Search Results (25)

Nickel-based superalloys are extensively used in high-temperature applications because of their exceptional oxidation and corrosion resistance. However, their performance in aggressive environments containing molten salts, such as Na₂SO₄ and V₂O₅, remains a critical challenge. This study investigated the hot corrosion behavior of Inconel 718, Udimet 710, Nimonic 75, and Inconel 625, focusing on the role of the alloying elements in the corrosion layers and degradation mechanisms. The superalloys were exposed to 50/50 wt.% Na₂SO₄–V₂O₅ at 900 °C for 8, 48, and 96 h, and their corrosion resistance was evaluated through weight gain measurements, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). These results indicate that Mo is a key factor in accelerating degradation, with Inconel 625 exhibiting the highest weight gain owing to the formation of thermally unstable Mo-rich phases. Fe also negatively impacted the stability of the protective scale of Inconel 718, contributing to an increased corrosion rate. In contrast, Nimonic 75 exhibited the best resistance, forming more of the NiCr₂O₄ spinel phase through the reaction of Cr₂O₃ with NiO from the high Ni and Cr contents in the corrosive layers. These findings highlight the importance of alloy composition in optimizing corrosion resistance and suggest that using superalloys with lower Mo and Fe contents and higher Cr and Ni concentrations can significantly enhance the durability of superalloys in molten salt environments. Full article

High energy density technologies for welding processes provide opportune solutions to joint metal materials and repair components in several industrial applications. Their high-performance levels are related to the high penetration depth and welding speed achievable. Moreover, the localized thermal input helps in reducing distortion and residual stresses in the welds, minimizing the extension of the fusion zone and heat-affected zone. The use of these welding technologies can be decisive in the employment of sophisticated alloys such as Ni-based superalloys, which are notoriously excellent candidates for industrial components subjected to high temperatures and corrosive work conditions. Nonetheless, the peculiar crystallographic and chemical complexity of Ni-based superalloys (whether characterized by polycrystalline, directionally solidified, or single-crystal microstructure) leads to high susceptibility to welding processes and, in general, challenging issues related to the microstructural features of the welded joints. The present review highlights the advantages and drawbacks of high energy density (Laser Beam and Electron Beam) welding techniques applied to Ni-based superalloy. The effects of process parameters on cracking susceptibility have been analyzed to better understand the correlation between them and the microstructure-mechanical properties of the welds. The weldability of three different polycrystalline Ni superalloys, one solid solution-strengthened alloy, Inconel 625, and two precipitation-strengthen alloys, Nimonic 263 and Inconel 718, is reviewed in detail. In addition, a variant of the latter, the AF955 alloy, is also presented for its great potential in terms of weldability. Full article

Wire Electric Discharge Machining (WEDM) is an unconventional machining technology that uses electrical impulses to generate very high temperatures to cut material. The WEDM process hence causes some unfortunate defects, such as cracks and burnt cavities, which can impact the correct functionality of the machined pieces and shorten their service life. This study was carried out to understand which materials remain defect-free after WEDM. The examined materials were the Ampcoloy 35 copper alloy, the high-entropy steels FeCoCrMnNi and FeCoCrMnNiC_0.2, and the B1914 and Nimonic 263 nickel alloys. The influence of the machining parameters, namely the pulse off time, gap voltage, discharge current, pulse on time, and wire feed, on the cutting speed and the surface topography of the machined piece was investigated. The surface morphology, the state of the subsurface layer in a cross-section, and the number of diffused elements from the wire electrode were analysed. All the analysed materials were found completely suitable for WEDM machining as they do not form any surface or subsurface defects. Full article

Engineers continue to be concerned about electrical discharge-machined components’ high energy consumption, machining debris, and poor dimensional precision. The aim of this research is to propose a hybrid neuro-genetic approach to improve the machinability of the electrical discharge machining (EDM) of the Nimonic C263 superalloy. This approach focuses on reducing the energy consumption and negative environmental impacts. The material removal rate (MRR), electrode wear ratio (EWR), specific energy consumption (SEC), surface roughness (Ra), machining debris (db), and circularity (C) are examined as a function of machining parameters such as the voltage (V), pulse on time (T_on), current (I), duty factor (τ), and electrode type. By employing the VIKOR method, all the responses are transformed into a distinctive VIKOR index (VI). Neuro-genetic methods (a hybrid VIKOR-based ANN-GA) can further enhance the best possible result from the VIKOR index. During this step, the hybrid technique (VIKOR-based ANN-GA) is used to estimate an overall improvement of 9.87% in the response, and an experiment is conducted to confirm this condition of optimal machining. This work is competent enough to provide aeroengineers with an energy-efficient, satisfying workplace by lowering the machining costs and increasing productivity. Full article

