Experimental investigation on the electrochemical machining of 00Cr12Ni9Mo4Cu2 material and multi-objective parameters optimization

Special stainless steel 00Cr12Ni9Mo4Cu2 has multiple composition and inhomogeneous tissues; short circuiting will frequently occur when using conventional electrolyte processing. This article analyzes the reason why the process of machining is difficult from the material composition and structure. We used the NaNO₃ and NaClO₃ electrolyte composite to select the appropriate concentration, and then by using the orthogonal experiment and gray relational analysis method, we discussed how the voltage, feed speed, and electrolyte pressure solved the problem of the material removal rate (MRR), surface roughness (SR), and side gap. Under optimal conditions of 20 V, an electrolyte composite concentration of 178 g/l NaNO₃ and 41 g/l NaClO₃, a feed rate of 0.7 mm/min, and an electrolyte pressure of 0.8 MPa, a material removal rate of 100.8 mm3/min, a surface roughness of Ra 0.8 μm, and a side gap of 0.16 mm were produced. Given the same voltage, with an increasing cathode feed rate, the MRR was shown to increase while the surface roughness value and the side gap decreased. Under the same cathode feed rate, the MRR decreases, while the side gap and the surface roughness increase as the electrochemical machining application voltage increases. This study proves that using a certain concentration of electrolyte composite is a simple, low-cost, and feasible approach in improving efficiency and quality.     

Investigation into fabrication of microslot arrays by electrochemical micromachining

Maskless electrochemical micromachining (EMM) is a prominent and unique surface texturing method to fabricate the arrays of microslots. This article investigates the generation of microslot arrays using maskless EMM method. The developed prototype maskless EMM setup consists of EMM cell, power supply connections, electrode holding devices and constricted vertical cross flow electrolyte system for the fabrication of microslot arrays economically. One textured cathode tool with SU-8 2150 mask is used to produce 22 microslot arrays. Influences of EMM process parameters including voltage, electrolyte concentration, inter electrode gap, flow rate and machining time on the machining performance that is, width overcut, depth and surface roughness (R_a) of microslot arrays are investigated. For lower width overcut, controlled depth, and lower surface roughness, machining with lower voltage, lower electrolyte concentration, lower inter electrode gap, higher flow rate and lower machining time are recommended. From the analysis, it is observed that the best machining conditions including inter electrode gap of 50?μm, applied voltage of 6 V, electrolyte concentration of 20?g L^?1, flow rate of 5.35 m³ hr^?1 and machining time of 1?min fabricate regular microslot array with mean width overcut of 24.321?μm, mean machining depth of 10.7?μm and mean surface roughness of 0.0101?μm.     

Enhancement of surface roughness in electrochemical machining of Ti6Al4V by pulsating electrolyte

Electrochemical machining (ECM) is widely used in machining a variety of components used in aerospace, defence, automotive and medical applications. The surface roughness of the ECM process has become important because of increased quality demands. Considerable attention has been paid to achieving low surface roughness in ECM. Surface roughness is closely related to the distribution of gases and Joule heat produced during the ECM process, which affect the electrolyte electric conductivity and directly determine the surface roughness. In this report, a pulsating electrolyte, which is one of the unsteady flows that are characterized by periodic fluctuations of the mass flow rate and pressure, is first introduced to the ECM process. The ECM process is affected by the pulsating electrolyte because it can modify the heat transfer. The goal of this report is to present experimental results of the surface roughness obtained on Ti6Al4V samples using a developed pulsating electrolyte supply system in ECM. It is observed that a lower surface roughness and higher material removal rate could be obtained by using a pulsating electrolyte with proper pulsating frequency and amplitude. In direct current ECM, the surface roughness Ra is 5.7 μm, the material removal rate is 0.85 g/min at a constant electrolyte, the lowest surface roughness is 3.69 μm and the largest material removal rate is 0.92 g/min, which are obtained at a pulsating frequency of 10 Hz and amplitude of 0.2 MPa. In pulsed current ECM, the surface roughness Ra and material removal rate are 0.67 μm and 0.38 g/min at a constant electrolyte, respectively, and both the minimum surface roughness Ra of 0.53 μm and maximum material removal rate of 0.39 g/min are observed when the proper pulsating electrolyte flow frequency and amplitude are used.     

