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The usage of molten salt in concentrated solar power plants leads to corrosion in energy storage container materials. However, the effect of temperature, duration and environmental conditions plays a major role in the hot corrosion mechanism of the components. The present research investigates the corrosion behavior of Inconel 600 (IN 600) and Hastelloy C-276 (HC-276) in a 55 wt.% Na2SO4 + 45 wt.% Diatomite molten salt environment. Hot corrosion studies were performed by immersion at 40, 80 and 120 h exposures. X-ray diffraction and scanning electron microscopy analysis examined the oxide phases and morphology formed on the corroded material. The mass loss observed at a maximum duration of 120 h is 0.002 g/cm2 for Inconel 600 and 0.8965 g/cm2 for Hastelloy C-276. The Inconel 600 shows less weight loss compared to Hastelloy C-276 due to the formation of a protective oxide layer of NiCr2O4. The materials exposed to molten salt show different surface morphology during the tested durations. [ABSTRACT FROM AUTHOR]

Extrusion technology is widely utilized in the rubber processing industry, with the extruder serving as the core equipment. As mixed rubber enters the extruder, it undergoes conveyance and plasticization, ultimately forming specific shapes and dimensions upon extrusion. The extruder head is a crucial component, playing a key role in achieving the final product's required size and shape. Factors such as its structure, materials, and manufacturing processes significantly impact the efficiency, product quality, and sustainability of the extrusion process. However, prolonged operation leads to severe wear of the extruder head, adversely affecting rubber product quality. Additionally, extruder head processing poses challenges, with maintenance and repair being complex procedures. Therefore, exploring a wear-resistant, long-lasting metal material for the extruder head without compromising mixed rubber performance is essential. This study focuses on severely worn extruder head metal materials, comparing wear levels after friction with STELLITE 6 alloy, Hastelloy C-276 alloy, 38CrMoAlA, and tungsten carbide with composite rubber. Results show that compared to the NR/BR composite material after Hastelloy C-276 alloy friction, rubber Payne effect increased by 4.4% (38CrMoAl), 3.2% (STELLITE 6), and 4.6% (tungsten carbide). Similarly, rubber dispersion decreased by 9.4% (38CrMoAl), 4.7% (STELLITE 6), and 9.8% (tungsten carbide). Rolling resistance increased by 18.1% (38CrMoAl), 16% (STELLITE 6), and 23.4% (tungsten carbide). Friction coefficient increased by 3.5% (38CrMoAl), 2.8% (STELLITE 6), and 4.3% (tungsten carbide). Wear volume increased by 39.3% (38CrMoAl), 45.3% (STELLITE 6), and 48.9% (tungsten carbide). Specifically, using Hastelloy C-276 alloy as the extruder head metal material yields the best NR/BR composite material dispersion, highest ten times tear strength, excellent anti-wet skid resistance, and minimum rolling resistance. Conversely, using the other alloys results in varying reductions in the physical and mechanical properties of NR/BR composite materials. This research is crucial for improving rubber product quality and extending extruder head lifespan. [ABSTRACT FROM AUTHOR]

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Superalloys are a much-needed material for abundant engineering fields, such as nuclear-powered reactor components and aeronautics. Owing to their exceptional characteristics, such as higher thermal conductivity, they can be difficult to machine using conventional processes. Modern approaches to machining have evolved to utilize these materials. One of the techniques studied in this project is electrical discharge in a wire machine. This process can help to reduce the energy consumption during machining and negative impact on the environment. In addition, shortening the operation time of the machine can help to minimize its impact on the environment. The duration of the pulse and applied current are independent factors considered in this study. Material removal rate, surface roughness, dimensional deviation, and form/orientation tolerance errors are deemed as performance measures. The goal of this investigation is to reduce the time required to machine and improve the surface finish of components by implementing a Grey-based artificial neural network model. This method is useful in foretelling the conditions of the Wire Electro Discharge Machining (WEDM) process. This paper uses the Taguchi design and Analysis of Variance (ANOVA) framework to analyze the model's variable inputs. The overall best coefficient of correlation (R = 0.9981) is fetched with an RMSE value of 0.0086. The material removal rate has been increased by decreasing the time taken for removal, which gives the possibility of consuming minimum energy. The finishing of the machined surface also improved. Moreover, this paper shows how to use an Artificial Neural Network (ANN) model with Grey Analysis. The results of the comparative analysis show that the values envisaged are closer with the actual values. The foretelling capacity of the evolved model is confirmed with the performance analysis of the developed model. [ABSTRACT FROM AUTHOR]