This study investigates the surface topography of microfinishing abrasive films and their machining capability on the Nimonic 80A superalloy, a high-performance nickel-based alloy commonly used in aerospace and gas turbine engine applications. Surface analysis was conducted on three abrasive films with nominal grain sizes of 30, 15, and 9 μm, exploring wear patterns, contact frequency, and distribution. To assess the distribution of grain apexes, Voronoi cells were employed. Results revealed distinct wear mechanisms, including torn abrasive grains and cracked bond surfaces, highlighting the importance of efficient chip removal mechanisms in microfinishing processes. Larger grain sizes exhibited fewer contacts with the workpiece but provided more storage space for machining products, while smaller grain sizes facilitated smoother surface finishes. The research demonstrated the effectiveness of microfinishing abrasive films in reducing surface irregularities. Additionally, surface analysis of worn abrasive tools provided insights into wear mechanisms and chip formation, with the segmentation of microchips contributing to efficient chip removal. These findings underscore the significance of selecting appropriate abrasive films and implementing effective chip removal mechanisms to optimize microfinishing processes and improve surface finishing quality in advanced material machining applications. It is worth emphasizing that no prior research has investigated the microfinishing of components crafted from Nimonic 80A utilizing abrasive films, rendering this study truly unique in its contribution to the field. Full article

Nimonic alloy is difficult to machine using traditional metal cutting techniques because of the high cutting forces required, poor surface integrity, and tool wear. Wire electrical discharge machining (WEDM) is used in a number of sectors to precisely machine complex forms of nickel-based alloy in order to attempt to overcome these challenges and provide high-quality products. The Taguchi-based design of experiments is utilized in this study to conduct the tests and analyses. The gap voltage (GV), pulse-on time (Ton), pulse-off time (Toff), and wire feed (WF), are considered as the variable process factors. GRA is used for the WEDM process optimization for the Nimonic-263 superalloy, which has multiple performance qualities including the material removal rate (MRR), surface roughness (SR), and kerf width (KW). ANOVA analysis was conducted to determine the factors’ importance and influence on the output variables. Multi objective optimization techniques were employed for assessing the machining performances of WEDM using GRA. The ideal input parameter combinations were determined to be a gap voltage (GV) of 40 V, a pulse-on time (Ton) of 8 µs, a pulse-off time (Toff) of 16 µs, and a wire feed (WF) of 4 m/min. A material removal rate of 8.238 mm³/min, surface roughness of 2.83 µm, and kerf width of 0.343 mm were obtained. The validation experiments conducted also demonstrated that the predicted and experimental values could accurately forecast the responses. Full article

The primary goal of this study was to investigate the formability of Nimonic 90 sheet which performs well at high temperatures and pressures, making it ideal for applications in the aerospace, processing, and manufacturing industries. In this present study, finite element analysis (FEA) and optimization of process parameters for formability of Nimonic 90 in sheet hydroforming were investigated. The material’s mechanical properties were obtained by uniaxial tensile tests as per the standard ASTM E8/E8M. The sheet hydroforming process was first simulated to obtain maximum pressure (53.46 MPa) using the FEA and was then validated using an experiment. The maximum pressure obtained was 50.5 MPa in experimentation. Since fully experimental or simulation designs are impractical, the Box–Behnken design (BBD) was used to investigate various process parameters. Formability was measured by the forming limit diagram (FLD) and maximum deformation achieved without failure. Analysis of variance (ANOVA) results also revealed that pressure and thickness were the most effective parameters for achieving maximum deformation without failure. Response surface methodology (RSM) optimizer was used to predict optimized process parameter to achieve maximized response (deformation) without failure. Experimental validation was carried out for the optimized parameters. The percentage of error between experimental and simulation results for maximum deformation was less than 5%. The findings revealed that all the aspects in the presented regression model and FEM simulation were effective on response values. Full article

