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Abstract Hastelloy B2 is a high-performance nickel-molybdenum alloy and has been used in micro reactor, pump, pipe, and corrosion-resistant equipment. Square holes are required in the above application components. Although square holes are easily produced by spending more electrodes wear in Electrical Discharge Machining (EDM). Moreover, the square hole with small electrode wear achieved is a challenging task in thermal machining. Hence, in this work, the effects of EDM process parameters on electrode taper angle, electrode radius, electrode wear length and cutting time of Hastelloy B2 are studied. Taguchi based VišekriterijumskoKompromisnoRangiranje (VIKOR) method is used to find the optimum process parameters and compared with Taguchi based Grey Relational Analysis (GRA) method for validation. The results showed that current and pulse duration greatly affects the electrode wear out surface and edges. The square electrodes with sharp edges and surfaces are fully transformed into hemispherical shapes at electrode ends due to an unstable spark with diffusion of heat. Also, the VIKOR method provides an alternative multi-criteria optimization method that enhances the process performance over the grey relational analysis due to comparability, uniqueness, assessment and prediction.

Hastelloy B2 is a high-performance nickel-molybdenum alloy and has been used in micro reactor, pump, pipe, and corrosion-resistant equipment. Square holes are required in the above application components. Although square holes are easily produced by spending more electrodes wear in Electrical Discharge Machining (EDM). Moreover, the square hole with small electrode wear achieved is a challenging task in thermal machining. Hence, in this work, the effects of EDM process parameters on electrode taper angle, electrode radius, electrode wear length and cutting time of Hastelloy B2 are studied. Taguchi based VišekriterijumskoKompromisnoRangiranje (VIKOR) method is used to find the optimum process parameters and compared with Taguchi based Grey Relational Analysis (GRA) method for validation. The results showed that current and pulse duration greatly affects the electrode wear out surface and edges. The square electrodes with sharp edges and surfaces are fully transformed into hemispherical shapes at electrode ends due to an unstable spark with diffusion of heat. Also, the VIKOR method provides an alternative multi-criteria optimization method that enhances the process performance over the grey relational analysis due to comparability, uniqueness, assessment and prediction. [ABSTRACT FROM AUTHOR]

The present study investigated the dissolution and oxidation corrosion behaviors of Hastelloy exposed to static liquid lead‐bismuth eutectic (LBE) at 500°C with an oxygen concentration of 1 × 10−6 mass%. Hastelloy exhibited better LBE corrosion resistance than the Monel alloy. Both dissolution and oxidation corrosion were observed in Hastelloy, and the maximum LBE penetration depth and spinel layer thickness in the corroded sample after 4000 h of exposure reached 120 ± 36 and 21 ± 12 µm, respectively. Annealing twin boundaries provided favorable paths of accelerated LBE penetration into the matrix, resulting in selective leaching of Ni. Microstructural characterization revealed that the spinel layer formed between penetrated LBE and base metal slowed down the elemental interdiffusion, thereby retarding the dissolution rate. Volumetric changes induced by LBE penetration promoted the formation of stacking faults and dislocations, which could provide more channels for elemental diffusion, leading to the propagation of dissolution attack. [ABSTRACT FROM AUTHOR]

In the present scenario, controlling surface characteristics of superalloys such as friction, wear rates, and fatigue failure needs special attention for various manufacturing applications. The present research work deals with the analyses of a fiber laser surface texturing of Hastelloy C-276 to utilize the generated surfaces for high power applications. Texturing on Hastelloy C-276 surface has been achieved with the overlapping of linear micro-grooves. The effects of laser process parameters like laser power, scan speed, pulse frequency, and duty cycle on the surface morphology like arithmetic mean surface roughness (Ra), skewness (Rsk), and kurtosis (Rku) have been studied. Empirical modeling of the process parameters for fiber laser surface texturing of Hastelloy C-276 has been carried out by response surface methodology. A sensitivity analysis is conducted here to find out the sensitivity of process variables on surface characteristics. The combination of laser power of 19.93 W, pulse frequency of 60 kHz, a duty cycle of 38.96%, and a scan speed of 8.41 mm/s lead to the optimized roughness criteria are 1.2 μm, − 0.35, and 3 for Ra, Rsk, and Rku respectively. [ABSTRACT FROM AUTHOR]