Changes of valency state during electro-chemical machining

When electro-chemical machining of medium and low carbon steels in NaCl electrolytes, a reduction in current efficiency results that is shown here by A.R. Mileham^*, R.M. Jones^** and S.J. Harvey^** to be associated with a change in the valency from Fe²⁺ and Fe³⁺ as either the current density is increased or the electrolyte inlet velocity reduced. During the valency transition, surface defects appear. Machining with Fe²⁺ rather than Fe³⁺ results in a slightly lower value of surface roughness (R_a)     

Free abrasive wire saw machining of ceramics

Currently, many kinds of ceramics are used in advanced industrial fields due to their superior mechanical properties, such as thermal, wear, corrosion resistance, and lightweight features. Wire saw machining ceramic (Al₂O₃) was investigated by ultrasonic vibration in this study. Taguchi approach is a powerful design tool for high-quality systems. Material removal rate, wafer surface roughness, steel wire wear, kerf width, and flatness during machining ceramic were selected as quality character factors to optimize the machining parameters (swinging angle, concentration, mixed grain and direction of ultrasonic vibration) to get the larger-the-better (material removal rate) and the smaller-the-better (wafer surface roughness, steel wire wear, kerf width and flatness) machining characteristics by Taguchi method. The results indicated that wire swinging produces a higher material removal rate and good wafer surface roughness. Ultrasonic vibration improved material removal rate, without affecting the flatness under different machining conditions. Experimental results show that the optimal wire saw machining parameters based on grey relational analysis can be determined effectively and material removal rate increases from 2.972 to 3.324 mm²/min, wafer surface roughness decreases from 0.37 to 0.34 μm, steel wire wear decreases from 0.78 to 0.77 μm, kerf width decreases from 0.352 to 0.350 mm, and flatness decreases from 7.51 to 7.22 μm are observed.     

Development and machinability evaluation of MgO doped Y-ZTA ceramic inserts for high-speed machining of steel

ABSTRACT

In current high productivity manufacturing era, it is necessary to develop non-conventional newer tool materials. Here, an attempt has been made for developing MgO doped zirconia-toughened alumina (Mg-ZTA) using powder metallurgy process route. The 3 mol% yttria stabilized zirconia (YSZ) (10 wt%), alumina (Al₂O₃) (90 wt%) with varying percentage of magnesium oxide (MgO) (0–1 wt%) are mixed to study the phase transformation and uniaxially pressed into square inserts with 0.8 mm nose radius and sintered at 1,600ºC for 1 h in pressure less condition. The maximum hardness of 17.04 GPa, fracture toughness of 5.09 MPa m^1/2 and flexural strength of 502 MPa, respectively, has been reached at 0.6 wt% of MgO due to more metastable tetragonal phase. The performance of the insert has been evaluated by machining AISI 4340 steel (radius 75 mm) in lathe. The performance with respect to flank wear, cutting force and surface roughness is quite impressive at different cutting speed even after 20 min of machining. It can be inferred that MgO doped ZTA insert can be used for medium to high-speed machining in current manufacturing scenario and is very promising to replace carbide or coated carbide inserts in coming days.     