In present investigation, the impact of nanoparticle concentration on the machining accomplishment of Hastelloy C-276 has been examined in turning operation. The outputs like temperature, surface roughness, chip reduction coefficient (CRC), tool wear, and friction coefficient along with angle of shear have been estimated. The graphene nanoparticles (GnP) have been blended into soybean oil in distinct weight/volume ratio of 0.5, 1 and 1.5%. The experimental observations revealed that higher concentration of nanoparticles has enhanced the heat carrying capacity of amalgamation by 12.28%, surface roughness (27.88%), Temperature (16.8%), tool wear (22.5%), CRC (17.5%), coefficient of friction (46.36%) and shear angle (15%). Scanning electron microscopy identified nose wear, abrasion, adhesion and loss of tool coating. Further, lower tool wear has been noticed at 1.5% concentration, while the complete failure of insert has been reported during 116 m/min, 0.246 mm/rev having 0.5% concentration. ANOVA results exhibited that surface roughness is highly influenced by speed rate (41.66%) trailed by feed rate (28.16%) and then after concentration (13.68%). Temperature is dominated by cutting speed (69.31%), concentration (14.53%) and feed rate (13.25%). Likewise, tool wear was majorly altered by cutting speed (67.2%) accompanied by feed rate (23.90%) and thirdly concentration of GnP (5.03%).

Austenitic stainless steel (ASS) grade is considered to be alternative material for Hastelloy C-276, due to its higher material and maintenance cost. Hence, the combination of joining the ASS and Hastelloy C-276 is advisable. In this investigation, Hastelloy C276 and 316L stainless steel materials were joined as similar weld of stainless steel 316 L and Hastelloy C276, as well as dissimilar joints between the Hastelloy C276 and 316L stainless steel using PCGTAW process. After welding, the specimens were characterized using optical microscopy and SEM with EDS. The cellular and columnar dendritic structure was obtained from Hastelloy C276—316L stainless steel dissimilar weldments. From the EDS results, it was confirmed that the Mo and Ni content was higher in sub-grain body as compared to the sub-grain boundary in the FZ zone of dissimilar joints. In the case of similar joints of SS 316 L, Mo content was low in sub-grain body, and Ni content was high, vice versa as compared to the sub-grain boundary. As compared to similar welded specimens, the UTS value was high (790 MPa) for Hastelloy C276—316L stainless steel dissimilar specimens prepared using PCGTAW. An improved micro-hardness value of 300 HV was found for Hastelloy C276-316L stainless steel dissimilar welded specimens, compared to similar joints in SS 316 L and HAS C-276. The recorded hardness value for similar (Hastelloy C276 and 316L stainless steel) joints is 230 HV and 245 HV, respectively. Based on the findings of this investigation, it is concluded that PCGTAW process is an appropriate welding technique for making sound welded joints between combinations of the two superior alloys Hastelloy C276 and 316L stainless steel. [ABSTRACT FROM AUTHOR]

