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In recent years, reverse electric discharge machining (R-EDM) has been evolved as a method for the fabrication of arrayed structures for surface texturing which find applications in fabrication of fins and component assembly. In this study, the feasibility of R-EDM process in the fabrication of arrayed features of ∅3 mm and height 2 mm on mild steel has been investigated utilizing response surface methodology (RSM)-based experimentation. Influence of control variables such as peak current (Ip), pulse-on time (Ton), and flushing pressure (Fp) on some of the vital geometric characteristics like taper and cylindricity error along with material removal rate (MRR), surface roughness (SR), microhardness, and surface morphology of pillared structure has been investigated. Analysis of variance (ANOVA) results show thatIphas a significant influence followed byTonon MRR.Iphas a significant contribution toward SR, taper, and cylindricity error. High microhardness was found in heat-affected zone (HAZ). The optimal combination of parameter obtained using principal component analysis (PCA)-based grey relational analysis (GRA) is determined to beIp = 10 A,Ton = 100 μs, andFp = 0.3 kg/cm2, which was further ascertained using confirmatory test. [ABSTRACT FROM AUTHOR]

Surface integrity in electric discharge machining (EDM) has always been a major concern in the manufacturing industry. Although, EDM with a powder suspended dielectric has shown good potential in enhancing the material removal rate and improving surface finish, influence of the same on the overall surface integrity is not very clear. The current work utilized the graphite powder and evaluated its role in combination with concentration and machining parameters, on surface roughness (Ra), surface crack density (SCD), white layer thickness, microhardness depth profile, possible phase changes, and residual stress during powder-mixed EDM (PMEDM) of Inconel 625 (a nickel-based super alloy), that is now-a-days regularly used in aerospace, chemical and marine industries. The results showed that significant reduction in surface roughness, crack density, and white layer thickness is possible with the PMEDM process. It also promoted formation of carbides and other alloy compounds which is responsible for augmentation of hardness in surface and subsurface region. The added particles also caused a decline in tensile residual stress of the machined samples. [ABSTRACT FROM AUTHOR]

Abstract: Inconel 825 belongs to the family of nickel-based super alloy and is widely used in the chemical and marine industry. Although most of the research work was concentrated on machinability of Inconel 718, no such work on the current grade of Inconel 825 has been reported so far. This grade of Inconel is particularly suitable for the applications requiring improved resistance to corrosion. The current study aims at investigating the effect of cutting speed and chemical vapour deposition (CVD) multilayer coating on machined surface integrity of Inconel 825 during dry turning, with particular emphasis on measurement of sub-surface hardness and white layers. Three regions were distinguished beneath the machined surface viz. (a) white layer, (b) plastic deformation region and (c) bulk material. It was observed that increase in cutting speed increased white layer thickness after machining with both uncoated and coated tools. CVD coated cemented carbide insert resulted in decrease in white layer thickness particularly in the lower range of cutting velocity when compared with that obtained by its uncoated counterpart. Vickers microhardness test clearly revealed the work hardening tendency of Inconel 825 with hardness being maximum in the sub- surface region and it decreased when measurements were gradually taken towards the centre of the workpiece. However, this tendency was found to be reduced with the use of multilayer coated tool. [Copyright &y& Elsevier]

Inconel 825 belongs to the family of nickel-based super alloys and is widely used in acid production equipment. Although most of the research work was concentrated on the machinability of Inconel 718, there is hardly any similar information on the current grade of Inconel 825 reported so far. The current study investigated the effect of cutting speed and multilayer (TiN/TiCN/Al 2 O 3 /ZrCN) coating deposited by chemical vapour deposition (CVD) on machined surface integrity of Inconel 825 during dry turning. Present paper particularly emphasized on measurement of sub-surface hardness. Fuzzy logic method was used to find predicted value of microhardness of sub-surface and was compared to the experimental and predicted values of both uncoated (ISO P 30 grade) and CVD coated tool. [ABSTRACT FROM AUTHOR]

This study deals with the effect of coating thickness on the characteristics and dry machining performance of TiN film deposited on cemented carbide inserts using closed-field unbalanced magnetron sputtering (CFUBMS). The turning inserts were coated with TiN film of varying thickness ranging from 1.8 µm to 6.7 µm. The deposited coatings were characterized using grazing incidence X-ray diffraction (GIXRD), Vickers and Knoop microhardness tester, and scratch tester. The machining performance of uncoated and coated carbide inserts was evaluated in dry turning of C40 steel. The in-house developed TiN-coated carbide insert exhibited around 16 times higher tool life compared to that of the uncoated insert. Performance test clearly showed the weakness of the uncoated K-type carbide relative to its TiN coated counterpart in machining of long chipping material like C40 steel. The present investigation clearly reveals that the developed TiN-coated tool has a potential for augmenting the cutting capability of uncoated K-type carbide, normally recommended for machining of short-chipping material like cast iron, for machining of even long-chipping material like steel. [ABSTRACT FROM AUTHOR]

Abstract: TiN–MoS x composite coatings were deposited by pulsed DC closed-field unbalanced magnetron sputtering (CFUBMS) using separate Ti and MoS2 targets in an Ar and N2 gas environment. The effect of substrate bias voltage on the structure and mechanical properties of TiN–MoS x composite coating has been studied. The structure and composition of the coating were evaluated using field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS) by X-ray and grazing incidence X-ray diffraction (GIXRD). Scratch adhesion tests, Vickers microhardness tests and ball-on-disc tests with a cemented carbide (WC-6%Co) ball were carried out to investigate mechanical properties of the coating. Application of substrate bias was found to transform the structure of TiN–MoS x composite coating from open columnar to a dense columnar structure. The changes in grain size and texture coefficient appear to be associated with variation in substrate bias voltage. The mechanical properties of the coating such as adhesion and composite microhardness were also observed to be related to the change in bias voltage. A maximum hardness of 22GPa was obtained for a coating deposited at substrate bias voltage of −40V. The improved structural and mechanical properties of the coating deposited at −40V were also reflected in its excellent wear resistance property. [Copyright &y& Elsevier]

One of the major concerns related to machining of Ni-based super alloy is surface integrity since it directly affects the performance of the machined component during its intended application. In the current study, the influence of cutting speed (51, 84 and 124 m/min) and CVD multilayer tool coating (TiN/TiCN/Al 2 O 3 /ZrCN) on various aspects of surface integrity such as surface roughness, crystal structure and microstructure of the surface and sub-surface region, thickness of white layer and work hardening tendency have been investigated during dry turning of Incoloy 825. Particular emphasis has been given to understand the mechanism of formation of modified surface layer and the associated process of dynamic recrystallization. The study indicated coated tool resulted in better surface finish compared to that obtained with uncoated tool only at high cutting speed. Various macro features of machined surface included feed mark, material smearing, surface ploughing, re-deposited materials and chip debris. Transformation of crystallographic phase of the machined surface could not be detected compared to that of bulk material. Increase in cutting speed caused gradual refinement of grains, and increased white layer thickness. Coated tool, on the other hand, resulted in the generation of large number of nucleation sites and consequently finer grains at high cutting speed, whereas the uncoated tool promoted growth of sharply defined recrystallized grains. The coated tool prevented the formation of white layer at low and medium cutting speed and also decreased work hardening tendency of Incoloy 825 when compared with that of uncoated tool. [ABSTRACT FROM AUTHOR]