Flow field design and experimental investigation of electrochemical machining on blisk cascade passage

Electrochemical machining (ECM) provides an economical and effective way for machining heat-resistant, high-strength materials into complex shapes that are difficult to machine using conventional methods. It has been applied in several industries, especially aerospace, to manufacture blisk. The electrolyte flow field is a critical factor in ECM process stability and precision. To improve the process stability and the efficiency of blisk cascade passages, ECM with a radial feeding electrode, a rational electrolyte flow mode for electrochemical machining called “Π shape flow mode”, is discussed in the paper. Three flow field models are described separately in this report: traditional lateral flow mode, positive flow mode and Π-shaped flow mode, and the electrolyte velocity and pressure distribution vectors for each flow mode are calculated by means of a finite element fluid analysis method. The simulation results show that the electrolyte flow is more uniform with the Π-shaped flow mode. The deformation of the cathode, which is caused by the pressure difference, is also analysed in this report. The cascade passage ECM with a radial feeding electrode was experimentally tested out to evaluate the rationality of the flow field, and the fluctuation of current during the process was less than 1 %, which means that the process that uses the Π-shaped flow mode is stable. The feeding velocity of the cathode with the Π-shaped flow mode is approximately 70 % higher than that with the other two flow modes, and the incidences of short circuiting are obviously decreased. The surface roughness of the blisk hub is only 0.15 μm, and the machining error of the hub is less than 0.1 mm. The results demonstrate that using the Π-shaped flow mode can enhance the quality, stability and efficiency of blisk cascade passage ECM.     

Electrical discharge precision machining parameters optimization investigation on S-03 special stainless steel

S-03 is a novel special stainless steel, which is widely used in precision aerospace parts and electrical discharge machining technology has the merit of high-accuracy machining. This paper aims to combine gray relational analysis and orthogonal experimental to optimize electrical discharge high-accuracy machining parameters. The four process parameters of gap voltage, peak discharge current, pulse width, and pulse interval are required to optimize in the fewest experiment times. The material removal rate and surface roughness are the objective parameters. The experiment were carried out based on Taguchi L9 orthogonal array, then we carried out the gray relational analysis to optimize the multi-objective machining parameter, finally, we verified the results through a confirmation experiment. The sequence of machining parameters from primary to secondary are as follows: discharge current 7A, pulse interval 100 μs, pulse width 50 μs, and gap voltage 70 V. Using the above machining parameters, we can obtain good surface roughness Ra1.7 μm, and material removal rate 13.3 mm³/min. The machined work piece almost has no surface modification layer. The results show that combining orthogonal experiment and gray relational analysis can further optimize machining parameters, the material removal rate increased by 23.8 %, and the surface roughness almost has no change.     

An experimental investigation on machining parameters of AISI D2 steel using WEDM

The performance of the wire electrodischarge machining (WEDM) machining process largely depends upon the selection of the appropriate machining variables. Optimization is one of the techniques used in manufacturing sectors to arrive for the best manufacturing conditions, which are essential for industries toward manufacturing of quality products at lowest cost. As there are many process variables involved in the WEDM machining process, it is difficult to choose a proper combination of these process variables in order to maximize material removal rate and to minimize tool wear and surface roughness. The objective of the this work is to investigate the effects of process variables like pulse on time, pulse off time, peak current, servo voltage, and wire feed on material removal rate (MRR), surface roughness (SR), gap voltage, gap current, and cutting rate in the WEDM machining process. The experiment has been done using Taguchi’s orthogonal array L27 (3⁵). Each experiment was conducted under different conditions of input parameters and statistically evaluated the experimental data by analysis of variance (ANOVA) using MINITAB and Design Expert tools. The present work also aims to develop mathematical models for correlating the inter-relationships of various WEDM machining parameters and performance parameters of machining on AISI D2 steel material using response surface methodology (RSM).The significant machining parameters and the optimal combination levels of machining parameters associated with performance parameters were also drawn. The observed optimal process parameter settings based on composite desirability (61.4 %) are pulse on time 112.66 μs, pulse off time 45 μs, spark gap voltage 46.95 V, wire feed 2 mm/min, peak current of 99.99 A for achieving maximum MRR, gap current, gap voltage, cutting rate, and minimum SR; finally, the results were experimentally verified.     

