consumption modeling in machining but few studies have been conducted on the use of these modeling techniques and the minimum quantity lubrication method has been rarely compared with the wet state in terms of energy consumption. Empirical experiments were used to confirm the modeling performed to predict energy consumption in the milling process. The results show that the proposed method is efficient and practical for predicting energy consumption with 5% error. After confirming the modeling, using two levels for feed rate and spindle speed and applying full factorial design of experiments, energy and power consumption in MQL and wet cutting modes using the power meter connected to the input 3-phase power cable of the milling machine were experimentally measured. Energy consumption in the minimum quantity lubrication method was decreased by 16% compared to the wet state. The average power consumption in MQL milling is 33% lower than in wet milling.

2This research investigates tool wear, elemental analysis (EDAX) on the machined surface, surface roughness, microhardness and microstructural changes in the cross-section of milled 304L stainless steel samples under dry and minimum quantity lubrication (MQL) methods. The MQL process was able to improve the surface roughness for all milling parameters from 17% to 41% compared to the corresponding dry conditions. In dry machining, defects such as built up edge, severe flank wear and tool chipping were created. In MQL mode, these defects were significantly reduced and tool chipping was almost eliminated. By increase of cutting speed and depth, the surface hardness has increased. Compared to the dry method, the MQL reduces the hardness values and hardened depth below the machined surface. According to EDAX analysis on dry and MQL machined surfaces, applying the roughest cutting parameters, it was determined that no change of chemical elements occurred on machined surfaces. Increasing cutting parameters or dry machining causes the plastic deformation to intensify, the microstructure is flattened and the microstructure grains are compressed in the vicinity of the machined surface. The maximum reduction in thickness of deformed layer in MQL compared to dry method is 39%. For each milling sample, there is a direct relationship between the hardened depth and thickness of the corresponding microstructurally deformed layer.

Consumption of cutting fluids imposes high costs on industry. These cutting fluids contaminate the environment and are harmful to human health. minimum quantity lubrication technique (MQL) is a new approach to reduction of cutting fluids consumption, improving efficiency of cutting fluid at machining zone and using harmless fluids. However, this technique faces cooling limitation in grinding. The purpose of this study is an accurate study of heat transfer mechanism in minimum quantity lubrication technique by its temperature numerical simulation and improving the cooling ability of its air jet by using a simple and inexpensive vortex tube. For this purpose, a system was designed and manufactured to measure the convection heat transfer coefficient of different conditions of MQL environments. The result of convection heat transfer tests shows 95% share of compressed air in heat transfer and also air pressure is a more important factor than temperature in cooling process. The result of temperature numerical simulation shows that by increasing pressure, the increasing rate of convection heat transfer coefficient decreases; also, the cooling ability temperature of the vortex tube at low thermal power is tangible. In grinding of soft steel, the minimum quantity lubrication technique with cold air (CAMQL) in comparison with other methods leads to significant reduction of tangential grinding force and friction coefficient, but in general, except in the case of optimum condition which has the highest heat transfer coefficient, surface finish is worse, which is related to low heat transfer coefficient of gases at low pressures.

In this experimental work, the effects of cutting fluid and different cutting parameters on surface roughness, tool wear, and chip morphology during turning of Al7075-T6 were investigated. Machining experiments have been done in different environments such as dry, wet, minimum quantity lubrication (MQL) as well as a homemade ultrasonic nozzle- minimum quantity lubrication (UN-MQL). Ultrasonic vibrations can be used to effectively atomize the cutting fluid into fine and uniform-sized droplets and smaller spray angles with a larger spray deposition distance. The MQL system and machining parameters were evaluated by the design of experiments (DOE) method which allows us to carry out the optimization analysis by performing a relatively small number of experiments while determining the influence on the machining performance using the analysis of variance technique. In the second step, an optimization of the machining parameters was sought using signal-to-noise ratio analysis. Therefore, the response surface methodology was determined in a regression analysis, which was used to model the influence of the parameters on the performance. The fine droplets produced by the UN-MQL system penetrate effectively into the machining zone. Finally, the chip morphology, tool wear and surfaces of the machined parts were examined using optical microscopy to identify the chip formation mechanism in different machining conditions. Cutting tool wear were also examined using the SEM tests to quantify the tool wear zones under specific process parameters. Experimental results show that applying UN-MQL system reduces the surface roughness and tool wear by up to 30% in comparison to the conventional MQL system.

In the current research, the effect of cutting depth and speed on surface topography, microhardness and microstructural changes in cross-sectional surface of turned parts under dry, wet, MQL and cryogenic cooling (CO2) conditions, on 304L stainless steel has been investigated. The main origin of surface topography defects was the formation of built up edge (BUE) on the cutting tool and its removal again. Also, the increase in cutting speed causes instability in the formation of BUE, as a result the volume of accumulated BUE decreases. Considering the improvement of surafce topography, in the order of priority, the efficiency of MQL, wet and cryogenic methods has been from the highest to the lowest compared to the dry method. the cross section of machined samples were prepared and it was observed that subsurface hardness of the samples decreases with the distance from the surface up to 34% and approaches the hardness of the bulk material. The hardness value in cross section of machined samples is directly related to the work hardening caused by severe plastic deformation on machined surface. With increase of cutting speed, the intensity of plastic deformation increases and the hardness under the surface increases. Different cooling and lubrication processes have a direct effect on thickness of the microstructural deformed layer. Under the highest value of cutting speed used in this research, the maximum reduction in thickness of the deformed layer of the microstructure in cryogenic and MQL conditions compared to the dry mode was equal to 62% and 28%, respectively

Cooling/lubricant fluids are typically used in machining processes to reduce the tool-workpiece friction, decrease machining heat and improve surface quality. In recent years, however, several laws have been used in place to protect human health and environment, requiring industry to reduce coolants consumption and expand the use of low-risk and renewable ones. For this reason, a recent new lubrication technique called minimum quantity lubrication (MQL) has been developed for the machining processes. Vegetable oils are kinds of bio-based lubricants and have a significant capacity to be used in MQL due to their environmentally friendly and renewable properties. Stainless steels are considered to be difficult to machining materials and hence their machinability improvement has always been the subject of research. In this investigation, the effects of MQL and type of lubricant in the milling process of martensitic stainless steel EN 1. 4903 have been studied. For this purpose, one type of vegetable oil derived from sesame seeds in two conditions including non-additive (pure) and with antioxidant additives, as well as one type of mineral oil have been applied in the experiments. Then, milling force, surface roughness and surface texture have been evaluated. Also, in order to compare the results with other lubrication methods, the tests have been performed under dry and wet conditions. The results show that the MQL compared to the conventional lubrication methods increases the machinability of stainless steel by reducing forces and improving surface quality. Moreover, the type of oil applied has a great influence on the process outputs.