X‐ray photoelectron spectroscopy (XPS) is a technique that is widely used to study thin oxide films because of its extremely high surface sensitivity. Utilizing the QUASES (Quantitative Analysis of Surfaces by Electron Spectroscopy) software package developed by Sven Tougaard (University of Southern Denmark), a user can obtain additional information that is not extracted in conventional XPS analysis, specifically the composition as a function of depth. Presented here is the QUASES analysis of four Ni‐Cr‐Mo alloys performed while testing various inelastic mean free path (IMFP) determination methods in the context of providing a framework for the analysis of complex oxides in QUASES. Ni‐Cr‐Mo alloys are often used to replace conventional materials under aggressive conditions, because of their exceptional corrosion resistance. Their corrosion resistance is conferred by the formation of an inert surface oxide film that protects the underlying metal. Using the QUASES software, the thickness of the air‐formed oxide on four Ni‐Cr‐Mo alloys was found to lie within the range of 2.5–3.6 nm. They were found to be composed of an inner Cr2O3 layer and an outer Cr (OH)3 layer, with a transition zone where the two coexisted. Oxidized Mo species, MoO2 and MoO3, were found in trace amounts at the boundary between the Cr2O3‐only and mixed Cr2O3/Cr (OH)3 regions of the oxide. We also determined that using 20% reduced IMFP values gave results similar to those obtained using electron effective attenuation length (EAL) values. Auger depth profiles showed comparable trends to the QUASES models. [ABSTRACT FROM AUTHOR]

The behaviors of conventional kerosene and powder added kerosene dielectrics are found to be affecting the machining efficiency due to degradation of dielectric properties, excess debris formation, recast layer formation and formation of nickel and molybdenum oxides on machined surface. Hence, the square holes have been carried out on Hastelloy in EDM using coconut oil. The results such as Material Removal Rate (MRR), Electrode Wear Rate (EWR) and Surface Roughness (SR) produced with coconut oil are compared to those obtained with kerosene and Si–Cu powder added kerosene. Overall analysis found that coconut oil has a higher improvement percentage than Si–Cu powder added kerosene and conventional kerosene. The coconut oil shows an improved performance measure of 60% in MRR, 25% in EWR and 30% in SR of Hastelloy. The Complex Proportional Assessment (COPRAS) method has improved performance measures. [ABSTRACT FROM AUTHOR]

The study examines the influence of various process parameters on Material Removal Rate (MRR), Tool Wear Rate (TWR) AND Surface Roughness (R _a ) during the machining of Hastelloy using Electrical Discharge Machining (EDM) machined under NaOH dielectric medium. Results showed that a 20% NaOH concentration optimizes MRR at 0.889 mm ^3 min ^−1 , while higher concentrations lead to process instability due to excessive bubble formation and discharge irregularities. The optimal current of 30 A improves MRR, but excessive melting occurs beyond this level, negatively impacting tool wear and surface finish. A pulse-on time of 45 μs produces the best surface finish of 1.786 μm), while longer pulse durations cause overheating and degrade surface quality. TWR was minimized at a gap distance of 2 mm, which allowed effective cooling and debris removal, reducing wear by 15%. Voltage levels between 12 V and 18 V resulted in the most stable discharges, yielding optimal MRR and Ra values. Lower current values stabilize TWR, while higher currents and longer pulse-on times increase wear. A gap distance of 2 mm minimizes TWR by ensuring effective cooling and debris removal. Optimal surface roughness is achieved with 30 A and 45 μs, where controlled discharges reduce surface imperfections. Higher NaOH concentrations induce rougher textures due to more aggressive sparks. SEM analysis confirms that process parameters significantly impact surface topography, characterized by craters, re-solidified debris, and microcracks. The optimized parameters identified from the results were 20% NaOH concentration, 30 A current, 45 μs pulse-on time, 2 mm gap distance, and voltage of 15 V.

A systematic microstructural characterization of alumina joined to Hastelloy C22® by means of a commercial active TiZrCuNi alloy, named BTi-5, as a filler metal is reviewed and discussed. The contact angles of the liquid BTi-5 alloy measured at 900°C for the two materials to be joined are 12° and 47° for alumina and Hastelloy C22® after 5 min, respectively, thus demonstrating good wetting and adhesion at 900 °C with very little interfacial reactivity or interdiffusion. The thermomechanical stresses caused by the difference in the coefficient of thermal expansion (CTE) between the Hastelloy C22® superalloy (≈15.3 × 10−6 K−1) and its alumina counterpart (≈8 × 10−6 K−1) were the key issues that had to be resolved to avoid failure in this joint. In this work, a circular configuration of the Hastelloy C22®/alumina joint was specifically designed to produce a feedthrough for sodium-based liquid metal batteries operating at high temperatures (up to 600 °C). In this configuration, adhesion between the metal and ceramic components was enhanced after cooling by compressive forces created on the joined area due to the difference in CTE between the two materials. [ABSTRACT FROM AUTHOR]