Effect of machining parameters on surface roughness and tool wear for 7075 Al alloy SiC composite

In the present study, an attempt has been made to investigate the influence of cutting speed, depth of cut, and feed rate on surface roughness during machining of 7075 Al alloy and 10 wt.% SiC particulate metal-matrix composites. The experiments were conducted on a CNC Turning Machine using tungsten carbide and polycrystalline diamond (PCD) inserts. Surface roughness of 7075Al alloy with 10 wt.% SiC composite during machining by tungsten carbide tool was found to be lower in the feed range of 0.1 to 0.3 mm/rev and depth of cut (DOC) range of 0.5 to 1.5 mm as compared to surface roughness at other process parameters considered. Above cutting speed of 220 m/min surface roughness of SiC composite during machining by PCD tool was less as compared to surface roughness at other values of cutting speed considered. Wear of tungsten carbide and PCD inserts was analyzed using a metallurgical microscope and scanning electron microscope. Flanks wear of carbide tool increased by a factor of 2.4 with the increase of cutting speed from 180 to 240 m/min at a feed of 0.1 mm/rev and a DOC of 0.5 mm. On the other hand, flanks wear of PCD insert increased by only a factor of 1.3 with the increase of cutting speed from 180 to 240 m/min at feed of 0.1 mm/rev and DOC 0.5 mm.     

Influence of laser heat treatment on microstructure and properties of surface layer of Waspaloy aimed for laser-assisted machining

In this study, a nickel-based superalloy, Waspaloy, was laser heat treated with diode laser. Single laser tracks were manufactured with different laser beam power densities between 63 and 331 kW/cm², and scanning laser beam speed ranged from 5 to 100 m/min. It was found that laser heat treatment of Waspaloy causes decrease in material hardness—the microhardness in laser tracks is about 300 HV0,1 while the microhardness of substrate is ranged from 300 to 600 HV0,1—which is a positive phenomenon for laser-assisted machining of investigated material. Impacts of laser heat treatment parameters on laser tracks properties were identified for obtaining multiple laser tracks with the most homogenous thickness. Moreover, roughness of heated layers was measured to specify surface quality after laser heat treatment. Multiple laser tracks were produced using different scanning laser beam speed and distances between laser tracks ranged from 0.125 to 1 mm. It was found that if scanning laser beam speed is 75 m/min and distance between laser tracks is equal to or lower than 0.25 mm, in microstructures of multiple laser tracks, cracks are occurring. The most suitable laser heat parameters for obtaining heated layers, and which can be used for laser-assisted machining, were identified as laser beam power density 178.3 kW/cm², scanning laser beam speed 5 m/min, and distance between laser tracks 0.125 mm.     

The effects of the silicon wafer resistivity on the performance of microelectrical discharge machining

In this study, the performance of Si wafer machining by employing the die-sinking microelectrical discharge machining technique is reported. Specifically, the machining performance was examined on both high- (1–10 Ω cm) and low-resistivity (0.001–0.005 Ω cm) Si wafers by means of using a range of discharge energies. In this regard, the machining time, material removal rate, surface quality, surface roughness, and material mapping, which are categorized among the important properties in micromachining, have been investigated. In order to analyze the surface properties and to perform the elemental analysis, the scanning electron microscope and energy-dispersive X-ray spectroscopy were used. In contrast, the 3D surface profiler was used to evaluate the roughness of machined surface. The results of this experimental study revealed that the electrical resistivity and discharge energy parameter of microelectrical discharge machining had a great influence on the Si wafer machining performances. The observations in this study indicated a decrease in machining time, high material removal rate, and high surface roughness with an increased discharge energy values. Overall, it was learnt that the minimum amount of energy required to machine Si wafer was 5 μJ for both low and high-resistivity Si. In addition, the highest material removal of 5.842 × 10^?5 mm³/s was observed for low-resistivity Si. On the contrary, the best surface roughness, R _a, of 0.6203 μm was achieved for high-resistivity Si and it also pointed to a higher carbon percentage after the machining process.     

