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In the present work, hydroxyapatite (HA)-50 wt.% TiO2 composite coating has been developed on Mg-alloy by laser cladding process using 400 W continuous wave fibre laser. A detailed microstructural characterisation has been done by using optical profilometry, field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction techniques. The wettability analysis has been done by the sessile method using hank's solution. The average roughness is 0.5 μm for the Mg-1% Ca alloy and 1.45 μm for laser-cladded surface. The microstructure analysis shows uniform deposition with the presence of porosities, particles and few cracks on the top surface of laser-cladded surface. The composition analysis shows the uniform and homogeneous distribution of Ca, Ti, P, and O on the laser-cladded surface. The phase analysis shows the presence α, β phase in Mg-1% Ca alloy and the presence of Ca2P2O7, Ca3(PO4)2, CaTiO3 and TiO2 (rutile) phases in the laser-cladded surface. There is an improvement in wettability of the laser-cladded surface as compared to as-received Mg alloy. [ABSTRACT FROM AUTHOR]

This article focuses on the morphology, shape, and size of NPs which are crucial steps in nanotechnology. The production of tungsten carbide (WC) nanoparticles and tool wear rate under different voltage and duty factors have been studied in two different dielectrics, i.e., EDM oil and kerosene. It has been seen that the generation of NPs and tool wear rate increases with an increase in voltage at a constant duty factor. The maximum amount of generated NPs was obtained at a duty factor of 20%, and voltage 40 V are 0.1013 gm and 0.0447 gm in EDM oil and kerosene, respectively. The higher value of tool wear rate was observed at duty factor 20%, and voltage 40 V are 0.000278 gm/min and 0.000192 gm/min in EDM oil and kerosene, respectively. The production of NPs is more, and the formation of carbide is less with using EDM oil as compared to kerosene. Field emission scanning electron microscopy (FESEM) image depicts that tungsten carbide nanoparticles are spherical, and carbon is in uneven shapes. Energy-dispersive X-ray spectroscopy (EDX) results reveal that the produced nanoparticles contain tungsten (W), Carbon (C), and Oxygen (O) in both dielectrics. [ABSTRACT FROM AUTHOR]

Tungsten microtool electrode is one of the preferred tool electrodes in micro electrochemical machining (µECM) of hard to machine materials. During the pilot experiments with different types of electrolytes materials (such as NaOH, HNO3, NaBr, KOH, H2SO4, NaCl, NaNO3 and HCl), it has been found that KOH(Aq.) and NaOH(Aq.) electrolytes are suitable for the fabrication of tungsten microtools through µECM process. Therefore in this research, a comparative study between NaOH(Aq.) and KOH(Aq.) electrolytes have been carried out in the fabrication of tungsten microtools through µECM. DC voltage (V), electrolyte concentration (Mol/L) and machining time (Minutes) are chosen as machining parameters in order to investigate their role on response outputs i.e. tool radius reduction (Δ) and material removal rate (MRR). Roles of machining parameters on the response output are analysed through Taguchi design technique and ANOVA is employed to determine the dominant machining parameters on the response outputs. Experimental results indicate 'Δ' and 'MRR' obtained with NaOH(Aq.) is greater than 'Δ' and 'MRR' obtained with KOH(Aq.) respectively at most of the experimental run. But microscopic view of the fabricated microtools indicate that the surface uniformity throughout the length of the microtools obtained with KOH(Aq.) electrolyte is favourable than NaOH(Aq.). [ABSTRACT FROM AUTHOR]

In this research, both eco-friendly and commercially available dielectric liquid (EDM oil, EDM oil + MoS2 powders (EDP), Sunflower oil (SF), and Sunflower oil + MoS2 powders (SFP)) was adopted to carry out the small area surface modification on Ti6Al4V sheet through the micro-EDM process. Brass rod (diameter: 0.95 mm) was used as the micro-tool electrode. The quality (surface roughness (Ra, Rq, Rz), recast layer (or coating) thickness (RLT), and the micro-hardness (MH)) of the coated surfaces was tested and compared with the change of input process parameters and dielectrics. The results indicate that the maximum micro-hardness of the coated layer for differently used dielectric mediums such as EDM oil, SF oil, EDP oil, and SFP oil is 495.9 HV, 619.05 HV, 665.42 HV, and 694.02 HV, respectively. Similarly, the coated layer thickness varies within the range of 4.56 to 24.42 μm (EDM oil), 7.24 to 28.31 μm (SF oil), 5.42 to 26.84 μm (EDP oil), and 4.66 to 32.75 μm (SFP oil). EDX plots suggest transfer of tool and the dielectric material (Ti, V, Al, C, Cu, Zn, Mo, S) to the substrate surface. [ABSTRACT FROM AUTHOR]