Hastelloy is categorized as difficult to cut superalloy widely used in aerospace, nuclear reactor components and chemical industry because of its magnificent strength and higher heat efficiency. Since, the machining of this material is quite difficult and hence suitable cooling systems are required to achieve sustainable manufacturing goals. The present investigation has been focused on the machining performance and sustainability assessment of turning Hastelloy C-276 in dry, flood and minimum quantity lubrication (MQL) environments. Taguchi L-9 array has been utilized to conduct and record the experimental output along with TOPSIS approach to evaluate the sustainability. The output responses viz. cutting forces, surface roughness, cutting temperature, energy consumption and carbon emission have been recorded at various levels of input variables. The experimental results revealed that MQL has minimized the cutting forces, surface roughness and temperature by margin of 20–38%. Likewise, energy expenditure and carbon emission was declined by 9–27% respectively compared to other conditions. Sustainability analysis explored best performance index during equal weightage criteria at 125 m/min, 0.246 and 0.8 mm doc under MQL. However, implementing assigned weightage system evaluated best condition for dry machining as 88 m/min and 0.246 mm/rev having same doc. SEM analysis of insert reported mainly abrasion and adhesion type of tool wear at all parametric range and machining conditions.

Surface integrity of a machining component is crucial in applications like aerospace, automobile and marine industries as it impacts corrosion and fatigue life. In this study, the Ultrasonic Magnetic Abrasion Finishing (UAMAF) setup along with a chemical coating was used to finish the Hastelloy C-276. The responses change in the surface finish (%∆Ra) and material removal (MR) were analyzed using different process variables such as power intensity, voltage, speed, wt.% of abrasives and working gap. Further chemical coating of yttrium acetate and di-ethanolamine was applied to UAMAF specimens using physical vapor deposition. Variables such as weight of etchant, chamber temperature and the number of coatings were considered in the coating process. From the experimental results, it was observed that the surface finish improved with all process parameters except the working gap. The surface finish first increased and then decreased with working gap in the UAMAF process. MR increased with wt.% of abrasives, power intensity, and voltage while it was decreased with working gap and speed. The initial average roughness of the workpiece was Ra = 1.3 µm, and after the MAF process it reduced to Ra = 0.325 µm; further, after UAMAF it reduced to Ra = 0.096 µm, and after chemo based UAMAF, it was reduced to Ra = 0.0224 µm. However, the %∆Ra improved by around 98.3 % before and after processing and the maximum MR observed was 22.19 mg. [ABSTRACT FROM AUTHOR]

Smart manufacturing is the demand of industry 4.0, in which the mass production of difficult-to-cut materials is of great concern to fulfil the goal of sustainable machining. Presently, the machining of superalloy is of upmost interest because of its wide application. However, the limited data on the turning of Hastelloy C-276 highlights its challenges during processing. Hence, the machining performance of superalloy considering surface quality, thermal aspects and chip reduction coefficient was examined with minimum quantity lubrication of several oils to address the sustainable development goal (SDG-12). The output responses were optimized through response surface methodology along with analysis of variance. The research exhibited that the output responses were dominated by cutting speed and feed rate having a percentage benefaction of 24.26% and 60%, respectively, whilst the depth of cut and lubricant type have an influence of 10–12%. No major difference in temperature range was reported during the different lubrication conditions. However, a substantial variation in surface roughness and the chip reduction coefficient was revealed. The percentage error evaluated in surface roughness, temperature and chip reduction coefficient was less than 5%, along with an overall desirability of 0.88, describing the usefulness of the model used. The SEM micrograph indicated a loss of coating, nose and flank wear during all lubrication conditions. Lastly, incorporating a circular economy has reduced the economic, ecological and environmental burden. [ABSTRACT FROM AUTHOR]

Machining is the most significant process for any manufacturing company to improve the quality of the finished component. The objective of this article is to analyse the process performance of Hastelloy C-276 using PVD (Physical Vapour Deposition) coated, uncoated and alumina-based ceramic tool inserts of high grade quality. Turning process was performed on NC (Numerical Control) machine by varying RPM, feed rate and depth of cut based on the Taguchi L9 orthogonal array approach. In this study, crank wear, flank wear, nose wear, SR (Surface Roughness), MRR (Material Removal Rate), tool temperature and feed force are examined during machining of hardened material and simultaneously static structural analysis of the tool insert along with the tool holder was performed using ANSYS mechanical. This research investigation helps in determining appropriate parameters with varied coated inserts to make the process easier, efficient and economical.