Dry machining of aluminum for proper selection of cutting tool: tool performance and tool wear

Machining of aluminum and its alloy is very difficult due to the adhesion and diffusion of aluminum, thus the formation of built-up edge (BUE) on the surface. The BUE, which affects the surface integrity and tool life significantly, affects the service and performance of the workpiece. The minimization of BUE was carried out by selection of proper cutting speed, feed, depth of cut, and cutting tool material. This paper presents machining of rolled aluminum at cutting speeds of 336, 426, and 540 m/min, the feeds of 0.045, 0.06, and 0.09 mm/rev, and a constant depth of cut of 0.2 mm in dry condition. Five cutting tools WC SPUN grade, WC SPGN grade, WC + PVD (physical vapor deposition) TiN coating, WC + Ti (C, N) + Al₂O₃ PVD multilayer coatings, and PCD (polycrystalline diamond) were utilized for the experiments. The surface roughness produced, total flank wear, and cut chip thicknesses were measured. The characterization of the tool was carried out by a scanning electron microscope (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) pattern. The chip underface was analyzed for the study of chip deformation produced after machining. The results indicated that the PCD tool provides better results in terms of roughness, tool wear, and smoother chip underface. It provides promising results in all aspects.     

Machining performance of a grooved tool in dry machining Ti-6Al-4 V

In this paper, dry machining experiment of Ti-6Al-4 V was carried out to investigate the machining performance of a grooved tool in terms of its wear mechanisms and the effects of cutting parameters (cutting speed, feed rate, and cutting depth) on tool life and surface roughness of the machined workpiece. The results showed that chip-groove configuration substantially improved the machining performance of cutting tool. The main wear mechanisms of the grooved tool were adhesive wear, stripping wear, crater wear, and dissolution-diffusion wear. The resistance to chipping was enhanced due to the decrease of contact pressure of tool-chip interface. And the resistance to plastic deformation of tool nose was weakened at the cutting speed of more than 60 m/min. The appropriate cutting speed and feed rate were less than 70 m/min and 0.10 mm/r, respectively. With cutting speed increasing, the surface roughness of machined workpiece decreased. A high feed rate helped the formation of higher surface roughness except 0.21 mm/r. When cutting depth increased, tool nose curvature and phase transformation of workpiece material had great impact on surface roughness.     

Investigations on the effects of Nano-fluid in ECM of die steel

Formation of spikes in the electrochemically machined workpiece prevents to achieve the better performance of ElectroChemical Machining (ECM). Hence, this research work attempts to investigate the effects of Nano-fluid i.e. Nano Copper particles suspended NaCl electrolyte on the ECM of High carbon high chromium (HCHCr) die steel with a hardness of 63HRc. The influencing parameters are voltage, tool feed rate and electrolyte discharge rate with mixing levels. Seventy-two experiments have been conducted using Nano-fluid and plain NaCl electrolyte based on design of the experiment. The Nano Copper particles in the electrolyte break the gas layer at the inter electrode gap resulting in better MRR and surface roughness due to improved current density across the gap. A maximum MRR of 458.869 mm³/min and a minimum surface roughness of 1.39 μm Ra are obtained using Nano-fluid. The developed ANOVA models prove the significances of influencing factors in obtaining the better performance of ECM.     

An experimental study on the ultrasonic machining characteristics of engineering ceramics

Engineering ceramics have many unique characteristics both in mechanical and physical properties such as high temperature hardness, high thermal, chemical and electrical resistance. However, its machinability is very poor in conventional machining due to its high hardness and severe tool wear. In the current experimental study, alumina (Al₂O₃) was ultrasonically machined using SiC abrasives under various machining conditions to investigate the material removal rate and surface quality of the machined samples. Under the applied amplitude of 0.02 mm, 27 kHz frequency, three slurry ratios of 1:1, 1:3 and 1:5 with different tool shapes and applied static pressure levels, the machining was conducted. Using the mesh number of 240 abrasive, slurry ratio of 1:1 and static pressure of 2.5 kg/cm², maximum material removal rate of 18.97 mm³/min was achieved. With mesh number of 600 SiC abrasives and static pressure of 3.0 kg/cm², best surface roughness of 0.76 pm Ra was obtained.     