• Hastelloy foil/steel composites with excellent mechanical properties was prepared by an improved explosive welding technique. • Explosive loading crucially affects the surface/interface morphology and thermodynamic properties of the composites. • A significant diversity in grain structure was exhibited at the bonding interface. • The corrosion resistance of hastelloy foil was highly maintained after being coated by steel under lower explosive load. Hastelloy foil/steel composite is of most interest in many industrial fields, as it has competitive advantages of excellent corrosion resistance and low cost. Due to the low thermal conductivity and thermal hardening property, traditional fusion-based connection methods fail to provide high-quality Hastelloy/steel composites. Here an improved explosive welding was introduced to prepare this composite, and the effect of the explosive amount was carefully investigated. The characterizations (including optical microscopy (OM), electron backscatter diffraction (EBSD), bending, nanoindentation, and electrochemical corrosion) were conducted to understand the bonding properties, and Smoothed Particle Hydrodynamics (SPH) simulation was used to investigate transient interface behavior. It was found that the self-developed explosive welding was a suitable method to produce superior Hastelloy/steel composites. Under reasonable welding parameters, both the surfaces of Hastelloy and Hastelloy/steel interface exhibited ideal welding patterns without defects, and the composite remained intact under 90° bending loading. The explosive load is a crucial factor determining bonding properties, and the undesirable features like wrinkles and melting area were found to be positively correlated with the explosive load, which reduced the corrosion resistance. This comprehensive research enabled to provide a new perspective for Hastelloy/steel preparation and improve the understanding of explosive welding process behavior. [ABSTRACT FROM AUTHOR]

Despite the recent developments in non-conventional manufacturing approaches, machining is still a prominent technique for the mass production of metallic components. However, given the difficult-to-machine nature and high heat generation during machining of Hastelloy-X, there is a lack of comparative investigations that can provide basics for sustainable process management in machining of Hastelloy-X. Different sustainable cooling approaches (dry, minimum quantity lubrication (MQL), cryogenic) and their impact on Hastelloy-X machining process behavior have been investigated in this study. Machining parameters such as constant cutting speed of 124 mm/min, feed rate of 0.15 mm/min, and cutting depth of 0.1 mm and cutting force, cutting temperature, and surface roughness were consider as output responses. It was observed that with the adaptation of cryogenic conditions, cutting forces can be reduced 5 to 14% in comparison with MQL and dry conditions. Cutting temperature and surface roughness values were however observed to be largely reduced with cryogenic cooling. The chipping and adhesion were found to be reduced with cryogenic cooling due to the reduction in workpiece softening behavior and increase in hardness to cutting tool. [ABSTRACT FROM AUTHOR]

Electrochemical micromachining (ECMM) is employed to machine Hastelloy C22 a nickel-based alloy, which is applied in chemical, food processing, and pharmaceutical industries. An L18-mixed orthogonal array (OA) experiment plan was considered along with a polytetrafluoroethylene (PTFE)-coated electrode (CE), normal electrode, and mixed electrolyte (equal weight of sodium nitrate (NaNO3) + oxalic salt (C2H2O4)). Criteria importance through inter-criteria correlation and simple additive weighting methods were used to obtain the optimum levels of factors for higher machining rate, lower overcut, and conicity (K). According to the analysis, the optimal parameter combination was PTFE CE with 20 g/L mixed electrolyte, 8 V, 85% duty cycle, and 90-Hz frequency. An analysis of variance (ANOVA) results showed that the electrode type contributes 21.15% and 41.26% for machining rate (MR) and overcut (OC), respectively. The electrolyte concentration is the most significant factor for conicity, which contributes 64.32%. [ABSTRACT FROM AUTHOR]

Electrochemical micromachining (ECMM) is mostly used for producing micro holes, micro slots, and micro channels. In this research work, copper nanoparticles were mixed with sodium bromide electrolyte for machining Hastelloy C276. The aim of this work is to find the influence of nanoparticles mixed electrolytes on the machining performance when machining voltage, electrolytic concentration, and amount of nanoparticles will improve the MRR, overcut feature, and the surface roughness of the micro holes. Machining performance was evaluated on the basis of MRR, radial overcut and surface roughness. Experimental results were correlated through the use of Taguchi-data envelopment analysis ranking (DEAR) based multicriteria optimisation method in order to find optimised parameter setting level. Based on the experimental results, nanoparticles mixed electrolytes were found playing a vital role in ECMM with increase in MRR and reduction in overcut and surface roughness at the optimized parameter setting level at machining voltage of 7 V, electrolyte concentration of 5 g/L and nanopowder suspension of 5 g/L. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fast and sensitive multi-elemental mapping of laser-deposited Hastelloy coating using UV-fs-LA-ICP-TOFMS. • Spatial distributions of major, minor and trace elements in the Hastelloy coating, interface and carbon steel substrate. • Detection of elements from external corrosive agents with heterogenous spatial distributions within the Hastelloy coating. • Quantification approach to determine the elemental concentrations in the Hastelloy coated carbon steel. Ultraviolet Femtosecond Laser Ablation-Inductively Coupled Plasma-Time of Flight Mass Spectrometry (UV-fs-LA-ICP-TOFMS) is critically evaluated for fast multi-elemental mapping of Hastelloy coated carbon steel that was immersed in a liquid corrosive environment for two months. The Hastelloy coating, which is a multi-elemental Cr-Fe-Ni-Mo-W matrix, is produced using laser cladding technology. A UV-fs laser is employed to reduce the ablation thermal effects improving the spatial resolution in the elemental analysis of the coating, interface and substrate. Moreover, the TOFMS is equipped with ion beam attenuation grids to expand its linear dynamic range, allowing the determination of major, minor and trace elements. In particular, spatial distribution of major (e.g., Co, Ni, Fe), minor (e.g., Mn, Si) and trace (e.g., Cu, In, Zn) elements from two sequential mapping analysis were determined. Quantification is achieved through Relative Sensitivity Factors calculated using matrix-matched external reference materials and making use of measurements carried out by SEM-EDX to determine the concentration of internal standard elements. Qualitative and quantitative elemental maps highlight diffusion processes at the coating-substrate interface. Moreover, correlated spatial distributions of ion signals from external corrosive elements (e.g., 32S, 138Ba, 202Hg, 205Tl, and 209Bi) were detected in localized regions within the material and on the external surface. [ABSTRACT FROM AUTHOR]