Hastelloy C-276 samples were cold-rolled with their thickness reduction of 7.5% and 15%, and then annealed at 1100 °C for 5–60 min in solid solution. The grain boundary character distributions (GBCDs) were characterized by a technique of electron back scatter diffraction (EBSD). Results indicated that, more convoluted Σ3 boundaries (i.e. incoherent Ʃ3 boundaries) are generated by reasonable annealing time in low strain (7.5%) sample during strain-induced boundary migration (SIBM) processing. They can induce higher Ʃ3n fraction and activate more interactions between special boundaries for GBE. Instead, more coherent Ʃ3 boundaries were produced by moderate strain (15%) and annealing treatment with the occurrence of static recrystallization (SRX). The recrystallized fine grains possess fewer incoherent Ʃ3 boundaries cannot promote to get more multiple twinning for optimization of GBCD. Therefore, reasonable deformation and annealing treatment parameters lead to more incoherent Ʃ3 boundaries would play an important role in the optimization of GBE.

Se analizó el comportamiento microestructural de la superaleación hastelloy C-276, la cual por su característica de resistencia a la corrosión, se emplea en un fluido que presenta diferentes elementos de concentración, además de la velocidad del mismo para su transporte. Se realizó el análisis de muestra sin estar expuesta a condiciones de trabajo y luego de retirada de servicio. Se determinó que entre los efectos más notables que afectan su funcionamiento están el fenómeno de la corrosión por picaduras y el intragranular, asociado al empobrecimiento de la capa de cromo en las áreas afectadas. Al establecer los perfiles de dureza, esta propiedad decrece en la medida que se encuentra la superaleación en contacto con el fluido.

In the present investigation, an attempt has been made to join Hastelloy C-276 nickel-based superalloy and AISI 321 austenitic stainless steel using ERNiCrMo-4 filler. The joints were fabricated by continuous and pulsed current gas tungsten arc welding processes. Experimental studies to ascertain the structure-property co-relationship with or without pulsed current mode were carried out using an optical microscope and scanning electron microscope. Further, the energy-dispersive spectroscope was used to evaluate the extent of microsegregation. The microstructure of fusion zone was obtained as finer cellular dendritic structure for pulsed current mode, whereas columnar structure was formed with small amount of cellular structure for continuous current mode. The scanning electron microscope examination witnessed the existence of migrated grain boundaries at the weld interfaces. Moreover, the presence of secondary phases such as P and μ was observed in continuous current weld joints, whereas they were absent in pulsed current weld joints, which needs to be further characterized. Moreover, pulsed current joints resulted in narrower weld bead, refined morphology, reduced elemental segregation and improved strength of the welded joints. The outcomes of the present investigation would help in obtaining good quality dissimilar joints for industrial applications and AISI 321 ASS being cheaper consequently led to cost-effective design also. [ABSTRACT FROM AUTHOR]

The metadynamic recrystallization (MDRX) behavior of a typical Ni-Cr-Mo-based superalloy Hastelloy C-276 was investigated using two-stage isothermal compression tests on a Gleeble thermal-mechanical simulator in the temperature range of 1050-1200 °C, the strain rate range of 0.1-5.0 s, the strains of 0.32, 0.45, and 0.6 at the first stage of compression, and the interval times of 0.5-30 s. The results show that the microstructure and the stress-strain relation of the studied superalloy vary during the interruption period due to the occurrence of MDRX. The MDRX softening fraction and recrystallized grain size increase rapidly with the increasing of interval time, deformation temperature, and strain rate. The effect of strain at the first stage of compression on MDRX is less pronounced. The kinetics of MDRX softening was established based on the flow stress curves, and the apparent activation energy of MDRX of Hastelloy C-276 is evaluated as 241 kJ/mol. [ABSTRACT FROM AUTHOR]