High-aspect-ratio cylindrical tungsten microtools were fabricated through the electrochemical micro-machining (µECM) process. The effects of eight different electrolytes in combination with the different major machining parameters were investigated and reported in this article. KOH(aq) electrolyte was found to be the most suitable electrolyte for the fabrication of tungsten microelectrodes. The Taguchi technique was utilized for optimizing the major process control parameters to minimize the taper angle of the fabricated micro-tools. During the tool fabrication process, the deposited electrochemical reaction on the tool surface played an important role to achieve controlled dissolution of the tool materials and helped in producing a uniform surface. The microtools of diameter 40 µm with aspect-ratio of about 175 were fabricated with the optimal settings of dominant machining parameters. The fabricated microtools were used to drill through drill-holes on a nickel plate of thickness 1050 µm using the same µECM setup. The detailed experimental investigations are carried out and conclusive remarks are drawn based on the experimental results. [ABSTRACT FROM AUTHOR]

This work contributes to the surface topographical study of miniature Ti-alloy coated samples prepared by the micro-electrical discharge coating process using powder mixed dielectric medium. Two phases of experiments were conducted, first phase: using tungsten disulfide mixed in de-ionized water and second phase: using molybdenum disulfide powders mixed in deionized water. The produced micro-parts from both the phases of experiments were characterized for micro-hardness, indentation depths, wettability (in terms of the surface contact angle), residual stress, surface roughness, and surface crack density. The results indicated that MoS2 coating is superior as compared to WS2 coating obtained through the micro-EDM process for tribological applications where lubrication is necessary. The WS2 coated samples have micro-hardness ranging from 705.8 HV to 880.34 HV, surface roughness from 0.604 microns to 0.660 microns, and a comparatively higher surface crack density and residual stresses are developed on the recast surface than the samples coated with MoS2 powders. The samples coated with MoS2 powders have a micro-hardness variation from 658.21 HV to 714.21 HV, surface roughness between 0.561 μm to 0.650 μm. [ABSTRACT FROM AUTHOR]

The paper brings forward a novel technique for localized solid lubrication coating in intricate structures. Green compact powder metallurgy electrodes (P/M) (diameter: 1 mm to 1.25 mm) were prepared from mixture of WS2 and brass powder at various mixing ratios. The prepared electrodes were used for the deposition process in micro-EDM. A permanent metal mold was fabricated to prepare the micro-EDM P/M tools. The coating operation was performed at different parameter combinations and the coated samples were characterized for evaluation of metallurgical and tribological properties. Maximum metal deposition rate (MDR) of 0.312 mg/min was obtained at powder mixing ratio of 50:50, machining voltage of 80 V, and 50 % duty factor. Uniform surface was observed at powder mixing ratio of 70:30 (WS2: Brass). Maximum micro-hardness of 578.55 HV was observed for coated surface whereas the same for base material was 280 HV. XRD analysis confirmed the presence of WS2, Al2O3 in the coating. Lower wear rate of coated surface was found as compared to uncoated work piece, and a reduction in friction coefficient 0.4 (uncoated work piece) to 0.07 (coated work piece) was obtained. [ABSTRACT FROM AUTHOR]

In the current investigation, solid-lubricant surfaces were prepared onto the mild steel work piece by means of electrical discharge coating process in electrical discharge machine (EDM). Hexagonal boron nitride (hBN) and copper (Cu) powder-based green compact electrodes, prepared in hot mounting press were used as an EDM tool. The loosely bonded material particles from the compact tool were transported to the mild steel surface. With the change of process parameters (powder mixture ratio, duty factor, and peak current), the variation in surface morphology, micro-hardness and tribological properties of hBN-Cu coating layer has been discussed. Following the investigation, field emission scanning electron microscopic (FESEM) images of coating indicated fewer gaps and pores for the powder lubricant mixing ratio of hBN: Cu/50:50, peak current value of 10 A and duty factor value of 70%. X-ray diffraction plot composed of prominent peaks of BN, Cu, along with Fe2O3 (intermetallic compound). Micro-hardness value of lubricant surfaces drastically reduced to the minimum of 75.76 HV (coating layer) from 180 HV (substrate). Moreover, pin on disk tribological test indicated the lubrication effect of hBN particles by revealing a major drop in wear value from 95.75 µm (work piece) to 1.52 µm (coating) and friction coefficient from 0.9 (work piece) to 0.1 (coating). [ABSTRACT FROM AUTHOR]