[Display omitted] • MgB 2 films deposited on ZnO-buffered Hastelloy substrate show ZnO thickness-dependent T c behavior. • To investigate local structure of MgB 2 , polarization-angle-dependent EXAFS measurements at 0°, 45°, and 90° were performed. • Polarized EXAFS analyses reveal distortion of boron plane depending on the ZnO thickness. • Bader charge analysis is adopted to explain ZnO thickness-dependent T c behavior. Herein, we investigated the mechanism by which the critical temperature (T c) of a magnesium diboride (MgB 2) superconductor is altered by the buffer layer. Zinc oxide (ZnO) layers with different thicknesses (28, 80, and 134 nm) were deposited epitaxially on a Hastelloy substrate beneath a ∼ 1 μm MgB 2 film. To measure the local structural distortion of the boron plane, three different angle polarizations (0°, 45°, and 90° parallel to the ab-axis) on the Mg K-edge, extended X-ray absorption fine structure (EXAFS) measurements were performed. The EXAFS analyses revealed that the ZnO buffer layer caused the boron layer to disorient, leading to buckling between the Mg and B layers, which affected the charge transfer capability in the intra-layer structure. Furthermore, the uneven distribution of B atoms amid the surrounding Mg atoms resulted in an asymmetric crystal structure, which leads to T c fluctuation. This study reveals the relationship between modifications made to the boron plane condition of MgB 2 by the ZnO buffer layer and the superconducting T c behavior of MgB 2. [ABSTRACT FROM AUTHOR]

A nickel based alloy with molybdenum, chromium and titanium (Ni–Cr-Mo-Ti alloy) has been indigenously developed for applications related to the Indian Molten Salt Breeder Rector (IMSBR). The present work involves investigation of the interaction of the above alloy with molten fluoride salt using an in-house developed Molten Salt Corrosion Test Facility (MSCTF). In a comparative study, the indigenous alloy along with other Ni based alloys, were exposed to molten fluoride salt, FLiNaK, under static conditions at 973 K (700 °C) in MSCTF. Salient results indicate that the extent of fluoride salt attack is directly proportional to the chromium content of the above alloys. In addition, the molten fluoride salt preferentially attacks the grain boundaries of the Ni–Cr-Mo-Ti alloy although the inherent carbide/nitride precipitates can also play a major role in the corrosion mechanism. [ABSTRACT FROM AUTHOR]

A hybrid approach through combining genetic algorithm (GA) and adaptive neuro-fuzzy inference system (ANFIS) for modeling the correlation of laser beam cutting (LBC) parameters and enhancing the quality performance characteristics of machined Hastelloy C276 is emphasized. The LBC experiments are performed by considering gas pressure (GP), cutting speed (CS), pulse energy (PE) and stand-off distance (SOD) as input parameters. The output responses are material removal rate (MRR), kerf taper (KT) and surface roughness (Ra) for the present investigation. The optimal ANFIS training variables are obtained through GA. The training, testing errors, and statistical validation parameter results exposed that the ANFIS learned by GA is outperformed in forecasting LBC responses. In addition, to obtain the optimal combinations of LBC parameters, the multi-response optimization based on maximizing MRR and minimizing KT and Ra was performed using a trained ANFIS network coupled with a whale optimization algorithm (WOA). The responses such as MRR of 236.98 mg/min, KT of 1.135° and Ra of 1.109 µm are forecasted for the optimum cutting conditions: GP of 3 bar, CS of 319.8 mm/min, PE of 5.93 J and SOD of 2.97 mm, respectively. Furthermore, the WOA predicted results are validated by conducting confirmatory experiments. [ABSTRACT FROM AUTHOR]

Usually porous metals are known as relatively excellent characteristic such as large surface area, light, lower heat capacity, high toughness and permeability for exhaust gas filter, hydrogen reformer catalyst support. The Ni alloys have high corrosion resistance, heat resistance and chemical stability for high temperature applications. In this study, the Ni-based porous metals have been developed with Hastelloy powder by gas atomization and water atomization in order to find the effects of powder shape on porous metal. Each Hastelloy powder is pressed on disk shape of 2 mm thickness with 12 tons using uniaxial press machine. The specimens are sintered at various temperatures in high vacuum condition. The pore properties were evaluated using Porometer and microstructures were observed with SEM.