Nickel-based superalloys are frequently used to manufacture the components that operate under cavitation erosion conditions, such as aircraft gas turbine construction, nuclear power systems, steam turbine power plants, and chemical and petrochemical industries. Their poor performance in terms of cavitation erosion leads to a significant reduction in service life. This paper compares four technological treatment methods to improve cavitation erosion resistance. The cavitation erosion experiments were carried out on a vibrating device with piezoceramic crystals in accordance with the prescriptions of the ASTM G32—2016 standard. The maximum depth of surface damage, the erosion rate, and the morphologies of the eroded surfaces during the cavitation erosion tests were characterized. The results indicate that the thermochemical plasma nitriding treatment can reduce mass losses and the erosion rate. The cavitation erosion resistance of the nitrided samples is approximately 2 times higher than that of the remelted TIG surfaces, approximately 2.4 times higher than that of the artificially aged hardened substrate, and 10.6 times higher than that of the solution heat-treated substrate. The improvement in cavitation erosion resistance for Nimonic 80A superalloy is attributed to the finishing of the surface microstructure, graining, and the presence of residual compressive stresses, factors that prevent crack initiation and propagation, thus blocking material removal during cavitation stresses. Full article

Laser boriding is a surface treatment that involves the simultaneous re-melting and mixing of the alloying material, containing amorphous boron blended with diluted polyvinyl alcohol, with the substrate material (Nimonic 80A-alloy). As a result of high cooling rates, the boride layer is formed from a solidifying molten pool. The thickness of the produced layer depends on the laser treatment parameters, e.g., power of the laser beam, scanning rate, and laser beam radius. These parameters influence the temperature distribution on the cross-section of laser tracks and, thus, directly determine the size of the molten pool, from which the boride layer is formed after crystallization. In the present study, laser borided layers were produced on Nimonic 80A alloy using a CO₂ molecular laser. Differences in the laser beam power used resulted in the formation of layers of different thicknesses, which resulted directly from the differences in the temperature distribution in the treated material. The amount of boron in the molten pool directly influenced the obtained hardness of the laser borided layer. It was found that the lower laser beam power had an advantageous effect on the hardness due to the higher percentage of nickel borides and chromium borides in the layer. The reasons for this situation are discussed in detail. Full article

In this experimental study, picosecond laser treatment was performed on a nickel-based superalloy Nimonic 263, aiming to investigate the surface effects induced by irradiation in different atmospheric conditions and, concerning changes in surface composition, regarding the possibility for improvement of its functionality. Besides the varying laser parameters, such as a number of pulses and pulse energy, environmental conditions are also varied. All surface modifications were carried out in standard laboratory conditions and a nitrogen- and argon-rich atmosphere. The resulting topography effects depend on the specific laser treatment and could be categorized as increased roughness, crater formation, and formation of the laser-induced periodic surface structures (LIPSS). Changes in the chemical surface composition are distinguished as the potential formation of the protective oxides/nitrides on the sample surface. Numerous characterization techniques analyse the resulting effects on the topography and surface parameters. The multi-response parametric optimization of the picosecond laser process was performed using an advanced statistical method based on Taguchi’s robust parameter design. Finally, the optimal parameter conditions for Nimonic 263 modification are suggested. Full article

Cavitation erosion of structural materials is a form of wear damage that affects the performance and life of components used in the aerospace, nuclear, and automotive industries, leading to an increase in the frequency of maintenance operations and redesign costs. The cavitation erosion behaviour of the nickel-based superalloy, Nimonic 80 A, was investigated using a piezoceramic crystal vibrator, according to the requirements of ASTM G32-2016. The results showed that plasma nitriding leads to a reduction in the mean erosion penetration depth by approximately ten times and of the erosion rate by the order of six times, compared to the solution heat-treated samples. Typical topographies of cavitation-eroded surfaces show a preferential degradation of the grain boundaries between the γ solid solution phases, of the twins’ boundary, and of the interface between the precipitated particles and the γ solid solution matrix. In the nitrided samples, the cracking initiation is determined by nitride particles, which are hard and brittle. Due to the high mechanical strength of the solid solution γ with the fcc crystal lattice, the appearance of the cavitation surface is uniform, and the fracture has a ductile character. Full article