Present industrial scenario attempts to achieve the sustainable manufacturing goal considering economic viability, ecological vulnerability, technological suitability and social acceptability. Also, in current manufacturing paradigm, the machining of fatigue resistance material like Hastelloy C-276 possessing vast applications in aerospace, nuclear and petroleum industries is still challenging. Consequently, leads to uneconomical process and degradation of environment during dry machining and conventional lubrication methods. The present investigations have been focused on economic and ecological sense of machining Hastelloy C-276 with reference to tool damage, surface roughness and lubrication action using different lubricating oils. The flash point, viscosity, and pH values of different oils have been measured using Pensky Marten apparatus, Fann viscometer, measuring strips and a digital pH meter. Additionally, the appearance, odour, and flow ability have been examined physically. The experimental results depicted that surface roughness has been improved by 1.5–62% during vegetable oil and 22% in used oil compared to synthetic oil at lower range of machining parameters. However, at higher levels of process variables, synthetic oil performed better than used oil by 29.2%–98.9% respectively. SEM micrograph indicated 26.17%–50% lower flank wear during vegetable oil compared to synthetic oil. However, Synthetic oil has reduced the tool wear by 3.7%–61.74% than used oil. Further, the coefficient of friction among three oils has varied from 17 to 22.5% manifesting that used oil have considerable lubrication effect. Moreover, the ANOVA analysis revealed that feed rate and lubricant type have an appreciable impact on shear angle and coefficient of friction with maximum percentage error of 3.03% and 6.38% respectively. Finally, minimum quantity lubricant (MQL) of vegetable and synthetic oil has offered a sustainable perspective due to excellent machining performance, better work place conditions, and high-tech lubrication methodology. • Preparation of Environment adaptiable Lubricants (EAL). • Experimental investigation into tool wear and Surface roughness using environmental adaptable lubricants. • Influence of Process parameter on tool wear, surface roughness, shear angle and coefficient of friction. • Evaluation of lubrication and wear mechanism during different lubrication conditions. • An Outlook on the Global economic, ecology of MWF, and comparative statement of economic, ecological and technological Sustainability. [ABSTRACT FROM AUTHOR]

C-276 nickel-based alloy is a difficult-to-cut material. In high-speed machining of Hastelloy C-276, notching is a prominent failure mode due to high mechanical properties of work piece, which results in the short tool life and low productivity. In this paper, a newly developed Ti(CN)-based cermet insert manufactured by a hot-pressing method is used to machine the C-276 nickel-based alloy, and its cutting performances are studied. Based on orthogonal experiment method, the influence of cutting parameters on tool life, material removal rates and surface roughness are investigated. Experimental research results indicate that the optimal cutting condition is a cutting speed of 50 m/min, depth of cut of 0.4 mm and feed rate of 0.15 mm/r if the tool life and material removal rates are considered comprehensively. In this case, the tool life is 32 min and material removal rates are 3000 mm/min, which is appropriate to the rough machining. If the tool life and surface roughness are considered, the better cutting condition is a cutting speed of 75 m/min, depth of cut of 0.6 mm and feed rate of 0.1 mm/r. In this case, the surface roughness is 0.59μm. Notch wear, flank wear, chipping at the tool nose, built-up edge(BUE) and micro-cracks are found when Ti(CN)-based cermet insert turned Hastelloy C-276. Oxidation, adhesive, abrasive and diffusion are the wear mechanisms, which can be investigated by the observations of scanning electron microscope and energy-dispersive spectroscopy. This research will help to guide studies on the evaluation of machining parameters to further advance the productivity of nickel based alloy Hastelloy C-276 machining. [ABSTRACT FROM AUTHOR]