Porous metals show not only extremely low density, but also excellent physical, mechanical and acoustic properties. In this study, Hastelloy powders prepared by gas atomization are used to manufacture 3D geometries of Hastelloy porous metal with above 90% porosity using electrostatic powder coating process. In order to control pore size and porosity, foam is sintered at 1200~1300°C and different powder coating amount. The pore properties are evaluated using SEM and Archimedes method. As powder coating amount and sintering temperature increased, porosity is decreased from 96.4 to 94.4%. And foam density is increased from 0.323 to 0.497 g/cm3 and pore size is decreased from 98 to 560 μm. When the sintering temperature is increased, foam thickness and strut thickness are decreased from 9.85 to 8.13mm and from 366 to 292 μm.

Abstract AISI D6 tool steel and AISI 304 stainless steel are among the most widely used material in the industry. However, this application field can still be expanded through the coatings deposition. In this regard, the objective of this work was to evaluate the impact of coatings application by cathodic cage technique using Hastelloy’s cathodic cage, on corrosion resistance of these steels. Two treatment temperatures were compared. The samples were characterized by Optical Microscopy, Scanning Electron Microscopy, Energy Dispersive Spectroscopy, X-Ray Diffraction with the application of the Rietveld routine and corrosion test. The results showed the formation of multiphase layers that contributed to corrosion potentials reduction for treatments at 400 °C, being more effective when applied on AISI D6. It was observed that the corrosion resistance is influenced by the temperature, which was attributed to the precipitation of chromium nitride and iron oxide at 450 ºC.

The super alloy exhibits great strength and fatigue behaviour when nickel (Ni) is present in major quantities. Moreover, it possesses good corrosive resistant behaviour at high temperatures. However, these alloys are very difficult to machine under normal machining conditions due to their great strength and low heat dissolution. In this work, machining was performed on Hastelloy C276 under various machining conditions (speed, feed and depth) and environments (dry and cryogenic). Liquid nitrogen was used as a coolant in the machining region. The machinability of Hastelloy C276 was investigated with machining forces, temperature, surface roughness and hardness under different cutting conditions. Turning experiments that resulted from passing LN2 drastically reduced temperature by up to 40%. Machining forces were minimal under cryogenic machining due to its effective lubrication property. Surface finish of the machined area improved by about 26% under cryogenic conditions. Both dry and cryogenic machining improved the hardness of the work material. The high cooling efficiency of LN2 improved hardness of the machined surface was about 8-15%. Chip width and side-flow of chip material were reduced under cryogenic cooling. Moreover, adhesion and abrasion wear were observed minimally in cryogenic machining compared to dry machining. But no significant difference was observed in notch wear for both types of machining. Machinability of Hastelloy C276 significantly improved when LN2 used as a cutting fluid. [ABSTRACT FROM AUTHOR]

The performance of Hastelloy C22 matrix composite with different reinforced particles is strongly related to microstructural aspect of the coating. In this study, a novel approach for fabricating advanced and high wear resistant nickel-based high-temperature composites by directed energy deposition (DED) was investigated, which enhances the Hastelloy C22 matrix by blending nano and micron WC particles. The microstructure and phase composition of the WC/C22 composite coatings were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The main phases of WC/C22 composite coating are γ-Ni, M 6 C, WC, W 2 C and M 12 C, where M 12 C and M 6 C are distributed at grain boundaries to inhibit grain growth and play the role of fine grain strengthening. In performance testing, the nano/micron WC/C22 composite coating showed a 71.04% increase in microhardness, a 92.3% reduction in mass loss, and significantly improved electrochemical corrosion performance compared to the C22 coating. • Reinforcement of Hastelloy C22 by directed energy deposition with composite nano and micron WC particles. • WC particles have a fine grain strengthening effect on the coating. • The microhardness of nano/micron WC/C22 composite coating is increased by 71.04%, and the mass loss is reduced by 92.31%. • Substantial improvement in corrosion resistance of WC/C22 composite coating. [ABSTRACT FROM AUTHOR]