Day-to-day interest is growing in the drilling of high aspect-ratio deep microholes in various hard-to-machine and newer materials. Besides cost-effectiveness in the manufacturing process, an accurate dimension with the good surface finish is essential for microhole drilling. The conventional methods encounter various problems such as residue stresses, heat generation near cutting zone, high tool-wear, etc. Electrochemical microdrilling (ECMD) is one of the cost-effective techniques, provide a better alternative in drilling microholes with reasonably accurate dimensions and good surface finish in various industrial applications especially in computer, electronic, and aerospace industries. This article reviews current researches and developments of electrochemical processes for circular microholes drilling. It highlights the effects of various key factors (such as the development of microtools, electrolyte, inter-electrode-gap monitoring and control, etc.) on the aspect-ratio and accuracy of circular microholes, produced by ECMD. For further research, it will open up various challenging opportunities, especially in the field of (i) development and handling of microtool electrodes, (ii) development and handling of electrolytes medium, (iii) development in monitoring and controlling techniques of inter-electrode-gap, and (iv) development in strategies for process control for drilling high quality, deep and high aspect-ratio circular microholes into hard-to-machine materials using ECMD. [ABSTRACT FROM AUTHOR]

Electrical discharge machining (EDM) process is popular for machining conductive and difficult-to-cut materials, but low material removal rate (MRR) and poor surface quality are major limitations of the process. These limitations can be overcome by adding the suitable powder in the dielectric. The powder particles influence electric field intensity during the EDM process which in turn improve its performance. The size (micro to nano) and properties of the mixed powder also influence the machining efficiency. In this regard, the objective of the present work is to study the performance of EDM process for machining Inconel 825 alloy by mixing Al2O3 nanopowder in deionized water. The experimental investigation revealed that maximum MRR of 47 mg/min and minimum SR of 1.487 µm, which are 44 and 51% higher in comparison to conventional EDM process, respectively, can be achieved by setting optimal combinations of process parameters. To analyze these observed process behavior, pulse-train data of the spark gap were acquired. The discharge waveform identifies the less arcing phenomenon in the modified EDM process compared to conventional EDM. Further, surface-topography of the machined surface was critically examined by capturing field emission scanning electron microscopy and atomic force microscopy images. [ABSTRACT FROM AUTHOR]

In this experimental study, the effects of major laser process control parameters, such as the laser power, beam scanning speed and assisting gas flow rate, on cut surface integrity defined by the kerf width, taper percentage, and the extent of heat affected zone (HAZ) were investigated. Response surface methodology (RSM) along with central composite design (CCD) of the experiment was used to optimize the process parameters to get better-cut surface quality. The optimum values of process parameters corresponding to cut surface with minimum defects are laser power 260 W, cutting speed 4500 mm per min, and assistance gas flow rate 14.23 l/min and the corresponding kerf width, taper percentage, and the width of HAZ are found to be 163.7 µm, 5.75%, and 573.28 µm. The confirmation experiments have been conducted that provide favorable results with an error of 2.70%, 1.87%, and 0.36%, for kerf width, taper percentage, and width of HAZ, respectively. [ABSTRACT FROM PUBLISHER]

In recent years, wire-electrical discharge machining (WEDM) has gained popularity in the industry due to its capability to generate complicated shapes in exotic materials, irrespective of their hardness. Conventional machining of Nimonic C-263 superalloy is an extremely difficult and costly process due to its high hardness and tool wear rate. The present research work investigates the influence of the WEDM process parameters on different performance measures during machining of Nimonic C-263 superalloy. A mathematical model for all four important performance measures, namely, cutting rate, surface roughness, spark gap, and wire wear ratio, was developed and the responses were used for studying the interrelationship between performance measures and process parameters. The optimal settings of operating conditions were predicted using desirability function. The effectiveness of multicut strategy was also investigated in the article. [ABSTRACT FROM AUTHOR]