A stress relaxation test has been carried out for Hastelloy C-276 at temperature of 800 °C and initial stress level of 250 MPa. Based on the experimental stress relaxation curve, the relationship between creep strain rate and stress has been derived. Then, a set of creep constitutive equations has been built and the values of constants arising in the constitutive equations have been determined by fitting the creep strain rate-stress curve. Close agreement between computed results and experimental ones is obtained for stress relaxation data. The creep constitutive equation set has been integrated with the commercial FE (finite element) solver MSC. Marc via the user defined subroutine, CRPLAW, for the vacuum hot bulge forming process modelling of Hastelloy C-276 thin-walled cylindrical workpiece. The temperature field, the radius-direction displacement field and the stress-strain field are calculated and analyzed. Furthermore, the bulging dimension and the final internal diameter of workpiece are predicted and the test results verify the reliability of the finite element method. [ABSTRACT FROM AUTHOR]

The aim of this paper was to introduce the study on burr formation mechanism of nickel-based Hastelloy C-276 in the turning process. The process is monitored using a high-speed camera mounted on a computer numerical control (CNC) turning machine. The captured photographs show that the burr starts appearing on the edge of an uncut surface when the engagement with the chip-workpiece contact area is complete and increases accordingly during the process of hitting the cutting edge and causing chipping wear. The study shows that the initializing of chip burr formation can be divided into two stages: creating and mounting up. Creating of burr formation is characterized by the 'reaction of shear formation' of the cutting force on the edge of chip for an unmachined surface, while mounting up increasing in size and forcing the chip to change its direction shoots up the rake face. This edge of the burr will separate and re-attach with the burr edge again during mounting up, thus creating a chain web shape on the edge of the uncut surface and causing edge chipping. The results show that the approach angle has a significant effect on burr formation. [ABSTRACT FROM AUTHOR]

Abstract: In this study, measurements of the thermal contact conductance (TCC) at the interfaces of Hastelloy C-276/Hastelloy C-276 and Hastelloy C-276/SS302 test pairs were conducted by a self-developed experimental setup based on the steady-state heat flux method. The reliability of experimental setup and method was validated by the repeated measurement of the thermal contact conductance between Hastelloy C-276 and Hastelloy C-276. In addition, the effects of contact pressure and interfacial temperature on thermal contact conductance were also discussed. This study not only provides a necessary database for the accurate numerical simulation but also lays a foundation for the optimal design of the shrink fitting process of rotor can. [Copyright &y& Elsevier]

Abstract: The heat transfer between rotor can/narrow air gap/silicon steel sheet has an important influence on the shrink fit process of reactor coolant pump rotor can. The accurate thermal conductance data are needed for the optimal design and numerical simulation of the shrink fit process of rotor can. Consequently, in this study, a set of new experimental apparatus and relevant procedure were developed to measure the thermal conductance at the interface between Hastelloy C-276/narrow air gap/silicon steel based on the transient method. The effects of the initial temperature of the Hastelloy C-276 specimen and the dimension of the air gap between the two test specimens on the thermal conductance were evaluated. [Copyright &y& Elsevier]

Abstract: In this study a pulsed Nd:YAG laser was used to join Hastelloy C-276 thin foil with 100 microns thickness. Pulse energy was varied from 1.0 to 2.25J at small increments of 0.25J with a 4ms pulse duration. The macro and microstructures of the welds were analyzed by optical and electronic microscopy, tensile shear test and microhardness. Sound laser welds without discontinuities were obtained with 1.5J pulse energy. Results indicate that using a precise control of the pulse energy, and so a control of the dilution rate, it is possible to weld Hastelloy C-276 thin foil by pulsed Nd:YAG laser. [Copyright &y& Elsevier]

Abstract: In this paper, it was indicated that the laser welding was well suitable to joining of thin Hastelloy C-276 sheet (0.5 mm thickness), and also the fine grain were observed in welding zone with invisible HAZ (heat affected zone). In addition, the smooth weld joint could be controlled by means of the laser parameter adjustment. On the other hand, it’s proposed that Ni–Cr–Co–Mo and austenite CFe15.1 cubic face-centered crystal structure should be existed in as-received and welding samples, as well as the cause of FWHM (Full Width at Half Maximum) widened and peak offset of joined samples were analyzed. [Copyright &y& Elsevier]