• Superconducting tapes on Hastelloy provide high critical current density, low AC losses, high magnetic field performance. For many years, the Ni–Mo–Cr superalloy Hastelloy® C-276™ has been employed as a substrate material for depositing superconducting REBa 2 Cu 3 O 7-x (RE - rare earth element) and MgB 2 layers with various intermediate buffer layers. The resulting superconducting tapes are widely used in various industrial applications. However, the presence of various intermediate buffer layers between the substrate and the superconducting layer can influence the magnetic and thermal properties. At present, there is a dearth of significant data in literature concerning the impact of buffer layers. In this study, we provide data on the physical properties of a commercial Hastelloy® C-276™ tape with deposited Al 2 O 3 /Y 2 O 3 /MgO/LaMnO 3 buffer layers, along with an electro-polished Hastelloy® C-276™ substrate. Physical properties such as magnetic susceptibility (dc) and specific heat, C p , were measured from 5 to 300 K and the chemical composition was investigated. In low magnetic fields and relevant temperature range (5–200 K), the magnetization of a Hastelloy substrate demonstrates the Curie law, while Hastelloy with deposited buffer layers demonstrates Curie-Weiss law. At the magnetic field of 9 T and temperature 5 K, the resultant relative specific magnetization, compared to electro-polished Hastelloy, was lower by 16%. For heat capacity, Debye T 3 law provides a good approximation from 22 to 48 K but the impact of buffer layers at 100 K was higher by 9.5%, compared to electro-polished Hastelloy, and decreases gradually with decreasing the temperature. [ABSTRACT FROM AUTHOR]

Abstract In this paper we aimed at investigating the flux pinning property of MgB 2 films on hastelloy tapes which are buffered on various thicknesses of SiC layers. We have observed that the increase in thickness of the SiC buffer layer is very closely related with the systematic improvement of the field dependence of the critical current densities (J c) of MgB 2 tapes while the values of J c decreased. According to the analysis of the pinning force density (F p), there exist two pinning sources both in the pure MgB 2 and in the MgB 2 film with the thinnest SiC buffer layer. On the while, the pinning source observed in the MgB 2 films with thicker SiC buffer layers appears to be different from those previously mentioned. The different pinning behaviors of MgB 2 films may suggest that there be an additional pinning center working on the MgB 2 films with thick SiC buffer layers. The microstructural analyses of MgB 2 films confirmed that intra-granular defects and columnar grain boundaries may be a dominant pinning mechanism in the pure MgB 2 and the MgB 2 film with 170 nm-thick SiC buffer layer. For the MgB 2 films with thicker SiC buffer layers, carbon diffusion into the MgB 2 film, which is defined by the Auger electron spectroscopy, may be the origin of the additional pinning mechanism. Highlights • MgB 2 films were deposited on hastelloy substrate with different thickness of SiC buffer layer. • As the SiC buffer layer is thicken, pinning mechanism has changed. • Carbon diffusion into MgB 2 film seems to be an additional pinning source. [ABSTRACT FROM AUTHOR]

Abstract In this study, an attempt is made to correlate the macrostructure of Nd: YAG laser butt welded Hastelloy C-276 joints obtained by numerical and experimental methods, and which were performed at varied process parameters viz., welding speed (350 mm/min-450 mm/min), pulse energy (10–14 J/mm) and pulse duration (6–8 ms). The numerical macrostructure of the weld zone is determined in SYSWELD 16 - a 3D finite element software package, while experimentation was performed in a 600 W Nd: YAG laser welding machine. Complete penetration is observed for the attempted conditions, though the morphology of the laser weld differs. The variation in the temperature distribution across the various regions of the weld zone and the hardness distribution is reported. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Ni, Cr, Mo and Fe dissolution were monitored as a function of time in the passive and transpassive domain. • Mo surface enrichment, probably as H 2 MoO 4 , was observed during potentiostatic experiments in the transpassive domain. • The excess Mo was released into the electrolyte when the potential returned to the passive domain. • It is proposed that Mo precipitation and redissolution are driven by changes in the local pH. • This phenomenon, reported here for the first time, may contribute to the positive effect of Mo on repassivation kinetics. Abstract The role of alloyed Mo during transpassive dissolution of four commercially available Ni-based alloys in neutral chloride solution was investigated by atomic emission spectroelectrochemistry. Time-resolved dissolution rates of Ni, Cr, Mo, and Fe were obtained as a function of applied potential. Mo enrichment occurred at the transpassive potentials and redissolved when the potential returned to the passive domain. These results suggest a mechanism of Mo enrichment and release that could play a significant role in repassivation in initially neutral electrolytes such as occurs during crevice corrosion. It is proposed that Mo precipitation and redissolution are driven by local pH changes. [ABSTRACT FROM AUTHOR]