Nowadays, advanced turning processes are extensively being adopted to perform different types of turning operations such as straight turning, taper turning on Hastelloy, Nimonic, and Inconel, stainless steel, and tool steel to fabricate better quality cylindrical and rotating parts such as miniature-bars, miniature-pins, miniature-electrodes, and miniature-tools. This paper presents a review of the previous research conducted on the turning of miniature cylindrical bars using thermoelectric-erosion based turning processes namely thermoelectric-erosion turning (TET) and wire-assisted thermoelectric-erosion turning (WTET). It also highlights work and tool electrode materials, types of dielectrics, detailed specifications of turning, types of turning, process parameters, performance measures, advantages and limitations, and key findings. The paper ends with conclusions and future research directions. This paper aims to facilitate researchers and scholars by highlighting the potential and capabilities of TET and WTET processes and providing relevant information for ease of fabrication of miniature parts and components from a wide range of difficult-to-machine materials. Full article

Powder mixed electrical discharge machining (PM-EDM) is a technological advancement in electrical discharge machining (EDM) processes where fine powder is added to dielectric to improve the machining rate and surface quality. In this paper, machining of Nimonic-90 was carried out using fabricated PM-EDM, setup by adding silicon powder to kerosene oil. The influence of four input process parameters viz. powder concentration (P_C), discharge current (I_P), spark on duration (S_ON), and spark off duration (S_OFF) has been investigated on surface roughness and recast layer thickness. L9 Taguchi orthogonal and grey relational analysis have been employed for experimental design and multi-response optimization, respectively. With the addition of silicon powder to kerosene oil, a significant decrease in surface roughness and recast layer thickness was noticed, as compared to pure kerosene. Spark on duration was the most significant parameter for both surface roughness and the recast layer thickness. The minimum surface roughness (3.107 µm) and the thinnest recast layer (14.926 μm) were obtained at optimum process parameters i.e., P_C = 12 g/L, I_P = 3 A, S_ON = 35 μs, and S_OFF = 49 μs using grey relational analysis. Full article

Plasma paste boriding was employed in order to produce the boride layers on Nimonic 80A-alloy. The process was carried out at temperatures of 1023 K, 1073 K and 1123 K for 3, 4 and 6 h in a gas mixture of 50% H₂-50% Ar. Borax paste was used as a boron source. The microstructure of the produced surface layers consisted of the mixture of nickel borides and chromium borides. The effect of processing temperature and duration on the thickness of the borided layers was observed. The theoretical thicknesses of the borided layers were estimated using an integral diffusion model. A good correlation was obtained between the theoretical (modeled) and experimental depths of the plasma paste borided layers. The boride layers were characterized by a high hardness ranging from 1160 HV to 2132 HV. The multiphase character of the produced layers resulted in differences in hardness. A significant improvement of the wear resistance of the plasma paste borided Nimonic 80A-alloy was observed in comparison with the non-borided alloy. Full article

Nickel-based superalloys are widely used in the aerospace, automotive, marine and medical sectors, owing to their high mechanical strength and corrosion resistance. However, they exhibit poor machinability due to low thermal conductivity, high shear modulus, strain hardening, etc. Various modifications have been incorporated into existing machining techniques to address these issues. One such modification is the incorporation of ultrasonic assistance to turning operations. The assisted process is popularly known as ultrasonic assisted turning (UAT), and uses ultrasonic vibration to the processing zone to cut the material. The present article investigates the effect of ultrasonic vibration on coated carbide tool wear for machining Nimonic-90 under dry and wet conditions. UAT and conventional turning (CT) were performed at constant cutting speed, feed rate and depth of cut. The results show that the main wear mechanisms were abrasion, chipping, notch wear and adhesion of the built-up edge in both processes. However, by using a coolant, the formation of the built-up edge was reduced. CT and UAT under dry conditions showed an approximate reduction of 20% in the width of flank wear compared to CT and UAT under wet conditions. UAT showed approximate reductions of 6–20% in cutting force and 13–27% in feed force compared to the CT process. The chips formed during UAT were thinner, smoother and shorter than those formed during CT. Full article