Abstract: This paper presents the results of a failure investigation carried out on a cast Hastelloy C-276 pump impeller that suffered general corrosion in 32% hydrochloric acid at ambient temperature in a chemical plant. Microscopic examination revealed that the attack was crystallographic in nature. The attack was more enhanced at the interdendritic arm spacing as well as the boundaries of columnar grains, resulting in deep grooves. Taking into consideration that the local temperature could reach up to 50°C in the summer months, Hastelloy C-276 was judged to be unsuitable material for applications involving 32% HCl. A search into a suitable alternative alloy did not provide a satisfactory answer. Therefore, rubber-lined pump impeller was considered the better alternative. [Copyright &y& Elsevier]

Abstract: The quench nozzles (Hastelloy C-276) installed in the firebox of an incinerator in the EDC unit of a Saudi petrochemical plant experienced frequent premature failures. One damaged quench nozzle (male and female parts), therefore, was investigated by chemical analysis, optical microscopy, and EDS techniques in order to find out the cause and preventive solutions. The study indicates that the quench nozzle was corroded likely due to hydrochloric acid (HCl) formed in the hot service following the failure of the refractory lining. The presence of both moisture and chloride (from EDC) made HCl formation possible. Upgrading the construction material to Alloy C-59 is recommended. Alternatively, ceramic coatings of SiC can be applied. [Copyright &y& Elsevier]

Abstract: Electron beam welding (EBW) technique is becoming popular in nuclear, chemical and aerospace industries due to its high penetration depth and fast cooling rate. Samples of Hastelloy C-276 have been welded by electron beam (EB). A scanning electron microscope (SEM) having the attachment of an energy dispersive system (EDS) has been employed to study the resulting microstructure and micro-eutectic phases. The microstructure of the molten zone (MZ) is found to be of fine lamellar type. The hardness of the MZ is found to be 35% higher compared to as-received alloy. The micro-eutectoids are rich in Mo and W. The X-ray diffraction patterns of the MZ show shifting of peaks towards higher angle compared to the diffraction pattern of the as-received alloy. Broadening of the peaks is also observed in the diffraction pattern of the MZ. Formation of the μ-phase was observed in the MZ after a tempering treatment at 950°C. [Copyright &y& Elsevier]

Abstract: We prepared multi-walled carbon nanotubes (MWCNTs) on Hastelloy C276® by a direct current (dc) plasma-assisted hot filament chemical vapor deposition in CH4/N2 atmosphere. Two-step deposition method, consisting of nucleation step and the subsequent CNT growth step, was employed and MWCNTs were grown by the catalytic growth with metal particles, which were precipitated from Hastelloy C276® and mainly consisted of Ni. The plasma generated at the current density of 30 mA/cm2 was necessary to form nuclei for CNT growth, while the reducing of the plasma current density to the range between 10 and 20 mA/cm2 was needed to grow MWCNTs. Based on these results, we proposed the possible mechanisms of the nucleus formation and MWCNT growth. [Copyright &y& Elsevier]

The pulsating current approach in tungsten inert gas (TIG) welding is adapted for joining Hastelloy C-276. Microstructure examination revealed the absence of micro-segregation while employing UNS N06022 filler. Due to the prevalence of higher tensile stresses in the un-peened conditions, tensile failures were observed in the weld regions of both the joints irrespective of fillers. Low energy laser shock peening without coating (LSPwC) was carried out on the weld zones on both the sides of the joints with the pulse densities 2500 and 7500 pulses per cm2. This laser surface treatment had remarkably increased the tensile strength of the welded joints by shifting the location of tensile failures well away from the fusion zones for all the cases. Similarly, a considerable increase is observed in the notch toughness of both the joints in the LSPwC condition. The enhancement in tensile strength and notch impact toughness of the welds could be ascribed to the residual compressive stresses induced which were then confirmed by Sin2ψ method in X-ray diffraction (XRD) technique. [ABSTRACT FROM AUTHOR]