Electrochemical micromachining (ECMM) is one of the most fruitful non-traditional micromachining processes to machine the intricate shapes and 3D geometries, but the real challenge is to machine microhole in the hard materials like nickel based alloys, titanium alloy, and stainless steel, etc. Machining of Hastelloy by traditional as well as by non-traditional methods is very difficult because of their high resistance to corrosion and unique strength. Hastelloy is a wrought corrosion-resistant alloy. This research paper investigates how optimization studies are carried out on electrochemical micromachining with multi response characteristics based on the TOPSIS method. The process parameters like voltage, electrolyte, and feed rate are optimized with multiresponse characteristic, which includes taper angle, entry and exit overcut. The optimal parameters obtained from this approach indicate that the lower radial overcut and taper angle was achieved with the combination of the electrochemical micromachining, such as 8V, 0.9mm/min feed rate and sodium perchlorate (NaClO4) electrolyte. TOPSIS approach and ANOVA were used to determine the significant parameter for the ECMM. [ABSTRACT FROM AUTHOR]

Joining γ-TiAl alloy to Ni-based superalloy Hastelloy using Ag-Cu sputtered coated Ti foil as brazing filler was investigated in this study. Brazing experiments were performed at 900, 950, and 980 °C with a dwelling stage of 10 min in vacuum. The microstructure and the chemical composition of the resulting interfaces were analyzed by scanning electron microscopy (SEM) and by energy dispersive X-ray spectroscopy (EDS), respectively. Sound joints were produced after brazing at 980 °C, presenting a multilayered interface, consisting mainly of Ti-Al and Ti-Ni-Al intermetallics close to the γ-TiAl alloy, and of Ti-rich, Ti-Ni, and Cr-Ni-Mo rich phases near Hastelloy. The hardness of the interface, ranging from around 300 to 1100 HV0.01, is higher than both base materials, but no segregation of either Ag solid solution or coarse intermetallic particles was observed. Therefore, the developed brazing filler also avoids the need to perform post-brazing heat treatments that aim to eliminate detrimental extensive segregation of either soft phases or of hard and brittle compounds. [ABSTRACT FROM AUTHOR]

The aim of this study is focused on the mechanical and the microstructural characterization of two Ni-based cast alloys: Hastelloy UNS N06200 and Hastelloy UNS N06022. The analysis has been performed through the observation of different microstructures obtained as a function of different cooling rates performed by the use of test blocks. After solidification, the specimens produced by different cooling rates have been extracted, and UNS N06200 samples have undergone a solution treatment process, while UNS N06022 samples have undergone a solution treatment followed by an ageing process. The mechanical properties have been measured, and some significant and consistent relationships have been pointed out with the heat treatment and the obtained microstructures. [ABSTRACT FROM AUTHOR]

In this study, the microstructure, mechanical properties and fracture behavior of hastelloy C276-BNi2 brazed joint were investigated. The results show that microstructure and mechanical properties of the joints are greatly affected by the test temperature and inner brazing defects. The brazed joint consists of four regions, i.e. filler zone, fine grain diffusion zone, coarse grain diffusion zone and parent zone. Because of element diffusion in brazing, the diffusion zone becomes harder and the filler zone becomes softer. Compared with base metal, both the yield strength and elongation of brazed joint are relatively small. The filler metal plays a key role in determining the mechanical properties of brazed joint. The specimen fractured in the filler zone with ductile mode by stepped pattern. Because of the existence of brazing defects between grain boundaries, the fracture was accelerated, both the yield strength and ultimate tensile strength of defect-containing joint were decreased compared to the defect-free joint. [ABSTRACT FROM AUTHOR]

The Koch–Haaf reaction of adamantanols was successfully carried out in a microflow system at room temperature. By combining an acid-tolerant hastelloy-made micromixer, a PTFE tube, and a hastelloy-made microextraction unit, a packaged reaction-to-workup system was developed. By means of the present system, the multigram scale synthesis of 1-adamantanecarboxylic acid was achieved in ca. one hour operation.

Joining γ-TiAl alloy to Ni-based superalloy Hastelloy using Ag-Cu sputtered coated Ti foil as brazing filler was investigated in this study. Brazing experiments were performed at 900, 950, and 980 °C with a dwelling stage of 10 min in vacuum. The microstructure and the chemical composition of the resulting interfaces were analyzed by scanning electron microscopy (SEM) and by energy dispersive X-ray spectroscopy (EDS), respectively. Sound joints were produced after brazing at 980 °C, presenting a multilayered interface, consisting mainly of Ti-Al and Ti-Ni-Al intermetallics close to the γ-TiAl alloy, and of Ti-rich, Ti-Ni, and Cr-Ni-Mo rich phases near Hastelloy. The hardness of the interface, ranging from around 300 to 1100 HV0.01, is higher than both base materials, but no segregation of either Ag solid solution or coarse intermetallic particles was observed. Therefore, the developed brazing filler also avoids the need to perform post-brazing heat treatments that aim to eliminate detrimental extensive segregation of either soft phases or of hard and brittle compounds.

