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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]

In industries including aerospace, automotive, and marine, a machined component's surface integrity is essential since it improves the corrosion resistance and fatigue life. Hastelloy C-276 is a superalloy based on nickel that is used in the chemical and petrochemical sectors due to its high hot strength, high heat resistance, and high corrosion resistance. In the present work, modelling and simulation of UAMAF process is done on flat work piece with the help of ANSYS Maxwell 16.0 software. The experimental setup for flat work piece on milling machine is modelled according to the dimensions of the experiment. These models are then simulated in ANSYS Maxwell 16.0. After validating the model, the obtained results of analysis were matched with the experimental output. If it is found that the simulation and experiment results vary within the acceptable range, then simulation models are accepted. [ABSTRACT FROM AUTHOR]

Hastelloy C-276 is a nickel-based superalloy having high hot strength, high thermal and corrosion resistance and has led to its use in the chemical and petrochemical industries. In the present study, the ultrasonic-assisted magnetic abrasive finishing process (UAMAF) was used to finish Hastelloy C-276. In the UAMAF process, an additional attachment of ultrasonic horn was added to MAF that applies axial vibrations to the workpiece with a frequency of (10–30 kHz). In this process, normal force and power consumption were measured at different levels of voltage, abrasive percentage, speed, working gap, and power intensity using response surface methodology. The results of UAMAF were compared to responses of MAF under similar experimental conditions. The force and power consumption were increased by 26.8% and 26.6% respectively for UAMAF process compared to MAF process. However, the finishing time was reduced by 60% increasing the production rate. Furthermore, the grind surfaces after MAF and UAMAF were also analyzed by using SEM images. [ABSTRACT FROM AUTHOR]

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]

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]

Hastelloy C-276 nickel alloy is widely preferred for nuclear power plant applications where steam generators operate at 600 °C. However, stainless steels are still used for tubes in steam gas reformers which necessitates welds between dissimilar materials. In this study, hastelloy C-276 and SS 316 L alloys were joined using GTAW process. The welding parameters of GTAW were optimized to minimize the defects in samples of similar (SS 316 L-SS 316 L, HAS C-276-HAS C-276), and dissimilar (HAS C-276-SS 316 L) joints. SEM/EDS results confirm the presence of columnar dendritic and cellular structure in fusion zone for dissimilar weldments (HAS C-276-SS 316 L). EDS results also revealed the presence of larger amount of Mo, W and lower amount of Ni in the subgrain boundary as compared to the subgrain body. Compared to the similar (HAS C-276- Has C-276) and dissimilar (HAS C-276-SS 316 L) welded joints FZs, the enrichment of Mo is lesser in SS 316 L-SS 316 L similar welded joints. Higher UTS was obtained for dissimilar (HAS C-276-SS 316 L) GTAW joints 780 MPa compared to the similar welded joints of SS316 (552 MPa) and HAS C-276 (740 MPa). The average microhardness for the dissimilar SS 316 L and HAS C-276 is 220 Hv, which is higher compared to the similar welded joints, SS 316 L and HAS C-276, i.e., 190 Hv and 210 Hv, respectively. This study shows that GTAW process is suitable to fabricate sound weld joints of similar (SS 316 L- SS 316 L, HAS C-276-HAS C-276), and dissimilar (HAS C-276-SS 316 L) alloys which are useful for the nuclear power plant boilers. [ABSTRACT FROM AUTHOR]

Hastelloy C-276 superalloy has a wide range of applications including petroleum and petrochemical industries. Since welding forms an essential fabrication method for joining different structures in these industries, selection of suitable welding parameters is a prime concern that is yet to be addressed for Hastelloy C-276. In the present study, optimization of process parameters for electron beam welding of 2.6-mm-thick Hastelloy C-276 sheet has been carried out to obtain weld bead having through-penetration and minimum weld (or melt) zone cross-sectional area. A simple optimization technique is employed in the present study to solve the multi-objective minimization problem. After carrying out the full factorial experiment using selected process parameters, various geometric elements of the weld bead are identified as the output responses. The regression equation is developed for each geometric element from the experimental data. The desired value of a geometric element is specified as a constraint for the corresponding regression equation. A number of regression equations (considering all the geometric elements) are solved in parallel to obtain an optimized set of process parameters, followed by a confirmation test. Further, the optimized melt zone is subjected to cyclic potentiodynamic polarization test to study its susceptibility to localized corrosion. It is observed that polarization curve characteristics of base metal and optimized melt zone are not significantly different; however, the repassivation potential of the melt zone is less than that of the base metal. A flowchart showing the layout of the employed optimization technique followed by corrosion test is attached. [ABSTRACT FROM AUTHOR]

Preparing a highly textured, flawless YBaCuO (YBCO) layer by ion-beam-assisted deposition (IBAD) requires a substrate with a smooth surface. In this paper, smooth tapes of Hastelloy C-276, a common template alloy, were prepared by electrochemical polishing, and the surface roughness the tapes was investigating by atomic force microscopy and scanning electron microscopy. By analyzing these results, it was discussed how the processing parameters affect the surface roughness, and it is found the following optimized processing parameters: current density of 0.104 A·cm, temperature of 50 °C, plate spacing of 9 cm and time of 150 s. With these optimized parameters, the substrate roughness decreases to less than 5 nm, meeting the requirements of IBAD. [ABSTRACT FROM AUTHOR]

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]

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]

Failure of furnace parts composed of stainless steel or nickel-base alloys has been observed following treatment of gallium-containing compounds at 800 to 1200°C. This work examines the effect of gallium suboxide (Ga2O) and gallium oxide (Ga2O3) on the chemical and mechanical properties of 304 SS, 316 SS, and Hastelloy C-276 in an effort to elucidate a failure mechanism. Results indicate that all three materials are subject to attack by gallium compounds. Elemental segregation, oxidation, and Ga uptake all occur following exposure. Ga2O gas appears to play the dominant role in alloy attack under reducing conditions. Increasing temperature is shown to increase the magnitude of attack, as measured by oxide thickness and gallium-metal uptake. Calculations of the system thermodynamics suggest that Cr, Mn, Si, and V alloying components are responsible for metal oxidation and concurrent gallium absorption. A homogeneous, large (>30 wt.%) gallium uptake resulted in brittle failure of 304 SS. Therefore, exposure to gallium compounds can result in premature failure of iron- and nickel-base structural alloys. [ABSTRACT FROM AUTHOR]