Comparison of different laser-assisted electrochemical methods based on surface morphology characteristics

This paper presents two different laser electrochemical machining (LECM) methods: point-by-point method and scan method. Experiments about the two LECM methods were performed on the aluminum alloy plates placed in a shallow container filled with NaNO₃ electrolyte 2 mm above. Then, the scanning electron microscopy and the optical profiling system were used to analyze machining quality and morphology characteristics of two different machining methods. For the point-by-point method, the shape accuracy at the starting point, finishing point, and node of line cross is lower. Compared with the point-by-point method, the better etching morphology was gained by the scan method in the experiments. The influence of the scan speed on machining quality and groove width was investigated. The better etching surface quality and the higher etching efficiency were gained when the scan speed varied from 0.1 to 0.15 mm/s. These results demonstrate that laser electrochemical machining by the scan method is a promising method to achieve complex profiles.     

Parametric optimization of CNC turning process for hybrid metal matrix composite

Machining of hybrid metal matrix composite is difficult as the particulates are abrasive in nature and they behave like a cutting edge during machining resulting in quick tool wear and induces vibration. An attempt was made in this experimental study to evaluate the machining characteristics of hybrid metal matrix composite, and a mathematical model was developed to predict the responses, namely surface finish, intensity of vibration and work-tool interface temperature for known cutting condition while machining was performed in computer numerical control lathe. Design of experiments approach was used to conduct the trials; response surface methodology was employed to formulate a mathematical model. The experimental study inferred that the vibration in V _x, V _y, and V _z were 41.59, 45.17, and 26.45 m/s², respectively, and surface finish R _a, R _q, and R _z were 1.76, 3.01, and 11.94 μm, respectively, with work-tool interface temperature ‘T’ of 51.74 °C for optimal machining parameters, say, cutting speed at 175 m/min, depth of cut at 0.25 mm and feed rate at 0.1 mm/rev during machining. Experimental results were in close conformity with response surface method overlay plot for responses.     

An integrated optimization of cutting parameters and tool path generation in ultraprecision raster milling

This paper provides a new methodology for the integrated optimization of cutting parameters and tool path generation (TPG) based on the development of prediction models for surface roughness and machining time in ultraprecision raster milling (UPRM). The proposed methodology simultaneously optimizes the cutting feed rate, the path interval, and the entry distance in the feed direction to achieve the best surface quality in a given machining time. Cutting tests are designed to verify the integrated optimization methodology. The experimental results show that, in the fabrication of plane surface, the changing of entry distance improves surface finish about 40 nm (R _a ) and 200 nm (R _t ) in vertical cutting and decreases about 8 nm (R _a ) and 35 nm (R _t ) in horizontal cutting with less than 2 s spending extra machining time. The optimal shift ratio decreases surface roughness about 7 nm (R _a ) and 26 nm (R _t ) in the fabrication of cylinder surfaces, while the total machining time only increases 2.5 s. This infers that the integrated optimization methodology contributes to improve surface quality without decreasing the machining efficiency in ultraprecision milling process.     

Optimizing machining parameters of silicon carbide ceramics with ED milling and mechanical grinding combined process

A novel combined process of machining silicon carbide (SiC) ceramics with electrical discharge milling and mechanical grinding is presented. The process is able to effectively machine a large surface area on SiC ceramics with a good surface quality. The effect of tool polarity on the process performance has been investigated. The effects of peak current, peak voltage, pulse on-time and pulse off-time on the material removal rate (MRR), electrode wear ratio (EWR), and surface roughness (SR) have been investigated with Taguchi experimental design. The mathematical models for the MRR, EWR, and SR have been established with the stepwise regression method. The experiment results show that the MRR, EWR, and SR can reach 46.2543 mm³/min, 20.7176%, and 0.0340 µm, respectively, with each optimal combination level of machining parameters.