Se realizó un estudio pormenorizado del proceso de soldeo fuerte en horno de alto vacío de la aleación base níquel Hastelloy B2 fortalecida por solución sólida. En una primera fase del trabajo se seleccionó el material de aporte acorde al material objeto de unión y a la fuente de calentamiento seleccionada. Posteriormente, se evaluó la influencia del gap (50 y 200 micrómetros) y tiempo de permanencia a temperatura de soldeo (10 y 90 minutos) sobre los microconstituyentes de la unión, relacionando la microestructura con las propiedades mecánicas de la junta. Los análisis metalográficos mostraron una unión constituida por una matriz rica en níquel, siliciuros de níquel y compuestos ternarios. Finalmente, los resultados de los ensayos mecánicos a esfuerzos cortantes mostraron una elevada resistencia para gaps de 50 micrómetros y tiempos de permanencia de 90 minutos.

In the present study, the wetting behavior of surfaces of various common metallic materials used in the water industry including C84400 brass, commercially pure aluminum (99.0% pure), Nickle–Molybdenum alloy (Hastelloy C22), and 316 Stainless Steel prepared by mechanical abrasion and contact angles of several materials after mechanical abrasion were measured. A model to estimate roughness factor, R f , and fraction of solid/oil interface, ƒ so , for surfaces prepared by mechanical abrasion is proposed based on the assumption that abrasive particles acting on a metallic surface would result in scratches parallel to each other and each scratch would have a semi-round cross-section. The model geometrically describes the relation between sandpaper particle size and water/oil contact angle predicted by both the Wenzel and Cassie–Baxter contact type, which can then be used for comparison with experimental data to find which regime is active. Results show that brass and Hastelloy followed Cassie–Baxter behavior, aluminum followed Wenzel behavior and stainless steel exhibited a transition from Wenzel to Cassie–Baxter. Microstructural studies have also been done to rule out effects beyond the Wenzel and Cassie–Baxter theories such as size of structural details. [ABSTRACT FROM AUTHOR]

MgB 2 is a promising candidate for superconductivity applications because of its metallic nature and its simple structure compared to other oxide superconductors. We have deposited MgB 2 thin films on the SiC buffered-Hastelloy substrates by a hybrid physical–chemical vapor deposition (HPCVD) method. SiC buffer layers of varying thicknesses were grown on the Hastelloy substrates by a pulsed laser deposition (PLD) technique. As the SiC buffer layers thicken, the grain size of MgB 2 films is distinctly decreased and the grains become much denser. MgB 2 film deposited on bare Hastelloy shows a sign of partial delamination at the interface. Interestingly, the delamination was considerably reduced when the SiC buffer layers with the thickness of 170 and 250 nm were added into the MgB 2 tape. This suggests that SiC buffer layers acted as an effective sticking agent, providing stronger adhesion to the MgB 2 –Hastelloy interface, hence the reduced delamination. [ABSTRACT FROM AUTHOR]

SiC p /Hastelloy composites were fabricated by pressureless Ti-activated infiltration process. The wetting and infiltration behaviors of Hastelloy on the SiC substrates and the interfacial reaction between the SiC particles and Hastelloy were investigated by real-time observation system, X-ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with energy X-ray dispersive spectroscopy (EDS) system. The results demonstrated that the Hastelloy had a good wettability on SiC ceramic and could spontaneously infiltrate into the Ti-activated SiC preform. Moreover, intensive interfacial reaction similar to SiC/Ni system was found between the SiC particles and Hastelloy, which induced defects in the microstructure. In order to inhibit the interfacial reaction, Al 2 O 3 coating on SiC particles was adopted as a diffusion barrier, which effectively reduced the extent of the interfacial reactions. [ABSTRACT FROM AUTHOR]

FLiNaK (LiF-NaF-KF: 46·5-11·5-42 mol.-%) is a promising candidate as high temperature coolant for next generation nuclear reactor coolants. Major technical challenge in implementation is the selection of structural material that can withstand corrosive nature of FLiNaK. Corrosion study of different alloys such as SS-316L, SS-317L, Inconel-625, Incoloy-800H, Hastelloy-B and Ni-201 was performed in FLiNaK salt. The tests were carried out in the temperature range of 650-850°C in graphite crucibles for 60 h under inert atmosphere. Weight loss of the alloy sample due to corrosion was measured, and corrosion rate was estimated. The salt composition after corrosion was analysed by inductively coupled plasma spectroscopy coupled with atomic emission spectroscopy. The surface morphology of the alloy samples was analysed by scanning electron microscopy. Ni-201 and Hastelloy-B showed better resistance to corrosion than other alloys. Corrosion rate was found to increase with increase in Cr content in the alloy. [ABSTRACT FROM AUTHOR]